International Geology Review, Vol. 44, 2002, p. 544–558. Copyright © 2002 by V. H. Winston & Son, Inc. All rights reserved. 0020-6814/02/602/544-15 $10.00. 544 Geology of Paleoproterozoic Gneiss- and Granitoid-Hosted Gold Mineralization in Southern Tapajós Gold Province, Amazonian Craton, Brazil EVANDRO LUIZ KLEIN, 1 MARCELO LACERDA V ASQUEZ, LUCIA T RAVASSOS DA ROSA-COSTA, AND JOSÉ MARIA DE AZEVEDO CARVALHO Companhia Pesquisas Resursos Minerais (CPRM)/Geological Survey of Brazil, Av. Dr. Freitas, 3645 Belém PA, Brazil, CEP: 66095-110 Abstract Vein-quartz gold mineralization in Southern Tapajós Province is hosted by arc-related, calc-alka- line tonalitic orthogneisses (Cuiú-Cuiú Complex, 2033–2005 Ma) and post-collisional, calc-alka- line, K-rich granitoids (Creporizão Intrusive Suite, 1997–1957 Ma). The deposits are structurally controlled and form typically tabular bodies that parallel the hosting structures, and are character- ized by quartz veins surrounded by halos of strongly altered wall rock, which are usually narrow and show weak to prominent ductile fabric. Steeply dipping fault-fill veins and shear veins account for 80% of the structural style, followed by breccia veins and lesser stockworks and veins hosted in low- angle reverse-oblique faults. Hosting structures vary from ductile-brittle to brittle in nature, and together with structural and textural evidence provided by the veins, indicate a wide range of depth of emplacement for the mineralization, from shallow to mid-crustal. Quartz and sericite are the main alteration minerals and pyrite is ubiquitous. We modify current structural models for the Tapajós Province, proposing the NW-SE–trending strike-slip event that affected the Creporizão Suite, and transposed the gneissic banding of the Cuiú- Cuiú Complex as the second (D2) major structural event in the province, occurring broadly coeval with the emplacement of the late-stage plutons of the Creporizão Suite (~1.97–1.95 Ga). Emplace- ment of low-angle fault-hosted veins, shear veins, and fault-fill veins that show evidence of plastic deformation (i.e., most of the deposits in Southern Tapajós Province) are related to this structural phase. Introduction STRUCTURALLY CONTROLLED vein-quartz (lode) gold deposits are more commonly associated with meta- morphic terrains, where they are hosted especially by low- to medium-grade metasupracrustal sequences, and minor intruding granitoids (grani- toid-greenstone association) of Archean to Cenozoic age (Kerrich and Cassidy, 1994; Groves et al., 1998; Goldfarb et al., 2001). These gold deposits show a variety of structural styles, vein textures, and alter- ation mineralogy, depending on many factors, such as the composition and metamorphic grade of the host rock, timing of gold deposition with respect to metamorphism and deformation, structural regime, and depth of formation (e.g., Cassidy et al., 1998; Groves et al., 1998). Nevertheless, they are consis- tent as a class and have been classified as green- stone-hosted (Robert et al., 1997) or orogenic (Groves et al., 1998) gold deposits. Granitoids and granitic gneisses are also hosts for this type of gold mineralization, with deposits showing many of the attributes displayed by supracrustal-hosted depos- its, and being considered a subgroup of the lode type of mineralization, at least within the Archean lode- gold deposits model (Cassidy et al., 1998). The Tapajós Gold Province of the Amazonian Craton has produced about 600 metric tons (t) of alluvial gold in the past 40 years (Faraco et al., 1997). It is a major magmatic province and contains more than 100 sub-economic gold deposits and showings, mostly hosted by granitoids of different (Paleoproterozoic) ages and affinities, as well as by gneisses, felsic to intermediate volcanic rocks, and minor gabbroic and metavolcanic-sedimentary rocks (Coutinho et al., 2000; Klein et al., in press), distributed along several gold camps and small dis- tricts. Most deposits are Au-bearing quartz veins, 1 Corresponding author: e-mail: [email protected]
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International Geology Review Vol 44 2002 p 544ndash558Copyright copy 2002 by V H Winston amp Son Inc All rights reserved
0020-681402602544-15 $1000 544
Geology of Paleoproterozoic Gneiss- and Granitoid-Hosted Gold Mineralization in Southern Tapajoacutes Gold Province
Amazonian Craton BrazilEVANDRO LUIZ KLEIN1 MARCELO LACERDA VASQUEZ LUCIA TRAVASSOS DA ROSA-COSTA
AND JOSEacute MARIA DE AZEVEDO CARVALHO
Companhia Pesquisas Resursos Minerais (CPRM)Geological Survey of Brazil Av Dr Freitas 3645 Beleacutem PA BrazilCEP 66095-110
Abstract
Vein-quartz gold mineralization in Southern Tapajoacutes Province is hosted by arc-related calc-alka-line tonalitic orthogneisses (Cuiuacute-Cuiuacute Complex 2033ndash2005 Ma) and post-collisional calc-alka-line K-rich granitoids (Creporizatildeo Intrusive Suite 1997ndash1957 Ma) The deposits are structurallycontrolled and form typically tabular bodies that parallel the hosting structures and are character-ized by quartz veins surrounded by halos of strongly altered wall rock which are usually narrow andshow weak to prominent ductile fabric Steeply dipping fault-fill veins and shear veins account for80 of the structural style followed by breccia veins and lesser stockworks and veins hosted in low-angle reverse-oblique faults Hosting structures vary from ductile-brittle to brittle in nature andtogether with structural and textural evidence provided by the veins indicate a wide range of depthof emplacement for the mineralization from shallow to mid-crustal Quartz and sericite are the mainalteration minerals and pyrite is ubiquitous
We modify current structural models for the Tapajoacutes Province proposing the NW-SEndashtrendingstrike-slip event that affected the Creporizatildeo Suite and transposed the gneissic banding of the Cuiuacute-Cuiuacute Complex as the second (D2) major structural event in the province occurring broadly coevalwith the emplacement of the late-stage plutons of the Creporizatildeo Suite (~197ndash195 Ga) Emplace-ment of low-angle fault-hosted veins shear veins and fault-fill veins that show evidence of plasticdeformation (ie most of the deposits in Southern Tapajoacutes Province) are related to this structuralphase
Introduction
STRUCTURALLY CONTROLLED vein-quartz (lode) golddeposits are more commonly associated with meta-morphic terrains where they are hosted especiallyby low- to medium-grade metasupracrustalsequences and minor intruding granitoids (grani-toid-greenstone association) of Archean to Cenozoicage (Kerrich and Cassidy 1994 Groves et al 1998Goldfarb et al 2001) These gold deposits show avariety of structural styles vein textures and alter-ation mineralogy depending on many factors suchas the composition and metamorphic grade of thehost rock timing of gold deposition with respect tometamorphism and deformation structural regimeand depth of formation (eg Cassidy et al 1998Groves et al 1998) Nevertheless they are consis-tent as a class and have been classified as green-
stone-hosted (Robert et al 1997) or orogenic(Groves et al 1998) gold deposits Granitoids andgranitic gneisses are also hosts for this type of goldmineralization with deposits showing many of theattributes displayed by supracrustal-hosted depos-its and being considered a subgroup of the lode typeof mineralization at least within the Archean lode-gold deposits model (Cassidy et al 1998)
The Tapajoacutes Gold Province of the AmazonianCraton has produced about 600 metric tons (t) ofalluvial gold in the past 40 years (Faraco et al1997) It is a major magmatic province and containsmore than 100 sub-economic gold deposits andshowings mostly hosted by granitoids of different(Paleoproterozoic) ages and affinities as well as bygneisses felsic to intermediate volcanic rocks andminor gabbroic and metavolcanic-sedimentaryrocks (Coutinho et al 2000 Klein et al in press)distributed along several gold camps and small dis-tricts Most deposits are Au-bearing quartz veins1Corresponding author e-mail ekleinamazoncombr
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 545
with stockworks and dissemination occurring subor-dinately (Klein et al 1999 Rosa-Costa and Car-valho 1999 Coutinho et al 2000) and distinctclassifications (such as mesothermal epithermalintrusion-related and orogenic) have been proposedfor individual deposits or to the province as a whole(Dreher et al 1998 Juliani 2001 Klein et al2001 Santos et al 2001)
In the southern portion of the Tapajoacutes Province aseries of gold camps contain deposits and prospectstypically hosted in orogenic gneisses (Cuiuacute-CuiuacuteComplex) and granitoids (Creporizatildeo IntrusiveSuite) The purpose of this paper is to summarize thegeological attributes of these deposits which areobservable at regional outcrop and hand-specimenscales with emphasis on their relationship withregional structures structural styles vein geometryand internal structures and textures Microscopicinformation is used when available A revaluation ofcurrent structural models and a tentative classifica-tion of the deposits are made as well
Geological Setting
The Tapajoacutes Gold Province (TGP) is located inthe central portion of the Amazonian Craton and ispart of the Ventuari-Tapajoacutes (according to Tassinariand Macambira 1999) or Tapajoacutes-Parima (in thesense of Santos et al 2000) geochronological prov-inces (Fig 1) The regional lithostratigraphy wasdefined by the mapping program performed byCPRMGeological Survey of Brazil (Almeida et al2000 Bahia and Quadros 2000 Ferreira et al2000 Klein and Vasquez 2000 Vasquez and Klein2000) The results of this program (Fig 2) alongwith the work of Santos et al (2000 2001) showeda protracted Paleoproterozoic magmatic metamor-phic and tectonic evolution spanning the periodfrom 2033 Ma to 1870 Ma
The oldest rocks found in the TGP are the green-schist-facies metavolcano-sedimentary sequence ofthe Jacareacanga Group and the amphibolite-faciesgneisses (plusmn granitoids migmatites amphibolites) ofthe Cuiuacute-Cuiuacute Complex both formed between 2033
FIG 1 Geochronological provinces of the Amazonian Craton according to (A) Tassinari and Macambira (1999) and(B) Santos et al (2000)
546 KLEIN ET AL
FIG 2 Geological map of the Tapajoacutes gold province (compiled and modified from Almeida et al 2000 Bahia andQuadros 2000 Ferreira et al 2000 Klein and Vasquez 2000 Vasquez and Klein 2000) showing the distribution of thegold depositscamps in the province
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 547
and 2005 Ma (Santos et al 2000 2001) Thesemetamorphic sequences have been intruded bycalc-alkaline granitoids of the Creporizatildeo (199ndash196 Ga) (Ricci et al 1999 Vasquez et al 2000)Tropas (190 Ga) (Santos et al 2001) and Parauari(189ndash188 Ga) (Vasquez et al 1999 Santos et al2000) intrusive suites as well as by a series of gab-broic rocks at 187 Ga (Santos et al 2001) Sedi-mentary deposits showing intra-arc characteristicsformed at ~190ndash189 Ga (Santos et al 2001) Thisorogenic period was followed by widespread felsicplutonic and volcanic activity at 187 Ga (Almeidaet al 1999 Vasquez et al 1999 Santos et al2000 Lamaratildeo et al 2001 Klein et al in press)related to extensional tectonics
It is the consensus that the orogenic evolution ofthe province comprises the accretion of magmaticarcs and related sedimentary basins However thenumber of arcs that have accreted is still debatableSantos et al (2000 2001) envisioned the evolutionof the orogenic domain through the sequentialaccretion of four magmatic arcs dated at 202 Ga(Cuiuacute-Cuiuacute Complex plus Jacareacanga Group)196 Ga (Creporizatildeo Suite) 190 Ga (Tropas Suite)and 188 Ga (Parauari Suite) These accretionaryevents have been followed by post-collisional intra-cratonic (granitoid and mafic) magmatism and sedi-ment deposition between 1870 Ma and 1780 MaConversely Vasquez et al (2001) considered theCreporizatildeo granitoids as post-collisional granitoidsstill related to the development of the Cuiuacute-Cuiuacutearc instead of considering it to be a different arc(see discussion below)
Structural framework
Remote sensing imagery and geophysical evi-dence show that the main structural features of theTapajoacutes Province are major NNW-SSEndash to NW-SEndashstriking linear or sinuous continuous to discontin-uous lineaments extending for tens to a few hun-dreds of kilometers (Fig 2) Field evidenceindicates that they represent mainly subverticalsinistral strike-slip faults and brittle-ductile shearzones This strike-slip system has been interpretedas a progressive and episodic compressive eventwith the maximum compressive stress vector (s1)around the east-west direction as shown by geomet-ric relationships of major and minor subsidiarystructures (Santos 1999 2000 Klein andVasquez 2000) On a regional scale these struc-tures have controlled the ascent and emplace-ment of several generations of granitoids and
volcanic and mafic rocks as well as the establish-ment of sedimentary basins and have outlinedtheir present shape and geometry (Klein et al1997 Santos 1999 Almeida et al 2000 Kleinand Vasquez 2000) It is likely that at least someof these structures may have been reactivatedduring the tectonic evolution of the Tapajoacutes Prov-ince However the timing of these events is notwell constrained yet
The oldest (D1) structural record is found in thewest-central portion of Tapajoacutes Province It isdefined by the NE-SWndashtrending gneissic banding ofthe Cuiuacute-Cuiuacute Complex and the schistosity of thevolcano-sedimentary Jacareacanga Group (Almeidaet al 2001) produced by a compressive event andis well preserved in the gneisses of the study areaThis deformation is not seen in younger rocks lead-ing Santos et al (2001) to establish the time intervalof 2005ndash1974 Ma as the timing of D1 which mayhave been synchronous with the metamorphic peakSantos et al (2001) defined a second deformationalevent (D2) represented by a high-angle N10E-strik-ing sinistral strike-slip shear zone of ductile-brittlecharacter affecting especially the Tropas Suite inthe western-central portion of the province and onlylocally affecting the Creporizatildeo and Parauari suitesThey placed the timing of this event to between1894 and 1883 Ma Furthermore they suggestedthat the brittle deformation which is younger than1883 Ma and which affected the Creporizatildeo andParauari granitoids could have been produced dur-ing the shallow emplacement of the Maloquinhagranitoids
However this structural evolution does notexplain satisfactorily the brittle-ductile deformationimprinted on the granitoids of the Creporizatildeo Suite(1997ndash1957 Ma) that are older than the Tropas Suite(190 Ga) The Creporizatildeo granitoids show a mag-matic foliation subparallel to a subvertical tectonicfoliation that strikes NW-SE and is clearly relatedto a brittle-ductile strike-slip regime This event hasnot been detected either in the Tropas Suite asstated by Santos et al (2001) nor in younger rocks(Parauari and Maloquinha suites volcanic rocks)Furthermore Almeida et al (2000 2001) docu-mented the transposition of the gneissic banding ofthe Cuiuacute-Cuiuacute rocks by NW-SE strike-slip shearzones Still a whole-rock Rb-Sr isochron age of1965 plusmn 16 Ma was reported by Tassinari (1996) forgranitoids of the Creporizatildeo Suite This age is closeto the zircon ages (U-Pb Pb-evaporation) for thelate-stage granitoids of the Creporizatildeo Suite and
548 KLEIN ET AL
may indicate that the emplacement of the post-colli-sional plutons was broadly coeval with the regionalNW-SE deformational event (Ricci et al 1999Vasquez et al 2001)
Hence we postulate a reappraisal of the struc-tural evolution of the Tapajoacutes Province as followsAn early deformation stage (D1) is represented bythe compressive event that imparted the gneissicbanding of the Cuiuacute-Cuiuacute Complex and the schis-tosity of the Jacareacanga Group occurring proba-bly between 2005 and 1997 Ma D2 is representedby the NW-SEndashtrending strike-slip event thataffected the granitoids of the Creporizatildeo Suite andoverprinted the gneissic banding of the Cuiuacute-Cuiuacuterocks occurring at ~197ndash195 Ga D3 is related tothe NNE-SSW strike-slip ductile shear zones thataffected the Tropas Suite between 1894 and 1883Ma Younger structures may have been reactivatedandor generated during the emplacement of thewidespread Maloquinha granitoids and are relatedto extensional tectonics
Gold deposit models
Studies of individual deposits in the TapajoacutesGold Province have been focused on fluid-inclusionproperties andor alteration assemblages leading tothe proposition that the deposits fit epithermal tomesothermal models (Dreher et al 1998 Klein etal 2001 Nunes et al 2001 Ronchi et al 2001)Province-scale models have been developed byCoutinho et al (2000) Santos (2000) and Santos etal (2001) Santos (2000) presented a structuralmodel relating the formation of the gold-quartz veinsto the regional-scale strike-slip fault systemCoutinho et al (2000) classified the deposits of theTapajoacutes Province as mesozonalepizonal orogenicdeposits and suggested two phases of mineraliza-tion based on model ages of sulfide minerals at196 Ga and 188 Ga Both phases postdated theregional metamorphic peak and have been associ-ated with compressional to transpressional tectonicsat the convergent plate margin of the accretionaryorogen Lead and stable (O H) isotopes togetherwith fluid-inclusion data suggest deep sources forgold mineralization (magmatic to juvenile) withpossibly meteoric water added in some deposits atshallow crustal levels
Santos et al (2001) proposed two classes of golddepositsmdashorogenic and intrusion related Orogenicdeposits have been subdivided into (1) turbidite-hosted consisting of mesozonal quartz-pyrite vein-lets or disseminations in ductile structures cutting
the supracrustal rocks of the Jacareacanga Group(2) magmatic arc-hosted consisting of mesozonalquartz-pyrite-carbonate veins and disseminationshosted in ductile-brittle structures cutting thegneisses of the Cuiuacute-Cuiuacute Complex and the grani-toids of the Tropas Suite Intrusion-related depositshave been subdivided into (1) epizonal quartz-pyrite veins and pyrite disseminations emplaced inshallow extensional brittle structures (similar toKorean-type deposits) cutting K-rich granitoids ofthe Creporizatildeo Parauari and Maloquinha suitesfrequently associated with mafic dikes (2) epizonaldisseminations and stockworks with hydrothermalmagnetite hosted in mafic and sedimentary rocksand sharing some characteristics with porphyry-typedeposits Using Pb and Ar isotopes Santos et al(2001) determined the timing of the intrusion-related deposits as being around 186 Ga They havenot established the age of the orogenic deposits buthave suggested that it might be similar to the age ofthe intrusion-related deposits with mineralizationdiffering in style host rocks and depth of emplace-ment They argued that the orogenic deposits wouldbe related to the final stages of evolution of theParauari arc whereas the intrusion-related depositswould be related either to the Parauari arc or to post-collisional granitoids (Maloquinha Suite)
Epithermal deposits have been described byJacobi (1999) Correcirca-Silva et al (2001) Juliani(2001) and Nunes et al (2001) for the east-centralportion of the province The deposits are hosted byfelsic to intermediate volcanic rocks and associatedvolcaniclastic rocks and consist of both low-sulfida-tion (adularia-sericite) and high-sulfidation (quartz-alunite) types Indirect dating suggests that mineral-ization formed at ~188 Ga and d34S data indicateda magmatic-hydrothermal source for the mineral-izing fluids and 330ordmC to 140ordmC as the formationtemperatures (Juliani 2001 Nunes et al 2001)Dreher et al (1998) also considered the epither-mal model for the Joel and David deposits How-ever Correcirca-Silva et al (2001) questioned thisclassification and argued that the adulariapresent in the Davi and Joel deposits is hosted inmafic rocks and could be related to this maficmagmatism Also Santos et al (2001) argued thatthese two deposits lack many important featuresof classic epithermal deposits such as the rela-tionship with contemporaneous volcanic rocks(the deposits are hosted by gabbro and granitoidrespectively) the low silver and adularia con-
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 549
tents and the absence of native silver and silversulfosalts in the ore mineralogy
Gold Deposits in the Southern Tapajoacutes Province (STP)
More than 20 deposits and showings are distrib-uted in several gold camps along the STP (Fig 3)These mineralizations are discussed below in termsof host rocks wall rock alteration and structuralcontrol The classification of structural styles of theveins is based mainly on the concepts of Hodgson(1989) and Robert and Poulsen (2001) taking intoaccount the type of host structure and the internalstructure and textures of the veins The mainattributes are summarized in Table 1
Host rocksGneisses and orogenic granitoids are the main
hosts for gold deposits in the Tapajoacutes Gold Provinceand account for virtually all the host rocks in STP(Table 1) The gneisses belong to the Cuiuacute-CuiuacuteComplex They consist of gray orthogneisses oftonalitic and granodioritic composition bearingmicrogranular enclaves of diorites and quartz-dior-ites along with granitoids and rare migmatites andamphibolites Structurally the gneisses show a per-vasive ductile fabric striking NNE-SSW or NW-SE
and migmatitic features are subordinate Thegeochemical characteristics of trace elements(LILE HFSE REE) are compatible with those ofprimitive arc-related calc-alkaline granitoids(Vasquez et al 2001) They are dominantly metalu-minous with lenses of peraluminous to strongly per-aluminous leucogranitoids occurring subordinatelySantos et al (2000 2001) obtained zircon U-PbSHRIMP ages between 2033 Ma and 2005 Ma forthis complex
The hosting granitoids are related to the Crep-orizatildeo Intrusive Suite which holds irregular- to sig-moidal-shaped batholiths and stocks (Fig 2) ofhornblende- andor biotite-bearing granitoids andmetagranitoids of syenogranitic to tonalitic composi-tion The granitoids are either foliated or granoblas-tic and the latter show preserved primary featuressuch as euhedral phenocrysts of K-feldspar unde-formed microgranular enclaves and synplutonicdikes Very often they show an igneous bandingmarked by the orientation of the K-feldspar pheno-crysts that parallels the NW-SEndashtrending tectonicfoliation Field mineralogical and textural evi-dence indicates emplacement of the granitoids in acrustal level compatible with greenschist or up tomiddle-amphibolite metamorphic conditions (Ricciet al 1999) and the presence of enclaves ofgneisses from the Cuiuacute-Cuiuacute Complex is evidence of
FIG 3 Geological map of the Southern Tapajoacutes Province showing the location of the gold deposits addressed in thisstudy
550 KLEIN ET AL
TAB
LE 1
Sum
mar
y of
Attr
ibut
es o
f Gol
d D
epos
its o
f the
Sou
ther
n Ta
pajoacute
s Pr
ovin
ce1
No
Cam
p or
dep
osit
(n
umbe
r of
vei
ns)
Stru
ctur
al s
tyle
Inte
rnal
str
uctu
reH
ost r
ock
(s
trat
igra
phic
uni
t)G
angu
e m
iner
alog
yO
re m
iner
alog
yV
ein
orie
ntat
ion
(str
ike
dip)
Sele
cted
ref
eren
ces
1G
oian
o (2
)B
recc
iaC
atac
last
icF
olia
ted
gran
itoi
d (C
IS)
mus
pyN
50E
88S
E N
20W
88
NE
N0E
80E
Sant
os 1
997
2Su
daacuteri
o (4
)F
FV
(plusmn
maf
ic
dike
)M
assi
ve c
atac
last
icG
rani
toid
s (C
CC
)py
N40
-60E
70-
88SE
-N
WR
osa-
Cos
ta a
nd C
arva
lho
199
9
3C
oman
dant
e M
acha
do
(2)
FF
VM
assi
ve c
omb
Fol
iate
d gr
anod
iori
te
(CC
C)
mus
pyN
40E
70S
E a
nd
N50
W6
5SW
Ros
a-C
osta
and
Car
valh
o 1
999
4P
atin
has
Shea
r ve
inM
assi
ve s
hear
edG
rano
dior
ite
(CC
C)
eppy
cpy
N20
E6
8SE
Ros
a-C
osta
and
Car
valh
o 1
999
Kle
in e
t al
200
05
Pau
drsquoA
rco
(3)
FF
VV
einl
ets
sa
ccha
roid
alQ
uart
z-di
orit
ic g
neis
s (C
CC
) m
us k
f c
hl
epcp
y p
yN
30E
65S
EK
lein
et a
l i
n pr
ess
6C
oman
dant
e R
enan
(2)
Shea
r ve
inM
assi
veTo
nali
tic
gnei
ss (
CC
C)
chl
ep
pyN
0-30
E6
088S
EK
lein
et a
l i
n pr
ess
7Ta
uari
FF
VM
assi
veG
rani
toid
(C
IS)
chl
ep
N30
E8
5NW
Kle
in e
t al
in
pres
s8
Our
o M
ilB
recc
ia +
m
afic
dik
eN
etw
orks
Gra
nito
id (
CIS
) +
m
afic
dik
eN
70E
70N
WSa
ntos
199
7
9C
eacuteu A
zul
Bre
ccia
Com
b fi
ber
Gra
nodi
orit
e (C
IS)
qz k
f se
r ep
hem
N70
E8
8SE
Kle
in e
t al
in
pres
s10
Aacutegu
a L
impa
Bre
ccia
Gra
nodi
orit
e (C
IS)
N60
W7
0NE
Kle
in e
t al
in
pres
s11
Roq
ue S
ante
iro
(2)
FF
VM
assi
veTo
nali
tic
gnei
ss (
CC
C)
chl
pyN
45E
75N
WN
40W
88N
EK
lein
et a
l i
n pr
ess
12Ta
boca
lF
FV
Mas
sive
Mon
zogr
anit
e (C
IS)
N70
E8
0NW
Kle
in e
t al
in
pres
s13
Vie
tnam
Shea
r ve
inL
amin
ated
Mon
zogr
anit
e (C
IS)
ser
pyN
70E
75N
WK
lein
et a
l i
n pr
ess
14N
ovo
Vie
tnam
Shea
r ve
inM
assi
ve l
amin
ated
Mon
zogr
anit
e (C
IS)
ser
pyN
55E
80S
EK
lein
et a
l i
n pr
ess
15In
depe
ndecircn
cia
Stoc
kwor
kM
assi
ve v
uggy
Apl
itic
mon
zogr
anit
e (P
IS
CIS
) m
uspy
N45
-80E
10-
60SE
Kle
in e
t al
in
pres
s
16Satilde
o R
aim
undo
LA
RF
Mon
zogr
anit
e (C
IS)
epN
45-6
0E2
5-40
SER
osa-
Cos
ta a
nd C
arva
lho
199
917
Bom
Jes
usF
FV
Lam
inat
edG
rani
toid
(C
IS)
ser
kf
py c
py g
alN
90E
88S
Sant
os 1
997
18B
oa V
ista
Zeacute
Ped
roF
FV
Mon
zogr
anit
e (C
IS)
pyN
70E
80S
ER
osa-
Cos
ta a
nd C
arva
lho
199
918
Boa
Vis
taM
inei
ro-1
Shea
r ve
in +
br
ecci
aM
assi
ve l
amin
ated
Mon
zogr
anit
e (C
IS)
qz s
er c
arb
chl
py c
pyN
30E
88S
EV
asqu
ez a
nd K
lein
200
0
18B
oa V
ista
Min
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Satildeo
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zogr
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rizatilde
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trus
ive
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eric
ite
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pido
te k
f = K
-fel
d-sp
ar c
hl =
chl
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e c
arb
= c
arbo
nate
qz
= q
uart
z p
y =
pyr
ite
cpy
= c
halc
opyr
ite
asp
y =
ars
enop
yrit
e g
al =
gal
ena
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 551
the intrusive character of the granitoids Whole-rockgeochemistry (Lamaratildeo et al 2001 Vasquez et al2001) has shown that the Creporizatildeo Suite repre-sents calc-alkaline metaluminous to peraluminousmedium- to high-K arc-related granitoids The REEpatterns show that they are more evolved than theCuiuacute-Cuiuacute granitoids and gneisses U-Pb and Pb-evaporation dating of zircon (Ricci et al 1999Vasquez et al 2000 Santos et al 2000 2001Lamaratildeo et al 2001) indicate crystallization agesbetween 1997 Ma and 1957 Ma This late timingwith respect to the Cuiuacute-Cuiuacute Complex along withthe geochemical characteristics the structural andmetamorphic differences the lack of volcano-sedi-mentary basins associated with the Creporizatildeo gran-itoids and their common association with regionalstrike-slip shear zones led Vasquez et al (2001) toconsider the Creporizatildeo Suite as representing apost-collisional magmatism still related to thedevelopment of the Cuiuacute-Cuiuacute magmatic arc andnot an individual arc (Creporizatildeo arc) as proposedby Santos et al (2001)
Ore mineralogy and wall-rock alteration
Many prospects are still undeveloped and work-ings are restricted to the oxidized (saprolite) zonewhere veins and structures are well preserved buthydrothermal alteration in the immediate host rockis overprinted by secondary processes Henceinformation in these cases is restricted to the veinassemblage and in a few cases to distal alterationwhich can be seen tens or a few hundreds of metersoff of the mineralized zone
Pyrite is the dominant sulfide mineral (Table 1)occurring in most of the deposits in general as dis-seminations filling fractures and cavities in thequartz veins in the contact between vein and hostrock or less commonly forming decimeter-wideaggregates (Fig 6) Chalcopyrite follows pyrite inimportance always occurring in association withpyrite whereas galena and arsenopyrite occur onlylocally
The gangue mineralogy shows little variationwith white mica being the main mineral (followingquartz) present in the quartz veins occurring how-ever in small amounts White mica is also wide-spread in the hydrothermally altered wall rocksoccurring in association with quartz minor amountsof chlorite and scarce carbonate K-feldspar andepidote
Structural controlInvestigation of mesoscopic and macroscopic
features of deposits of the STP showed that they arestrictly structurally controlled in all scalesRegional structures may have played importantroles acting as conduits for mineralizing fluids andcontrolling the distribution of the deposits The goldcamps are located close to or bounded by majorfirst-order faults and shear zones located in low-strain domains between them and rarely withinthese deformation zones (Figs 2 and 3) At campand deposit scales the orientation of the mineral-ized veins is controlled by the orientation andorgeometry of the hosting lower-order structures(Klein et al 1999 Santos 1999 2000)
Structural styles and internal structure
Fault-fill veins This type is by far the most com-mon structural style in STP and in the province as awhole (Klein et al 1999) The deposits consist of asingle quartz vein emplaced in subvertical struc-tures (Fig 4) These are mostly faults with subordi-
FIG 4 Photograph of the surface exposure of a fault-fillvein (outlined by the heavy lines) at Mineiro-2 The hydro-thermal envelope is outlined by the dashed line
552 KLEIN ET AL
nate narrow brittle-ductile shear zones Theirorientations are variable with concentrations ofveins along the N20degndash70degE and N40ndash50W direc-tions The veins are centimeter- to decimeter-thickand consist of milky quartz with minor (lt5) K-feldspar white mica chlorite and sulfide mineralsOccasionally thin extensionalndashoblique quartz toquartzo-feldspathic veinlets occur attached to themain quartz vein (Fig 5) The internal structure ofthe veins is dominantly formed by massive quartz(Fig 6) Laminated saccharoidal and open-spacefilling (comb) textures and hydrothermal brecciasare subordinate A few veins are positioned at thecontact between mafic dikes and the altered countryrock or even cut across the dikes suggesting inthese cases their late timing with respect to thedikes In one situation (Pau DrsquoArco) mineralizationlacks a major quartz vein (only a few discontinuousveinlets are present) and occurs as disseminationsin the hydrothermal zone that surrounds a subverti-cal strike-slip fault
Shear veins In greenstone-hosted deposits shearveins are usually described as fault-fill veinsbecause they occupy faults and the central parts ofshear zones (Hodgson 1989) and because it is con-sidered difficult to define if the veins formed as aresult of displacements along a shear fracture or asthe result of dilation of preexisting shear fractures orductile fabric (eg Robert and Poulsen 2001 and
references therein) In STP shear and fault-fill veinsshare a series of characteristics However in thispaper we prefer to classify them separately at leastfor descriptive purposes because shear veins differfrom fault-fill veins by the fact that they have beenemplaced in ductile-brittle structures (ComandanteRenan Novo Vietnam Fig 5) andor show effects ofductile deformation such as quartz grains withundulose extinction and deformation bands sur-rounded by small recrystallized subgrains (Patin-has) microscopic shear zones (Mineiro-1) andductile fabric either in the vein or in the immediatehost rock (Novo Vietnam) (Fig 5) The internalstructure is chiefly massive to laminated andsheared (Figs 6 and 7) Extensional features suchas breccias and en echelon sulfides (Fig 7) also arepresent
Low- (to moderate-) angle reverse-oblique faultsTwo examples have been observed At the Boa Vistagold field along with fault-fill and breccia veinspresent in several occurrences the main mineraliza-tion consists of a series of subparallel verticallystacked sigmoidal quartz veins (Fig 8A) separatedby hydrothermally altered and strongly foliated hostrock (schist) The veins show variable thicknessfrom a few centimeters up to one meter and strike toN45ordmndash80ordmW dipping 30ordm to 45ordm to the southwestInternally the milky veins show massive to saccha-roidal textures Small amounts of pyrite and minor
FIG 5 Sketch map (plan view) of the shear vein at Novo Vietnam The vein is surrounded by mylonitized wall rockand shows extensional veinlets attached on both sides The vein is massive to laminated and continuous but is formedby discontinuous veinlets (inset) between the two bends
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 553
arsenopyrite are disseminated throughout the veinsand altered wall rock Pyrite occurs filling smallfractures in quartz as well and sericite is presentboth in the vein and in the immediate wall rock
Given the weathered character of the terrainfresh rocks could not be observed in the mineralizedzone and the nature of the host rock could not beconfidently determined A few tens of meters off themineralized zone an undeformed porphyritic maficvolcanic rock crops out The region in turn is dom-inated by granitoids of the Creporizatildeo Suite that isthe host for all other occurrences in the same goldfield The hosting schist may derive from one ofthese two rock types by a combination of intense
deformation and high fluidrock ratios Alterna-tively it may represent a fragment of the metavol-cano-sedimentary sequence of the JacareacangaGroup which has not as yet been recognized in thisportion of the Tapajoacutes Province occurring as mega-xenoliths or roof pendants within the granitoids ofthe Creporizatildeo Suite
In the Satildeo Raimundo deposit mineralizationoccurs in narrow hydrothermal halos envelopinganastomosed shearfault planes in brittle-ductileshear zones (Fig 8B) The hosting shear zones strikeN45ordmndash60ordmE and dip 25ordmndash40ordm SE and the mineralizedzones are up to 2 meters thick (Rosa-Costa and Car-valho 1999) Quartz is generally absent and occurs
FIG 6 A Milky massive quartz with high pyrite contents at Patinhas B Sheared sulfide-poor quartz vein (Patinhas)C Quartz vein with sulfide minerals filling cavities (Novo Vietnam)
FIG 7 Vein structures at Mineiro-1 A Laminated quartz-pyrite veinlet (V) crosscutting the hydrothermally alteredhost rock Alteration is zoned and symmetric (arrows) B Milky massive quartz with extensional fracture filled by sulfideminerals with an en echelon distribution C Hydrothermal breccia formed by quartz (white) and hydrothermally alteredhost rock (grey)
554 KLEIN ET AL
only as small isolated and discontinuous veinletspositioned in the fault planes The host rock is amonzogranite of the Creporizatildeo Suite
Breccia veins Four main occurrences have beenrecorded forming tabular structures of less than 1 min thickness The breccia veins at Ceacuteu Azul andAacutegua Limpa consist of fragments of milky quartzwith angular to rounded shape ranging in size frommm to a few cm (Fig 9) set in a fine-grained red-dish to greenish hydrothermal matrix composed ofquartz feldspar and hematite along with fine-grained sericite and epidote Microscopically dif-ferent quartz fragments show textures such as comband rosettes indicating the shallow emplacement ofthese veins (Dowling and Morrison 1989 Vearn-combe 1993) At Goiano and Ouro Mil the brecciashave less matrix and the quartz fragments are moreangular than in the two other examples
Brecciation occurs also as a minor portion of ashear vein at the Mineiro-1 prospect in the BoaVista gold camp These breccias also differ from theformer by the fact that the angular quartz fragmentsare set in a matrix composed of altered wall rock(Fig 7C)
Stockworks This style has been identified at theIndependecircncia deposit It consists of multidirec-tional quartz veins a few centimeters thick envel-
oped by narrow halos of hydrothermal alterationThe veins are generally widely spaced occurring inan area of ~100 m times tens of meters Locally how-ever they are closely spaced with several individ-ual hydrothermal halos overlapping each otherforming larger areas of hydrothermally altered hostrock The quartz has a milky to smoky characterand shows cavities usually filled by sulfide miner-als Epidote and white mica are common gangueminerals In places large pockets of hydrothermalalteration lacking quartz veins are observed aswell Minor stockworks and networks (the veins as awhole show the same orientation of the veinbrec-cia) occur at Ouro Mil in both margins of the mainbreccia vein (Santos 1997)
Discussion and Concluding Remarks
Gold deposits in the Tapajoacutes Province are hostedin a variety of metamorphic and magmatic rocks InSouthern Tapajoacutes Province (STP) with one excep-tion only orthogneisses of the Cuiuacute-Cuiuacute Complexand orogenic granitoids of the Creporizatildeo Suite areknown hosts for gold Hosting granitoids are domi-nantly monzogranitic in composition whereas theorthogneisses show tonalitic and granodioritic com-positions
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 555
The deposits have been classified in a few struc-tural styles according to the hosting structurestructural regime in which they have been formedand internal structures and textures of the veinsAccordingly fault-fill and shear veins are the domi-nant style followed by subordinate occurrences ofveins hosted in low-angle reverse-oblique faultsbreccia veins and stockworks More than one stylemay occur in the same gold camp and even in a sin-gle deposit
Fault-fill and shear veins as well as brecciaveins form moderately to steeply dipping tabularbodies that seldom exceed one meter in thicknessand are hosted by strike-slip faults and shear zonesto which they are parallel The vein quartz is domi-nantly massive with laminated saccharoidal andcomb textures occurring subordinately Shearingand cataclasis of the veins is widespread suggest-ing along with other textural and structural evi-dence their positioning in active faults and shearzones or deformation after formation In most casesquartz white mica and pyrite compose the veinmineralogy and along with minor chlorite carbon-ate epidote and K-feldspar they overprint the pri-mary mineralogy of the hosting granitoids and theamphibolite-facies paragenesis of the hostinggneisses
The breccias have likely been produced duringfracture propagation by physical brecciation whichoccurs when the amount of stress exceeds the brittleresistance of the rock by mechanisms such as tec-tonic comminution andor fluid-assisted brecciation(Jeacutebrak 1997) Furthermore they indicate activeseismic slip during mineralization (Robert andPoulsen 2001)
The origin of the large stockwork at Independecircn-cia may be ascribed to hydraulic fracturing occur-ring over a cupola of a small aplitic granitoidrelated to or intruding the regional coarse-grainedmonzogranite of the Creporizatildeo Suite In the latterhypothesis it could be related either to a late-stagepluton of the Creporizatildeo Suite or to a younger grani-toid suite (Parauari) This definition requires geo-chronological support
Deposits and gold camps show strong structuralcontrol at all scales The hosting structures havebeen formed under a dominantly brittle-ductile tobrittle regime and consist of strike slip faults shearfractures intersection and bending of faults andlithological andor lithostratigraphic contactsExtensional fractures have not been characterizedas hosting structures because evidence of displace-
ment andor shearing is virtually always present inthe veins Extensional features are present howeveras en echelon arrays of sulfide minerals and as vein-lets attached to the main longitudinal fault veinsDeposits hosted in granitoids show a more brittlebehavior whereas those hosted in gneisses tend todisplay more ductile features This can result eitherfrom the depth of vein formation or from high fluidrock ratios even in shallow levels of the crust
Formation of deposits occurred in a range ofcrustal depth from mesozonal to epizonal condi-tions as indicated by the internal structure of thequartz veins and by the nature of the hosting struc-tures This is also supported by fluid inclusion stud-ies in a few deposits such as Guarim (Klein et al2001) and Patinhas (Klein et al 2000) both depos-its hosted in gneisses of the Cuiuacute-Cuiuacute ComplexFluid composition is nearly identical but P-T dataalong with textural and structural evidence suggestthat Guarim (outside STP) formed between 4 and 7km whereas Patinhas (within STP) formed at deeperlevels
Hence shear veins and fault-fill veins may beconsidered at least in part and from a structuralview as a single class of structural style with theirdifferences being ascribed to different depths ofemplacement and structural overprint It is not ourintention however to state that all of these veinsformed in a single gold-forming event The issue ofhow many mineralizing events have occurred in theTapajoacutes Province is still unresolved
Santos (1999 2000) studying 23 depositsthroughout the province (including three deposits inSTP) reported a set of characteristics similar tothose we have found in STP He concluded that alldeposits are related to a regional NW-SEndashtrendingstrike-slip fault system and that the orientation of
FIG 9 Breccia vein at Ceacuteu Azul
556 KLEIN ET AL
the lower-order hosting structures is compatiblewith Riedelrsquos system with the direction of the mainstress vector around the E-W direction Orientationsthat do not fit the model may be related to heteroge-neities in the local stress field However nothinghas been said about the timing of this strike-slipsystem in relation to the magmatic metamorphicand tectonic evolution of the province
Coutinho et al (2000) reported model ages thatcluster around 196 Ga and 188 Ga and main-tained that these two ages reflect two mineralizingepochs Santos et al (2001) invoked a single eventat 186 Ga However as stated by Santos et al(2001) the tectonic regime at 186 Ga is brittle Thismodel does not explain the ductile emplacementandor deformed mineralization hosted especially bythe Cuiuacute-Cuiuacute gneisses and by the metavolcano-sedimentary sequences Another (older) mineraliz-ing phase is thus required
We proposed early in this paper that the majorstrike-slip regime that affected the Creporizatildeo Suiteand older units likely occurred between 197 and195 Ga Mineralization hosted in the Cuiuacute-Cuiuacutegneisses (at least in STP) is post-tectonic and post-metamorphic with respect to the host rocks sincehosting structures clearly crosscut the metamorphicbanding and the hydrothermal mineralogy is retro-gressive in relation to the metamorphic paragenesisDeformation affecting the Creporizatildeo granitoids isbrittle-ductile to brittle whereas deformation affect-ing younger granitoids is brittle Thus it is valid toinfer as a working hypothesis that at least in partgold mineralization in STP formed during regionalstrike-slip deformation and emplacement of late-stage plutons of the Creporizatildeo Suite at ~197ndash195Ga a time interval that is in agreement with thatobtained by Coutinho et al (2000) The structuresmay have been reactivated during younger deforma-tional episode(s) and gold deposits may haveformed at this stage as well
The challenge is to decipher which depositsformed at each metallogenic epoch From a struc-tural point of view it is likely that the deposits inSouthern Tapajoacutes Province that have been emplacedat deeper levels of the crust and that show evidenceof plastic deformation (ie the shear veins and thedeposits hosted in low-angle reverse-oblique faultssee Table 1) formed in the older phase Fault-fillveins that occur in association with these deposits inthe same gold camp (eg Boa Vista) probablyformed in the same event The rest of the fault-fillveins (with textures and structures indicating
emplacement in shallow brittle structures associ-ated or not with mafic dikes and showing no associ-ation with shear veins in the same gold camp) aswell as the breccia veins and stockworks may haveformed either in the older or in the younger phaseWe do not have elements to define this Thisrequires much more isotopic data along with addi-tional fluid-inclusion and stable-isotope informationto constrain physico-chemical conditions of golddeposition as well as knowledge of the sources andnature of the mineralizing fluids and the absolutetiming of gold deposition
The attributes shown by the gold deposits in STP(namely the regional structural setting depositstyle vein textures and hydrothermal mineralogy)along with scarce fluid-inclusion data fit with boththe orogenic (magmatic arc-hosted) and intrusion-related models as proposed by Santos et al (2001)the latter sharing characteristics with Korean-typedeposits (Robert et al 1997) as well
Acknowledgments
Alfreu dos Santos (formerly of CPRM) partici-pated in the field work and supervised the TapajoacutesProject His help is acknowledged This is a contri-bution to the project PRONEX-CNPq-FADESP6621031998-0ndashprocess no 4200000
REFERENCES
Almeida M E Brito M F L Ferreira A L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaVila Mamatildee Anatilde (SB21-V-D) Estados do Paraacute e Ama-zonas escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Almeida M E Brito M F L and Macambira M J B1999 Caroccedilal Granite 207Pb206Pb evaporation age inpost-collisional granitoids of Tapajoacutes Gold ProvinceAmazonian region Brazil [abs] in II South AmericanSymposium on Isotope Geology Coacuterdoba ArgentinaActas p 3ndash6
Almeida M E Ferreira A L Brito M F L and Mon-teiro M A S 2001 Evoluccedilatildeo tectono-estrutural daProviacutencia Tapajoacutes com base na geologia das folhas VilaMamatildee Anatilde e Jacareacanga (1250000) regiatildeo limitedos estados do Amazonas e Paraacute in Reis N J andMonteiro M A S orgs Contribuiccedilotildees agrave Geologia daAmazocircnia v 2 Manaus Brazil SBG-NO p 57ndash112
Bahia R B C and Quadros M L E S 2000 Geologiae recursos minerais da Folha Caracol (SB21-X-C)
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 557
Estado do Paraacute Escala 1250000 Brasiacutelia BrazilCPRMGeological Survey of Brazil (CD-ROM)
Cassidy K F Groves D I and McNaughton N J 1998Late-Archean granitoid-hosted lode-gold depositsYilgarn Craton Western Australia Deposit character-istics crustal architecture and implications for oregenesis Ore Geology Reviews v 13 p 65ndash102
Correcirca-Silva R H Juliani C Bettencourt J S NunesC M D and Almeida T I R 2001 Caracterizaccedilatildeode um sistema epitermal low-sulfidation (ou adulaacuteria-sericita) hospedado em vulcacircnicas e vulcanoclaacutesticasdo Grupo Iriri na Proviacutencia auriacutefera do Tapajoacutes (PA)[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Coutinho M G N Santos J O S Fallick A E andLafon J M 2000 Orogenic gold deposits in TapajoacutesMineral Province Amazon Brazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Dowling K and Morrison G 1989 Application ofquartz textures to the classification of gold depositsusing North Queensland examples Economic GeologyMonograph v 6 p 342ndash355
Dreher A M Vlach S and Martini S L 1998 Adu-laria associated with epithermal gold veins in theTapajoacutes Mineral Province Paraacute State Northern BrazilRevista Brasileira de Geociecircncias v 28 p 397ndash404
Faraco M T L Carvalho J M A and Klein E L1997 Carta metalogeneacutetica da Proviacutencia Auriacutefera doTapajoacutes in Costa M L and Angeacutelica R S orgsContribuiccedilotildees agrave Geologia da Amazocircnia Beleacutem BrazilFINEPSBG-NO p 423ndash437
Ferreira A L Almeida M E Brito M F L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaJacareacanga (SB21-Y-B) Estados do Paraacute e Amazo-nas escala 1250000 Brasiacutelia Brazil CPRMGeolog-ical Survey of Brazil (CD-ROM)
Goldfarb R J Groves D I and Gardoll S 2001 Oro-genic gold and geologic time A global synthesis OreGeology Reviews v 18 p 1ndash75
Groves D I Goldfarb R J Gebre-Mariam M Hage-mann S and Robert F 1998 Orogenic gold depos-its A proposed classification in the context of theircrustal distribution and relationship to other golddeposit types Ore Geology Reviews v 13 p 7ndash27
Hodgson C J 1989 The structure of shear-related vein-type gold deposits A review Ore Geology Reviews v4 p 231ndash273
Jacobi P 1999 The discovery of epithermal Au-Cu-MoProterozoic deposits in the Tapajoacutes Province BrazilRevista Brasileira de Geociecircncias v 29 p 277ndash279
Jeacutebrak M 1997 Hydrothermal breccias in vein-type oredeposits A review of mechanisms morphology andsize distribution Ore Geology Reviews v 12 p 111ndash134
Juliani C 2001 Metalogecircnese do ouro e metais de baseassociadas com o vulcanismo-plutonismo da porccedilatildeo Wda Proviacutencia Auriacutefera do Tapajoacutes [ext abs] in VIISimpoacutesio de Geologia da Amazocircnia Beleacutem Brazil(CD-ROM)
Kerrich R and Cassidy K F 1994 Temporal relation-ships of lode gold mineralization to accretion magma-tism metamorphism and deformationmdashArchean topresent A review Ore Geology Reviews v 9 p 263ndash310
Klein E L Almeida M E Vasquez M L BahiaR B C Quadros M L E S and Ferreira A L inpress Geologia e recursos minerais da Proviacutencia Min-eral do Tapajoacutes Estados do Paraacute e Amazonas Escala1 500000 Brasiacutelia Brazil CPRMGeological Surveyof Brazil
Klein E L Rosa-Costa L T and Carvalho J M A2000 Fluid inclusion studies at the Patinhas gold-quartz mineralisation Tapajoacutes Gold Province Brazil[abs] in XXXI International Geological Congress Riode Janeiro Brazil (CD-ROM)
Klein E L Santos R A Fuzikawa K and AngeacutelicaR S 2001 Hydrothermal fluid evolution and struc-tural control of the brittle-style Guarim lode-gold min-eralisation Tapajoacutes Province Amazonian CratonBrazil Mineralium Deposita v 36 p 149ndash164
Klein E L and Vasquez M L 2000 Projeto EspecialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Vila Riozinho (SB21-Z-A) Estadodo Paraacute escala 1250000 Brasiacutelia Brazil CPRMGeological Survey of Brazil (CD-ROM)
Klein E L Vasquez M L Santos A and Martins RC 1997 Structural elements of the Maloquinha Intru-sive Suite in Tapajoacutes Mineral Province northern Bra-zil and the emplacement of the plutons [ext abs] inII International Symposium on Granites and Associ-ated Mineralizations ISGAM II Salvador Brazil p313ndash314
Klein E L Vasquez M L Santos A and Rosa-CostaL T 1999 Geologia e controle estrutural das mineral-izaccedilotildees auriacuteferas na Folha Vila Riozinho e NW daFolha Rio Novo Proviacutencia Tapajoacutes [ext abs] in VISimpoacutesio de Geologia da Amazocircnia Manaus Brazil p128ndash131
Lamaratildeo C N DallrsquoAgnol R and Lafon J M 2001Geocronologia e geoquiacutemica das associaccedilotildees vulcacircni-cas e plutocircnicas da regiatildeo de Vila Riozinho ProviacutenciaAuriacutefera do Tapajoacutes [ext abs] in VII Simpoacutesio deGeologia da Amazocircnia Beleacutem Brazil (CD-ROM)
Nunes C M D Juliani C Correcirca-Silva R H Mon-teiro L V S Bettencourt J S Neumann R AlcoverNeto A and Rye R O 2001 Caracterizaccedilatildeo de umsistema epitermal high-sulfidation vulcacircnico pale-oproterozoacuteico da Proviacutencia Auriacutefera do Tapajoacutes Paraacute[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
558 KLEIN ET AL
Ricci P S F Vasquez M L Santos A Klein E LJorge Joatildeo X S and Martins R C 1999 SuiacuteteIntrusiva Creporizatildeo ndash Proviacutencia Tapajoacutes Proposta ecriteacuterios de definiccedilatildeo [ext abs] in VI Simpoacutesio deGeologia da Amazocircnia Manaus Brazil p 519ndash522
Robert F and Poulsen K H 2001 Vein formation anddeformation in greenstone gold deposits in RichardsJ P and Tosdal R M eds Structural controls on oregenesis Reviews in Economic Geology v 14 p 111ndash155
Robert F Poulsen K H and Dubeacute B 1997 Golddeposits and their geological classification in GubinsA G ed Proceedings of Exploration 97 TorontoCanada p 209ndash220
Ronchi L H DallrsquoAgnol R Araujo J C Ribeiro VLamaratildeo C N Borges R M K and Fuzikawa K2001 Fluidos relacionados agraves alteraccedilotildees hidrotermaisno depoacutesito de ouro do Granito Satildeo JorgendashPA [extabs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Rosa-Costa L T and Carvalho J M A 1999 Tipologiade mineralizaccedilotildees auriacuteferas da regiatildeo sul da ProviacutenciaTapajoacutesndashParaacute [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 176ndash179
Santos J O S Groves D I Hartmann L A MouraM A and McNaughton N J 2001 Gold deposits ofthe Tapajoacutes and Alta Floresta Domains Tapajoacutes-Parima orogenic belt Amazon Craton Brazil Minera-lium Deposita v 36 p 279ndash299
Santos J O S Hartmann L A Gaudette H E GrovesD I McNaughton N J and Fletcher I R 2000 Anew understanding of the provinces of the AmazonCraton based on integration of field mapping and U-Pband Sm-Nd geochronology Gondwana Research v 3p 453ndash488
Santos R A 1997 Contribuiccedilatildeo agrave anaacutelise estrutural dejazimentos auriacuteferos do rio Tapajoacutes SW do Paraacute e SEdo Amazonas Garimpos Abacaxis Espiacuterito SantoBom Jesus Goiano Fazenda Pison Ouro Mil SantaIsabel Majestade e Carneirinho Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 1999 Controle estrutural das mineralizaccedilotildees deouro da Proviacutencia Mineral do Tapajoacutes Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 2000 Formation of gold-quartz veins controlledby the strike-slip fault mega-system in Tapajoacutes Min-eral Province Amazon Brazil [abs] in XXXI Interna-tional Geological Congress Rio de Janeiro Brazil(CD-ROM)
Tassinari C C G 1996 O mapa geocronoloacutegico do Craacute-ton Amazocircnico no Brasil Revisatildeo dos dados isotoacutepi-cos Unpubl Tese de Livre Docecircncia Universidade deSatildeo Paulo 139 p
Tassinari C C G and Macambira M J B 1999 Geo-chronological provinces of the Amazonian Craton Epi-sodes v 22 p 174ndash182
Vasquez M L and Klein E L 2000 Projeto especialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Rio Novo (SB21-Z-C) Estado doParaacute escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Vasquez M L Klein E L Macambira M J B SantosA Bahia R B C Ricci P S F and QuadrosM L E S 2000 Geochronology of granitoids maficintrusions and mineralizations of the Tapajoacutes GoldProvincendashAmazonian CratonndashBrazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Vasquez M L Klein E L Quadros M L E S BahiaR B C Santos A Ricci P S F Sachett C RSilva C M G and Macambira M J B 1999 Mag-matismo Uatumatilde na Proviacutencia Tapajoacutesmdashnovos dadosgeocronoloacutegicos [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 471ndash474
Vasquez M L Klein E L and Ricci P S F 2001Granitoacuteides poacutes-colisionais da porccedilatildeo leste da Proviacuten-cia Tapajoacutes [ext abs] in VII Simpoacutesio de Geologia daAmazocircnia Beleacutem Brazil (CD-ROM)
Vearncombe J R 1993 Quartz vein morphology andimplications for formation depth and classification ofArchaean gold-vein deposits Ore Geology Reviews v8 p 407ndash424
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 545
with stockworks and dissemination occurring subor-dinately (Klein et al 1999 Rosa-Costa and Car-valho 1999 Coutinho et al 2000) and distinctclassifications (such as mesothermal epithermalintrusion-related and orogenic) have been proposedfor individual deposits or to the province as a whole(Dreher et al 1998 Juliani 2001 Klein et al2001 Santos et al 2001)
In the southern portion of the Tapajoacutes Province aseries of gold camps contain deposits and prospectstypically hosted in orogenic gneisses (Cuiuacute-CuiuacuteComplex) and granitoids (Creporizatildeo IntrusiveSuite) The purpose of this paper is to summarize thegeological attributes of these deposits which areobservable at regional outcrop and hand-specimenscales with emphasis on their relationship withregional structures structural styles vein geometryand internal structures and textures Microscopicinformation is used when available A revaluation ofcurrent structural models and a tentative classifica-tion of the deposits are made as well
Geological Setting
The Tapajoacutes Gold Province (TGP) is located inthe central portion of the Amazonian Craton and ispart of the Ventuari-Tapajoacutes (according to Tassinariand Macambira 1999) or Tapajoacutes-Parima (in thesense of Santos et al 2000) geochronological prov-inces (Fig 1) The regional lithostratigraphy wasdefined by the mapping program performed byCPRMGeological Survey of Brazil (Almeida et al2000 Bahia and Quadros 2000 Ferreira et al2000 Klein and Vasquez 2000 Vasquez and Klein2000) The results of this program (Fig 2) alongwith the work of Santos et al (2000 2001) showeda protracted Paleoproterozoic magmatic metamor-phic and tectonic evolution spanning the periodfrom 2033 Ma to 1870 Ma
The oldest rocks found in the TGP are the green-schist-facies metavolcano-sedimentary sequence ofthe Jacareacanga Group and the amphibolite-faciesgneisses (plusmn granitoids migmatites amphibolites) ofthe Cuiuacute-Cuiuacute Complex both formed between 2033
FIG 1 Geochronological provinces of the Amazonian Craton according to (A) Tassinari and Macambira (1999) and(B) Santos et al (2000)
546 KLEIN ET AL
FIG 2 Geological map of the Tapajoacutes gold province (compiled and modified from Almeida et al 2000 Bahia andQuadros 2000 Ferreira et al 2000 Klein and Vasquez 2000 Vasquez and Klein 2000) showing the distribution of thegold depositscamps in the province
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 547
and 2005 Ma (Santos et al 2000 2001) Thesemetamorphic sequences have been intruded bycalc-alkaline granitoids of the Creporizatildeo (199ndash196 Ga) (Ricci et al 1999 Vasquez et al 2000)Tropas (190 Ga) (Santos et al 2001) and Parauari(189ndash188 Ga) (Vasquez et al 1999 Santos et al2000) intrusive suites as well as by a series of gab-broic rocks at 187 Ga (Santos et al 2001) Sedi-mentary deposits showing intra-arc characteristicsformed at ~190ndash189 Ga (Santos et al 2001) Thisorogenic period was followed by widespread felsicplutonic and volcanic activity at 187 Ga (Almeidaet al 1999 Vasquez et al 1999 Santos et al2000 Lamaratildeo et al 2001 Klein et al in press)related to extensional tectonics
It is the consensus that the orogenic evolution ofthe province comprises the accretion of magmaticarcs and related sedimentary basins However thenumber of arcs that have accreted is still debatableSantos et al (2000 2001) envisioned the evolutionof the orogenic domain through the sequentialaccretion of four magmatic arcs dated at 202 Ga(Cuiuacute-Cuiuacute Complex plus Jacareacanga Group)196 Ga (Creporizatildeo Suite) 190 Ga (Tropas Suite)and 188 Ga (Parauari Suite) These accretionaryevents have been followed by post-collisional intra-cratonic (granitoid and mafic) magmatism and sedi-ment deposition between 1870 Ma and 1780 MaConversely Vasquez et al (2001) considered theCreporizatildeo granitoids as post-collisional granitoidsstill related to the development of the Cuiuacute-Cuiuacutearc instead of considering it to be a different arc(see discussion below)
Structural framework
Remote sensing imagery and geophysical evi-dence show that the main structural features of theTapajoacutes Province are major NNW-SSEndash to NW-SEndashstriking linear or sinuous continuous to discontin-uous lineaments extending for tens to a few hun-dreds of kilometers (Fig 2) Field evidenceindicates that they represent mainly subverticalsinistral strike-slip faults and brittle-ductile shearzones This strike-slip system has been interpretedas a progressive and episodic compressive eventwith the maximum compressive stress vector (s1)around the east-west direction as shown by geomet-ric relationships of major and minor subsidiarystructures (Santos 1999 2000 Klein andVasquez 2000) On a regional scale these struc-tures have controlled the ascent and emplace-ment of several generations of granitoids and
volcanic and mafic rocks as well as the establish-ment of sedimentary basins and have outlinedtheir present shape and geometry (Klein et al1997 Santos 1999 Almeida et al 2000 Kleinand Vasquez 2000) It is likely that at least someof these structures may have been reactivatedduring the tectonic evolution of the Tapajoacutes Prov-ince However the timing of these events is notwell constrained yet
The oldest (D1) structural record is found in thewest-central portion of Tapajoacutes Province It isdefined by the NE-SWndashtrending gneissic banding ofthe Cuiuacute-Cuiuacute Complex and the schistosity of thevolcano-sedimentary Jacareacanga Group (Almeidaet al 2001) produced by a compressive event andis well preserved in the gneisses of the study areaThis deformation is not seen in younger rocks lead-ing Santos et al (2001) to establish the time intervalof 2005ndash1974 Ma as the timing of D1 which mayhave been synchronous with the metamorphic peakSantos et al (2001) defined a second deformationalevent (D2) represented by a high-angle N10E-strik-ing sinistral strike-slip shear zone of ductile-brittlecharacter affecting especially the Tropas Suite inthe western-central portion of the province and onlylocally affecting the Creporizatildeo and Parauari suitesThey placed the timing of this event to between1894 and 1883 Ma Furthermore they suggestedthat the brittle deformation which is younger than1883 Ma and which affected the Creporizatildeo andParauari granitoids could have been produced dur-ing the shallow emplacement of the Maloquinhagranitoids
However this structural evolution does notexplain satisfactorily the brittle-ductile deformationimprinted on the granitoids of the Creporizatildeo Suite(1997ndash1957 Ma) that are older than the Tropas Suite(190 Ga) The Creporizatildeo granitoids show a mag-matic foliation subparallel to a subvertical tectonicfoliation that strikes NW-SE and is clearly relatedto a brittle-ductile strike-slip regime This event hasnot been detected either in the Tropas Suite asstated by Santos et al (2001) nor in younger rocks(Parauari and Maloquinha suites volcanic rocks)Furthermore Almeida et al (2000 2001) docu-mented the transposition of the gneissic banding ofthe Cuiuacute-Cuiuacute rocks by NW-SE strike-slip shearzones Still a whole-rock Rb-Sr isochron age of1965 plusmn 16 Ma was reported by Tassinari (1996) forgranitoids of the Creporizatildeo Suite This age is closeto the zircon ages (U-Pb Pb-evaporation) for thelate-stage granitoids of the Creporizatildeo Suite and
548 KLEIN ET AL
may indicate that the emplacement of the post-colli-sional plutons was broadly coeval with the regionalNW-SE deformational event (Ricci et al 1999Vasquez et al 2001)
Hence we postulate a reappraisal of the struc-tural evolution of the Tapajoacutes Province as followsAn early deformation stage (D1) is represented bythe compressive event that imparted the gneissicbanding of the Cuiuacute-Cuiuacute Complex and the schis-tosity of the Jacareacanga Group occurring proba-bly between 2005 and 1997 Ma D2 is representedby the NW-SEndashtrending strike-slip event thataffected the granitoids of the Creporizatildeo Suite andoverprinted the gneissic banding of the Cuiuacute-Cuiuacuterocks occurring at ~197ndash195 Ga D3 is related tothe NNE-SSW strike-slip ductile shear zones thataffected the Tropas Suite between 1894 and 1883Ma Younger structures may have been reactivatedandor generated during the emplacement of thewidespread Maloquinha granitoids and are relatedto extensional tectonics
Gold deposit models
Studies of individual deposits in the TapajoacutesGold Province have been focused on fluid-inclusionproperties andor alteration assemblages leading tothe proposition that the deposits fit epithermal tomesothermal models (Dreher et al 1998 Klein etal 2001 Nunes et al 2001 Ronchi et al 2001)Province-scale models have been developed byCoutinho et al (2000) Santos (2000) and Santos etal (2001) Santos (2000) presented a structuralmodel relating the formation of the gold-quartz veinsto the regional-scale strike-slip fault systemCoutinho et al (2000) classified the deposits of theTapajoacutes Province as mesozonalepizonal orogenicdeposits and suggested two phases of mineraliza-tion based on model ages of sulfide minerals at196 Ga and 188 Ga Both phases postdated theregional metamorphic peak and have been associ-ated with compressional to transpressional tectonicsat the convergent plate margin of the accretionaryorogen Lead and stable (O H) isotopes togetherwith fluid-inclusion data suggest deep sources forgold mineralization (magmatic to juvenile) withpossibly meteoric water added in some deposits atshallow crustal levels
Santos et al (2001) proposed two classes of golddepositsmdashorogenic and intrusion related Orogenicdeposits have been subdivided into (1) turbidite-hosted consisting of mesozonal quartz-pyrite vein-lets or disseminations in ductile structures cutting
the supracrustal rocks of the Jacareacanga Group(2) magmatic arc-hosted consisting of mesozonalquartz-pyrite-carbonate veins and disseminationshosted in ductile-brittle structures cutting thegneisses of the Cuiuacute-Cuiuacute Complex and the grani-toids of the Tropas Suite Intrusion-related depositshave been subdivided into (1) epizonal quartz-pyrite veins and pyrite disseminations emplaced inshallow extensional brittle structures (similar toKorean-type deposits) cutting K-rich granitoids ofthe Creporizatildeo Parauari and Maloquinha suitesfrequently associated with mafic dikes (2) epizonaldisseminations and stockworks with hydrothermalmagnetite hosted in mafic and sedimentary rocksand sharing some characteristics with porphyry-typedeposits Using Pb and Ar isotopes Santos et al(2001) determined the timing of the intrusion-related deposits as being around 186 Ga They havenot established the age of the orogenic deposits buthave suggested that it might be similar to the age ofthe intrusion-related deposits with mineralizationdiffering in style host rocks and depth of emplace-ment They argued that the orogenic deposits wouldbe related to the final stages of evolution of theParauari arc whereas the intrusion-related depositswould be related either to the Parauari arc or to post-collisional granitoids (Maloquinha Suite)
Epithermal deposits have been described byJacobi (1999) Correcirca-Silva et al (2001) Juliani(2001) and Nunes et al (2001) for the east-centralportion of the province The deposits are hosted byfelsic to intermediate volcanic rocks and associatedvolcaniclastic rocks and consist of both low-sulfida-tion (adularia-sericite) and high-sulfidation (quartz-alunite) types Indirect dating suggests that mineral-ization formed at ~188 Ga and d34S data indicateda magmatic-hydrothermal source for the mineral-izing fluids and 330ordmC to 140ordmC as the formationtemperatures (Juliani 2001 Nunes et al 2001)Dreher et al (1998) also considered the epither-mal model for the Joel and David deposits How-ever Correcirca-Silva et al (2001) questioned thisclassification and argued that the adulariapresent in the Davi and Joel deposits is hosted inmafic rocks and could be related to this maficmagmatism Also Santos et al (2001) argued thatthese two deposits lack many important featuresof classic epithermal deposits such as the rela-tionship with contemporaneous volcanic rocks(the deposits are hosted by gabbro and granitoidrespectively) the low silver and adularia con-
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 549
tents and the absence of native silver and silversulfosalts in the ore mineralogy
Gold Deposits in the Southern Tapajoacutes Province (STP)
More than 20 deposits and showings are distrib-uted in several gold camps along the STP (Fig 3)These mineralizations are discussed below in termsof host rocks wall rock alteration and structuralcontrol The classification of structural styles of theveins is based mainly on the concepts of Hodgson(1989) and Robert and Poulsen (2001) taking intoaccount the type of host structure and the internalstructure and textures of the veins The mainattributes are summarized in Table 1
Host rocksGneisses and orogenic granitoids are the main
hosts for gold deposits in the Tapajoacutes Gold Provinceand account for virtually all the host rocks in STP(Table 1) The gneisses belong to the Cuiuacute-CuiuacuteComplex They consist of gray orthogneisses oftonalitic and granodioritic composition bearingmicrogranular enclaves of diorites and quartz-dior-ites along with granitoids and rare migmatites andamphibolites Structurally the gneisses show a per-vasive ductile fabric striking NNE-SSW or NW-SE
and migmatitic features are subordinate Thegeochemical characteristics of trace elements(LILE HFSE REE) are compatible with those ofprimitive arc-related calc-alkaline granitoids(Vasquez et al 2001) They are dominantly metalu-minous with lenses of peraluminous to strongly per-aluminous leucogranitoids occurring subordinatelySantos et al (2000 2001) obtained zircon U-PbSHRIMP ages between 2033 Ma and 2005 Ma forthis complex
The hosting granitoids are related to the Crep-orizatildeo Intrusive Suite which holds irregular- to sig-moidal-shaped batholiths and stocks (Fig 2) ofhornblende- andor biotite-bearing granitoids andmetagranitoids of syenogranitic to tonalitic composi-tion The granitoids are either foliated or granoblas-tic and the latter show preserved primary featuressuch as euhedral phenocrysts of K-feldspar unde-formed microgranular enclaves and synplutonicdikes Very often they show an igneous bandingmarked by the orientation of the K-feldspar pheno-crysts that parallels the NW-SEndashtrending tectonicfoliation Field mineralogical and textural evi-dence indicates emplacement of the granitoids in acrustal level compatible with greenschist or up tomiddle-amphibolite metamorphic conditions (Ricciet al 1999) and the presence of enclaves ofgneisses from the Cuiuacute-Cuiuacute Complex is evidence of
FIG 3 Geological map of the Southern Tapajoacutes Province showing the location of the gold deposits addressed in thisstudy
550 KLEIN ET AL
TAB
LE 1
Sum
mar
y of
Attr
ibut
es o
f Gol
d D
epos
its o
f the
Sou
ther
n Ta
pajoacute
s Pr
ovin
ce1
No
Cam
p or
dep
osit
(n
umbe
r of
vei
ns)
Stru
ctur
al s
tyle
Inte
rnal
str
uctu
reH
ost r
ock
(s
trat
igra
phic
uni
t)G
angu
e m
iner
alog
yO
re m
iner
alog
yV
ein
orie
ntat
ion
(str
ike
dip)
Sele
cted
ref
eren
ces
1G
oian
o (2
)B
recc
iaC
atac
last
icF
olia
ted
gran
itoi
d (C
IS)
mus
pyN
50E
88S
E N
20W
88
NE
N0E
80E
Sant
os 1
997
2Su
daacuteri
o (4
)F
FV
(plusmn
maf
ic
dike
)M
assi
ve c
atac
last
icG
rani
toid
s (C
CC
)py
N40
-60E
70-
88SE
-N
WR
osa-
Cos
ta a
nd C
arva
lho
199
9
3C
oman
dant
e M
acha
do
(2)
FF
VM
assi
ve c
omb
Fol
iate
d gr
anod
iori
te
(CC
C)
mus
pyN
40E
70S
E a
nd
N50
W6
5SW
Ros
a-C
osta
and
Car
valh
o 1
999
4P
atin
has
Shea
r ve
inM
assi
ve s
hear
edG
rano
dior
ite
(CC
C)
eppy
cpy
N20
E6
8SE
Ros
a-C
osta
and
Car
valh
o 1
999
Kle
in e
t al
200
05
Pau
drsquoA
rco
(3)
FF
VV
einl
ets
sa
ccha
roid
alQ
uart
z-di
orit
ic g
neis
s (C
CC
) m
us k
f c
hl
epcp
y p
yN
30E
65S
EK
lein
et a
l i
n pr
ess
6C
oman
dant
e R
enan
(2)
Shea
r ve
inM
assi
veTo
nali
tic
gnei
ss (
CC
C)
chl
ep
pyN
0-30
E6
088S
EK
lein
et a
l i
n pr
ess
7Ta
uari
FF
VM
assi
veG
rani
toid
(C
IS)
chl
ep
N30
E8
5NW
Kle
in e
t al
in
pres
s8
Our
o M
ilB
recc
ia +
m
afic
dik
eN
etw
orks
Gra
nito
id (
CIS
) +
m
afic
dik
eN
70E
70N
WSa
ntos
199
7
9C
eacuteu A
zul
Bre
ccia
Com
b fi
ber
Gra
nodi
orit
e (C
IS)
qz k
f se
r ep
hem
N70
E8
8SE
Kle
in e
t al
in
pres
s10
Aacutegu
a L
impa
Bre
ccia
Gra
nodi
orit
e (C
IS)
N60
W7
0NE
Kle
in e
t al
in
pres
s11
Roq
ue S
ante
iro
(2)
FF
VM
assi
veTo
nali
tic
gnei
ss (
CC
C)
chl
pyN
45E
75N
WN
40W
88N
EK
lein
et a
l i
n pr
ess
12Ta
boca
lF
FV
Mas
sive
Mon
zogr
anit
e (C
IS)
N70
E8
0NW
Kle
in e
t al
in
pres
s13
Vie
tnam
Shea
r ve
inL
amin
ated
Mon
zogr
anit
e (C
IS)
ser
pyN
70E
75N
WK
lein
et a
l i
n pr
ess
14N
ovo
Vie
tnam
Shea
r ve
inM
assi
ve l
amin
ated
Mon
zogr
anit
e (C
IS)
ser
pyN
55E
80S
EK
lein
et a
l i
n pr
ess
15In
depe
ndecircn
cia
Stoc
kwor
kM
assi
ve v
uggy
Apl
itic
mon
zogr
anit
e (P
IS
CIS
) m
uspy
N45
-80E
10-
60SE
Kle
in e
t al
in
pres
s
16Satilde
o R
aim
undo
LA
RF
Mon
zogr
anit
e (C
IS)
epN
45-6
0E2
5-40
SER
osa-
Cos
ta a
nd C
arva
lho
199
917
Bom
Jes
usF
FV
Lam
inat
edG
rani
toid
(C
IS)
ser
kf
py c
py g
alN
90E
88S
Sant
os 1
997
18B
oa V
ista
Zeacute
Ped
roF
FV
Mon
zogr
anit
e (C
IS)
pyN
70E
80S
ER
osa-
Cos
ta a
nd C
arva
lho
199
918
Boa
Vis
taM
inei
ro-1
Shea
r ve
in +
br
ecci
aM
assi
ve l
amin
ated
Mon
zogr
anit
e (C
IS)
qz s
er c
arb
chl
py c
pyN
30E
88S
EV
asqu
ez a
nd K
lein
200
0
18B
oa V
ista
Min
eiro
-2F
FV
Mas
sive
Mon
zogr
anit
e (C
IS)
chl
ser
ep
pyN
20E
75S
EV
asqu
ez a
nd K
lein
200
018
Boa
Vis
taL
AR
FM
assi
ve s
acch
aroi
dal
Maf
ic v
olca
nic
and
schi
st (
)se
rpy
asp
yN
45-8
0W3
0-45
SWK
lein
et a
l i
n p
ress
Ros
a-C
osta
and
Car
valh
o 1
999
19P
lana
lto
FF
VM
assi
veG
rani
toid
(C
CC
)N
40E
75S
EK
lein
et a
l i
n pr
ess
20B
abil
ocircnia
FF
VM
assi
veM
onzo
gran
ite
(CIS
)se
rpy
N45
W4
5SW
Kle
in e
t al
in
pres
s21
Satildeo
Joseacute
FF
VM
assi
ve s
acch
aroi
dal
Mon
zogr
anit
e (C
IS)
epN
45W
63N
EK
lein
et a
l i
n pr
ess
1 Leg
end
FF
V =
fau
lt-f
ill
vein
CIS
= C
repo
rizatilde
o In
trus
ive
Suit
e C
CC
= C
uiuacute-
Cui
uacute C
ompl
ex P
IS =
Par
auar
i Int
rusi
ve S
uite
mus
= m
usco
vite
ser
= s
eric
ite
ep
= e
pido
te k
f = K
-fel
d-sp
ar c
hl =
chl
orit
e c
arb
= c
arbo
nate
qz
= q
uart
z p
y =
pyr
ite
cpy
= c
halc
opyr
ite
asp
y =
ars
enop
yrit
e g
al =
gal
ena
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 551
the intrusive character of the granitoids Whole-rockgeochemistry (Lamaratildeo et al 2001 Vasquez et al2001) has shown that the Creporizatildeo Suite repre-sents calc-alkaline metaluminous to peraluminousmedium- to high-K arc-related granitoids The REEpatterns show that they are more evolved than theCuiuacute-Cuiuacute granitoids and gneisses U-Pb and Pb-evaporation dating of zircon (Ricci et al 1999Vasquez et al 2000 Santos et al 2000 2001Lamaratildeo et al 2001) indicate crystallization agesbetween 1997 Ma and 1957 Ma This late timingwith respect to the Cuiuacute-Cuiuacute Complex along withthe geochemical characteristics the structural andmetamorphic differences the lack of volcano-sedi-mentary basins associated with the Creporizatildeo gran-itoids and their common association with regionalstrike-slip shear zones led Vasquez et al (2001) toconsider the Creporizatildeo Suite as representing apost-collisional magmatism still related to thedevelopment of the Cuiuacute-Cuiuacute magmatic arc andnot an individual arc (Creporizatildeo arc) as proposedby Santos et al (2001)
Ore mineralogy and wall-rock alteration
Many prospects are still undeveloped and work-ings are restricted to the oxidized (saprolite) zonewhere veins and structures are well preserved buthydrothermal alteration in the immediate host rockis overprinted by secondary processes Henceinformation in these cases is restricted to the veinassemblage and in a few cases to distal alterationwhich can be seen tens or a few hundreds of metersoff of the mineralized zone
Pyrite is the dominant sulfide mineral (Table 1)occurring in most of the deposits in general as dis-seminations filling fractures and cavities in thequartz veins in the contact between vein and hostrock or less commonly forming decimeter-wideaggregates (Fig 6) Chalcopyrite follows pyrite inimportance always occurring in association withpyrite whereas galena and arsenopyrite occur onlylocally
The gangue mineralogy shows little variationwith white mica being the main mineral (followingquartz) present in the quartz veins occurring how-ever in small amounts White mica is also wide-spread in the hydrothermally altered wall rocksoccurring in association with quartz minor amountsof chlorite and scarce carbonate K-feldspar andepidote
Structural controlInvestigation of mesoscopic and macroscopic
features of deposits of the STP showed that they arestrictly structurally controlled in all scalesRegional structures may have played importantroles acting as conduits for mineralizing fluids andcontrolling the distribution of the deposits The goldcamps are located close to or bounded by majorfirst-order faults and shear zones located in low-strain domains between them and rarely withinthese deformation zones (Figs 2 and 3) At campand deposit scales the orientation of the mineral-ized veins is controlled by the orientation andorgeometry of the hosting lower-order structures(Klein et al 1999 Santos 1999 2000)
Structural styles and internal structure
Fault-fill veins This type is by far the most com-mon structural style in STP and in the province as awhole (Klein et al 1999) The deposits consist of asingle quartz vein emplaced in subvertical struc-tures (Fig 4) These are mostly faults with subordi-
FIG 4 Photograph of the surface exposure of a fault-fillvein (outlined by the heavy lines) at Mineiro-2 The hydro-thermal envelope is outlined by the dashed line
552 KLEIN ET AL
nate narrow brittle-ductile shear zones Theirorientations are variable with concentrations ofveins along the N20degndash70degE and N40ndash50W direc-tions The veins are centimeter- to decimeter-thickand consist of milky quartz with minor (lt5) K-feldspar white mica chlorite and sulfide mineralsOccasionally thin extensionalndashoblique quartz toquartzo-feldspathic veinlets occur attached to themain quartz vein (Fig 5) The internal structure ofthe veins is dominantly formed by massive quartz(Fig 6) Laminated saccharoidal and open-spacefilling (comb) textures and hydrothermal brecciasare subordinate A few veins are positioned at thecontact between mafic dikes and the altered countryrock or even cut across the dikes suggesting inthese cases their late timing with respect to thedikes In one situation (Pau DrsquoArco) mineralizationlacks a major quartz vein (only a few discontinuousveinlets are present) and occurs as disseminationsin the hydrothermal zone that surrounds a subverti-cal strike-slip fault
Shear veins In greenstone-hosted deposits shearveins are usually described as fault-fill veinsbecause they occupy faults and the central parts ofshear zones (Hodgson 1989) and because it is con-sidered difficult to define if the veins formed as aresult of displacements along a shear fracture or asthe result of dilation of preexisting shear fractures orductile fabric (eg Robert and Poulsen 2001 and
references therein) In STP shear and fault-fill veinsshare a series of characteristics However in thispaper we prefer to classify them separately at leastfor descriptive purposes because shear veins differfrom fault-fill veins by the fact that they have beenemplaced in ductile-brittle structures (ComandanteRenan Novo Vietnam Fig 5) andor show effects ofductile deformation such as quartz grains withundulose extinction and deformation bands sur-rounded by small recrystallized subgrains (Patin-has) microscopic shear zones (Mineiro-1) andductile fabric either in the vein or in the immediatehost rock (Novo Vietnam) (Fig 5) The internalstructure is chiefly massive to laminated andsheared (Figs 6 and 7) Extensional features suchas breccias and en echelon sulfides (Fig 7) also arepresent
Low- (to moderate-) angle reverse-oblique faultsTwo examples have been observed At the Boa Vistagold field along with fault-fill and breccia veinspresent in several occurrences the main mineraliza-tion consists of a series of subparallel verticallystacked sigmoidal quartz veins (Fig 8A) separatedby hydrothermally altered and strongly foliated hostrock (schist) The veins show variable thicknessfrom a few centimeters up to one meter and strike toN45ordmndash80ordmW dipping 30ordm to 45ordm to the southwestInternally the milky veins show massive to saccha-roidal textures Small amounts of pyrite and minor
FIG 5 Sketch map (plan view) of the shear vein at Novo Vietnam The vein is surrounded by mylonitized wall rockand shows extensional veinlets attached on both sides The vein is massive to laminated and continuous but is formedby discontinuous veinlets (inset) between the two bends
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 553
arsenopyrite are disseminated throughout the veinsand altered wall rock Pyrite occurs filling smallfractures in quartz as well and sericite is presentboth in the vein and in the immediate wall rock
Given the weathered character of the terrainfresh rocks could not be observed in the mineralizedzone and the nature of the host rock could not beconfidently determined A few tens of meters off themineralized zone an undeformed porphyritic maficvolcanic rock crops out The region in turn is dom-inated by granitoids of the Creporizatildeo Suite that isthe host for all other occurrences in the same goldfield The hosting schist may derive from one ofthese two rock types by a combination of intense
deformation and high fluidrock ratios Alterna-tively it may represent a fragment of the metavol-cano-sedimentary sequence of the JacareacangaGroup which has not as yet been recognized in thisportion of the Tapajoacutes Province occurring as mega-xenoliths or roof pendants within the granitoids ofthe Creporizatildeo Suite
In the Satildeo Raimundo deposit mineralizationoccurs in narrow hydrothermal halos envelopinganastomosed shearfault planes in brittle-ductileshear zones (Fig 8B) The hosting shear zones strikeN45ordmndash60ordmE and dip 25ordmndash40ordm SE and the mineralizedzones are up to 2 meters thick (Rosa-Costa and Car-valho 1999) Quartz is generally absent and occurs
FIG 6 A Milky massive quartz with high pyrite contents at Patinhas B Sheared sulfide-poor quartz vein (Patinhas)C Quartz vein with sulfide minerals filling cavities (Novo Vietnam)
FIG 7 Vein structures at Mineiro-1 A Laminated quartz-pyrite veinlet (V) crosscutting the hydrothermally alteredhost rock Alteration is zoned and symmetric (arrows) B Milky massive quartz with extensional fracture filled by sulfideminerals with an en echelon distribution C Hydrothermal breccia formed by quartz (white) and hydrothermally alteredhost rock (grey)
554 KLEIN ET AL
only as small isolated and discontinuous veinletspositioned in the fault planes The host rock is amonzogranite of the Creporizatildeo Suite
Breccia veins Four main occurrences have beenrecorded forming tabular structures of less than 1 min thickness The breccia veins at Ceacuteu Azul andAacutegua Limpa consist of fragments of milky quartzwith angular to rounded shape ranging in size frommm to a few cm (Fig 9) set in a fine-grained red-dish to greenish hydrothermal matrix composed ofquartz feldspar and hematite along with fine-grained sericite and epidote Microscopically dif-ferent quartz fragments show textures such as comband rosettes indicating the shallow emplacement ofthese veins (Dowling and Morrison 1989 Vearn-combe 1993) At Goiano and Ouro Mil the brecciashave less matrix and the quartz fragments are moreangular than in the two other examples
Brecciation occurs also as a minor portion of ashear vein at the Mineiro-1 prospect in the BoaVista gold camp These breccias also differ from theformer by the fact that the angular quartz fragmentsare set in a matrix composed of altered wall rock(Fig 7C)
Stockworks This style has been identified at theIndependecircncia deposit It consists of multidirec-tional quartz veins a few centimeters thick envel-
oped by narrow halos of hydrothermal alterationThe veins are generally widely spaced occurring inan area of ~100 m times tens of meters Locally how-ever they are closely spaced with several individ-ual hydrothermal halos overlapping each otherforming larger areas of hydrothermally altered hostrock The quartz has a milky to smoky characterand shows cavities usually filled by sulfide miner-als Epidote and white mica are common gangueminerals In places large pockets of hydrothermalalteration lacking quartz veins are observed aswell Minor stockworks and networks (the veins as awhole show the same orientation of the veinbrec-cia) occur at Ouro Mil in both margins of the mainbreccia vein (Santos 1997)
Discussion and Concluding Remarks
Gold deposits in the Tapajoacutes Province are hostedin a variety of metamorphic and magmatic rocks InSouthern Tapajoacutes Province (STP) with one excep-tion only orthogneisses of the Cuiuacute-Cuiuacute Complexand orogenic granitoids of the Creporizatildeo Suite areknown hosts for gold Hosting granitoids are domi-nantly monzogranitic in composition whereas theorthogneisses show tonalitic and granodioritic com-positions
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 555
The deposits have been classified in a few struc-tural styles according to the hosting structurestructural regime in which they have been formedand internal structures and textures of the veinsAccordingly fault-fill and shear veins are the domi-nant style followed by subordinate occurrences ofveins hosted in low-angle reverse-oblique faultsbreccia veins and stockworks More than one stylemay occur in the same gold camp and even in a sin-gle deposit
Fault-fill and shear veins as well as brecciaveins form moderately to steeply dipping tabularbodies that seldom exceed one meter in thicknessand are hosted by strike-slip faults and shear zonesto which they are parallel The vein quartz is domi-nantly massive with laminated saccharoidal andcomb textures occurring subordinately Shearingand cataclasis of the veins is widespread suggest-ing along with other textural and structural evi-dence their positioning in active faults and shearzones or deformation after formation In most casesquartz white mica and pyrite compose the veinmineralogy and along with minor chlorite carbon-ate epidote and K-feldspar they overprint the pri-mary mineralogy of the hosting granitoids and theamphibolite-facies paragenesis of the hostinggneisses
The breccias have likely been produced duringfracture propagation by physical brecciation whichoccurs when the amount of stress exceeds the brittleresistance of the rock by mechanisms such as tec-tonic comminution andor fluid-assisted brecciation(Jeacutebrak 1997) Furthermore they indicate activeseismic slip during mineralization (Robert andPoulsen 2001)
The origin of the large stockwork at Independecircn-cia may be ascribed to hydraulic fracturing occur-ring over a cupola of a small aplitic granitoidrelated to or intruding the regional coarse-grainedmonzogranite of the Creporizatildeo Suite In the latterhypothesis it could be related either to a late-stagepluton of the Creporizatildeo Suite or to a younger grani-toid suite (Parauari) This definition requires geo-chronological support
Deposits and gold camps show strong structuralcontrol at all scales The hosting structures havebeen formed under a dominantly brittle-ductile tobrittle regime and consist of strike slip faults shearfractures intersection and bending of faults andlithological andor lithostratigraphic contactsExtensional fractures have not been characterizedas hosting structures because evidence of displace-
ment andor shearing is virtually always present inthe veins Extensional features are present howeveras en echelon arrays of sulfide minerals and as vein-lets attached to the main longitudinal fault veinsDeposits hosted in granitoids show a more brittlebehavior whereas those hosted in gneisses tend todisplay more ductile features This can result eitherfrom the depth of vein formation or from high fluidrock ratios even in shallow levels of the crust
Formation of deposits occurred in a range ofcrustal depth from mesozonal to epizonal condi-tions as indicated by the internal structure of thequartz veins and by the nature of the hosting struc-tures This is also supported by fluid inclusion stud-ies in a few deposits such as Guarim (Klein et al2001) and Patinhas (Klein et al 2000) both depos-its hosted in gneisses of the Cuiuacute-Cuiuacute ComplexFluid composition is nearly identical but P-T dataalong with textural and structural evidence suggestthat Guarim (outside STP) formed between 4 and 7km whereas Patinhas (within STP) formed at deeperlevels
Hence shear veins and fault-fill veins may beconsidered at least in part and from a structuralview as a single class of structural style with theirdifferences being ascribed to different depths ofemplacement and structural overprint It is not ourintention however to state that all of these veinsformed in a single gold-forming event The issue ofhow many mineralizing events have occurred in theTapajoacutes Province is still unresolved
Santos (1999 2000) studying 23 depositsthroughout the province (including three deposits inSTP) reported a set of characteristics similar tothose we have found in STP He concluded that alldeposits are related to a regional NW-SEndashtrendingstrike-slip fault system and that the orientation of
FIG 9 Breccia vein at Ceacuteu Azul
556 KLEIN ET AL
the lower-order hosting structures is compatiblewith Riedelrsquos system with the direction of the mainstress vector around the E-W direction Orientationsthat do not fit the model may be related to heteroge-neities in the local stress field However nothinghas been said about the timing of this strike-slipsystem in relation to the magmatic metamorphicand tectonic evolution of the province
Coutinho et al (2000) reported model ages thatcluster around 196 Ga and 188 Ga and main-tained that these two ages reflect two mineralizingepochs Santos et al (2001) invoked a single eventat 186 Ga However as stated by Santos et al(2001) the tectonic regime at 186 Ga is brittle Thismodel does not explain the ductile emplacementandor deformed mineralization hosted especially bythe Cuiuacute-Cuiuacute gneisses and by the metavolcano-sedimentary sequences Another (older) mineraliz-ing phase is thus required
We proposed early in this paper that the majorstrike-slip regime that affected the Creporizatildeo Suiteand older units likely occurred between 197 and195 Ga Mineralization hosted in the Cuiuacute-Cuiuacutegneisses (at least in STP) is post-tectonic and post-metamorphic with respect to the host rocks sincehosting structures clearly crosscut the metamorphicbanding and the hydrothermal mineralogy is retro-gressive in relation to the metamorphic paragenesisDeformation affecting the Creporizatildeo granitoids isbrittle-ductile to brittle whereas deformation affect-ing younger granitoids is brittle Thus it is valid toinfer as a working hypothesis that at least in partgold mineralization in STP formed during regionalstrike-slip deformation and emplacement of late-stage plutons of the Creporizatildeo Suite at ~197ndash195Ga a time interval that is in agreement with thatobtained by Coutinho et al (2000) The structuresmay have been reactivated during younger deforma-tional episode(s) and gold deposits may haveformed at this stage as well
The challenge is to decipher which depositsformed at each metallogenic epoch From a struc-tural point of view it is likely that the deposits inSouthern Tapajoacutes Province that have been emplacedat deeper levels of the crust and that show evidenceof plastic deformation (ie the shear veins and thedeposits hosted in low-angle reverse-oblique faultssee Table 1) formed in the older phase Fault-fillveins that occur in association with these deposits inthe same gold camp (eg Boa Vista) probablyformed in the same event The rest of the fault-fillveins (with textures and structures indicating
emplacement in shallow brittle structures associ-ated or not with mafic dikes and showing no associ-ation with shear veins in the same gold camp) aswell as the breccia veins and stockworks may haveformed either in the older or in the younger phaseWe do not have elements to define this Thisrequires much more isotopic data along with addi-tional fluid-inclusion and stable-isotope informationto constrain physico-chemical conditions of golddeposition as well as knowledge of the sources andnature of the mineralizing fluids and the absolutetiming of gold deposition
The attributes shown by the gold deposits in STP(namely the regional structural setting depositstyle vein textures and hydrothermal mineralogy)along with scarce fluid-inclusion data fit with boththe orogenic (magmatic arc-hosted) and intrusion-related models as proposed by Santos et al (2001)the latter sharing characteristics with Korean-typedeposits (Robert et al 1997) as well
Acknowledgments
Alfreu dos Santos (formerly of CPRM) partici-pated in the field work and supervised the TapajoacutesProject His help is acknowledged This is a contri-bution to the project PRONEX-CNPq-FADESP6621031998-0ndashprocess no 4200000
REFERENCES
Almeida M E Brito M F L Ferreira A L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaVila Mamatildee Anatilde (SB21-V-D) Estados do Paraacute e Ama-zonas escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Almeida M E Brito M F L and Macambira M J B1999 Caroccedilal Granite 207Pb206Pb evaporation age inpost-collisional granitoids of Tapajoacutes Gold ProvinceAmazonian region Brazil [abs] in II South AmericanSymposium on Isotope Geology Coacuterdoba ArgentinaActas p 3ndash6
Almeida M E Ferreira A L Brito M F L and Mon-teiro M A S 2001 Evoluccedilatildeo tectono-estrutural daProviacutencia Tapajoacutes com base na geologia das folhas VilaMamatildee Anatilde e Jacareacanga (1250000) regiatildeo limitedos estados do Amazonas e Paraacute in Reis N J andMonteiro M A S orgs Contribuiccedilotildees agrave Geologia daAmazocircnia v 2 Manaus Brazil SBG-NO p 57ndash112
Bahia R B C and Quadros M L E S 2000 Geologiae recursos minerais da Folha Caracol (SB21-X-C)
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 557
Estado do Paraacute Escala 1250000 Brasiacutelia BrazilCPRMGeological Survey of Brazil (CD-ROM)
Cassidy K F Groves D I and McNaughton N J 1998Late-Archean granitoid-hosted lode-gold depositsYilgarn Craton Western Australia Deposit character-istics crustal architecture and implications for oregenesis Ore Geology Reviews v 13 p 65ndash102
Correcirca-Silva R H Juliani C Bettencourt J S NunesC M D and Almeida T I R 2001 Caracterizaccedilatildeode um sistema epitermal low-sulfidation (ou adulaacuteria-sericita) hospedado em vulcacircnicas e vulcanoclaacutesticasdo Grupo Iriri na Proviacutencia auriacutefera do Tapajoacutes (PA)[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Coutinho M G N Santos J O S Fallick A E andLafon J M 2000 Orogenic gold deposits in TapajoacutesMineral Province Amazon Brazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Dowling K and Morrison G 1989 Application ofquartz textures to the classification of gold depositsusing North Queensland examples Economic GeologyMonograph v 6 p 342ndash355
Dreher A M Vlach S and Martini S L 1998 Adu-laria associated with epithermal gold veins in theTapajoacutes Mineral Province Paraacute State Northern BrazilRevista Brasileira de Geociecircncias v 28 p 397ndash404
Faraco M T L Carvalho J M A and Klein E L1997 Carta metalogeneacutetica da Proviacutencia Auriacutefera doTapajoacutes in Costa M L and Angeacutelica R S orgsContribuiccedilotildees agrave Geologia da Amazocircnia Beleacutem BrazilFINEPSBG-NO p 423ndash437
Ferreira A L Almeida M E Brito M F L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaJacareacanga (SB21-Y-B) Estados do Paraacute e Amazo-nas escala 1250000 Brasiacutelia Brazil CPRMGeolog-ical Survey of Brazil (CD-ROM)
Goldfarb R J Groves D I and Gardoll S 2001 Oro-genic gold and geologic time A global synthesis OreGeology Reviews v 18 p 1ndash75
Groves D I Goldfarb R J Gebre-Mariam M Hage-mann S and Robert F 1998 Orogenic gold depos-its A proposed classification in the context of theircrustal distribution and relationship to other golddeposit types Ore Geology Reviews v 13 p 7ndash27
Hodgson C J 1989 The structure of shear-related vein-type gold deposits A review Ore Geology Reviews v4 p 231ndash273
Jacobi P 1999 The discovery of epithermal Au-Cu-MoProterozoic deposits in the Tapajoacutes Province BrazilRevista Brasileira de Geociecircncias v 29 p 277ndash279
Jeacutebrak M 1997 Hydrothermal breccias in vein-type oredeposits A review of mechanisms morphology andsize distribution Ore Geology Reviews v 12 p 111ndash134
Juliani C 2001 Metalogecircnese do ouro e metais de baseassociadas com o vulcanismo-plutonismo da porccedilatildeo Wda Proviacutencia Auriacutefera do Tapajoacutes [ext abs] in VIISimpoacutesio de Geologia da Amazocircnia Beleacutem Brazil(CD-ROM)
Kerrich R and Cassidy K F 1994 Temporal relation-ships of lode gold mineralization to accretion magma-tism metamorphism and deformationmdashArchean topresent A review Ore Geology Reviews v 9 p 263ndash310
Klein E L Almeida M E Vasquez M L BahiaR B C Quadros M L E S and Ferreira A L inpress Geologia e recursos minerais da Proviacutencia Min-eral do Tapajoacutes Estados do Paraacute e Amazonas Escala1 500000 Brasiacutelia Brazil CPRMGeological Surveyof Brazil
Klein E L Rosa-Costa L T and Carvalho J M A2000 Fluid inclusion studies at the Patinhas gold-quartz mineralisation Tapajoacutes Gold Province Brazil[abs] in XXXI International Geological Congress Riode Janeiro Brazil (CD-ROM)
Klein E L Santos R A Fuzikawa K and AngeacutelicaR S 2001 Hydrothermal fluid evolution and struc-tural control of the brittle-style Guarim lode-gold min-eralisation Tapajoacutes Province Amazonian CratonBrazil Mineralium Deposita v 36 p 149ndash164
Klein E L and Vasquez M L 2000 Projeto EspecialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Vila Riozinho (SB21-Z-A) Estadodo Paraacute escala 1250000 Brasiacutelia Brazil CPRMGeological Survey of Brazil (CD-ROM)
Klein E L Vasquez M L Santos A and Martins RC 1997 Structural elements of the Maloquinha Intru-sive Suite in Tapajoacutes Mineral Province northern Bra-zil and the emplacement of the plutons [ext abs] inII International Symposium on Granites and Associ-ated Mineralizations ISGAM II Salvador Brazil p313ndash314
Klein E L Vasquez M L Santos A and Rosa-CostaL T 1999 Geologia e controle estrutural das mineral-izaccedilotildees auriacuteferas na Folha Vila Riozinho e NW daFolha Rio Novo Proviacutencia Tapajoacutes [ext abs] in VISimpoacutesio de Geologia da Amazocircnia Manaus Brazil p128ndash131
Lamaratildeo C N DallrsquoAgnol R and Lafon J M 2001Geocronologia e geoquiacutemica das associaccedilotildees vulcacircni-cas e plutocircnicas da regiatildeo de Vila Riozinho ProviacutenciaAuriacutefera do Tapajoacutes [ext abs] in VII Simpoacutesio deGeologia da Amazocircnia Beleacutem Brazil (CD-ROM)
Nunes C M D Juliani C Correcirca-Silva R H Mon-teiro L V S Bettencourt J S Neumann R AlcoverNeto A and Rye R O 2001 Caracterizaccedilatildeo de umsistema epitermal high-sulfidation vulcacircnico pale-oproterozoacuteico da Proviacutencia Auriacutefera do Tapajoacutes Paraacute[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
558 KLEIN ET AL
Ricci P S F Vasquez M L Santos A Klein E LJorge Joatildeo X S and Martins R C 1999 SuiacuteteIntrusiva Creporizatildeo ndash Proviacutencia Tapajoacutes Proposta ecriteacuterios de definiccedilatildeo [ext abs] in VI Simpoacutesio deGeologia da Amazocircnia Manaus Brazil p 519ndash522
Robert F and Poulsen K H 2001 Vein formation anddeformation in greenstone gold deposits in RichardsJ P and Tosdal R M eds Structural controls on oregenesis Reviews in Economic Geology v 14 p 111ndash155
Robert F Poulsen K H and Dubeacute B 1997 Golddeposits and their geological classification in GubinsA G ed Proceedings of Exploration 97 TorontoCanada p 209ndash220
Ronchi L H DallrsquoAgnol R Araujo J C Ribeiro VLamaratildeo C N Borges R M K and Fuzikawa K2001 Fluidos relacionados agraves alteraccedilotildees hidrotermaisno depoacutesito de ouro do Granito Satildeo JorgendashPA [extabs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Rosa-Costa L T and Carvalho J M A 1999 Tipologiade mineralizaccedilotildees auriacuteferas da regiatildeo sul da ProviacutenciaTapajoacutesndashParaacute [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 176ndash179
Santos J O S Groves D I Hartmann L A MouraM A and McNaughton N J 2001 Gold deposits ofthe Tapajoacutes and Alta Floresta Domains Tapajoacutes-Parima orogenic belt Amazon Craton Brazil Minera-lium Deposita v 36 p 279ndash299
Santos J O S Hartmann L A Gaudette H E GrovesD I McNaughton N J and Fletcher I R 2000 Anew understanding of the provinces of the AmazonCraton based on integration of field mapping and U-Pband Sm-Nd geochronology Gondwana Research v 3p 453ndash488
Santos R A 1997 Contribuiccedilatildeo agrave anaacutelise estrutural dejazimentos auriacuteferos do rio Tapajoacutes SW do Paraacute e SEdo Amazonas Garimpos Abacaxis Espiacuterito SantoBom Jesus Goiano Fazenda Pison Ouro Mil SantaIsabel Majestade e Carneirinho Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 1999 Controle estrutural das mineralizaccedilotildees deouro da Proviacutencia Mineral do Tapajoacutes Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 2000 Formation of gold-quartz veins controlledby the strike-slip fault mega-system in Tapajoacutes Min-eral Province Amazon Brazil [abs] in XXXI Interna-tional Geological Congress Rio de Janeiro Brazil(CD-ROM)
Tassinari C C G 1996 O mapa geocronoloacutegico do Craacute-ton Amazocircnico no Brasil Revisatildeo dos dados isotoacutepi-cos Unpubl Tese de Livre Docecircncia Universidade deSatildeo Paulo 139 p
Tassinari C C G and Macambira M J B 1999 Geo-chronological provinces of the Amazonian Craton Epi-sodes v 22 p 174ndash182
Vasquez M L and Klein E L 2000 Projeto especialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Rio Novo (SB21-Z-C) Estado doParaacute escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Vasquez M L Klein E L Macambira M J B SantosA Bahia R B C Ricci P S F and QuadrosM L E S 2000 Geochronology of granitoids maficintrusions and mineralizations of the Tapajoacutes GoldProvincendashAmazonian CratonndashBrazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Vasquez M L Klein E L Quadros M L E S BahiaR B C Santos A Ricci P S F Sachett C RSilva C M G and Macambira M J B 1999 Mag-matismo Uatumatilde na Proviacutencia Tapajoacutesmdashnovos dadosgeocronoloacutegicos [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 471ndash474
Vasquez M L Klein E L and Ricci P S F 2001Granitoacuteides poacutes-colisionais da porccedilatildeo leste da Proviacuten-cia Tapajoacutes [ext abs] in VII Simpoacutesio de Geologia daAmazocircnia Beleacutem Brazil (CD-ROM)
Vearncombe J R 1993 Quartz vein morphology andimplications for formation depth and classification ofArchaean gold-vein deposits Ore Geology Reviews v8 p 407ndash424
546 KLEIN ET AL
FIG 2 Geological map of the Tapajoacutes gold province (compiled and modified from Almeida et al 2000 Bahia andQuadros 2000 Ferreira et al 2000 Klein and Vasquez 2000 Vasquez and Klein 2000) showing the distribution of thegold depositscamps in the province
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 547
and 2005 Ma (Santos et al 2000 2001) Thesemetamorphic sequences have been intruded bycalc-alkaline granitoids of the Creporizatildeo (199ndash196 Ga) (Ricci et al 1999 Vasquez et al 2000)Tropas (190 Ga) (Santos et al 2001) and Parauari(189ndash188 Ga) (Vasquez et al 1999 Santos et al2000) intrusive suites as well as by a series of gab-broic rocks at 187 Ga (Santos et al 2001) Sedi-mentary deposits showing intra-arc characteristicsformed at ~190ndash189 Ga (Santos et al 2001) Thisorogenic period was followed by widespread felsicplutonic and volcanic activity at 187 Ga (Almeidaet al 1999 Vasquez et al 1999 Santos et al2000 Lamaratildeo et al 2001 Klein et al in press)related to extensional tectonics
It is the consensus that the orogenic evolution ofthe province comprises the accretion of magmaticarcs and related sedimentary basins However thenumber of arcs that have accreted is still debatableSantos et al (2000 2001) envisioned the evolutionof the orogenic domain through the sequentialaccretion of four magmatic arcs dated at 202 Ga(Cuiuacute-Cuiuacute Complex plus Jacareacanga Group)196 Ga (Creporizatildeo Suite) 190 Ga (Tropas Suite)and 188 Ga (Parauari Suite) These accretionaryevents have been followed by post-collisional intra-cratonic (granitoid and mafic) magmatism and sedi-ment deposition between 1870 Ma and 1780 MaConversely Vasquez et al (2001) considered theCreporizatildeo granitoids as post-collisional granitoidsstill related to the development of the Cuiuacute-Cuiuacutearc instead of considering it to be a different arc(see discussion below)
Structural framework
Remote sensing imagery and geophysical evi-dence show that the main structural features of theTapajoacutes Province are major NNW-SSEndash to NW-SEndashstriking linear or sinuous continuous to discontin-uous lineaments extending for tens to a few hun-dreds of kilometers (Fig 2) Field evidenceindicates that they represent mainly subverticalsinistral strike-slip faults and brittle-ductile shearzones This strike-slip system has been interpretedas a progressive and episodic compressive eventwith the maximum compressive stress vector (s1)around the east-west direction as shown by geomet-ric relationships of major and minor subsidiarystructures (Santos 1999 2000 Klein andVasquez 2000) On a regional scale these struc-tures have controlled the ascent and emplace-ment of several generations of granitoids and
volcanic and mafic rocks as well as the establish-ment of sedimentary basins and have outlinedtheir present shape and geometry (Klein et al1997 Santos 1999 Almeida et al 2000 Kleinand Vasquez 2000) It is likely that at least someof these structures may have been reactivatedduring the tectonic evolution of the Tapajoacutes Prov-ince However the timing of these events is notwell constrained yet
The oldest (D1) structural record is found in thewest-central portion of Tapajoacutes Province It isdefined by the NE-SWndashtrending gneissic banding ofthe Cuiuacute-Cuiuacute Complex and the schistosity of thevolcano-sedimentary Jacareacanga Group (Almeidaet al 2001) produced by a compressive event andis well preserved in the gneisses of the study areaThis deformation is not seen in younger rocks lead-ing Santos et al (2001) to establish the time intervalof 2005ndash1974 Ma as the timing of D1 which mayhave been synchronous with the metamorphic peakSantos et al (2001) defined a second deformationalevent (D2) represented by a high-angle N10E-strik-ing sinistral strike-slip shear zone of ductile-brittlecharacter affecting especially the Tropas Suite inthe western-central portion of the province and onlylocally affecting the Creporizatildeo and Parauari suitesThey placed the timing of this event to between1894 and 1883 Ma Furthermore they suggestedthat the brittle deformation which is younger than1883 Ma and which affected the Creporizatildeo andParauari granitoids could have been produced dur-ing the shallow emplacement of the Maloquinhagranitoids
However this structural evolution does notexplain satisfactorily the brittle-ductile deformationimprinted on the granitoids of the Creporizatildeo Suite(1997ndash1957 Ma) that are older than the Tropas Suite(190 Ga) The Creporizatildeo granitoids show a mag-matic foliation subparallel to a subvertical tectonicfoliation that strikes NW-SE and is clearly relatedto a brittle-ductile strike-slip regime This event hasnot been detected either in the Tropas Suite asstated by Santos et al (2001) nor in younger rocks(Parauari and Maloquinha suites volcanic rocks)Furthermore Almeida et al (2000 2001) docu-mented the transposition of the gneissic banding ofthe Cuiuacute-Cuiuacute rocks by NW-SE strike-slip shearzones Still a whole-rock Rb-Sr isochron age of1965 plusmn 16 Ma was reported by Tassinari (1996) forgranitoids of the Creporizatildeo Suite This age is closeto the zircon ages (U-Pb Pb-evaporation) for thelate-stage granitoids of the Creporizatildeo Suite and
548 KLEIN ET AL
may indicate that the emplacement of the post-colli-sional plutons was broadly coeval with the regionalNW-SE deformational event (Ricci et al 1999Vasquez et al 2001)
Hence we postulate a reappraisal of the struc-tural evolution of the Tapajoacutes Province as followsAn early deformation stage (D1) is represented bythe compressive event that imparted the gneissicbanding of the Cuiuacute-Cuiuacute Complex and the schis-tosity of the Jacareacanga Group occurring proba-bly between 2005 and 1997 Ma D2 is representedby the NW-SEndashtrending strike-slip event thataffected the granitoids of the Creporizatildeo Suite andoverprinted the gneissic banding of the Cuiuacute-Cuiuacuterocks occurring at ~197ndash195 Ga D3 is related tothe NNE-SSW strike-slip ductile shear zones thataffected the Tropas Suite between 1894 and 1883Ma Younger structures may have been reactivatedandor generated during the emplacement of thewidespread Maloquinha granitoids and are relatedto extensional tectonics
Gold deposit models
Studies of individual deposits in the TapajoacutesGold Province have been focused on fluid-inclusionproperties andor alteration assemblages leading tothe proposition that the deposits fit epithermal tomesothermal models (Dreher et al 1998 Klein etal 2001 Nunes et al 2001 Ronchi et al 2001)Province-scale models have been developed byCoutinho et al (2000) Santos (2000) and Santos etal (2001) Santos (2000) presented a structuralmodel relating the formation of the gold-quartz veinsto the regional-scale strike-slip fault systemCoutinho et al (2000) classified the deposits of theTapajoacutes Province as mesozonalepizonal orogenicdeposits and suggested two phases of mineraliza-tion based on model ages of sulfide minerals at196 Ga and 188 Ga Both phases postdated theregional metamorphic peak and have been associ-ated with compressional to transpressional tectonicsat the convergent plate margin of the accretionaryorogen Lead and stable (O H) isotopes togetherwith fluid-inclusion data suggest deep sources forgold mineralization (magmatic to juvenile) withpossibly meteoric water added in some deposits atshallow crustal levels
Santos et al (2001) proposed two classes of golddepositsmdashorogenic and intrusion related Orogenicdeposits have been subdivided into (1) turbidite-hosted consisting of mesozonal quartz-pyrite vein-lets or disseminations in ductile structures cutting
the supracrustal rocks of the Jacareacanga Group(2) magmatic arc-hosted consisting of mesozonalquartz-pyrite-carbonate veins and disseminationshosted in ductile-brittle structures cutting thegneisses of the Cuiuacute-Cuiuacute Complex and the grani-toids of the Tropas Suite Intrusion-related depositshave been subdivided into (1) epizonal quartz-pyrite veins and pyrite disseminations emplaced inshallow extensional brittle structures (similar toKorean-type deposits) cutting K-rich granitoids ofthe Creporizatildeo Parauari and Maloquinha suitesfrequently associated with mafic dikes (2) epizonaldisseminations and stockworks with hydrothermalmagnetite hosted in mafic and sedimentary rocksand sharing some characteristics with porphyry-typedeposits Using Pb and Ar isotopes Santos et al(2001) determined the timing of the intrusion-related deposits as being around 186 Ga They havenot established the age of the orogenic deposits buthave suggested that it might be similar to the age ofthe intrusion-related deposits with mineralizationdiffering in style host rocks and depth of emplace-ment They argued that the orogenic deposits wouldbe related to the final stages of evolution of theParauari arc whereas the intrusion-related depositswould be related either to the Parauari arc or to post-collisional granitoids (Maloquinha Suite)
Epithermal deposits have been described byJacobi (1999) Correcirca-Silva et al (2001) Juliani(2001) and Nunes et al (2001) for the east-centralportion of the province The deposits are hosted byfelsic to intermediate volcanic rocks and associatedvolcaniclastic rocks and consist of both low-sulfida-tion (adularia-sericite) and high-sulfidation (quartz-alunite) types Indirect dating suggests that mineral-ization formed at ~188 Ga and d34S data indicateda magmatic-hydrothermal source for the mineral-izing fluids and 330ordmC to 140ordmC as the formationtemperatures (Juliani 2001 Nunes et al 2001)Dreher et al (1998) also considered the epither-mal model for the Joel and David deposits How-ever Correcirca-Silva et al (2001) questioned thisclassification and argued that the adulariapresent in the Davi and Joel deposits is hosted inmafic rocks and could be related to this maficmagmatism Also Santos et al (2001) argued thatthese two deposits lack many important featuresof classic epithermal deposits such as the rela-tionship with contemporaneous volcanic rocks(the deposits are hosted by gabbro and granitoidrespectively) the low silver and adularia con-
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 549
tents and the absence of native silver and silversulfosalts in the ore mineralogy
Gold Deposits in the Southern Tapajoacutes Province (STP)
More than 20 deposits and showings are distrib-uted in several gold camps along the STP (Fig 3)These mineralizations are discussed below in termsof host rocks wall rock alteration and structuralcontrol The classification of structural styles of theveins is based mainly on the concepts of Hodgson(1989) and Robert and Poulsen (2001) taking intoaccount the type of host structure and the internalstructure and textures of the veins The mainattributes are summarized in Table 1
Host rocksGneisses and orogenic granitoids are the main
hosts for gold deposits in the Tapajoacutes Gold Provinceand account for virtually all the host rocks in STP(Table 1) The gneisses belong to the Cuiuacute-CuiuacuteComplex They consist of gray orthogneisses oftonalitic and granodioritic composition bearingmicrogranular enclaves of diorites and quartz-dior-ites along with granitoids and rare migmatites andamphibolites Structurally the gneisses show a per-vasive ductile fabric striking NNE-SSW or NW-SE
and migmatitic features are subordinate Thegeochemical characteristics of trace elements(LILE HFSE REE) are compatible with those ofprimitive arc-related calc-alkaline granitoids(Vasquez et al 2001) They are dominantly metalu-minous with lenses of peraluminous to strongly per-aluminous leucogranitoids occurring subordinatelySantos et al (2000 2001) obtained zircon U-PbSHRIMP ages between 2033 Ma and 2005 Ma forthis complex
The hosting granitoids are related to the Crep-orizatildeo Intrusive Suite which holds irregular- to sig-moidal-shaped batholiths and stocks (Fig 2) ofhornblende- andor biotite-bearing granitoids andmetagranitoids of syenogranitic to tonalitic composi-tion The granitoids are either foliated or granoblas-tic and the latter show preserved primary featuressuch as euhedral phenocrysts of K-feldspar unde-formed microgranular enclaves and synplutonicdikes Very often they show an igneous bandingmarked by the orientation of the K-feldspar pheno-crysts that parallels the NW-SEndashtrending tectonicfoliation Field mineralogical and textural evi-dence indicates emplacement of the granitoids in acrustal level compatible with greenschist or up tomiddle-amphibolite metamorphic conditions (Ricciet al 1999) and the presence of enclaves ofgneisses from the Cuiuacute-Cuiuacute Complex is evidence of
FIG 3 Geological map of the Southern Tapajoacutes Province showing the location of the gold deposits addressed in thisstudy
550 KLEIN ET AL
TAB
LE 1
Sum
mar
y of
Attr
ibut
es o
f Gol
d D
epos
its o
f the
Sou
ther
n Ta
pajoacute
s Pr
ovin
ce1
No
Cam
p or
dep
osit
(n
umbe
r of
vei
ns)
Stru
ctur
al s
tyle
Inte
rnal
str
uctu
reH
ost r
ock
(s
trat
igra
phic
uni
t)G
angu
e m
iner
alog
yO
re m
iner
alog
yV
ein
orie
ntat
ion
(str
ike
dip)
Sele
cted
ref
eren
ces
1G
oian
o (2
)B
recc
iaC
atac
last
icF
olia
ted
gran
itoi
d (C
IS)
mus
pyN
50E
88S
E N
20W
88
NE
N0E
80E
Sant
os 1
997
2Su
daacuteri
o (4
)F
FV
(plusmn
maf
ic
dike
)M
assi
ve c
atac
last
icG
rani
toid
s (C
CC
)py
N40
-60E
70-
88SE
-N
WR
osa-
Cos
ta a
nd C
arva
lho
199
9
3C
oman
dant
e M
acha
do
(2)
FF
VM
assi
ve c
omb
Fol
iate
d gr
anod
iori
te
(CC
C)
mus
pyN
40E
70S
E a
nd
N50
W6
5SW
Ros
a-C
osta
and
Car
valh
o 1
999
4P
atin
has
Shea
r ve
inM
assi
ve s
hear
edG
rano
dior
ite
(CC
C)
eppy
cpy
N20
E6
8SE
Ros
a-C
osta
and
Car
valh
o 1
999
Kle
in e
t al
200
05
Pau
drsquoA
rco
(3)
FF
VV
einl
ets
sa
ccha
roid
alQ
uart
z-di
orit
ic g
neis
s (C
CC
) m
us k
f c
hl
epcp
y p
yN
30E
65S
EK
lein
et a
l i
n pr
ess
6C
oman
dant
e R
enan
(2)
Shea
r ve
inM
assi
veTo
nali
tic
gnei
ss (
CC
C)
chl
ep
pyN
0-30
E6
088S
EK
lein
et a
l i
n pr
ess
7Ta
uari
FF
VM
assi
veG
rani
toid
(C
IS)
chl
ep
N30
E8
5NW
Kle
in e
t al
in
pres
s8
Our
o M
ilB
recc
ia +
m
afic
dik
eN
etw
orks
Gra
nito
id (
CIS
) +
m
afic
dik
eN
70E
70N
WSa
ntos
199
7
9C
eacuteu A
zul
Bre
ccia
Com
b fi
ber
Gra
nodi
orit
e (C
IS)
qz k
f se
r ep
hem
N70
E8
8SE
Kle
in e
t al
in
pres
s10
Aacutegu
a L
impa
Bre
ccia
Gra
nodi
orit
e (C
IS)
N60
W7
0NE
Kle
in e
t al
in
pres
s11
Roq
ue S
ante
iro
(2)
FF
VM
assi
veTo
nali
tic
gnei
ss (
CC
C)
chl
pyN
45E
75N
WN
40W
88N
EK
lein
et a
l i
n pr
ess
12Ta
boca
lF
FV
Mas
sive
Mon
zogr
anit
e (C
IS)
N70
E8
0NW
Kle
in e
t al
in
pres
s13
Vie
tnam
Shea
r ve
inL
amin
ated
Mon
zogr
anit
e (C
IS)
ser
pyN
70E
75N
WK
lein
et a
l i
n pr
ess
14N
ovo
Vie
tnam
Shea
r ve
inM
assi
ve l
amin
ated
Mon
zogr
anit
e (C
IS)
ser
pyN
55E
80S
EK
lein
et a
l i
n pr
ess
15In
depe
ndecircn
cia
Stoc
kwor
kM
assi
ve v
uggy
Apl
itic
mon
zogr
anit
e (P
IS
CIS
) m
uspy
N45
-80E
10-
60SE
Kle
in e
t al
in
pres
s
16Satilde
o R
aim
undo
LA
RF
Mon
zogr
anit
e (C
IS)
epN
45-6
0E2
5-40
SER
osa-
Cos
ta a
nd C
arva
lho
199
917
Bom
Jes
usF
FV
Lam
inat
edG
rani
toid
(C
IS)
ser
kf
py c
py g
alN
90E
88S
Sant
os 1
997
18B
oa V
ista
Zeacute
Ped
roF
FV
Mon
zogr
anit
e (C
IS)
pyN
70E
80S
ER
osa-
Cos
ta a
nd C
arva
lho
199
918
Boa
Vis
taM
inei
ro-1
Shea
r ve
in +
br
ecci
aM
assi
ve l
amin
ated
Mon
zogr
anit
e (C
IS)
qz s
er c
arb
chl
py c
pyN
30E
88S
EV
asqu
ez a
nd K
lein
200
0
18B
oa V
ista
Min
eiro
-2F
FV
Mas
sive
Mon
zogr
anit
e (C
IS)
chl
ser
ep
pyN
20E
75S
EV
asqu
ez a
nd K
lein
200
018
Boa
Vis
taL
AR
FM
assi
ve s
acch
aroi
dal
Maf
ic v
olca
nic
and
schi
st (
)se
rpy
asp
yN
45-8
0W3
0-45
SWK
lein
et a
l i
n p
ress
Ros
a-C
osta
and
Car
valh
o 1
999
19P
lana
lto
FF
VM
assi
veG
rani
toid
(C
CC
)N
40E
75S
EK
lein
et a
l i
n pr
ess
20B
abil
ocircnia
FF
VM
assi
veM
onzo
gran
ite
(CIS
)se
rpy
N45
W4
5SW
Kle
in e
t al
in
pres
s21
Satildeo
Joseacute
FF
VM
assi
ve s
acch
aroi
dal
Mon
zogr
anit
e (C
IS)
epN
45W
63N
EK
lein
et a
l i
n pr
ess
1 Leg
end
FF
V =
fau
lt-f
ill
vein
CIS
= C
repo
rizatilde
o In
trus
ive
Suit
e C
CC
= C
uiuacute-
Cui
uacute C
ompl
ex P
IS =
Par
auar
i Int
rusi
ve S
uite
mus
= m
usco
vite
ser
= s
eric
ite
ep
= e
pido
te k
f = K
-fel
d-sp
ar c
hl =
chl
orit
e c
arb
= c
arbo
nate
qz
= q
uart
z p
y =
pyr
ite
cpy
= c
halc
opyr
ite
asp
y =
ars
enop
yrit
e g
al =
gal
ena
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 551
the intrusive character of the granitoids Whole-rockgeochemistry (Lamaratildeo et al 2001 Vasquez et al2001) has shown that the Creporizatildeo Suite repre-sents calc-alkaline metaluminous to peraluminousmedium- to high-K arc-related granitoids The REEpatterns show that they are more evolved than theCuiuacute-Cuiuacute granitoids and gneisses U-Pb and Pb-evaporation dating of zircon (Ricci et al 1999Vasquez et al 2000 Santos et al 2000 2001Lamaratildeo et al 2001) indicate crystallization agesbetween 1997 Ma and 1957 Ma This late timingwith respect to the Cuiuacute-Cuiuacute Complex along withthe geochemical characteristics the structural andmetamorphic differences the lack of volcano-sedi-mentary basins associated with the Creporizatildeo gran-itoids and their common association with regionalstrike-slip shear zones led Vasquez et al (2001) toconsider the Creporizatildeo Suite as representing apost-collisional magmatism still related to thedevelopment of the Cuiuacute-Cuiuacute magmatic arc andnot an individual arc (Creporizatildeo arc) as proposedby Santos et al (2001)
Ore mineralogy and wall-rock alteration
Many prospects are still undeveloped and work-ings are restricted to the oxidized (saprolite) zonewhere veins and structures are well preserved buthydrothermal alteration in the immediate host rockis overprinted by secondary processes Henceinformation in these cases is restricted to the veinassemblage and in a few cases to distal alterationwhich can be seen tens or a few hundreds of metersoff of the mineralized zone
Pyrite is the dominant sulfide mineral (Table 1)occurring in most of the deposits in general as dis-seminations filling fractures and cavities in thequartz veins in the contact between vein and hostrock or less commonly forming decimeter-wideaggregates (Fig 6) Chalcopyrite follows pyrite inimportance always occurring in association withpyrite whereas galena and arsenopyrite occur onlylocally
The gangue mineralogy shows little variationwith white mica being the main mineral (followingquartz) present in the quartz veins occurring how-ever in small amounts White mica is also wide-spread in the hydrothermally altered wall rocksoccurring in association with quartz minor amountsof chlorite and scarce carbonate K-feldspar andepidote
Structural controlInvestigation of mesoscopic and macroscopic
features of deposits of the STP showed that they arestrictly structurally controlled in all scalesRegional structures may have played importantroles acting as conduits for mineralizing fluids andcontrolling the distribution of the deposits The goldcamps are located close to or bounded by majorfirst-order faults and shear zones located in low-strain domains between them and rarely withinthese deformation zones (Figs 2 and 3) At campand deposit scales the orientation of the mineral-ized veins is controlled by the orientation andorgeometry of the hosting lower-order structures(Klein et al 1999 Santos 1999 2000)
Structural styles and internal structure
Fault-fill veins This type is by far the most com-mon structural style in STP and in the province as awhole (Klein et al 1999) The deposits consist of asingle quartz vein emplaced in subvertical struc-tures (Fig 4) These are mostly faults with subordi-
FIG 4 Photograph of the surface exposure of a fault-fillvein (outlined by the heavy lines) at Mineiro-2 The hydro-thermal envelope is outlined by the dashed line
552 KLEIN ET AL
nate narrow brittle-ductile shear zones Theirorientations are variable with concentrations ofveins along the N20degndash70degE and N40ndash50W direc-tions The veins are centimeter- to decimeter-thickand consist of milky quartz with minor (lt5) K-feldspar white mica chlorite and sulfide mineralsOccasionally thin extensionalndashoblique quartz toquartzo-feldspathic veinlets occur attached to themain quartz vein (Fig 5) The internal structure ofthe veins is dominantly formed by massive quartz(Fig 6) Laminated saccharoidal and open-spacefilling (comb) textures and hydrothermal brecciasare subordinate A few veins are positioned at thecontact between mafic dikes and the altered countryrock or even cut across the dikes suggesting inthese cases their late timing with respect to thedikes In one situation (Pau DrsquoArco) mineralizationlacks a major quartz vein (only a few discontinuousveinlets are present) and occurs as disseminationsin the hydrothermal zone that surrounds a subverti-cal strike-slip fault
Shear veins In greenstone-hosted deposits shearveins are usually described as fault-fill veinsbecause they occupy faults and the central parts ofshear zones (Hodgson 1989) and because it is con-sidered difficult to define if the veins formed as aresult of displacements along a shear fracture or asthe result of dilation of preexisting shear fractures orductile fabric (eg Robert and Poulsen 2001 and
references therein) In STP shear and fault-fill veinsshare a series of characteristics However in thispaper we prefer to classify them separately at leastfor descriptive purposes because shear veins differfrom fault-fill veins by the fact that they have beenemplaced in ductile-brittle structures (ComandanteRenan Novo Vietnam Fig 5) andor show effects ofductile deformation such as quartz grains withundulose extinction and deformation bands sur-rounded by small recrystallized subgrains (Patin-has) microscopic shear zones (Mineiro-1) andductile fabric either in the vein or in the immediatehost rock (Novo Vietnam) (Fig 5) The internalstructure is chiefly massive to laminated andsheared (Figs 6 and 7) Extensional features suchas breccias and en echelon sulfides (Fig 7) also arepresent
Low- (to moderate-) angle reverse-oblique faultsTwo examples have been observed At the Boa Vistagold field along with fault-fill and breccia veinspresent in several occurrences the main mineraliza-tion consists of a series of subparallel verticallystacked sigmoidal quartz veins (Fig 8A) separatedby hydrothermally altered and strongly foliated hostrock (schist) The veins show variable thicknessfrom a few centimeters up to one meter and strike toN45ordmndash80ordmW dipping 30ordm to 45ordm to the southwestInternally the milky veins show massive to saccha-roidal textures Small amounts of pyrite and minor
FIG 5 Sketch map (plan view) of the shear vein at Novo Vietnam The vein is surrounded by mylonitized wall rockand shows extensional veinlets attached on both sides The vein is massive to laminated and continuous but is formedby discontinuous veinlets (inset) between the two bends
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 553
arsenopyrite are disseminated throughout the veinsand altered wall rock Pyrite occurs filling smallfractures in quartz as well and sericite is presentboth in the vein and in the immediate wall rock
Given the weathered character of the terrainfresh rocks could not be observed in the mineralizedzone and the nature of the host rock could not beconfidently determined A few tens of meters off themineralized zone an undeformed porphyritic maficvolcanic rock crops out The region in turn is dom-inated by granitoids of the Creporizatildeo Suite that isthe host for all other occurrences in the same goldfield The hosting schist may derive from one ofthese two rock types by a combination of intense
deformation and high fluidrock ratios Alterna-tively it may represent a fragment of the metavol-cano-sedimentary sequence of the JacareacangaGroup which has not as yet been recognized in thisportion of the Tapajoacutes Province occurring as mega-xenoliths or roof pendants within the granitoids ofthe Creporizatildeo Suite
In the Satildeo Raimundo deposit mineralizationoccurs in narrow hydrothermal halos envelopinganastomosed shearfault planes in brittle-ductileshear zones (Fig 8B) The hosting shear zones strikeN45ordmndash60ordmE and dip 25ordmndash40ordm SE and the mineralizedzones are up to 2 meters thick (Rosa-Costa and Car-valho 1999) Quartz is generally absent and occurs
FIG 6 A Milky massive quartz with high pyrite contents at Patinhas B Sheared sulfide-poor quartz vein (Patinhas)C Quartz vein with sulfide minerals filling cavities (Novo Vietnam)
FIG 7 Vein structures at Mineiro-1 A Laminated quartz-pyrite veinlet (V) crosscutting the hydrothermally alteredhost rock Alteration is zoned and symmetric (arrows) B Milky massive quartz with extensional fracture filled by sulfideminerals with an en echelon distribution C Hydrothermal breccia formed by quartz (white) and hydrothermally alteredhost rock (grey)
554 KLEIN ET AL
only as small isolated and discontinuous veinletspositioned in the fault planes The host rock is amonzogranite of the Creporizatildeo Suite
Breccia veins Four main occurrences have beenrecorded forming tabular structures of less than 1 min thickness The breccia veins at Ceacuteu Azul andAacutegua Limpa consist of fragments of milky quartzwith angular to rounded shape ranging in size frommm to a few cm (Fig 9) set in a fine-grained red-dish to greenish hydrothermal matrix composed ofquartz feldspar and hematite along with fine-grained sericite and epidote Microscopically dif-ferent quartz fragments show textures such as comband rosettes indicating the shallow emplacement ofthese veins (Dowling and Morrison 1989 Vearn-combe 1993) At Goiano and Ouro Mil the brecciashave less matrix and the quartz fragments are moreangular than in the two other examples
Brecciation occurs also as a minor portion of ashear vein at the Mineiro-1 prospect in the BoaVista gold camp These breccias also differ from theformer by the fact that the angular quartz fragmentsare set in a matrix composed of altered wall rock(Fig 7C)
Stockworks This style has been identified at theIndependecircncia deposit It consists of multidirec-tional quartz veins a few centimeters thick envel-
oped by narrow halos of hydrothermal alterationThe veins are generally widely spaced occurring inan area of ~100 m times tens of meters Locally how-ever they are closely spaced with several individ-ual hydrothermal halos overlapping each otherforming larger areas of hydrothermally altered hostrock The quartz has a milky to smoky characterand shows cavities usually filled by sulfide miner-als Epidote and white mica are common gangueminerals In places large pockets of hydrothermalalteration lacking quartz veins are observed aswell Minor stockworks and networks (the veins as awhole show the same orientation of the veinbrec-cia) occur at Ouro Mil in both margins of the mainbreccia vein (Santos 1997)
Discussion and Concluding Remarks
Gold deposits in the Tapajoacutes Province are hostedin a variety of metamorphic and magmatic rocks InSouthern Tapajoacutes Province (STP) with one excep-tion only orthogneisses of the Cuiuacute-Cuiuacute Complexand orogenic granitoids of the Creporizatildeo Suite areknown hosts for gold Hosting granitoids are domi-nantly monzogranitic in composition whereas theorthogneisses show tonalitic and granodioritic com-positions
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 555
The deposits have been classified in a few struc-tural styles according to the hosting structurestructural regime in which they have been formedand internal structures and textures of the veinsAccordingly fault-fill and shear veins are the domi-nant style followed by subordinate occurrences ofveins hosted in low-angle reverse-oblique faultsbreccia veins and stockworks More than one stylemay occur in the same gold camp and even in a sin-gle deposit
Fault-fill and shear veins as well as brecciaveins form moderately to steeply dipping tabularbodies that seldom exceed one meter in thicknessand are hosted by strike-slip faults and shear zonesto which they are parallel The vein quartz is domi-nantly massive with laminated saccharoidal andcomb textures occurring subordinately Shearingand cataclasis of the veins is widespread suggest-ing along with other textural and structural evi-dence their positioning in active faults and shearzones or deformation after formation In most casesquartz white mica and pyrite compose the veinmineralogy and along with minor chlorite carbon-ate epidote and K-feldspar they overprint the pri-mary mineralogy of the hosting granitoids and theamphibolite-facies paragenesis of the hostinggneisses
The breccias have likely been produced duringfracture propagation by physical brecciation whichoccurs when the amount of stress exceeds the brittleresistance of the rock by mechanisms such as tec-tonic comminution andor fluid-assisted brecciation(Jeacutebrak 1997) Furthermore they indicate activeseismic slip during mineralization (Robert andPoulsen 2001)
The origin of the large stockwork at Independecircn-cia may be ascribed to hydraulic fracturing occur-ring over a cupola of a small aplitic granitoidrelated to or intruding the regional coarse-grainedmonzogranite of the Creporizatildeo Suite In the latterhypothesis it could be related either to a late-stagepluton of the Creporizatildeo Suite or to a younger grani-toid suite (Parauari) This definition requires geo-chronological support
Deposits and gold camps show strong structuralcontrol at all scales The hosting structures havebeen formed under a dominantly brittle-ductile tobrittle regime and consist of strike slip faults shearfractures intersection and bending of faults andlithological andor lithostratigraphic contactsExtensional fractures have not been characterizedas hosting structures because evidence of displace-
ment andor shearing is virtually always present inthe veins Extensional features are present howeveras en echelon arrays of sulfide minerals and as vein-lets attached to the main longitudinal fault veinsDeposits hosted in granitoids show a more brittlebehavior whereas those hosted in gneisses tend todisplay more ductile features This can result eitherfrom the depth of vein formation or from high fluidrock ratios even in shallow levels of the crust
Formation of deposits occurred in a range ofcrustal depth from mesozonal to epizonal condi-tions as indicated by the internal structure of thequartz veins and by the nature of the hosting struc-tures This is also supported by fluid inclusion stud-ies in a few deposits such as Guarim (Klein et al2001) and Patinhas (Klein et al 2000) both depos-its hosted in gneisses of the Cuiuacute-Cuiuacute ComplexFluid composition is nearly identical but P-T dataalong with textural and structural evidence suggestthat Guarim (outside STP) formed between 4 and 7km whereas Patinhas (within STP) formed at deeperlevels
Hence shear veins and fault-fill veins may beconsidered at least in part and from a structuralview as a single class of structural style with theirdifferences being ascribed to different depths ofemplacement and structural overprint It is not ourintention however to state that all of these veinsformed in a single gold-forming event The issue ofhow many mineralizing events have occurred in theTapajoacutes Province is still unresolved
Santos (1999 2000) studying 23 depositsthroughout the province (including three deposits inSTP) reported a set of characteristics similar tothose we have found in STP He concluded that alldeposits are related to a regional NW-SEndashtrendingstrike-slip fault system and that the orientation of
FIG 9 Breccia vein at Ceacuteu Azul
556 KLEIN ET AL
the lower-order hosting structures is compatiblewith Riedelrsquos system with the direction of the mainstress vector around the E-W direction Orientationsthat do not fit the model may be related to heteroge-neities in the local stress field However nothinghas been said about the timing of this strike-slipsystem in relation to the magmatic metamorphicand tectonic evolution of the province
Coutinho et al (2000) reported model ages thatcluster around 196 Ga and 188 Ga and main-tained that these two ages reflect two mineralizingepochs Santos et al (2001) invoked a single eventat 186 Ga However as stated by Santos et al(2001) the tectonic regime at 186 Ga is brittle Thismodel does not explain the ductile emplacementandor deformed mineralization hosted especially bythe Cuiuacute-Cuiuacute gneisses and by the metavolcano-sedimentary sequences Another (older) mineraliz-ing phase is thus required
We proposed early in this paper that the majorstrike-slip regime that affected the Creporizatildeo Suiteand older units likely occurred between 197 and195 Ga Mineralization hosted in the Cuiuacute-Cuiuacutegneisses (at least in STP) is post-tectonic and post-metamorphic with respect to the host rocks sincehosting structures clearly crosscut the metamorphicbanding and the hydrothermal mineralogy is retro-gressive in relation to the metamorphic paragenesisDeformation affecting the Creporizatildeo granitoids isbrittle-ductile to brittle whereas deformation affect-ing younger granitoids is brittle Thus it is valid toinfer as a working hypothesis that at least in partgold mineralization in STP formed during regionalstrike-slip deformation and emplacement of late-stage plutons of the Creporizatildeo Suite at ~197ndash195Ga a time interval that is in agreement with thatobtained by Coutinho et al (2000) The structuresmay have been reactivated during younger deforma-tional episode(s) and gold deposits may haveformed at this stage as well
The challenge is to decipher which depositsformed at each metallogenic epoch From a struc-tural point of view it is likely that the deposits inSouthern Tapajoacutes Province that have been emplacedat deeper levels of the crust and that show evidenceof plastic deformation (ie the shear veins and thedeposits hosted in low-angle reverse-oblique faultssee Table 1) formed in the older phase Fault-fillveins that occur in association with these deposits inthe same gold camp (eg Boa Vista) probablyformed in the same event The rest of the fault-fillveins (with textures and structures indicating
emplacement in shallow brittle structures associ-ated or not with mafic dikes and showing no associ-ation with shear veins in the same gold camp) aswell as the breccia veins and stockworks may haveformed either in the older or in the younger phaseWe do not have elements to define this Thisrequires much more isotopic data along with addi-tional fluid-inclusion and stable-isotope informationto constrain physico-chemical conditions of golddeposition as well as knowledge of the sources andnature of the mineralizing fluids and the absolutetiming of gold deposition
The attributes shown by the gold deposits in STP(namely the regional structural setting depositstyle vein textures and hydrothermal mineralogy)along with scarce fluid-inclusion data fit with boththe orogenic (magmatic arc-hosted) and intrusion-related models as proposed by Santos et al (2001)the latter sharing characteristics with Korean-typedeposits (Robert et al 1997) as well
Acknowledgments
Alfreu dos Santos (formerly of CPRM) partici-pated in the field work and supervised the TapajoacutesProject His help is acknowledged This is a contri-bution to the project PRONEX-CNPq-FADESP6621031998-0ndashprocess no 4200000
REFERENCES
Almeida M E Brito M F L Ferreira A L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaVila Mamatildee Anatilde (SB21-V-D) Estados do Paraacute e Ama-zonas escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Almeida M E Brito M F L and Macambira M J B1999 Caroccedilal Granite 207Pb206Pb evaporation age inpost-collisional granitoids of Tapajoacutes Gold ProvinceAmazonian region Brazil [abs] in II South AmericanSymposium on Isotope Geology Coacuterdoba ArgentinaActas p 3ndash6
Almeida M E Ferreira A L Brito M F L and Mon-teiro M A S 2001 Evoluccedilatildeo tectono-estrutural daProviacutencia Tapajoacutes com base na geologia das folhas VilaMamatildee Anatilde e Jacareacanga (1250000) regiatildeo limitedos estados do Amazonas e Paraacute in Reis N J andMonteiro M A S orgs Contribuiccedilotildees agrave Geologia daAmazocircnia v 2 Manaus Brazil SBG-NO p 57ndash112
Bahia R B C and Quadros M L E S 2000 Geologiae recursos minerais da Folha Caracol (SB21-X-C)
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 557
Estado do Paraacute Escala 1250000 Brasiacutelia BrazilCPRMGeological Survey of Brazil (CD-ROM)
Cassidy K F Groves D I and McNaughton N J 1998Late-Archean granitoid-hosted lode-gold depositsYilgarn Craton Western Australia Deposit character-istics crustal architecture and implications for oregenesis Ore Geology Reviews v 13 p 65ndash102
Correcirca-Silva R H Juliani C Bettencourt J S NunesC M D and Almeida T I R 2001 Caracterizaccedilatildeode um sistema epitermal low-sulfidation (ou adulaacuteria-sericita) hospedado em vulcacircnicas e vulcanoclaacutesticasdo Grupo Iriri na Proviacutencia auriacutefera do Tapajoacutes (PA)[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Coutinho M G N Santos J O S Fallick A E andLafon J M 2000 Orogenic gold deposits in TapajoacutesMineral Province Amazon Brazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Dowling K and Morrison G 1989 Application ofquartz textures to the classification of gold depositsusing North Queensland examples Economic GeologyMonograph v 6 p 342ndash355
Dreher A M Vlach S and Martini S L 1998 Adu-laria associated with epithermal gold veins in theTapajoacutes Mineral Province Paraacute State Northern BrazilRevista Brasileira de Geociecircncias v 28 p 397ndash404
Faraco M T L Carvalho J M A and Klein E L1997 Carta metalogeneacutetica da Proviacutencia Auriacutefera doTapajoacutes in Costa M L and Angeacutelica R S orgsContribuiccedilotildees agrave Geologia da Amazocircnia Beleacutem BrazilFINEPSBG-NO p 423ndash437
Ferreira A L Almeida M E Brito M F L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaJacareacanga (SB21-Y-B) Estados do Paraacute e Amazo-nas escala 1250000 Brasiacutelia Brazil CPRMGeolog-ical Survey of Brazil (CD-ROM)
Goldfarb R J Groves D I and Gardoll S 2001 Oro-genic gold and geologic time A global synthesis OreGeology Reviews v 18 p 1ndash75
Groves D I Goldfarb R J Gebre-Mariam M Hage-mann S and Robert F 1998 Orogenic gold depos-its A proposed classification in the context of theircrustal distribution and relationship to other golddeposit types Ore Geology Reviews v 13 p 7ndash27
Hodgson C J 1989 The structure of shear-related vein-type gold deposits A review Ore Geology Reviews v4 p 231ndash273
Jacobi P 1999 The discovery of epithermal Au-Cu-MoProterozoic deposits in the Tapajoacutes Province BrazilRevista Brasileira de Geociecircncias v 29 p 277ndash279
Jeacutebrak M 1997 Hydrothermal breccias in vein-type oredeposits A review of mechanisms morphology andsize distribution Ore Geology Reviews v 12 p 111ndash134
Juliani C 2001 Metalogecircnese do ouro e metais de baseassociadas com o vulcanismo-plutonismo da porccedilatildeo Wda Proviacutencia Auriacutefera do Tapajoacutes [ext abs] in VIISimpoacutesio de Geologia da Amazocircnia Beleacutem Brazil(CD-ROM)
Kerrich R and Cassidy K F 1994 Temporal relation-ships of lode gold mineralization to accretion magma-tism metamorphism and deformationmdashArchean topresent A review Ore Geology Reviews v 9 p 263ndash310
Klein E L Almeida M E Vasquez M L BahiaR B C Quadros M L E S and Ferreira A L inpress Geologia e recursos minerais da Proviacutencia Min-eral do Tapajoacutes Estados do Paraacute e Amazonas Escala1 500000 Brasiacutelia Brazil CPRMGeological Surveyof Brazil
Klein E L Rosa-Costa L T and Carvalho J M A2000 Fluid inclusion studies at the Patinhas gold-quartz mineralisation Tapajoacutes Gold Province Brazil[abs] in XXXI International Geological Congress Riode Janeiro Brazil (CD-ROM)
Klein E L Santos R A Fuzikawa K and AngeacutelicaR S 2001 Hydrothermal fluid evolution and struc-tural control of the brittle-style Guarim lode-gold min-eralisation Tapajoacutes Province Amazonian CratonBrazil Mineralium Deposita v 36 p 149ndash164
Klein E L and Vasquez M L 2000 Projeto EspecialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Vila Riozinho (SB21-Z-A) Estadodo Paraacute escala 1250000 Brasiacutelia Brazil CPRMGeological Survey of Brazil (CD-ROM)
Klein E L Vasquez M L Santos A and Martins RC 1997 Structural elements of the Maloquinha Intru-sive Suite in Tapajoacutes Mineral Province northern Bra-zil and the emplacement of the plutons [ext abs] inII International Symposium on Granites and Associ-ated Mineralizations ISGAM II Salvador Brazil p313ndash314
Klein E L Vasquez M L Santos A and Rosa-CostaL T 1999 Geologia e controle estrutural das mineral-izaccedilotildees auriacuteferas na Folha Vila Riozinho e NW daFolha Rio Novo Proviacutencia Tapajoacutes [ext abs] in VISimpoacutesio de Geologia da Amazocircnia Manaus Brazil p128ndash131
Lamaratildeo C N DallrsquoAgnol R and Lafon J M 2001Geocronologia e geoquiacutemica das associaccedilotildees vulcacircni-cas e plutocircnicas da regiatildeo de Vila Riozinho ProviacutenciaAuriacutefera do Tapajoacutes [ext abs] in VII Simpoacutesio deGeologia da Amazocircnia Beleacutem Brazil (CD-ROM)
Nunes C M D Juliani C Correcirca-Silva R H Mon-teiro L V S Bettencourt J S Neumann R AlcoverNeto A and Rye R O 2001 Caracterizaccedilatildeo de umsistema epitermal high-sulfidation vulcacircnico pale-oproterozoacuteico da Proviacutencia Auriacutefera do Tapajoacutes Paraacute[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
558 KLEIN ET AL
Ricci P S F Vasquez M L Santos A Klein E LJorge Joatildeo X S and Martins R C 1999 SuiacuteteIntrusiva Creporizatildeo ndash Proviacutencia Tapajoacutes Proposta ecriteacuterios de definiccedilatildeo [ext abs] in VI Simpoacutesio deGeologia da Amazocircnia Manaus Brazil p 519ndash522
Robert F and Poulsen K H 2001 Vein formation anddeformation in greenstone gold deposits in RichardsJ P and Tosdal R M eds Structural controls on oregenesis Reviews in Economic Geology v 14 p 111ndash155
Robert F Poulsen K H and Dubeacute B 1997 Golddeposits and their geological classification in GubinsA G ed Proceedings of Exploration 97 TorontoCanada p 209ndash220
Ronchi L H DallrsquoAgnol R Araujo J C Ribeiro VLamaratildeo C N Borges R M K and Fuzikawa K2001 Fluidos relacionados agraves alteraccedilotildees hidrotermaisno depoacutesito de ouro do Granito Satildeo JorgendashPA [extabs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Rosa-Costa L T and Carvalho J M A 1999 Tipologiade mineralizaccedilotildees auriacuteferas da regiatildeo sul da ProviacutenciaTapajoacutesndashParaacute [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 176ndash179
Santos J O S Groves D I Hartmann L A MouraM A and McNaughton N J 2001 Gold deposits ofthe Tapajoacutes and Alta Floresta Domains Tapajoacutes-Parima orogenic belt Amazon Craton Brazil Minera-lium Deposita v 36 p 279ndash299
Santos J O S Hartmann L A Gaudette H E GrovesD I McNaughton N J and Fletcher I R 2000 Anew understanding of the provinces of the AmazonCraton based on integration of field mapping and U-Pband Sm-Nd geochronology Gondwana Research v 3p 453ndash488
Santos R A 1997 Contribuiccedilatildeo agrave anaacutelise estrutural dejazimentos auriacuteferos do rio Tapajoacutes SW do Paraacute e SEdo Amazonas Garimpos Abacaxis Espiacuterito SantoBom Jesus Goiano Fazenda Pison Ouro Mil SantaIsabel Majestade e Carneirinho Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 1999 Controle estrutural das mineralizaccedilotildees deouro da Proviacutencia Mineral do Tapajoacutes Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 2000 Formation of gold-quartz veins controlledby the strike-slip fault mega-system in Tapajoacutes Min-eral Province Amazon Brazil [abs] in XXXI Interna-tional Geological Congress Rio de Janeiro Brazil(CD-ROM)
Tassinari C C G 1996 O mapa geocronoloacutegico do Craacute-ton Amazocircnico no Brasil Revisatildeo dos dados isotoacutepi-cos Unpubl Tese de Livre Docecircncia Universidade deSatildeo Paulo 139 p
Tassinari C C G and Macambira M J B 1999 Geo-chronological provinces of the Amazonian Craton Epi-sodes v 22 p 174ndash182
Vasquez M L and Klein E L 2000 Projeto especialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Rio Novo (SB21-Z-C) Estado doParaacute escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Vasquez M L Klein E L Macambira M J B SantosA Bahia R B C Ricci P S F and QuadrosM L E S 2000 Geochronology of granitoids maficintrusions and mineralizations of the Tapajoacutes GoldProvincendashAmazonian CratonndashBrazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Vasquez M L Klein E L Quadros M L E S BahiaR B C Santos A Ricci P S F Sachett C RSilva C M G and Macambira M J B 1999 Mag-matismo Uatumatilde na Proviacutencia Tapajoacutesmdashnovos dadosgeocronoloacutegicos [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 471ndash474
Vasquez M L Klein E L and Ricci P S F 2001Granitoacuteides poacutes-colisionais da porccedilatildeo leste da Proviacuten-cia Tapajoacutes [ext abs] in VII Simpoacutesio de Geologia daAmazocircnia Beleacutem Brazil (CD-ROM)
Vearncombe J R 1993 Quartz vein morphology andimplications for formation depth and classification ofArchaean gold-vein deposits Ore Geology Reviews v8 p 407ndash424
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 547
and 2005 Ma (Santos et al 2000 2001) Thesemetamorphic sequences have been intruded bycalc-alkaline granitoids of the Creporizatildeo (199ndash196 Ga) (Ricci et al 1999 Vasquez et al 2000)Tropas (190 Ga) (Santos et al 2001) and Parauari(189ndash188 Ga) (Vasquez et al 1999 Santos et al2000) intrusive suites as well as by a series of gab-broic rocks at 187 Ga (Santos et al 2001) Sedi-mentary deposits showing intra-arc characteristicsformed at ~190ndash189 Ga (Santos et al 2001) Thisorogenic period was followed by widespread felsicplutonic and volcanic activity at 187 Ga (Almeidaet al 1999 Vasquez et al 1999 Santos et al2000 Lamaratildeo et al 2001 Klein et al in press)related to extensional tectonics
It is the consensus that the orogenic evolution ofthe province comprises the accretion of magmaticarcs and related sedimentary basins However thenumber of arcs that have accreted is still debatableSantos et al (2000 2001) envisioned the evolutionof the orogenic domain through the sequentialaccretion of four magmatic arcs dated at 202 Ga(Cuiuacute-Cuiuacute Complex plus Jacareacanga Group)196 Ga (Creporizatildeo Suite) 190 Ga (Tropas Suite)and 188 Ga (Parauari Suite) These accretionaryevents have been followed by post-collisional intra-cratonic (granitoid and mafic) magmatism and sedi-ment deposition between 1870 Ma and 1780 MaConversely Vasquez et al (2001) considered theCreporizatildeo granitoids as post-collisional granitoidsstill related to the development of the Cuiuacute-Cuiuacutearc instead of considering it to be a different arc(see discussion below)
Structural framework
Remote sensing imagery and geophysical evi-dence show that the main structural features of theTapajoacutes Province are major NNW-SSEndash to NW-SEndashstriking linear or sinuous continuous to discontin-uous lineaments extending for tens to a few hun-dreds of kilometers (Fig 2) Field evidenceindicates that they represent mainly subverticalsinistral strike-slip faults and brittle-ductile shearzones This strike-slip system has been interpretedas a progressive and episodic compressive eventwith the maximum compressive stress vector (s1)around the east-west direction as shown by geomet-ric relationships of major and minor subsidiarystructures (Santos 1999 2000 Klein andVasquez 2000) On a regional scale these struc-tures have controlled the ascent and emplace-ment of several generations of granitoids and
volcanic and mafic rocks as well as the establish-ment of sedimentary basins and have outlinedtheir present shape and geometry (Klein et al1997 Santos 1999 Almeida et al 2000 Kleinand Vasquez 2000) It is likely that at least someof these structures may have been reactivatedduring the tectonic evolution of the Tapajoacutes Prov-ince However the timing of these events is notwell constrained yet
The oldest (D1) structural record is found in thewest-central portion of Tapajoacutes Province It isdefined by the NE-SWndashtrending gneissic banding ofthe Cuiuacute-Cuiuacute Complex and the schistosity of thevolcano-sedimentary Jacareacanga Group (Almeidaet al 2001) produced by a compressive event andis well preserved in the gneisses of the study areaThis deformation is not seen in younger rocks lead-ing Santos et al (2001) to establish the time intervalof 2005ndash1974 Ma as the timing of D1 which mayhave been synchronous with the metamorphic peakSantos et al (2001) defined a second deformationalevent (D2) represented by a high-angle N10E-strik-ing sinistral strike-slip shear zone of ductile-brittlecharacter affecting especially the Tropas Suite inthe western-central portion of the province and onlylocally affecting the Creporizatildeo and Parauari suitesThey placed the timing of this event to between1894 and 1883 Ma Furthermore they suggestedthat the brittle deformation which is younger than1883 Ma and which affected the Creporizatildeo andParauari granitoids could have been produced dur-ing the shallow emplacement of the Maloquinhagranitoids
However this structural evolution does notexplain satisfactorily the brittle-ductile deformationimprinted on the granitoids of the Creporizatildeo Suite(1997ndash1957 Ma) that are older than the Tropas Suite(190 Ga) The Creporizatildeo granitoids show a mag-matic foliation subparallel to a subvertical tectonicfoliation that strikes NW-SE and is clearly relatedto a brittle-ductile strike-slip regime This event hasnot been detected either in the Tropas Suite asstated by Santos et al (2001) nor in younger rocks(Parauari and Maloquinha suites volcanic rocks)Furthermore Almeida et al (2000 2001) docu-mented the transposition of the gneissic banding ofthe Cuiuacute-Cuiuacute rocks by NW-SE strike-slip shearzones Still a whole-rock Rb-Sr isochron age of1965 plusmn 16 Ma was reported by Tassinari (1996) forgranitoids of the Creporizatildeo Suite This age is closeto the zircon ages (U-Pb Pb-evaporation) for thelate-stage granitoids of the Creporizatildeo Suite and
548 KLEIN ET AL
may indicate that the emplacement of the post-colli-sional plutons was broadly coeval with the regionalNW-SE deformational event (Ricci et al 1999Vasquez et al 2001)
Hence we postulate a reappraisal of the struc-tural evolution of the Tapajoacutes Province as followsAn early deformation stage (D1) is represented bythe compressive event that imparted the gneissicbanding of the Cuiuacute-Cuiuacute Complex and the schis-tosity of the Jacareacanga Group occurring proba-bly between 2005 and 1997 Ma D2 is representedby the NW-SEndashtrending strike-slip event thataffected the granitoids of the Creporizatildeo Suite andoverprinted the gneissic banding of the Cuiuacute-Cuiuacuterocks occurring at ~197ndash195 Ga D3 is related tothe NNE-SSW strike-slip ductile shear zones thataffected the Tropas Suite between 1894 and 1883Ma Younger structures may have been reactivatedandor generated during the emplacement of thewidespread Maloquinha granitoids and are relatedto extensional tectonics
Gold deposit models
Studies of individual deposits in the TapajoacutesGold Province have been focused on fluid-inclusionproperties andor alteration assemblages leading tothe proposition that the deposits fit epithermal tomesothermal models (Dreher et al 1998 Klein etal 2001 Nunes et al 2001 Ronchi et al 2001)Province-scale models have been developed byCoutinho et al (2000) Santos (2000) and Santos etal (2001) Santos (2000) presented a structuralmodel relating the formation of the gold-quartz veinsto the regional-scale strike-slip fault systemCoutinho et al (2000) classified the deposits of theTapajoacutes Province as mesozonalepizonal orogenicdeposits and suggested two phases of mineraliza-tion based on model ages of sulfide minerals at196 Ga and 188 Ga Both phases postdated theregional metamorphic peak and have been associ-ated with compressional to transpressional tectonicsat the convergent plate margin of the accretionaryorogen Lead and stable (O H) isotopes togetherwith fluid-inclusion data suggest deep sources forgold mineralization (magmatic to juvenile) withpossibly meteoric water added in some deposits atshallow crustal levels
Santos et al (2001) proposed two classes of golddepositsmdashorogenic and intrusion related Orogenicdeposits have been subdivided into (1) turbidite-hosted consisting of mesozonal quartz-pyrite vein-lets or disseminations in ductile structures cutting
the supracrustal rocks of the Jacareacanga Group(2) magmatic arc-hosted consisting of mesozonalquartz-pyrite-carbonate veins and disseminationshosted in ductile-brittle structures cutting thegneisses of the Cuiuacute-Cuiuacute Complex and the grani-toids of the Tropas Suite Intrusion-related depositshave been subdivided into (1) epizonal quartz-pyrite veins and pyrite disseminations emplaced inshallow extensional brittle structures (similar toKorean-type deposits) cutting K-rich granitoids ofthe Creporizatildeo Parauari and Maloquinha suitesfrequently associated with mafic dikes (2) epizonaldisseminations and stockworks with hydrothermalmagnetite hosted in mafic and sedimentary rocksand sharing some characteristics with porphyry-typedeposits Using Pb and Ar isotopes Santos et al(2001) determined the timing of the intrusion-related deposits as being around 186 Ga They havenot established the age of the orogenic deposits buthave suggested that it might be similar to the age ofthe intrusion-related deposits with mineralizationdiffering in style host rocks and depth of emplace-ment They argued that the orogenic deposits wouldbe related to the final stages of evolution of theParauari arc whereas the intrusion-related depositswould be related either to the Parauari arc or to post-collisional granitoids (Maloquinha Suite)
Epithermal deposits have been described byJacobi (1999) Correcirca-Silva et al (2001) Juliani(2001) and Nunes et al (2001) for the east-centralportion of the province The deposits are hosted byfelsic to intermediate volcanic rocks and associatedvolcaniclastic rocks and consist of both low-sulfida-tion (adularia-sericite) and high-sulfidation (quartz-alunite) types Indirect dating suggests that mineral-ization formed at ~188 Ga and d34S data indicateda magmatic-hydrothermal source for the mineral-izing fluids and 330ordmC to 140ordmC as the formationtemperatures (Juliani 2001 Nunes et al 2001)Dreher et al (1998) also considered the epither-mal model for the Joel and David deposits How-ever Correcirca-Silva et al (2001) questioned thisclassification and argued that the adulariapresent in the Davi and Joel deposits is hosted inmafic rocks and could be related to this maficmagmatism Also Santos et al (2001) argued thatthese two deposits lack many important featuresof classic epithermal deposits such as the rela-tionship with contemporaneous volcanic rocks(the deposits are hosted by gabbro and granitoidrespectively) the low silver and adularia con-
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 549
tents and the absence of native silver and silversulfosalts in the ore mineralogy
Gold Deposits in the Southern Tapajoacutes Province (STP)
More than 20 deposits and showings are distrib-uted in several gold camps along the STP (Fig 3)These mineralizations are discussed below in termsof host rocks wall rock alteration and structuralcontrol The classification of structural styles of theveins is based mainly on the concepts of Hodgson(1989) and Robert and Poulsen (2001) taking intoaccount the type of host structure and the internalstructure and textures of the veins The mainattributes are summarized in Table 1
Host rocksGneisses and orogenic granitoids are the main
hosts for gold deposits in the Tapajoacutes Gold Provinceand account for virtually all the host rocks in STP(Table 1) The gneisses belong to the Cuiuacute-CuiuacuteComplex They consist of gray orthogneisses oftonalitic and granodioritic composition bearingmicrogranular enclaves of diorites and quartz-dior-ites along with granitoids and rare migmatites andamphibolites Structurally the gneisses show a per-vasive ductile fabric striking NNE-SSW or NW-SE
and migmatitic features are subordinate Thegeochemical characteristics of trace elements(LILE HFSE REE) are compatible with those ofprimitive arc-related calc-alkaline granitoids(Vasquez et al 2001) They are dominantly metalu-minous with lenses of peraluminous to strongly per-aluminous leucogranitoids occurring subordinatelySantos et al (2000 2001) obtained zircon U-PbSHRIMP ages between 2033 Ma and 2005 Ma forthis complex
The hosting granitoids are related to the Crep-orizatildeo Intrusive Suite which holds irregular- to sig-moidal-shaped batholiths and stocks (Fig 2) ofhornblende- andor biotite-bearing granitoids andmetagranitoids of syenogranitic to tonalitic composi-tion The granitoids are either foliated or granoblas-tic and the latter show preserved primary featuressuch as euhedral phenocrysts of K-feldspar unde-formed microgranular enclaves and synplutonicdikes Very often they show an igneous bandingmarked by the orientation of the K-feldspar pheno-crysts that parallels the NW-SEndashtrending tectonicfoliation Field mineralogical and textural evi-dence indicates emplacement of the granitoids in acrustal level compatible with greenschist or up tomiddle-amphibolite metamorphic conditions (Ricciet al 1999) and the presence of enclaves ofgneisses from the Cuiuacute-Cuiuacute Complex is evidence of
FIG 3 Geological map of the Southern Tapajoacutes Province showing the location of the gold deposits addressed in thisstudy
550 KLEIN ET AL
TAB
LE 1
Sum
mar
y of
Attr
ibut
es o
f Gol
d D
epos
its o
f the
Sou
ther
n Ta
pajoacute
s Pr
ovin
ce1
No
Cam
p or
dep
osit
(n
umbe
r of
vei
ns)
Stru
ctur
al s
tyle
Inte
rnal
str
uctu
reH
ost r
ock
(s
trat
igra
phic
uni
t)G
angu
e m
iner
alog
yO
re m
iner
alog
yV
ein
orie
ntat
ion
(str
ike
dip)
Sele
cted
ref
eren
ces
1G
oian
o (2
)B
recc
iaC
atac
last
icF
olia
ted
gran
itoi
d (C
IS)
mus
pyN
50E
88S
E N
20W
88
NE
N0E
80E
Sant
os 1
997
2Su
daacuteri
o (4
)F
FV
(plusmn
maf
ic
dike
)M
assi
ve c
atac
last
icG
rani
toid
s (C
CC
)py
N40
-60E
70-
88SE
-N
WR
osa-
Cos
ta a
nd C
arva
lho
199
9
3C
oman
dant
e M
acha
do
(2)
FF
VM
assi
ve c
omb
Fol
iate
d gr
anod
iori
te
(CC
C)
mus
pyN
40E
70S
E a
nd
N50
W6
5SW
Ros
a-C
osta
and
Car
valh
o 1
999
4P
atin
has
Shea
r ve
inM
assi
ve s
hear
edG
rano
dior
ite
(CC
C)
eppy
cpy
N20
E6
8SE
Ros
a-C
osta
and
Car
valh
o 1
999
Kle
in e
t al
200
05
Pau
drsquoA
rco
(3)
FF
VV
einl
ets
sa
ccha
roid
alQ
uart
z-di
orit
ic g
neis
s (C
CC
) m
us k
f c
hl
epcp
y p
yN
30E
65S
EK
lein
et a
l i
n pr
ess
6C
oman
dant
e R
enan
(2)
Shea
r ve
inM
assi
veTo
nali
tic
gnei
ss (
CC
C)
chl
ep
pyN
0-30
E6
088S
EK
lein
et a
l i
n pr
ess
7Ta
uari
FF
VM
assi
veG
rani
toid
(C
IS)
chl
ep
N30
E8
5NW
Kle
in e
t al
in
pres
s8
Our
o M
ilB
recc
ia +
m
afic
dik
eN
etw
orks
Gra
nito
id (
CIS
) +
m
afic
dik
eN
70E
70N
WSa
ntos
199
7
9C
eacuteu A
zul
Bre
ccia
Com
b fi
ber
Gra
nodi
orit
e (C
IS)
qz k
f se
r ep
hem
N70
E8
8SE
Kle
in e
t al
in
pres
s10
Aacutegu
a L
impa
Bre
ccia
Gra
nodi
orit
e (C
IS)
N60
W7
0NE
Kle
in e
t al
in
pres
s11
Roq
ue S
ante
iro
(2)
FF
VM
assi
veTo
nali
tic
gnei
ss (
CC
C)
chl
pyN
45E
75N
WN
40W
88N
EK
lein
et a
l i
n pr
ess
12Ta
boca
lF
FV
Mas
sive
Mon
zogr
anit
e (C
IS)
N70
E8
0NW
Kle
in e
t al
in
pres
s13
Vie
tnam
Shea
r ve
inL
amin
ated
Mon
zogr
anit
e (C
IS)
ser
pyN
70E
75N
WK
lein
et a
l i
n pr
ess
14N
ovo
Vie
tnam
Shea
r ve
inM
assi
ve l
amin
ated
Mon
zogr
anit
e (C
IS)
ser
pyN
55E
80S
EK
lein
et a
l i
n pr
ess
15In
depe
ndecircn
cia
Stoc
kwor
kM
assi
ve v
uggy
Apl
itic
mon
zogr
anit
e (P
IS
CIS
) m
uspy
N45
-80E
10-
60SE
Kle
in e
t al
in
pres
s
16Satilde
o R
aim
undo
LA
RF
Mon
zogr
anit
e (C
IS)
epN
45-6
0E2
5-40
SER
osa-
Cos
ta a
nd C
arva
lho
199
917
Bom
Jes
usF
FV
Lam
inat
edG
rani
toid
(C
IS)
ser
kf
py c
py g
alN
90E
88S
Sant
os 1
997
18B
oa V
ista
Zeacute
Ped
roF
FV
Mon
zogr
anit
e (C
IS)
pyN
70E
80S
ER
osa-
Cos
ta a
nd C
arva
lho
199
918
Boa
Vis
taM
inei
ro-1
Shea
r ve
in +
br
ecci
aM
assi
ve l
amin
ated
Mon
zogr
anit
e (C
IS)
qz s
er c
arb
chl
py c
pyN
30E
88S
EV
asqu
ez a
nd K
lein
200
0
18B
oa V
ista
Min
eiro
-2F
FV
Mas
sive
Mon
zogr
anit
e (C
IS)
chl
ser
ep
pyN
20E
75S
EV
asqu
ez a
nd K
lein
200
018
Boa
Vis
taL
AR
FM
assi
ve s
acch
aroi
dal
Maf
ic v
olca
nic
and
schi
st (
)se
rpy
asp
yN
45-8
0W3
0-45
SWK
lein
et a
l i
n p
ress
Ros
a-C
osta
and
Car
valh
o 1
999
19P
lana
lto
FF
VM
assi
veG
rani
toid
(C
CC
)N
40E
75S
EK
lein
et a
l i
n pr
ess
20B
abil
ocircnia
FF
VM
assi
veM
onzo
gran
ite
(CIS
)se
rpy
N45
W4
5SW
Kle
in e
t al
in
pres
s21
Satildeo
Joseacute
FF
VM
assi
ve s
acch
aroi
dal
Mon
zogr
anit
e (C
IS)
epN
45W
63N
EK
lein
et a
l i
n pr
ess
1 Leg
end
FF
V =
fau
lt-f
ill
vein
CIS
= C
repo
rizatilde
o In
trus
ive
Suit
e C
CC
= C
uiuacute-
Cui
uacute C
ompl
ex P
IS =
Par
auar
i Int
rusi
ve S
uite
mus
= m
usco
vite
ser
= s
eric
ite
ep
= e
pido
te k
f = K
-fel
d-sp
ar c
hl =
chl
orit
e c
arb
= c
arbo
nate
qz
= q
uart
z p
y =
pyr
ite
cpy
= c
halc
opyr
ite
asp
y =
ars
enop
yrit
e g
al =
gal
ena
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 551
the intrusive character of the granitoids Whole-rockgeochemistry (Lamaratildeo et al 2001 Vasquez et al2001) has shown that the Creporizatildeo Suite repre-sents calc-alkaline metaluminous to peraluminousmedium- to high-K arc-related granitoids The REEpatterns show that they are more evolved than theCuiuacute-Cuiuacute granitoids and gneisses U-Pb and Pb-evaporation dating of zircon (Ricci et al 1999Vasquez et al 2000 Santos et al 2000 2001Lamaratildeo et al 2001) indicate crystallization agesbetween 1997 Ma and 1957 Ma This late timingwith respect to the Cuiuacute-Cuiuacute Complex along withthe geochemical characteristics the structural andmetamorphic differences the lack of volcano-sedi-mentary basins associated with the Creporizatildeo gran-itoids and their common association with regionalstrike-slip shear zones led Vasquez et al (2001) toconsider the Creporizatildeo Suite as representing apost-collisional magmatism still related to thedevelopment of the Cuiuacute-Cuiuacute magmatic arc andnot an individual arc (Creporizatildeo arc) as proposedby Santos et al (2001)
Ore mineralogy and wall-rock alteration
Many prospects are still undeveloped and work-ings are restricted to the oxidized (saprolite) zonewhere veins and structures are well preserved buthydrothermal alteration in the immediate host rockis overprinted by secondary processes Henceinformation in these cases is restricted to the veinassemblage and in a few cases to distal alterationwhich can be seen tens or a few hundreds of metersoff of the mineralized zone
Pyrite is the dominant sulfide mineral (Table 1)occurring in most of the deposits in general as dis-seminations filling fractures and cavities in thequartz veins in the contact between vein and hostrock or less commonly forming decimeter-wideaggregates (Fig 6) Chalcopyrite follows pyrite inimportance always occurring in association withpyrite whereas galena and arsenopyrite occur onlylocally
The gangue mineralogy shows little variationwith white mica being the main mineral (followingquartz) present in the quartz veins occurring how-ever in small amounts White mica is also wide-spread in the hydrothermally altered wall rocksoccurring in association with quartz minor amountsof chlorite and scarce carbonate K-feldspar andepidote
Structural controlInvestigation of mesoscopic and macroscopic
features of deposits of the STP showed that they arestrictly structurally controlled in all scalesRegional structures may have played importantroles acting as conduits for mineralizing fluids andcontrolling the distribution of the deposits The goldcamps are located close to or bounded by majorfirst-order faults and shear zones located in low-strain domains between them and rarely withinthese deformation zones (Figs 2 and 3) At campand deposit scales the orientation of the mineral-ized veins is controlled by the orientation andorgeometry of the hosting lower-order structures(Klein et al 1999 Santos 1999 2000)
Structural styles and internal structure
Fault-fill veins This type is by far the most com-mon structural style in STP and in the province as awhole (Klein et al 1999) The deposits consist of asingle quartz vein emplaced in subvertical struc-tures (Fig 4) These are mostly faults with subordi-
FIG 4 Photograph of the surface exposure of a fault-fillvein (outlined by the heavy lines) at Mineiro-2 The hydro-thermal envelope is outlined by the dashed line
552 KLEIN ET AL
nate narrow brittle-ductile shear zones Theirorientations are variable with concentrations ofveins along the N20degndash70degE and N40ndash50W direc-tions The veins are centimeter- to decimeter-thickand consist of milky quartz with minor (lt5) K-feldspar white mica chlorite and sulfide mineralsOccasionally thin extensionalndashoblique quartz toquartzo-feldspathic veinlets occur attached to themain quartz vein (Fig 5) The internal structure ofthe veins is dominantly formed by massive quartz(Fig 6) Laminated saccharoidal and open-spacefilling (comb) textures and hydrothermal brecciasare subordinate A few veins are positioned at thecontact between mafic dikes and the altered countryrock or even cut across the dikes suggesting inthese cases their late timing with respect to thedikes In one situation (Pau DrsquoArco) mineralizationlacks a major quartz vein (only a few discontinuousveinlets are present) and occurs as disseminationsin the hydrothermal zone that surrounds a subverti-cal strike-slip fault
Shear veins In greenstone-hosted deposits shearveins are usually described as fault-fill veinsbecause they occupy faults and the central parts ofshear zones (Hodgson 1989) and because it is con-sidered difficult to define if the veins formed as aresult of displacements along a shear fracture or asthe result of dilation of preexisting shear fractures orductile fabric (eg Robert and Poulsen 2001 and
references therein) In STP shear and fault-fill veinsshare a series of characteristics However in thispaper we prefer to classify them separately at leastfor descriptive purposes because shear veins differfrom fault-fill veins by the fact that they have beenemplaced in ductile-brittle structures (ComandanteRenan Novo Vietnam Fig 5) andor show effects ofductile deformation such as quartz grains withundulose extinction and deformation bands sur-rounded by small recrystallized subgrains (Patin-has) microscopic shear zones (Mineiro-1) andductile fabric either in the vein or in the immediatehost rock (Novo Vietnam) (Fig 5) The internalstructure is chiefly massive to laminated andsheared (Figs 6 and 7) Extensional features suchas breccias and en echelon sulfides (Fig 7) also arepresent
Low- (to moderate-) angle reverse-oblique faultsTwo examples have been observed At the Boa Vistagold field along with fault-fill and breccia veinspresent in several occurrences the main mineraliza-tion consists of a series of subparallel verticallystacked sigmoidal quartz veins (Fig 8A) separatedby hydrothermally altered and strongly foliated hostrock (schist) The veins show variable thicknessfrom a few centimeters up to one meter and strike toN45ordmndash80ordmW dipping 30ordm to 45ordm to the southwestInternally the milky veins show massive to saccha-roidal textures Small amounts of pyrite and minor
FIG 5 Sketch map (plan view) of the shear vein at Novo Vietnam The vein is surrounded by mylonitized wall rockand shows extensional veinlets attached on both sides The vein is massive to laminated and continuous but is formedby discontinuous veinlets (inset) between the two bends
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 553
arsenopyrite are disseminated throughout the veinsand altered wall rock Pyrite occurs filling smallfractures in quartz as well and sericite is presentboth in the vein and in the immediate wall rock
Given the weathered character of the terrainfresh rocks could not be observed in the mineralizedzone and the nature of the host rock could not beconfidently determined A few tens of meters off themineralized zone an undeformed porphyritic maficvolcanic rock crops out The region in turn is dom-inated by granitoids of the Creporizatildeo Suite that isthe host for all other occurrences in the same goldfield The hosting schist may derive from one ofthese two rock types by a combination of intense
deformation and high fluidrock ratios Alterna-tively it may represent a fragment of the metavol-cano-sedimentary sequence of the JacareacangaGroup which has not as yet been recognized in thisportion of the Tapajoacutes Province occurring as mega-xenoliths or roof pendants within the granitoids ofthe Creporizatildeo Suite
In the Satildeo Raimundo deposit mineralizationoccurs in narrow hydrothermal halos envelopinganastomosed shearfault planes in brittle-ductileshear zones (Fig 8B) The hosting shear zones strikeN45ordmndash60ordmE and dip 25ordmndash40ordm SE and the mineralizedzones are up to 2 meters thick (Rosa-Costa and Car-valho 1999) Quartz is generally absent and occurs
FIG 6 A Milky massive quartz with high pyrite contents at Patinhas B Sheared sulfide-poor quartz vein (Patinhas)C Quartz vein with sulfide minerals filling cavities (Novo Vietnam)
FIG 7 Vein structures at Mineiro-1 A Laminated quartz-pyrite veinlet (V) crosscutting the hydrothermally alteredhost rock Alteration is zoned and symmetric (arrows) B Milky massive quartz with extensional fracture filled by sulfideminerals with an en echelon distribution C Hydrothermal breccia formed by quartz (white) and hydrothermally alteredhost rock (grey)
554 KLEIN ET AL
only as small isolated and discontinuous veinletspositioned in the fault planes The host rock is amonzogranite of the Creporizatildeo Suite
Breccia veins Four main occurrences have beenrecorded forming tabular structures of less than 1 min thickness The breccia veins at Ceacuteu Azul andAacutegua Limpa consist of fragments of milky quartzwith angular to rounded shape ranging in size frommm to a few cm (Fig 9) set in a fine-grained red-dish to greenish hydrothermal matrix composed ofquartz feldspar and hematite along with fine-grained sericite and epidote Microscopically dif-ferent quartz fragments show textures such as comband rosettes indicating the shallow emplacement ofthese veins (Dowling and Morrison 1989 Vearn-combe 1993) At Goiano and Ouro Mil the brecciashave less matrix and the quartz fragments are moreangular than in the two other examples
Brecciation occurs also as a minor portion of ashear vein at the Mineiro-1 prospect in the BoaVista gold camp These breccias also differ from theformer by the fact that the angular quartz fragmentsare set in a matrix composed of altered wall rock(Fig 7C)
Stockworks This style has been identified at theIndependecircncia deposit It consists of multidirec-tional quartz veins a few centimeters thick envel-
oped by narrow halos of hydrothermal alterationThe veins are generally widely spaced occurring inan area of ~100 m times tens of meters Locally how-ever they are closely spaced with several individ-ual hydrothermal halos overlapping each otherforming larger areas of hydrothermally altered hostrock The quartz has a milky to smoky characterand shows cavities usually filled by sulfide miner-als Epidote and white mica are common gangueminerals In places large pockets of hydrothermalalteration lacking quartz veins are observed aswell Minor stockworks and networks (the veins as awhole show the same orientation of the veinbrec-cia) occur at Ouro Mil in both margins of the mainbreccia vein (Santos 1997)
Discussion and Concluding Remarks
Gold deposits in the Tapajoacutes Province are hostedin a variety of metamorphic and magmatic rocks InSouthern Tapajoacutes Province (STP) with one excep-tion only orthogneisses of the Cuiuacute-Cuiuacute Complexand orogenic granitoids of the Creporizatildeo Suite areknown hosts for gold Hosting granitoids are domi-nantly monzogranitic in composition whereas theorthogneisses show tonalitic and granodioritic com-positions
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 555
The deposits have been classified in a few struc-tural styles according to the hosting structurestructural regime in which they have been formedand internal structures and textures of the veinsAccordingly fault-fill and shear veins are the domi-nant style followed by subordinate occurrences ofveins hosted in low-angle reverse-oblique faultsbreccia veins and stockworks More than one stylemay occur in the same gold camp and even in a sin-gle deposit
Fault-fill and shear veins as well as brecciaveins form moderately to steeply dipping tabularbodies that seldom exceed one meter in thicknessand are hosted by strike-slip faults and shear zonesto which they are parallel The vein quartz is domi-nantly massive with laminated saccharoidal andcomb textures occurring subordinately Shearingand cataclasis of the veins is widespread suggest-ing along with other textural and structural evi-dence their positioning in active faults and shearzones or deformation after formation In most casesquartz white mica and pyrite compose the veinmineralogy and along with minor chlorite carbon-ate epidote and K-feldspar they overprint the pri-mary mineralogy of the hosting granitoids and theamphibolite-facies paragenesis of the hostinggneisses
The breccias have likely been produced duringfracture propagation by physical brecciation whichoccurs when the amount of stress exceeds the brittleresistance of the rock by mechanisms such as tec-tonic comminution andor fluid-assisted brecciation(Jeacutebrak 1997) Furthermore they indicate activeseismic slip during mineralization (Robert andPoulsen 2001)
The origin of the large stockwork at Independecircn-cia may be ascribed to hydraulic fracturing occur-ring over a cupola of a small aplitic granitoidrelated to or intruding the regional coarse-grainedmonzogranite of the Creporizatildeo Suite In the latterhypothesis it could be related either to a late-stagepluton of the Creporizatildeo Suite or to a younger grani-toid suite (Parauari) This definition requires geo-chronological support
Deposits and gold camps show strong structuralcontrol at all scales The hosting structures havebeen formed under a dominantly brittle-ductile tobrittle regime and consist of strike slip faults shearfractures intersection and bending of faults andlithological andor lithostratigraphic contactsExtensional fractures have not been characterizedas hosting structures because evidence of displace-
ment andor shearing is virtually always present inthe veins Extensional features are present howeveras en echelon arrays of sulfide minerals and as vein-lets attached to the main longitudinal fault veinsDeposits hosted in granitoids show a more brittlebehavior whereas those hosted in gneisses tend todisplay more ductile features This can result eitherfrom the depth of vein formation or from high fluidrock ratios even in shallow levels of the crust
Formation of deposits occurred in a range ofcrustal depth from mesozonal to epizonal condi-tions as indicated by the internal structure of thequartz veins and by the nature of the hosting struc-tures This is also supported by fluid inclusion stud-ies in a few deposits such as Guarim (Klein et al2001) and Patinhas (Klein et al 2000) both depos-its hosted in gneisses of the Cuiuacute-Cuiuacute ComplexFluid composition is nearly identical but P-T dataalong with textural and structural evidence suggestthat Guarim (outside STP) formed between 4 and 7km whereas Patinhas (within STP) formed at deeperlevels
Hence shear veins and fault-fill veins may beconsidered at least in part and from a structuralview as a single class of structural style with theirdifferences being ascribed to different depths ofemplacement and structural overprint It is not ourintention however to state that all of these veinsformed in a single gold-forming event The issue ofhow many mineralizing events have occurred in theTapajoacutes Province is still unresolved
Santos (1999 2000) studying 23 depositsthroughout the province (including three deposits inSTP) reported a set of characteristics similar tothose we have found in STP He concluded that alldeposits are related to a regional NW-SEndashtrendingstrike-slip fault system and that the orientation of
FIG 9 Breccia vein at Ceacuteu Azul
556 KLEIN ET AL
the lower-order hosting structures is compatiblewith Riedelrsquos system with the direction of the mainstress vector around the E-W direction Orientationsthat do not fit the model may be related to heteroge-neities in the local stress field However nothinghas been said about the timing of this strike-slipsystem in relation to the magmatic metamorphicand tectonic evolution of the province
Coutinho et al (2000) reported model ages thatcluster around 196 Ga and 188 Ga and main-tained that these two ages reflect two mineralizingepochs Santos et al (2001) invoked a single eventat 186 Ga However as stated by Santos et al(2001) the tectonic regime at 186 Ga is brittle Thismodel does not explain the ductile emplacementandor deformed mineralization hosted especially bythe Cuiuacute-Cuiuacute gneisses and by the metavolcano-sedimentary sequences Another (older) mineraliz-ing phase is thus required
We proposed early in this paper that the majorstrike-slip regime that affected the Creporizatildeo Suiteand older units likely occurred between 197 and195 Ga Mineralization hosted in the Cuiuacute-Cuiuacutegneisses (at least in STP) is post-tectonic and post-metamorphic with respect to the host rocks sincehosting structures clearly crosscut the metamorphicbanding and the hydrothermal mineralogy is retro-gressive in relation to the metamorphic paragenesisDeformation affecting the Creporizatildeo granitoids isbrittle-ductile to brittle whereas deformation affect-ing younger granitoids is brittle Thus it is valid toinfer as a working hypothesis that at least in partgold mineralization in STP formed during regionalstrike-slip deformation and emplacement of late-stage plutons of the Creporizatildeo Suite at ~197ndash195Ga a time interval that is in agreement with thatobtained by Coutinho et al (2000) The structuresmay have been reactivated during younger deforma-tional episode(s) and gold deposits may haveformed at this stage as well
The challenge is to decipher which depositsformed at each metallogenic epoch From a struc-tural point of view it is likely that the deposits inSouthern Tapajoacutes Province that have been emplacedat deeper levels of the crust and that show evidenceof plastic deformation (ie the shear veins and thedeposits hosted in low-angle reverse-oblique faultssee Table 1) formed in the older phase Fault-fillveins that occur in association with these deposits inthe same gold camp (eg Boa Vista) probablyformed in the same event The rest of the fault-fillveins (with textures and structures indicating
emplacement in shallow brittle structures associ-ated or not with mafic dikes and showing no associ-ation with shear veins in the same gold camp) aswell as the breccia veins and stockworks may haveformed either in the older or in the younger phaseWe do not have elements to define this Thisrequires much more isotopic data along with addi-tional fluid-inclusion and stable-isotope informationto constrain physico-chemical conditions of golddeposition as well as knowledge of the sources andnature of the mineralizing fluids and the absolutetiming of gold deposition
The attributes shown by the gold deposits in STP(namely the regional structural setting depositstyle vein textures and hydrothermal mineralogy)along with scarce fluid-inclusion data fit with boththe orogenic (magmatic arc-hosted) and intrusion-related models as proposed by Santos et al (2001)the latter sharing characteristics with Korean-typedeposits (Robert et al 1997) as well
Acknowledgments
Alfreu dos Santos (formerly of CPRM) partici-pated in the field work and supervised the TapajoacutesProject His help is acknowledged This is a contri-bution to the project PRONEX-CNPq-FADESP6621031998-0ndashprocess no 4200000
REFERENCES
Almeida M E Brito M F L Ferreira A L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaVila Mamatildee Anatilde (SB21-V-D) Estados do Paraacute e Ama-zonas escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Almeida M E Brito M F L and Macambira M J B1999 Caroccedilal Granite 207Pb206Pb evaporation age inpost-collisional granitoids of Tapajoacutes Gold ProvinceAmazonian region Brazil [abs] in II South AmericanSymposium on Isotope Geology Coacuterdoba ArgentinaActas p 3ndash6
Almeida M E Ferreira A L Brito M F L and Mon-teiro M A S 2001 Evoluccedilatildeo tectono-estrutural daProviacutencia Tapajoacutes com base na geologia das folhas VilaMamatildee Anatilde e Jacareacanga (1250000) regiatildeo limitedos estados do Amazonas e Paraacute in Reis N J andMonteiro M A S orgs Contribuiccedilotildees agrave Geologia daAmazocircnia v 2 Manaus Brazil SBG-NO p 57ndash112
Bahia R B C and Quadros M L E S 2000 Geologiae recursos minerais da Folha Caracol (SB21-X-C)
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 557
Estado do Paraacute Escala 1250000 Brasiacutelia BrazilCPRMGeological Survey of Brazil (CD-ROM)
Cassidy K F Groves D I and McNaughton N J 1998Late-Archean granitoid-hosted lode-gold depositsYilgarn Craton Western Australia Deposit character-istics crustal architecture and implications for oregenesis Ore Geology Reviews v 13 p 65ndash102
Correcirca-Silva R H Juliani C Bettencourt J S NunesC M D and Almeida T I R 2001 Caracterizaccedilatildeode um sistema epitermal low-sulfidation (ou adulaacuteria-sericita) hospedado em vulcacircnicas e vulcanoclaacutesticasdo Grupo Iriri na Proviacutencia auriacutefera do Tapajoacutes (PA)[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Coutinho M G N Santos J O S Fallick A E andLafon J M 2000 Orogenic gold deposits in TapajoacutesMineral Province Amazon Brazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Dowling K and Morrison G 1989 Application ofquartz textures to the classification of gold depositsusing North Queensland examples Economic GeologyMonograph v 6 p 342ndash355
Dreher A M Vlach S and Martini S L 1998 Adu-laria associated with epithermal gold veins in theTapajoacutes Mineral Province Paraacute State Northern BrazilRevista Brasileira de Geociecircncias v 28 p 397ndash404
Faraco M T L Carvalho J M A and Klein E L1997 Carta metalogeneacutetica da Proviacutencia Auriacutefera doTapajoacutes in Costa M L and Angeacutelica R S orgsContribuiccedilotildees agrave Geologia da Amazocircnia Beleacutem BrazilFINEPSBG-NO p 423ndash437
Ferreira A L Almeida M E Brito M F L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaJacareacanga (SB21-Y-B) Estados do Paraacute e Amazo-nas escala 1250000 Brasiacutelia Brazil CPRMGeolog-ical Survey of Brazil (CD-ROM)
Goldfarb R J Groves D I and Gardoll S 2001 Oro-genic gold and geologic time A global synthesis OreGeology Reviews v 18 p 1ndash75
Groves D I Goldfarb R J Gebre-Mariam M Hage-mann S and Robert F 1998 Orogenic gold depos-its A proposed classification in the context of theircrustal distribution and relationship to other golddeposit types Ore Geology Reviews v 13 p 7ndash27
Hodgson C J 1989 The structure of shear-related vein-type gold deposits A review Ore Geology Reviews v4 p 231ndash273
Jacobi P 1999 The discovery of epithermal Au-Cu-MoProterozoic deposits in the Tapajoacutes Province BrazilRevista Brasileira de Geociecircncias v 29 p 277ndash279
Jeacutebrak M 1997 Hydrothermal breccias in vein-type oredeposits A review of mechanisms morphology andsize distribution Ore Geology Reviews v 12 p 111ndash134
Juliani C 2001 Metalogecircnese do ouro e metais de baseassociadas com o vulcanismo-plutonismo da porccedilatildeo Wda Proviacutencia Auriacutefera do Tapajoacutes [ext abs] in VIISimpoacutesio de Geologia da Amazocircnia Beleacutem Brazil(CD-ROM)
Kerrich R and Cassidy K F 1994 Temporal relation-ships of lode gold mineralization to accretion magma-tism metamorphism and deformationmdashArchean topresent A review Ore Geology Reviews v 9 p 263ndash310
Klein E L Almeida M E Vasquez M L BahiaR B C Quadros M L E S and Ferreira A L inpress Geologia e recursos minerais da Proviacutencia Min-eral do Tapajoacutes Estados do Paraacute e Amazonas Escala1 500000 Brasiacutelia Brazil CPRMGeological Surveyof Brazil
Klein E L Rosa-Costa L T and Carvalho J M A2000 Fluid inclusion studies at the Patinhas gold-quartz mineralisation Tapajoacutes Gold Province Brazil[abs] in XXXI International Geological Congress Riode Janeiro Brazil (CD-ROM)
Klein E L Santos R A Fuzikawa K and AngeacutelicaR S 2001 Hydrothermal fluid evolution and struc-tural control of the brittle-style Guarim lode-gold min-eralisation Tapajoacutes Province Amazonian CratonBrazil Mineralium Deposita v 36 p 149ndash164
Klein E L and Vasquez M L 2000 Projeto EspecialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Vila Riozinho (SB21-Z-A) Estadodo Paraacute escala 1250000 Brasiacutelia Brazil CPRMGeological Survey of Brazil (CD-ROM)
Klein E L Vasquez M L Santos A and Martins RC 1997 Structural elements of the Maloquinha Intru-sive Suite in Tapajoacutes Mineral Province northern Bra-zil and the emplacement of the plutons [ext abs] inII International Symposium on Granites and Associ-ated Mineralizations ISGAM II Salvador Brazil p313ndash314
Klein E L Vasquez M L Santos A and Rosa-CostaL T 1999 Geologia e controle estrutural das mineral-izaccedilotildees auriacuteferas na Folha Vila Riozinho e NW daFolha Rio Novo Proviacutencia Tapajoacutes [ext abs] in VISimpoacutesio de Geologia da Amazocircnia Manaus Brazil p128ndash131
Lamaratildeo C N DallrsquoAgnol R and Lafon J M 2001Geocronologia e geoquiacutemica das associaccedilotildees vulcacircni-cas e plutocircnicas da regiatildeo de Vila Riozinho ProviacutenciaAuriacutefera do Tapajoacutes [ext abs] in VII Simpoacutesio deGeologia da Amazocircnia Beleacutem Brazil (CD-ROM)
Nunes C M D Juliani C Correcirca-Silva R H Mon-teiro L V S Bettencourt J S Neumann R AlcoverNeto A and Rye R O 2001 Caracterizaccedilatildeo de umsistema epitermal high-sulfidation vulcacircnico pale-oproterozoacuteico da Proviacutencia Auriacutefera do Tapajoacutes Paraacute[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
558 KLEIN ET AL
Ricci P S F Vasquez M L Santos A Klein E LJorge Joatildeo X S and Martins R C 1999 SuiacuteteIntrusiva Creporizatildeo ndash Proviacutencia Tapajoacutes Proposta ecriteacuterios de definiccedilatildeo [ext abs] in VI Simpoacutesio deGeologia da Amazocircnia Manaus Brazil p 519ndash522
Robert F and Poulsen K H 2001 Vein formation anddeformation in greenstone gold deposits in RichardsJ P and Tosdal R M eds Structural controls on oregenesis Reviews in Economic Geology v 14 p 111ndash155
Robert F Poulsen K H and Dubeacute B 1997 Golddeposits and their geological classification in GubinsA G ed Proceedings of Exploration 97 TorontoCanada p 209ndash220
Ronchi L H DallrsquoAgnol R Araujo J C Ribeiro VLamaratildeo C N Borges R M K and Fuzikawa K2001 Fluidos relacionados agraves alteraccedilotildees hidrotermaisno depoacutesito de ouro do Granito Satildeo JorgendashPA [extabs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Rosa-Costa L T and Carvalho J M A 1999 Tipologiade mineralizaccedilotildees auriacuteferas da regiatildeo sul da ProviacutenciaTapajoacutesndashParaacute [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 176ndash179
Santos J O S Groves D I Hartmann L A MouraM A and McNaughton N J 2001 Gold deposits ofthe Tapajoacutes and Alta Floresta Domains Tapajoacutes-Parima orogenic belt Amazon Craton Brazil Minera-lium Deposita v 36 p 279ndash299
Santos J O S Hartmann L A Gaudette H E GrovesD I McNaughton N J and Fletcher I R 2000 Anew understanding of the provinces of the AmazonCraton based on integration of field mapping and U-Pband Sm-Nd geochronology Gondwana Research v 3p 453ndash488
Santos R A 1997 Contribuiccedilatildeo agrave anaacutelise estrutural dejazimentos auriacuteferos do rio Tapajoacutes SW do Paraacute e SEdo Amazonas Garimpos Abacaxis Espiacuterito SantoBom Jesus Goiano Fazenda Pison Ouro Mil SantaIsabel Majestade e Carneirinho Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 1999 Controle estrutural das mineralizaccedilotildees deouro da Proviacutencia Mineral do Tapajoacutes Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 2000 Formation of gold-quartz veins controlledby the strike-slip fault mega-system in Tapajoacutes Min-eral Province Amazon Brazil [abs] in XXXI Interna-tional Geological Congress Rio de Janeiro Brazil(CD-ROM)
Tassinari C C G 1996 O mapa geocronoloacutegico do Craacute-ton Amazocircnico no Brasil Revisatildeo dos dados isotoacutepi-cos Unpubl Tese de Livre Docecircncia Universidade deSatildeo Paulo 139 p
Tassinari C C G and Macambira M J B 1999 Geo-chronological provinces of the Amazonian Craton Epi-sodes v 22 p 174ndash182
Vasquez M L and Klein E L 2000 Projeto especialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Rio Novo (SB21-Z-C) Estado doParaacute escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Vasquez M L Klein E L Macambira M J B SantosA Bahia R B C Ricci P S F and QuadrosM L E S 2000 Geochronology of granitoids maficintrusions and mineralizations of the Tapajoacutes GoldProvincendashAmazonian CratonndashBrazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Vasquez M L Klein E L Quadros M L E S BahiaR B C Santos A Ricci P S F Sachett C RSilva C M G and Macambira M J B 1999 Mag-matismo Uatumatilde na Proviacutencia Tapajoacutesmdashnovos dadosgeocronoloacutegicos [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 471ndash474
Vasquez M L Klein E L and Ricci P S F 2001Granitoacuteides poacutes-colisionais da porccedilatildeo leste da Proviacuten-cia Tapajoacutes [ext abs] in VII Simpoacutesio de Geologia daAmazocircnia Beleacutem Brazil (CD-ROM)
Vearncombe J R 1993 Quartz vein morphology andimplications for formation depth and classification ofArchaean gold-vein deposits Ore Geology Reviews v8 p 407ndash424
548 KLEIN ET AL
may indicate that the emplacement of the post-colli-sional plutons was broadly coeval with the regionalNW-SE deformational event (Ricci et al 1999Vasquez et al 2001)
Hence we postulate a reappraisal of the struc-tural evolution of the Tapajoacutes Province as followsAn early deformation stage (D1) is represented bythe compressive event that imparted the gneissicbanding of the Cuiuacute-Cuiuacute Complex and the schis-tosity of the Jacareacanga Group occurring proba-bly between 2005 and 1997 Ma D2 is representedby the NW-SEndashtrending strike-slip event thataffected the granitoids of the Creporizatildeo Suite andoverprinted the gneissic banding of the Cuiuacute-Cuiuacuterocks occurring at ~197ndash195 Ga D3 is related tothe NNE-SSW strike-slip ductile shear zones thataffected the Tropas Suite between 1894 and 1883Ma Younger structures may have been reactivatedandor generated during the emplacement of thewidespread Maloquinha granitoids and are relatedto extensional tectonics
Gold deposit models
Studies of individual deposits in the TapajoacutesGold Province have been focused on fluid-inclusionproperties andor alteration assemblages leading tothe proposition that the deposits fit epithermal tomesothermal models (Dreher et al 1998 Klein etal 2001 Nunes et al 2001 Ronchi et al 2001)Province-scale models have been developed byCoutinho et al (2000) Santos (2000) and Santos etal (2001) Santos (2000) presented a structuralmodel relating the formation of the gold-quartz veinsto the regional-scale strike-slip fault systemCoutinho et al (2000) classified the deposits of theTapajoacutes Province as mesozonalepizonal orogenicdeposits and suggested two phases of mineraliza-tion based on model ages of sulfide minerals at196 Ga and 188 Ga Both phases postdated theregional metamorphic peak and have been associ-ated with compressional to transpressional tectonicsat the convergent plate margin of the accretionaryorogen Lead and stable (O H) isotopes togetherwith fluid-inclusion data suggest deep sources forgold mineralization (magmatic to juvenile) withpossibly meteoric water added in some deposits atshallow crustal levels
Santos et al (2001) proposed two classes of golddepositsmdashorogenic and intrusion related Orogenicdeposits have been subdivided into (1) turbidite-hosted consisting of mesozonal quartz-pyrite vein-lets or disseminations in ductile structures cutting
the supracrustal rocks of the Jacareacanga Group(2) magmatic arc-hosted consisting of mesozonalquartz-pyrite-carbonate veins and disseminationshosted in ductile-brittle structures cutting thegneisses of the Cuiuacute-Cuiuacute Complex and the grani-toids of the Tropas Suite Intrusion-related depositshave been subdivided into (1) epizonal quartz-pyrite veins and pyrite disseminations emplaced inshallow extensional brittle structures (similar toKorean-type deposits) cutting K-rich granitoids ofthe Creporizatildeo Parauari and Maloquinha suitesfrequently associated with mafic dikes (2) epizonaldisseminations and stockworks with hydrothermalmagnetite hosted in mafic and sedimentary rocksand sharing some characteristics with porphyry-typedeposits Using Pb and Ar isotopes Santos et al(2001) determined the timing of the intrusion-related deposits as being around 186 Ga They havenot established the age of the orogenic deposits buthave suggested that it might be similar to the age ofthe intrusion-related deposits with mineralizationdiffering in style host rocks and depth of emplace-ment They argued that the orogenic deposits wouldbe related to the final stages of evolution of theParauari arc whereas the intrusion-related depositswould be related either to the Parauari arc or to post-collisional granitoids (Maloquinha Suite)
Epithermal deposits have been described byJacobi (1999) Correcirca-Silva et al (2001) Juliani(2001) and Nunes et al (2001) for the east-centralportion of the province The deposits are hosted byfelsic to intermediate volcanic rocks and associatedvolcaniclastic rocks and consist of both low-sulfida-tion (adularia-sericite) and high-sulfidation (quartz-alunite) types Indirect dating suggests that mineral-ization formed at ~188 Ga and d34S data indicateda magmatic-hydrothermal source for the mineral-izing fluids and 330ordmC to 140ordmC as the formationtemperatures (Juliani 2001 Nunes et al 2001)Dreher et al (1998) also considered the epither-mal model for the Joel and David deposits How-ever Correcirca-Silva et al (2001) questioned thisclassification and argued that the adulariapresent in the Davi and Joel deposits is hosted inmafic rocks and could be related to this maficmagmatism Also Santos et al (2001) argued thatthese two deposits lack many important featuresof classic epithermal deposits such as the rela-tionship with contemporaneous volcanic rocks(the deposits are hosted by gabbro and granitoidrespectively) the low silver and adularia con-
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 549
tents and the absence of native silver and silversulfosalts in the ore mineralogy
Gold Deposits in the Southern Tapajoacutes Province (STP)
More than 20 deposits and showings are distrib-uted in several gold camps along the STP (Fig 3)These mineralizations are discussed below in termsof host rocks wall rock alteration and structuralcontrol The classification of structural styles of theveins is based mainly on the concepts of Hodgson(1989) and Robert and Poulsen (2001) taking intoaccount the type of host structure and the internalstructure and textures of the veins The mainattributes are summarized in Table 1
Host rocksGneisses and orogenic granitoids are the main
hosts for gold deposits in the Tapajoacutes Gold Provinceand account for virtually all the host rocks in STP(Table 1) The gneisses belong to the Cuiuacute-CuiuacuteComplex They consist of gray orthogneisses oftonalitic and granodioritic composition bearingmicrogranular enclaves of diorites and quartz-dior-ites along with granitoids and rare migmatites andamphibolites Structurally the gneisses show a per-vasive ductile fabric striking NNE-SSW or NW-SE
and migmatitic features are subordinate Thegeochemical characteristics of trace elements(LILE HFSE REE) are compatible with those ofprimitive arc-related calc-alkaline granitoids(Vasquez et al 2001) They are dominantly metalu-minous with lenses of peraluminous to strongly per-aluminous leucogranitoids occurring subordinatelySantos et al (2000 2001) obtained zircon U-PbSHRIMP ages between 2033 Ma and 2005 Ma forthis complex
The hosting granitoids are related to the Crep-orizatildeo Intrusive Suite which holds irregular- to sig-moidal-shaped batholiths and stocks (Fig 2) ofhornblende- andor biotite-bearing granitoids andmetagranitoids of syenogranitic to tonalitic composi-tion The granitoids are either foliated or granoblas-tic and the latter show preserved primary featuressuch as euhedral phenocrysts of K-feldspar unde-formed microgranular enclaves and synplutonicdikes Very often they show an igneous bandingmarked by the orientation of the K-feldspar pheno-crysts that parallels the NW-SEndashtrending tectonicfoliation Field mineralogical and textural evi-dence indicates emplacement of the granitoids in acrustal level compatible with greenschist or up tomiddle-amphibolite metamorphic conditions (Ricciet al 1999) and the presence of enclaves ofgneisses from the Cuiuacute-Cuiuacute Complex is evidence of
FIG 3 Geological map of the Southern Tapajoacutes Province showing the location of the gold deposits addressed in thisstudy
550 KLEIN ET AL
TAB
LE 1
Sum
mar
y of
Attr
ibut
es o
f Gol
d D
epos
its o
f the
Sou
ther
n Ta
pajoacute
s Pr
ovin
ce1
No
Cam
p or
dep
osit
(n
umbe
r of
vei
ns)
Stru
ctur
al s
tyle
Inte
rnal
str
uctu
reH
ost r
ock
(s
trat
igra
phic
uni
t)G
angu
e m
iner
alog
yO
re m
iner
alog
yV
ein
orie
ntat
ion
(str
ike
dip)
Sele
cted
ref
eren
ces
1G
oian
o (2
)B
recc
iaC
atac
last
icF
olia
ted
gran
itoi
d (C
IS)
mus
pyN
50E
88S
E N
20W
88
NE
N0E
80E
Sant
os 1
997
2Su
daacuteri
o (4
)F
FV
(plusmn
maf
ic
dike
)M
assi
ve c
atac
last
icG
rani
toid
s (C
CC
)py
N40
-60E
70-
88SE
-N
WR
osa-
Cos
ta a
nd C
arva
lho
199
9
3C
oman
dant
e M
acha
do
(2)
FF
VM
assi
ve c
omb
Fol
iate
d gr
anod
iori
te
(CC
C)
mus
pyN
40E
70S
E a
nd
N50
W6
5SW
Ros
a-C
osta
and
Car
valh
o 1
999
4P
atin
has
Shea
r ve
inM
assi
ve s
hear
edG
rano
dior
ite
(CC
C)
eppy
cpy
N20
E6
8SE
Ros
a-C
osta
and
Car
valh
o 1
999
Kle
in e
t al
200
05
Pau
drsquoA
rco
(3)
FF
VV
einl
ets
sa
ccha
roid
alQ
uart
z-di
orit
ic g
neis
s (C
CC
) m
us k
f c
hl
epcp
y p
yN
30E
65S
EK
lein
et a
l i
n pr
ess
6C
oman
dant
e R
enan
(2)
Shea
r ve
inM
assi
veTo
nali
tic
gnei
ss (
CC
C)
chl
ep
pyN
0-30
E6
088S
EK
lein
et a
l i
n pr
ess
7Ta
uari
FF
VM
assi
veG
rani
toid
(C
IS)
chl
ep
N30
E8
5NW
Kle
in e
t al
in
pres
s8
Our
o M
ilB
recc
ia +
m
afic
dik
eN
etw
orks
Gra
nito
id (
CIS
) +
m
afic
dik
eN
70E
70N
WSa
ntos
199
7
9C
eacuteu A
zul
Bre
ccia
Com
b fi
ber
Gra
nodi
orit
e (C
IS)
qz k
f se
r ep
hem
N70
E8
8SE
Kle
in e
t al
in
pres
s10
Aacutegu
a L
impa
Bre
ccia
Gra
nodi
orit
e (C
IS)
N60
W7
0NE
Kle
in e
t al
in
pres
s11
Roq
ue S
ante
iro
(2)
FF
VM
assi
veTo
nali
tic
gnei
ss (
CC
C)
chl
pyN
45E
75N
WN
40W
88N
EK
lein
et a
l i
n pr
ess
12Ta
boca
lF
FV
Mas
sive
Mon
zogr
anit
e (C
IS)
N70
E8
0NW
Kle
in e
t al
in
pres
s13
Vie
tnam
Shea
r ve
inL
amin
ated
Mon
zogr
anit
e (C
IS)
ser
pyN
70E
75N
WK
lein
et a
l i
n pr
ess
14N
ovo
Vie
tnam
Shea
r ve
inM
assi
ve l
amin
ated
Mon
zogr
anit
e (C
IS)
ser
pyN
55E
80S
EK
lein
et a
l i
n pr
ess
15In
depe
ndecircn
cia
Stoc
kwor
kM
assi
ve v
uggy
Apl
itic
mon
zogr
anit
e (P
IS
CIS
) m
uspy
N45
-80E
10-
60SE
Kle
in e
t al
in
pres
s
16Satilde
o R
aim
undo
LA
RF
Mon
zogr
anit
e (C
IS)
epN
45-6
0E2
5-40
SER
osa-
Cos
ta a
nd C
arva
lho
199
917
Bom
Jes
usF
FV
Lam
inat
edG
rani
toid
(C
IS)
ser
kf
py c
py g
alN
90E
88S
Sant
os 1
997
18B
oa V
ista
Zeacute
Ped
roF
FV
Mon
zogr
anit
e (C
IS)
pyN
70E
80S
ER
osa-
Cos
ta a
nd C
arva
lho
199
918
Boa
Vis
taM
inei
ro-1
Shea
r ve
in +
br
ecci
aM
assi
ve l
amin
ated
Mon
zogr
anit
e (C
IS)
qz s
er c
arb
chl
py c
pyN
30E
88S
EV
asqu
ez a
nd K
lein
200
0
18B
oa V
ista
Min
eiro
-2F
FV
Mas
sive
Mon
zogr
anit
e (C
IS)
chl
ser
ep
pyN
20E
75S
EV
asqu
ez a
nd K
lein
200
018
Boa
Vis
taL
AR
FM
assi
ve s
acch
aroi
dal
Maf
ic v
olca
nic
and
schi
st (
)se
rpy
asp
yN
45-8
0W3
0-45
SWK
lein
et a
l i
n p
ress
Ros
a-C
osta
and
Car
valh
o 1
999
19P
lana
lto
FF
VM
assi
veG
rani
toid
(C
CC
)N
40E
75S
EK
lein
et a
l i
n pr
ess
20B
abil
ocircnia
FF
VM
assi
veM
onzo
gran
ite
(CIS
)se
rpy
N45
W4
5SW
Kle
in e
t al
in
pres
s21
Satildeo
Joseacute
FF
VM
assi
ve s
acch
aroi
dal
Mon
zogr
anit
e (C
IS)
epN
45W
63N
EK
lein
et a
l i
n pr
ess
1 Leg
end
FF
V =
fau
lt-f
ill
vein
CIS
= C
repo
rizatilde
o In
trus
ive
Suit
e C
CC
= C
uiuacute-
Cui
uacute C
ompl
ex P
IS =
Par
auar
i Int
rusi
ve S
uite
mus
= m
usco
vite
ser
= s
eric
ite
ep
= e
pido
te k
f = K
-fel
d-sp
ar c
hl =
chl
orit
e c
arb
= c
arbo
nate
qz
= q
uart
z p
y =
pyr
ite
cpy
= c
halc
opyr
ite
asp
y =
ars
enop
yrit
e g
al =
gal
ena
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 551
the intrusive character of the granitoids Whole-rockgeochemistry (Lamaratildeo et al 2001 Vasquez et al2001) has shown that the Creporizatildeo Suite repre-sents calc-alkaline metaluminous to peraluminousmedium- to high-K arc-related granitoids The REEpatterns show that they are more evolved than theCuiuacute-Cuiuacute granitoids and gneisses U-Pb and Pb-evaporation dating of zircon (Ricci et al 1999Vasquez et al 2000 Santos et al 2000 2001Lamaratildeo et al 2001) indicate crystallization agesbetween 1997 Ma and 1957 Ma This late timingwith respect to the Cuiuacute-Cuiuacute Complex along withthe geochemical characteristics the structural andmetamorphic differences the lack of volcano-sedi-mentary basins associated with the Creporizatildeo gran-itoids and their common association with regionalstrike-slip shear zones led Vasquez et al (2001) toconsider the Creporizatildeo Suite as representing apost-collisional magmatism still related to thedevelopment of the Cuiuacute-Cuiuacute magmatic arc andnot an individual arc (Creporizatildeo arc) as proposedby Santos et al (2001)
Ore mineralogy and wall-rock alteration
Many prospects are still undeveloped and work-ings are restricted to the oxidized (saprolite) zonewhere veins and structures are well preserved buthydrothermal alteration in the immediate host rockis overprinted by secondary processes Henceinformation in these cases is restricted to the veinassemblage and in a few cases to distal alterationwhich can be seen tens or a few hundreds of metersoff of the mineralized zone
Pyrite is the dominant sulfide mineral (Table 1)occurring in most of the deposits in general as dis-seminations filling fractures and cavities in thequartz veins in the contact between vein and hostrock or less commonly forming decimeter-wideaggregates (Fig 6) Chalcopyrite follows pyrite inimportance always occurring in association withpyrite whereas galena and arsenopyrite occur onlylocally
The gangue mineralogy shows little variationwith white mica being the main mineral (followingquartz) present in the quartz veins occurring how-ever in small amounts White mica is also wide-spread in the hydrothermally altered wall rocksoccurring in association with quartz minor amountsof chlorite and scarce carbonate K-feldspar andepidote
Structural controlInvestigation of mesoscopic and macroscopic
features of deposits of the STP showed that they arestrictly structurally controlled in all scalesRegional structures may have played importantroles acting as conduits for mineralizing fluids andcontrolling the distribution of the deposits The goldcamps are located close to or bounded by majorfirst-order faults and shear zones located in low-strain domains between them and rarely withinthese deformation zones (Figs 2 and 3) At campand deposit scales the orientation of the mineral-ized veins is controlled by the orientation andorgeometry of the hosting lower-order structures(Klein et al 1999 Santos 1999 2000)
Structural styles and internal structure
Fault-fill veins This type is by far the most com-mon structural style in STP and in the province as awhole (Klein et al 1999) The deposits consist of asingle quartz vein emplaced in subvertical struc-tures (Fig 4) These are mostly faults with subordi-
FIG 4 Photograph of the surface exposure of a fault-fillvein (outlined by the heavy lines) at Mineiro-2 The hydro-thermal envelope is outlined by the dashed line
552 KLEIN ET AL
nate narrow brittle-ductile shear zones Theirorientations are variable with concentrations ofveins along the N20degndash70degE and N40ndash50W direc-tions The veins are centimeter- to decimeter-thickand consist of milky quartz with minor (lt5) K-feldspar white mica chlorite and sulfide mineralsOccasionally thin extensionalndashoblique quartz toquartzo-feldspathic veinlets occur attached to themain quartz vein (Fig 5) The internal structure ofthe veins is dominantly formed by massive quartz(Fig 6) Laminated saccharoidal and open-spacefilling (comb) textures and hydrothermal brecciasare subordinate A few veins are positioned at thecontact between mafic dikes and the altered countryrock or even cut across the dikes suggesting inthese cases their late timing with respect to thedikes In one situation (Pau DrsquoArco) mineralizationlacks a major quartz vein (only a few discontinuousveinlets are present) and occurs as disseminationsin the hydrothermal zone that surrounds a subverti-cal strike-slip fault
Shear veins In greenstone-hosted deposits shearveins are usually described as fault-fill veinsbecause they occupy faults and the central parts ofshear zones (Hodgson 1989) and because it is con-sidered difficult to define if the veins formed as aresult of displacements along a shear fracture or asthe result of dilation of preexisting shear fractures orductile fabric (eg Robert and Poulsen 2001 and
references therein) In STP shear and fault-fill veinsshare a series of characteristics However in thispaper we prefer to classify them separately at leastfor descriptive purposes because shear veins differfrom fault-fill veins by the fact that they have beenemplaced in ductile-brittle structures (ComandanteRenan Novo Vietnam Fig 5) andor show effects ofductile deformation such as quartz grains withundulose extinction and deformation bands sur-rounded by small recrystallized subgrains (Patin-has) microscopic shear zones (Mineiro-1) andductile fabric either in the vein or in the immediatehost rock (Novo Vietnam) (Fig 5) The internalstructure is chiefly massive to laminated andsheared (Figs 6 and 7) Extensional features suchas breccias and en echelon sulfides (Fig 7) also arepresent
Low- (to moderate-) angle reverse-oblique faultsTwo examples have been observed At the Boa Vistagold field along with fault-fill and breccia veinspresent in several occurrences the main mineraliza-tion consists of a series of subparallel verticallystacked sigmoidal quartz veins (Fig 8A) separatedby hydrothermally altered and strongly foliated hostrock (schist) The veins show variable thicknessfrom a few centimeters up to one meter and strike toN45ordmndash80ordmW dipping 30ordm to 45ordm to the southwestInternally the milky veins show massive to saccha-roidal textures Small amounts of pyrite and minor
FIG 5 Sketch map (plan view) of the shear vein at Novo Vietnam The vein is surrounded by mylonitized wall rockand shows extensional veinlets attached on both sides The vein is massive to laminated and continuous but is formedby discontinuous veinlets (inset) between the two bends
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 553
arsenopyrite are disseminated throughout the veinsand altered wall rock Pyrite occurs filling smallfractures in quartz as well and sericite is presentboth in the vein and in the immediate wall rock
Given the weathered character of the terrainfresh rocks could not be observed in the mineralizedzone and the nature of the host rock could not beconfidently determined A few tens of meters off themineralized zone an undeformed porphyritic maficvolcanic rock crops out The region in turn is dom-inated by granitoids of the Creporizatildeo Suite that isthe host for all other occurrences in the same goldfield The hosting schist may derive from one ofthese two rock types by a combination of intense
deformation and high fluidrock ratios Alterna-tively it may represent a fragment of the metavol-cano-sedimentary sequence of the JacareacangaGroup which has not as yet been recognized in thisportion of the Tapajoacutes Province occurring as mega-xenoliths or roof pendants within the granitoids ofthe Creporizatildeo Suite
In the Satildeo Raimundo deposit mineralizationoccurs in narrow hydrothermal halos envelopinganastomosed shearfault planes in brittle-ductileshear zones (Fig 8B) The hosting shear zones strikeN45ordmndash60ordmE and dip 25ordmndash40ordm SE and the mineralizedzones are up to 2 meters thick (Rosa-Costa and Car-valho 1999) Quartz is generally absent and occurs
FIG 6 A Milky massive quartz with high pyrite contents at Patinhas B Sheared sulfide-poor quartz vein (Patinhas)C Quartz vein with sulfide minerals filling cavities (Novo Vietnam)
FIG 7 Vein structures at Mineiro-1 A Laminated quartz-pyrite veinlet (V) crosscutting the hydrothermally alteredhost rock Alteration is zoned and symmetric (arrows) B Milky massive quartz with extensional fracture filled by sulfideminerals with an en echelon distribution C Hydrothermal breccia formed by quartz (white) and hydrothermally alteredhost rock (grey)
554 KLEIN ET AL
only as small isolated and discontinuous veinletspositioned in the fault planes The host rock is amonzogranite of the Creporizatildeo Suite
Breccia veins Four main occurrences have beenrecorded forming tabular structures of less than 1 min thickness The breccia veins at Ceacuteu Azul andAacutegua Limpa consist of fragments of milky quartzwith angular to rounded shape ranging in size frommm to a few cm (Fig 9) set in a fine-grained red-dish to greenish hydrothermal matrix composed ofquartz feldspar and hematite along with fine-grained sericite and epidote Microscopically dif-ferent quartz fragments show textures such as comband rosettes indicating the shallow emplacement ofthese veins (Dowling and Morrison 1989 Vearn-combe 1993) At Goiano and Ouro Mil the brecciashave less matrix and the quartz fragments are moreangular than in the two other examples
Brecciation occurs also as a minor portion of ashear vein at the Mineiro-1 prospect in the BoaVista gold camp These breccias also differ from theformer by the fact that the angular quartz fragmentsare set in a matrix composed of altered wall rock(Fig 7C)
Stockworks This style has been identified at theIndependecircncia deposit It consists of multidirec-tional quartz veins a few centimeters thick envel-
oped by narrow halos of hydrothermal alterationThe veins are generally widely spaced occurring inan area of ~100 m times tens of meters Locally how-ever they are closely spaced with several individ-ual hydrothermal halos overlapping each otherforming larger areas of hydrothermally altered hostrock The quartz has a milky to smoky characterand shows cavities usually filled by sulfide miner-als Epidote and white mica are common gangueminerals In places large pockets of hydrothermalalteration lacking quartz veins are observed aswell Minor stockworks and networks (the veins as awhole show the same orientation of the veinbrec-cia) occur at Ouro Mil in both margins of the mainbreccia vein (Santos 1997)
Discussion and Concluding Remarks
Gold deposits in the Tapajoacutes Province are hostedin a variety of metamorphic and magmatic rocks InSouthern Tapajoacutes Province (STP) with one excep-tion only orthogneisses of the Cuiuacute-Cuiuacute Complexand orogenic granitoids of the Creporizatildeo Suite areknown hosts for gold Hosting granitoids are domi-nantly monzogranitic in composition whereas theorthogneisses show tonalitic and granodioritic com-positions
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 555
The deposits have been classified in a few struc-tural styles according to the hosting structurestructural regime in which they have been formedand internal structures and textures of the veinsAccordingly fault-fill and shear veins are the domi-nant style followed by subordinate occurrences ofveins hosted in low-angle reverse-oblique faultsbreccia veins and stockworks More than one stylemay occur in the same gold camp and even in a sin-gle deposit
Fault-fill and shear veins as well as brecciaveins form moderately to steeply dipping tabularbodies that seldom exceed one meter in thicknessand are hosted by strike-slip faults and shear zonesto which they are parallel The vein quartz is domi-nantly massive with laminated saccharoidal andcomb textures occurring subordinately Shearingand cataclasis of the veins is widespread suggest-ing along with other textural and structural evi-dence their positioning in active faults and shearzones or deformation after formation In most casesquartz white mica and pyrite compose the veinmineralogy and along with minor chlorite carbon-ate epidote and K-feldspar they overprint the pri-mary mineralogy of the hosting granitoids and theamphibolite-facies paragenesis of the hostinggneisses
The breccias have likely been produced duringfracture propagation by physical brecciation whichoccurs when the amount of stress exceeds the brittleresistance of the rock by mechanisms such as tec-tonic comminution andor fluid-assisted brecciation(Jeacutebrak 1997) Furthermore they indicate activeseismic slip during mineralization (Robert andPoulsen 2001)
The origin of the large stockwork at Independecircn-cia may be ascribed to hydraulic fracturing occur-ring over a cupola of a small aplitic granitoidrelated to or intruding the regional coarse-grainedmonzogranite of the Creporizatildeo Suite In the latterhypothesis it could be related either to a late-stagepluton of the Creporizatildeo Suite or to a younger grani-toid suite (Parauari) This definition requires geo-chronological support
Deposits and gold camps show strong structuralcontrol at all scales The hosting structures havebeen formed under a dominantly brittle-ductile tobrittle regime and consist of strike slip faults shearfractures intersection and bending of faults andlithological andor lithostratigraphic contactsExtensional fractures have not been characterizedas hosting structures because evidence of displace-
ment andor shearing is virtually always present inthe veins Extensional features are present howeveras en echelon arrays of sulfide minerals and as vein-lets attached to the main longitudinal fault veinsDeposits hosted in granitoids show a more brittlebehavior whereas those hosted in gneisses tend todisplay more ductile features This can result eitherfrom the depth of vein formation or from high fluidrock ratios even in shallow levels of the crust
Formation of deposits occurred in a range ofcrustal depth from mesozonal to epizonal condi-tions as indicated by the internal structure of thequartz veins and by the nature of the hosting struc-tures This is also supported by fluid inclusion stud-ies in a few deposits such as Guarim (Klein et al2001) and Patinhas (Klein et al 2000) both depos-its hosted in gneisses of the Cuiuacute-Cuiuacute ComplexFluid composition is nearly identical but P-T dataalong with textural and structural evidence suggestthat Guarim (outside STP) formed between 4 and 7km whereas Patinhas (within STP) formed at deeperlevels
Hence shear veins and fault-fill veins may beconsidered at least in part and from a structuralview as a single class of structural style with theirdifferences being ascribed to different depths ofemplacement and structural overprint It is not ourintention however to state that all of these veinsformed in a single gold-forming event The issue ofhow many mineralizing events have occurred in theTapajoacutes Province is still unresolved
Santos (1999 2000) studying 23 depositsthroughout the province (including three deposits inSTP) reported a set of characteristics similar tothose we have found in STP He concluded that alldeposits are related to a regional NW-SEndashtrendingstrike-slip fault system and that the orientation of
FIG 9 Breccia vein at Ceacuteu Azul
556 KLEIN ET AL
the lower-order hosting structures is compatiblewith Riedelrsquos system with the direction of the mainstress vector around the E-W direction Orientationsthat do not fit the model may be related to heteroge-neities in the local stress field However nothinghas been said about the timing of this strike-slipsystem in relation to the magmatic metamorphicand tectonic evolution of the province
Coutinho et al (2000) reported model ages thatcluster around 196 Ga and 188 Ga and main-tained that these two ages reflect two mineralizingepochs Santos et al (2001) invoked a single eventat 186 Ga However as stated by Santos et al(2001) the tectonic regime at 186 Ga is brittle Thismodel does not explain the ductile emplacementandor deformed mineralization hosted especially bythe Cuiuacute-Cuiuacute gneisses and by the metavolcano-sedimentary sequences Another (older) mineraliz-ing phase is thus required
We proposed early in this paper that the majorstrike-slip regime that affected the Creporizatildeo Suiteand older units likely occurred between 197 and195 Ga Mineralization hosted in the Cuiuacute-Cuiuacutegneisses (at least in STP) is post-tectonic and post-metamorphic with respect to the host rocks sincehosting structures clearly crosscut the metamorphicbanding and the hydrothermal mineralogy is retro-gressive in relation to the metamorphic paragenesisDeformation affecting the Creporizatildeo granitoids isbrittle-ductile to brittle whereas deformation affect-ing younger granitoids is brittle Thus it is valid toinfer as a working hypothesis that at least in partgold mineralization in STP formed during regionalstrike-slip deformation and emplacement of late-stage plutons of the Creporizatildeo Suite at ~197ndash195Ga a time interval that is in agreement with thatobtained by Coutinho et al (2000) The structuresmay have been reactivated during younger deforma-tional episode(s) and gold deposits may haveformed at this stage as well
The challenge is to decipher which depositsformed at each metallogenic epoch From a struc-tural point of view it is likely that the deposits inSouthern Tapajoacutes Province that have been emplacedat deeper levels of the crust and that show evidenceof plastic deformation (ie the shear veins and thedeposits hosted in low-angle reverse-oblique faultssee Table 1) formed in the older phase Fault-fillveins that occur in association with these deposits inthe same gold camp (eg Boa Vista) probablyformed in the same event The rest of the fault-fillveins (with textures and structures indicating
emplacement in shallow brittle structures associ-ated or not with mafic dikes and showing no associ-ation with shear veins in the same gold camp) aswell as the breccia veins and stockworks may haveformed either in the older or in the younger phaseWe do not have elements to define this Thisrequires much more isotopic data along with addi-tional fluid-inclusion and stable-isotope informationto constrain physico-chemical conditions of golddeposition as well as knowledge of the sources andnature of the mineralizing fluids and the absolutetiming of gold deposition
The attributes shown by the gold deposits in STP(namely the regional structural setting depositstyle vein textures and hydrothermal mineralogy)along with scarce fluid-inclusion data fit with boththe orogenic (magmatic arc-hosted) and intrusion-related models as proposed by Santos et al (2001)the latter sharing characteristics with Korean-typedeposits (Robert et al 1997) as well
Acknowledgments
Alfreu dos Santos (formerly of CPRM) partici-pated in the field work and supervised the TapajoacutesProject His help is acknowledged This is a contri-bution to the project PRONEX-CNPq-FADESP6621031998-0ndashprocess no 4200000
REFERENCES
Almeida M E Brito M F L Ferreira A L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaVila Mamatildee Anatilde (SB21-V-D) Estados do Paraacute e Ama-zonas escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Almeida M E Brito M F L and Macambira M J B1999 Caroccedilal Granite 207Pb206Pb evaporation age inpost-collisional granitoids of Tapajoacutes Gold ProvinceAmazonian region Brazil [abs] in II South AmericanSymposium on Isotope Geology Coacuterdoba ArgentinaActas p 3ndash6
Almeida M E Ferreira A L Brito M F L and Mon-teiro M A S 2001 Evoluccedilatildeo tectono-estrutural daProviacutencia Tapajoacutes com base na geologia das folhas VilaMamatildee Anatilde e Jacareacanga (1250000) regiatildeo limitedos estados do Amazonas e Paraacute in Reis N J andMonteiro M A S orgs Contribuiccedilotildees agrave Geologia daAmazocircnia v 2 Manaus Brazil SBG-NO p 57ndash112
Bahia R B C and Quadros M L E S 2000 Geologiae recursos minerais da Folha Caracol (SB21-X-C)
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 557
Estado do Paraacute Escala 1250000 Brasiacutelia BrazilCPRMGeological Survey of Brazil (CD-ROM)
Cassidy K F Groves D I and McNaughton N J 1998Late-Archean granitoid-hosted lode-gold depositsYilgarn Craton Western Australia Deposit character-istics crustal architecture and implications for oregenesis Ore Geology Reviews v 13 p 65ndash102
Correcirca-Silva R H Juliani C Bettencourt J S NunesC M D and Almeida T I R 2001 Caracterizaccedilatildeode um sistema epitermal low-sulfidation (ou adulaacuteria-sericita) hospedado em vulcacircnicas e vulcanoclaacutesticasdo Grupo Iriri na Proviacutencia auriacutefera do Tapajoacutes (PA)[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Coutinho M G N Santos J O S Fallick A E andLafon J M 2000 Orogenic gold deposits in TapajoacutesMineral Province Amazon Brazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Dowling K and Morrison G 1989 Application ofquartz textures to the classification of gold depositsusing North Queensland examples Economic GeologyMonograph v 6 p 342ndash355
Dreher A M Vlach S and Martini S L 1998 Adu-laria associated with epithermal gold veins in theTapajoacutes Mineral Province Paraacute State Northern BrazilRevista Brasileira de Geociecircncias v 28 p 397ndash404
Faraco M T L Carvalho J M A and Klein E L1997 Carta metalogeneacutetica da Proviacutencia Auriacutefera doTapajoacutes in Costa M L and Angeacutelica R S orgsContribuiccedilotildees agrave Geologia da Amazocircnia Beleacutem BrazilFINEPSBG-NO p 423ndash437
Ferreira A L Almeida M E Brito M F L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaJacareacanga (SB21-Y-B) Estados do Paraacute e Amazo-nas escala 1250000 Brasiacutelia Brazil CPRMGeolog-ical Survey of Brazil (CD-ROM)
Goldfarb R J Groves D I and Gardoll S 2001 Oro-genic gold and geologic time A global synthesis OreGeology Reviews v 18 p 1ndash75
Groves D I Goldfarb R J Gebre-Mariam M Hage-mann S and Robert F 1998 Orogenic gold depos-its A proposed classification in the context of theircrustal distribution and relationship to other golddeposit types Ore Geology Reviews v 13 p 7ndash27
Hodgson C J 1989 The structure of shear-related vein-type gold deposits A review Ore Geology Reviews v4 p 231ndash273
Jacobi P 1999 The discovery of epithermal Au-Cu-MoProterozoic deposits in the Tapajoacutes Province BrazilRevista Brasileira de Geociecircncias v 29 p 277ndash279
Jeacutebrak M 1997 Hydrothermal breccias in vein-type oredeposits A review of mechanisms morphology andsize distribution Ore Geology Reviews v 12 p 111ndash134
Juliani C 2001 Metalogecircnese do ouro e metais de baseassociadas com o vulcanismo-plutonismo da porccedilatildeo Wda Proviacutencia Auriacutefera do Tapajoacutes [ext abs] in VIISimpoacutesio de Geologia da Amazocircnia Beleacutem Brazil(CD-ROM)
Kerrich R and Cassidy K F 1994 Temporal relation-ships of lode gold mineralization to accretion magma-tism metamorphism and deformationmdashArchean topresent A review Ore Geology Reviews v 9 p 263ndash310
Klein E L Almeida M E Vasquez M L BahiaR B C Quadros M L E S and Ferreira A L inpress Geologia e recursos minerais da Proviacutencia Min-eral do Tapajoacutes Estados do Paraacute e Amazonas Escala1 500000 Brasiacutelia Brazil CPRMGeological Surveyof Brazil
Klein E L Rosa-Costa L T and Carvalho J M A2000 Fluid inclusion studies at the Patinhas gold-quartz mineralisation Tapajoacutes Gold Province Brazil[abs] in XXXI International Geological Congress Riode Janeiro Brazil (CD-ROM)
Klein E L Santos R A Fuzikawa K and AngeacutelicaR S 2001 Hydrothermal fluid evolution and struc-tural control of the brittle-style Guarim lode-gold min-eralisation Tapajoacutes Province Amazonian CratonBrazil Mineralium Deposita v 36 p 149ndash164
Klein E L and Vasquez M L 2000 Projeto EspecialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Vila Riozinho (SB21-Z-A) Estadodo Paraacute escala 1250000 Brasiacutelia Brazil CPRMGeological Survey of Brazil (CD-ROM)
Klein E L Vasquez M L Santos A and Martins RC 1997 Structural elements of the Maloquinha Intru-sive Suite in Tapajoacutes Mineral Province northern Bra-zil and the emplacement of the plutons [ext abs] inII International Symposium on Granites and Associ-ated Mineralizations ISGAM II Salvador Brazil p313ndash314
Klein E L Vasquez M L Santos A and Rosa-CostaL T 1999 Geologia e controle estrutural das mineral-izaccedilotildees auriacuteferas na Folha Vila Riozinho e NW daFolha Rio Novo Proviacutencia Tapajoacutes [ext abs] in VISimpoacutesio de Geologia da Amazocircnia Manaus Brazil p128ndash131
Lamaratildeo C N DallrsquoAgnol R and Lafon J M 2001Geocronologia e geoquiacutemica das associaccedilotildees vulcacircni-cas e plutocircnicas da regiatildeo de Vila Riozinho ProviacutenciaAuriacutefera do Tapajoacutes [ext abs] in VII Simpoacutesio deGeologia da Amazocircnia Beleacutem Brazil (CD-ROM)
Nunes C M D Juliani C Correcirca-Silva R H Mon-teiro L V S Bettencourt J S Neumann R AlcoverNeto A and Rye R O 2001 Caracterizaccedilatildeo de umsistema epitermal high-sulfidation vulcacircnico pale-oproterozoacuteico da Proviacutencia Auriacutefera do Tapajoacutes Paraacute[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
558 KLEIN ET AL
Ricci P S F Vasquez M L Santos A Klein E LJorge Joatildeo X S and Martins R C 1999 SuiacuteteIntrusiva Creporizatildeo ndash Proviacutencia Tapajoacutes Proposta ecriteacuterios de definiccedilatildeo [ext abs] in VI Simpoacutesio deGeologia da Amazocircnia Manaus Brazil p 519ndash522
Robert F and Poulsen K H 2001 Vein formation anddeformation in greenstone gold deposits in RichardsJ P and Tosdal R M eds Structural controls on oregenesis Reviews in Economic Geology v 14 p 111ndash155
Robert F Poulsen K H and Dubeacute B 1997 Golddeposits and their geological classification in GubinsA G ed Proceedings of Exploration 97 TorontoCanada p 209ndash220
Ronchi L H DallrsquoAgnol R Araujo J C Ribeiro VLamaratildeo C N Borges R M K and Fuzikawa K2001 Fluidos relacionados agraves alteraccedilotildees hidrotermaisno depoacutesito de ouro do Granito Satildeo JorgendashPA [extabs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Rosa-Costa L T and Carvalho J M A 1999 Tipologiade mineralizaccedilotildees auriacuteferas da regiatildeo sul da ProviacutenciaTapajoacutesndashParaacute [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 176ndash179
Santos J O S Groves D I Hartmann L A MouraM A and McNaughton N J 2001 Gold deposits ofthe Tapajoacutes and Alta Floresta Domains Tapajoacutes-Parima orogenic belt Amazon Craton Brazil Minera-lium Deposita v 36 p 279ndash299
Santos J O S Hartmann L A Gaudette H E GrovesD I McNaughton N J and Fletcher I R 2000 Anew understanding of the provinces of the AmazonCraton based on integration of field mapping and U-Pband Sm-Nd geochronology Gondwana Research v 3p 453ndash488
Santos R A 1997 Contribuiccedilatildeo agrave anaacutelise estrutural dejazimentos auriacuteferos do rio Tapajoacutes SW do Paraacute e SEdo Amazonas Garimpos Abacaxis Espiacuterito SantoBom Jesus Goiano Fazenda Pison Ouro Mil SantaIsabel Majestade e Carneirinho Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 1999 Controle estrutural das mineralizaccedilotildees deouro da Proviacutencia Mineral do Tapajoacutes Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 2000 Formation of gold-quartz veins controlledby the strike-slip fault mega-system in Tapajoacutes Min-eral Province Amazon Brazil [abs] in XXXI Interna-tional Geological Congress Rio de Janeiro Brazil(CD-ROM)
Tassinari C C G 1996 O mapa geocronoloacutegico do Craacute-ton Amazocircnico no Brasil Revisatildeo dos dados isotoacutepi-cos Unpubl Tese de Livre Docecircncia Universidade deSatildeo Paulo 139 p
Tassinari C C G and Macambira M J B 1999 Geo-chronological provinces of the Amazonian Craton Epi-sodes v 22 p 174ndash182
Vasquez M L and Klein E L 2000 Projeto especialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Rio Novo (SB21-Z-C) Estado doParaacute escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Vasquez M L Klein E L Macambira M J B SantosA Bahia R B C Ricci P S F and QuadrosM L E S 2000 Geochronology of granitoids maficintrusions and mineralizations of the Tapajoacutes GoldProvincendashAmazonian CratonndashBrazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Vasquez M L Klein E L Quadros M L E S BahiaR B C Santos A Ricci P S F Sachett C RSilva C M G and Macambira M J B 1999 Mag-matismo Uatumatilde na Proviacutencia Tapajoacutesmdashnovos dadosgeocronoloacutegicos [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 471ndash474
Vasquez M L Klein E L and Ricci P S F 2001Granitoacuteides poacutes-colisionais da porccedilatildeo leste da Proviacuten-cia Tapajoacutes [ext abs] in VII Simpoacutesio de Geologia daAmazocircnia Beleacutem Brazil (CD-ROM)
Vearncombe J R 1993 Quartz vein morphology andimplications for formation depth and classification ofArchaean gold-vein deposits Ore Geology Reviews v8 p 407ndash424
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 549
tents and the absence of native silver and silversulfosalts in the ore mineralogy
Gold Deposits in the Southern Tapajoacutes Province (STP)
More than 20 deposits and showings are distrib-uted in several gold camps along the STP (Fig 3)These mineralizations are discussed below in termsof host rocks wall rock alteration and structuralcontrol The classification of structural styles of theveins is based mainly on the concepts of Hodgson(1989) and Robert and Poulsen (2001) taking intoaccount the type of host structure and the internalstructure and textures of the veins The mainattributes are summarized in Table 1
Host rocksGneisses and orogenic granitoids are the main
hosts for gold deposits in the Tapajoacutes Gold Provinceand account for virtually all the host rocks in STP(Table 1) The gneisses belong to the Cuiuacute-CuiuacuteComplex They consist of gray orthogneisses oftonalitic and granodioritic composition bearingmicrogranular enclaves of diorites and quartz-dior-ites along with granitoids and rare migmatites andamphibolites Structurally the gneisses show a per-vasive ductile fabric striking NNE-SSW or NW-SE
and migmatitic features are subordinate Thegeochemical characteristics of trace elements(LILE HFSE REE) are compatible with those ofprimitive arc-related calc-alkaline granitoids(Vasquez et al 2001) They are dominantly metalu-minous with lenses of peraluminous to strongly per-aluminous leucogranitoids occurring subordinatelySantos et al (2000 2001) obtained zircon U-PbSHRIMP ages between 2033 Ma and 2005 Ma forthis complex
The hosting granitoids are related to the Crep-orizatildeo Intrusive Suite which holds irregular- to sig-moidal-shaped batholiths and stocks (Fig 2) ofhornblende- andor biotite-bearing granitoids andmetagranitoids of syenogranitic to tonalitic composi-tion The granitoids are either foliated or granoblas-tic and the latter show preserved primary featuressuch as euhedral phenocrysts of K-feldspar unde-formed microgranular enclaves and synplutonicdikes Very often they show an igneous bandingmarked by the orientation of the K-feldspar pheno-crysts that parallels the NW-SEndashtrending tectonicfoliation Field mineralogical and textural evi-dence indicates emplacement of the granitoids in acrustal level compatible with greenschist or up tomiddle-amphibolite metamorphic conditions (Ricciet al 1999) and the presence of enclaves ofgneisses from the Cuiuacute-Cuiuacute Complex is evidence of
FIG 3 Geological map of the Southern Tapajoacutes Province showing the location of the gold deposits addressed in thisstudy
550 KLEIN ET AL
TAB
LE 1
Sum
mar
y of
Attr
ibut
es o
f Gol
d D
epos
its o
f the
Sou
ther
n Ta
pajoacute
s Pr
ovin
ce1
No
Cam
p or
dep
osit
(n
umbe
r of
vei
ns)
Stru
ctur
al s
tyle
Inte
rnal
str
uctu
reH
ost r
ock
(s
trat
igra
phic
uni
t)G
angu
e m
iner
alog
yO
re m
iner
alog
yV
ein
orie
ntat
ion
(str
ike
dip)
Sele
cted
ref
eren
ces
1G
oian
o (2
)B
recc
iaC
atac
last
icF
olia
ted
gran
itoi
d (C
IS)
mus
pyN
50E
88S
E N
20W
88
NE
N0E
80E
Sant
os 1
997
2Su
daacuteri
o (4
)F
FV
(plusmn
maf
ic
dike
)M
assi
ve c
atac
last
icG
rani
toid
s (C
CC
)py
N40
-60E
70-
88SE
-N
WR
osa-
Cos
ta a
nd C
arva
lho
199
9
3C
oman
dant
e M
acha
do
(2)
FF
VM
assi
ve c
omb
Fol
iate
d gr
anod
iori
te
(CC
C)
mus
pyN
40E
70S
E a
nd
N50
W6
5SW
Ros
a-C
osta
and
Car
valh
o 1
999
4P
atin
has
Shea
r ve
inM
assi
ve s
hear
edG
rano
dior
ite
(CC
C)
eppy
cpy
N20
E6
8SE
Ros
a-C
osta
and
Car
valh
o 1
999
Kle
in e
t al
200
05
Pau
drsquoA
rco
(3)
FF
VV
einl
ets
sa
ccha
roid
alQ
uart
z-di
orit
ic g
neis
s (C
CC
) m
us k
f c
hl
epcp
y p
yN
30E
65S
EK
lein
et a
l i
n pr
ess
6C
oman
dant
e R
enan
(2)
Shea
r ve
inM
assi
veTo
nali
tic
gnei
ss (
CC
C)
chl
ep
pyN
0-30
E6
088S
EK
lein
et a
l i
n pr
ess
7Ta
uari
FF
VM
assi
veG
rani
toid
(C
IS)
chl
ep
N30
E8
5NW
Kle
in e
t al
in
pres
s8
Our
o M
ilB
recc
ia +
m
afic
dik
eN
etw
orks
Gra
nito
id (
CIS
) +
m
afic
dik
eN
70E
70N
WSa
ntos
199
7
9C
eacuteu A
zul
Bre
ccia
Com
b fi
ber
Gra
nodi
orit
e (C
IS)
qz k
f se
r ep
hem
N70
E8
8SE
Kle
in e
t al
in
pres
s10
Aacutegu
a L
impa
Bre
ccia
Gra
nodi
orit
e (C
IS)
N60
W7
0NE
Kle
in e
t al
in
pres
s11
Roq
ue S
ante
iro
(2)
FF
VM
assi
veTo
nali
tic
gnei
ss (
CC
C)
chl
pyN
45E
75N
WN
40W
88N
EK
lein
et a
l i
n pr
ess
12Ta
boca
lF
FV
Mas
sive
Mon
zogr
anit
e (C
IS)
N70
E8
0NW
Kle
in e
t al
in
pres
s13
Vie
tnam
Shea
r ve
inL
amin
ated
Mon
zogr
anit
e (C
IS)
ser
pyN
70E
75N
WK
lein
et a
l i
n pr
ess
14N
ovo
Vie
tnam
Shea
r ve
inM
assi
ve l
amin
ated
Mon
zogr
anit
e (C
IS)
ser
pyN
55E
80S
EK
lein
et a
l i
n pr
ess
15In
depe
ndecircn
cia
Stoc
kwor
kM
assi
ve v
uggy
Apl
itic
mon
zogr
anit
e (P
IS
CIS
) m
uspy
N45
-80E
10-
60SE
Kle
in e
t al
in
pres
s
16Satilde
o R
aim
undo
LA
RF
Mon
zogr
anit
e (C
IS)
epN
45-6
0E2
5-40
SER
osa-
Cos
ta a
nd C
arva
lho
199
917
Bom
Jes
usF
FV
Lam
inat
edG
rani
toid
(C
IS)
ser
kf
py c
py g
alN
90E
88S
Sant
os 1
997
18B
oa V
ista
Zeacute
Ped
roF
FV
Mon
zogr
anit
e (C
IS)
pyN
70E
80S
ER
osa-
Cos
ta a
nd C
arva
lho
199
918
Boa
Vis
taM
inei
ro-1
Shea
r ve
in +
br
ecci
aM
assi
ve l
amin
ated
Mon
zogr
anit
e (C
IS)
qz s
er c
arb
chl
py c
pyN
30E
88S
EV
asqu
ez a
nd K
lein
200
0
18B
oa V
ista
Min
eiro
-2F
FV
Mas
sive
Mon
zogr
anit
e (C
IS)
chl
ser
ep
pyN
20E
75S
EV
asqu
ez a
nd K
lein
200
018
Boa
Vis
taL
AR
FM
assi
ve s
acch
aroi
dal
Maf
ic v
olca
nic
and
schi
st (
)se
rpy
asp
yN
45-8
0W3
0-45
SWK
lein
et a
l i
n p
ress
Ros
a-C
osta
and
Car
valh
o 1
999
19P
lana
lto
FF
VM
assi
veG
rani
toid
(C
CC
)N
40E
75S
EK
lein
et a
l i
n pr
ess
20B
abil
ocircnia
FF
VM
assi
veM
onzo
gran
ite
(CIS
)se
rpy
N45
W4
5SW
Kle
in e
t al
in
pres
s21
Satildeo
Joseacute
FF
VM
assi
ve s
acch
aroi
dal
Mon
zogr
anit
e (C
IS)
epN
45W
63N
EK
lein
et a
l i
n pr
ess
1 Leg
end
FF
V =
fau
lt-f
ill
vein
CIS
= C
repo
rizatilde
o In
trus
ive
Suit
e C
CC
= C
uiuacute-
Cui
uacute C
ompl
ex P
IS =
Par
auar
i Int
rusi
ve S
uite
mus
= m
usco
vite
ser
= s
eric
ite
ep
= e
pido
te k
f = K
-fel
d-sp
ar c
hl =
chl
orit
e c
arb
= c
arbo
nate
qz
= q
uart
z p
y =
pyr
ite
cpy
= c
halc
opyr
ite
asp
y =
ars
enop
yrit
e g
al =
gal
ena
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 551
the intrusive character of the granitoids Whole-rockgeochemistry (Lamaratildeo et al 2001 Vasquez et al2001) has shown that the Creporizatildeo Suite repre-sents calc-alkaline metaluminous to peraluminousmedium- to high-K arc-related granitoids The REEpatterns show that they are more evolved than theCuiuacute-Cuiuacute granitoids and gneisses U-Pb and Pb-evaporation dating of zircon (Ricci et al 1999Vasquez et al 2000 Santos et al 2000 2001Lamaratildeo et al 2001) indicate crystallization agesbetween 1997 Ma and 1957 Ma This late timingwith respect to the Cuiuacute-Cuiuacute Complex along withthe geochemical characteristics the structural andmetamorphic differences the lack of volcano-sedi-mentary basins associated with the Creporizatildeo gran-itoids and their common association with regionalstrike-slip shear zones led Vasquez et al (2001) toconsider the Creporizatildeo Suite as representing apost-collisional magmatism still related to thedevelopment of the Cuiuacute-Cuiuacute magmatic arc andnot an individual arc (Creporizatildeo arc) as proposedby Santos et al (2001)
Ore mineralogy and wall-rock alteration
Many prospects are still undeveloped and work-ings are restricted to the oxidized (saprolite) zonewhere veins and structures are well preserved buthydrothermal alteration in the immediate host rockis overprinted by secondary processes Henceinformation in these cases is restricted to the veinassemblage and in a few cases to distal alterationwhich can be seen tens or a few hundreds of metersoff of the mineralized zone
Pyrite is the dominant sulfide mineral (Table 1)occurring in most of the deposits in general as dis-seminations filling fractures and cavities in thequartz veins in the contact between vein and hostrock or less commonly forming decimeter-wideaggregates (Fig 6) Chalcopyrite follows pyrite inimportance always occurring in association withpyrite whereas galena and arsenopyrite occur onlylocally
The gangue mineralogy shows little variationwith white mica being the main mineral (followingquartz) present in the quartz veins occurring how-ever in small amounts White mica is also wide-spread in the hydrothermally altered wall rocksoccurring in association with quartz minor amountsof chlorite and scarce carbonate K-feldspar andepidote
Structural controlInvestigation of mesoscopic and macroscopic
features of deposits of the STP showed that they arestrictly structurally controlled in all scalesRegional structures may have played importantroles acting as conduits for mineralizing fluids andcontrolling the distribution of the deposits The goldcamps are located close to or bounded by majorfirst-order faults and shear zones located in low-strain domains between them and rarely withinthese deformation zones (Figs 2 and 3) At campand deposit scales the orientation of the mineral-ized veins is controlled by the orientation andorgeometry of the hosting lower-order structures(Klein et al 1999 Santos 1999 2000)
Structural styles and internal structure
Fault-fill veins This type is by far the most com-mon structural style in STP and in the province as awhole (Klein et al 1999) The deposits consist of asingle quartz vein emplaced in subvertical struc-tures (Fig 4) These are mostly faults with subordi-
FIG 4 Photograph of the surface exposure of a fault-fillvein (outlined by the heavy lines) at Mineiro-2 The hydro-thermal envelope is outlined by the dashed line
552 KLEIN ET AL
nate narrow brittle-ductile shear zones Theirorientations are variable with concentrations ofveins along the N20degndash70degE and N40ndash50W direc-tions The veins are centimeter- to decimeter-thickand consist of milky quartz with minor (lt5) K-feldspar white mica chlorite and sulfide mineralsOccasionally thin extensionalndashoblique quartz toquartzo-feldspathic veinlets occur attached to themain quartz vein (Fig 5) The internal structure ofthe veins is dominantly formed by massive quartz(Fig 6) Laminated saccharoidal and open-spacefilling (comb) textures and hydrothermal brecciasare subordinate A few veins are positioned at thecontact between mafic dikes and the altered countryrock or even cut across the dikes suggesting inthese cases their late timing with respect to thedikes In one situation (Pau DrsquoArco) mineralizationlacks a major quartz vein (only a few discontinuousveinlets are present) and occurs as disseminationsin the hydrothermal zone that surrounds a subverti-cal strike-slip fault
Shear veins In greenstone-hosted deposits shearveins are usually described as fault-fill veinsbecause they occupy faults and the central parts ofshear zones (Hodgson 1989) and because it is con-sidered difficult to define if the veins formed as aresult of displacements along a shear fracture or asthe result of dilation of preexisting shear fractures orductile fabric (eg Robert and Poulsen 2001 and
references therein) In STP shear and fault-fill veinsshare a series of characteristics However in thispaper we prefer to classify them separately at leastfor descriptive purposes because shear veins differfrom fault-fill veins by the fact that they have beenemplaced in ductile-brittle structures (ComandanteRenan Novo Vietnam Fig 5) andor show effects ofductile deformation such as quartz grains withundulose extinction and deformation bands sur-rounded by small recrystallized subgrains (Patin-has) microscopic shear zones (Mineiro-1) andductile fabric either in the vein or in the immediatehost rock (Novo Vietnam) (Fig 5) The internalstructure is chiefly massive to laminated andsheared (Figs 6 and 7) Extensional features suchas breccias and en echelon sulfides (Fig 7) also arepresent
Low- (to moderate-) angle reverse-oblique faultsTwo examples have been observed At the Boa Vistagold field along with fault-fill and breccia veinspresent in several occurrences the main mineraliza-tion consists of a series of subparallel verticallystacked sigmoidal quartz veins (Fig 8A) separatedby hydrothermally altered and strongly foliated hostrock (schist) The veins show variable thicknessfrom a few centimeters up to one meter and strike toN45ordmndash80ordmW dipping 30ordm to 45ordm to the southwestInternally the milky veins show massive to saccha-roidal textures Small amounts of pyrite and minor
FIG 5 Sketch map (plan view) of the shear vein at Novo Vietnam The vein is surrounded by mylonitized wall rockand shows extensional veinlets attached on both sides The vein is massive to laminated and continuous but is formedby discontinuous veinlets (inset) between the two bends
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 553
arsenopyrite are disseminated throughout the veinsand altered wall rock Pyrite occurs filling smallfractures in quartz as well and sericite is presentboth in the vein and in the immediate wall rock
Given the weathered character of the terrainfresh rocks could not be observed in the mineralizedzone and the nature of the host rock could not beconfidently determined A few tens of meters off themineralized zone an undeformed porphyritic maficvolcanic rock crops out The region in turn is dom-inated by granitoids of the Creporizatildeo Suite that isthe host for all other occurrences in the same goldfield The hosting schist may derive from one ofthese two rock types by a combination of intense
deformation and high fluidrock ratios Alterna-tively it may represent a fragment of the metavol-cano-sedimentary sequence of the JacareacangaGroup which has not as yet been recognized in thisportion of the Tapajoacutes Province occurring as mega-xenoliths or roof pendants within the granitoids ofthe Creporizatildeo Suite
In the Satildeo Raimundo deposit mineralizationoccurs in narrow hydrothermal halos envelopinganastomosed shearfault planes in brittle-ductileshear zones (Fig 8B) The hosting shear zones strikeN45ordmndash60ordmE and dip 25ordmndash40ordm SE and the mineralizedzones are up to 2 meters thick (Rosa-Costa and Car-valho 1999) Quartz is generally absent and occurs
FIG 6 A Milky massive quartz with high pyrite contents at Patinhas B Sheared sulfide-poor quartz vein (Patinhas)C Quartz vein with sulfide minerals filling cavities (Novo Vietnam)
FIG 7 Vein structures at Mineiro-1 A Laminated quartz-pyrite veinlet (V) crosscutting the hydrothermally alteredhost rock Alteration is zoned and symmetric (arrows) B Milky massive quartz with extensional fracture filled by sulfideminerals with an en echelon distribution C Hydrothermal breccia formed by quartz (white) and hydrothermally alteredhost rock (grey)
554 KLEIN ET AL
only as small isolated and discontinuous veinletspositioned in the fault planes The host rock is amonzogranite of the Creporizatildeo Suite
Breccia veins Four main occurrences have beenrecorded forming tabular structures of less than 1 min thickness The breccia veins at Ceacuteu Azul andAacutegua Limpa consist of fragments of milky quartzwith angular to rounded shape ranging in size frommm to a few cm (Fig 9) set in a fine-grained red-dish to greenish hydrothermal matrix composed ofquartz feldspar and hematite along with fine-grained sericite and epidote Microscopically dif-ferent quartz fragments show textures such as comband rosettes indicating the shallow emplacement ofthese veins (Dowling and Morrison 1989 Vearn-combe 1993) At Goiano and Ouro Mil the brecciashave less matrix and the quartz fragments are moreangular than in the two other examples
Brecciation occurs also as a minor portion of ashear vein at the Mineiro-1 prospect in the BoaVista gold camp These breccias also differ from theformer by the fact that the angular quartz fragmentsare set in a matrix composed of altered wall rock(Fig 7C)
Stockworks This style has been identified at theIndependecircncia deposit It consists of multidirec-tional quartz veins a few centimeters thick envel-
oped by narrow halos of hydrothermal alterationThe veins are generally widely spaced occurring inan area of ~100 m times tens of meters Locally how-ever they are closely spaced with several individ-ual hydrothermal halos overlapping each otherforming larger areas of hydrothermally altered hostrock The quartz has a milky to smoky characterand shows cavities usually filled by sulfide miner-als Epidote and white mica are common gangueminerals In places large pockets of hydrothermalalteration lacking quartz veins are observed aswell Minor stockworks and networks (the veins as awhole show the same orientation of the veinbrec-cia) occur at Ouro Mil in both margins of the mainbreccia vein (Santos 1997)
Discussion and Concluding Remarks
Gold deposits in the Tapajoacutes Province are hostedin a variety of metamorphic and magmatic rocks InSouthern Tapajoacutes Province (STP) with one excep-tion only orthogneisses of the Cuiuacute-Cuiuacute Complexand orogenic granitoids of the Creporizatildeo Suite areknown hosts for gold Hosting granitoids are domi-nantly monzogranitic in composition whereas theorthogneisses show tonalitic and granodioritic com-positions
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 555
The deposits have been classified in a few struc-tural styles according to the hosting structurestructural regime in which they have been formedand internal structures and textures of the veinsAccordingly fault-fill and shear veins are the domi-nant style followed by subordinate occurrences ofveins hosted in low-angle reverse-oblique faultsbreccia veins and stockworks More than one stylemay occur in the same gold camp and even in a sin-gle deposit
Fault-fill and shear veins as well as brecciaveins form moderately to steeply dipping tabularbodies that seldom exceed one meter in thicknessand are hosted by strike-slip faults and shear zonesto which they are parallel The vein quartz is domi-nantly massive with laminated saccharoidal andcomb textures occurring subordinately Shearingand cataclasis of the veins is widespread suggest-ing along with other textural and structural evi-dence their positioning in active faults and shearzones or deformation after formation In most casesquartz white mica and pyrite compose the veinmineralogy and along with minor chlorite carbon-ate epidote and K-feldspar they overprint the pri-mary mineralogy of the hosting granitoids and theamphibolite-facies paragenesis of the hostinggneisses
The breccias have likely been produced duringfracture propagation by physical brecciation whichoccurs when the amount of stress exceeds the brittleresistance of the rock by mechanisms such as tec-tonic comminution andor fluid-assisted brecciation(Jeacutebrak 1997) Furthermore they indicate activeseismic slip during mineralization (Robert andPoulsen 2001)
The origin of the large stockwork at Independecircn-cia may be ascribed to hydraulic fracturing occur-ring over a cupola of a small aplitic granitoidrelated to or intruding the regional coarse-grainedmonzogranite of the Creporizatildeo Suite In the latterhypothesis it could be related either to a late-stagepluton of the Creporizatildeo Suite or to a younger grani-toid suite (Parauari) This definition requires geo-chronological support
Deposits and gold camps show strong structuralcontrol at all scales The hosting structures havebeen formed under a dominantly brittle-ductile tobrittle regime and consist of strike slip faults shearfractures intersection and bending of faults andlithological andor lithostratigraphic contactsExtensional fractures have not been characterizedas hosting structures because evidence of displace-
ment andor shearing is virtually always present inthe veins Extensional features are present howeveras en echelon arrays of sulfide minerals and as vein-lets attached to the main longitudinal fault veinsDeposits hosted in granitoids show a more brittlebehavior whereas those hosted in gneisses tend todisplay more ductile features This can result eitherfrom the depth of vein formation or from high fluidrock ratios even in shallow levels of the crust
Formation of deposits occurred in a range ofcrustal depth from mesozonal to epizonal condi-tions as indicated by the internal structure of thequartz veins and by the nature of the hosting struc-tures This is also supported by fluid inclusion stud-ies in a few deposits such as Guarim (Klein et al2001) and Patinhas (Klein et al 2000) both depos-its hosted in gneisses of the Cuiuacute-Cuiuacute ComplexFluid composition is nearly identical but P-T dataalong with textural and structural evidence suggestthat Guarim (outside STP) formed between 4 and 7km whereas Patinhas (within STP) formed at deeperlevels
Hence shear veins and fault-fill veins may beconsidered at least in part and from a structuralview as a single class of structural style with theirdifferences being ascribed to different depths ofemplacement and structural overprint It is not ourintention however to state that all of these veinsformed in a single gold-forming event The issue ofhow many mineralizing events have occurred in theTapajoacutes Province is still unresolved
Santos (1999 2000) studying 23 depositsthroughout the province (including three deposits inSTP) reported a set of characteristics similar tothose we have found in STP He concluded that alldeposits are related to a regional NW-SEndashtrendingstrike-slip fault system and that the orientation of
FIG 9 Breccia vein at Ceacuteu Azul
556 KLEIN ET AL
the lower-order hosting structures is compatiblewith Riedelrsquos system with the direction of the mainstress vector around the E-W direction Orientationsthat do not fit the model may be related to heteroge-neities in the local stress field However nothinghas been said about the timing of this strike-slipsystem in relation to the magmatic metamorphicand tectonic evolution of the province
Coutinho et al (2000) reported model ages thatcluster around 196 Ga and 188 Ga and main-tained that these two ages reflect two mineralizingepochs Santos et al (2001) invoked a single eventat 186 Ga However as stated by Santos et al(2001) the tectonic regime at 186 Ga is brittle Thismodel does not explain the ductile emplacementandor deformed mineralization hosted especially bythe Cuiuacute-Cuiuacute gneisses and by the metavolcano-sedimentary sequences Another (older) mineraliz-ing phase is thus required
We proposed early in this paper that the majorstrike-slip regime that affected the Creporizatildeo Suiteand older units likely occurred between 197 and195 Ga Mineralization hosted in the Cuiuacute-Cuiuacutegneisses (at least in STP) is post-tectonic and post-metamorphic with respect to the host rocks sincehosting structures clearly crosscut the metamorphicbanding and the hydrothermal mineralogy is retro-gressive in relation to the metamorphic paragenesisDeformation affecting the Creporizatildeo granitoids isbrittle-ductile to brittle whereas deformation affect-ing younger granitoids is brittle Thus it is valid toinfer as a working hypothesis that at least in partgold mineralization in STP formed during regionalstrike-slip deformation and emplacement of late-stage plutons of the Creporizatildeo Suite at ~197ndash195Ga a time interval that is in agreement with thatobtained by Coutinho et al (2000) The structuresmay have been reactivated during younger deforma-tional episode(s) and gold deposits may haveformed at this stage as well
The challenge is to decipher which depositsformed at each metallogenic epoch From a struc-tural point of view it is likely that the deposits inSouthern Tapajoacutes Province that have been emplacedat deeper levels of the crust and that show evidenceof plastic deformation (ie the shear veins and thedeposits hosted in low-angle reverse-oblique faultssee Table 1) formed in the older phase Fault-fillveins that occur in association with these deposits inthe same gold camp (eg Boa Vista) probablyformed in the same event The rest of the fault-fillveins (with textures and structures indicating
emplacement in shallow brittle structures associ-ated or not with mafic dikes and showing no associ-ation with shear veins in the same gold camp) aswell as the breccia veins and stockworks may haveformed either in the older or in the younger phaseWe do not have elements to define this Thisrequires much more isotopic data along with addi-tional fluid-inclusion and stable-isotope informationto constrain physico-chemical conditions of golddeposition as well as knowledge of the sources andnature of the mineralizing fluids and the absolutetiming of gold deposition
The attributes shown by the gold deposits in STP(namely the regional structural setting depositstyle vein textures and hydrothermal mineralogy)along with scarce fluid-inclusion data fit with boththe orogenic (magmatic arc-hosted) and intrusion-related models as proposed by Santos et al (2001)the latter sharing characteristics with Korean-typedeposits (Robert et al 1997) as well
Acknowledgments
Alfreu dos Santos (formerly of CPRM) partici-pated in the field work and supervised the TapajoacutesProject His help is acknowledged This is a contri-bution to the project PRONEX-CNPq-FADESP6621031998-0ndashprocess no 4200000
REFERENCES
Almeida M E Brito M F L Ferreira A L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaVila Mamatildee Anatilde (SB21-V-D) Estados do Paraacute e Ama-zonas escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Almeida M E Brito M F L and Macambira M J B1999 Caroccedilal Granite 207Pb206Pb evaporation age inpost-collisional granitoids of Tapajoacutes Gold ProvinceAmazonian region Brazil [abs] in II South AmericanSymposium on Isotope Geology Coacuterdoba ArgentinaActas p 3ndash6
Almeida M E Ferreira A L Brito M F L and Mon-teiro M A S 2001 Evoluccedilatildeo tectono-estrutural daProviacutencia Tapajoacutes com base na geologia das folhas VilaMamatildee Anatilde e Jacareacanga (1250000) regiatildeo limitedos estados do Amazonas e Paraacute in Reis N J andMonteiro M A S orgs Contribuiccedilotildees agrave Geologia daAmazocircnia v 2 Manaus Brazil SBG-NO p 57ndash112
Bahia R B C and Quadros M L E S 2000 Geologiae recursos minerais da Folha Caracol (SB21-X-C)
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 557
Estado do Paraacute Escala 1250000 Brasiacutelia BrazilCPRMGeological Survey of Brazil (CD-ROM)
Cassidy K F Groves D I and McNaughton N J 1998Late-Archean granitoid-hosted lode-gold depositsYilgarn Craton Western Australia Deposit character-istics crustal architecture and implications for oregenesis Ore Geology Reviews v 13 p 65ndash102
Correcirca-Silva R H Juliani C Bettencourt J S NunesC M D and Almeida T I R 2001 Caracterizaccedilatildeode um sistema epitermal low-sulfidation (ou adulaacuteria-sericita) hospedado em vulcacircnicas e vulcanoclaacutesticasdo Grupo Iriri na Proviacutencia auriacutefera do Tapajoacutes (PA)[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Coutinho M G N Santos J O S Fallick A E andLafon J M 2000 Orogenic gold deposits in TapajoacutesMineral Province Amazon Brazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Dowling K and Morrison G 1989 Application ofquartz textures to the classification of gold depositsusing North Queensland examples Economic GeologyMonograph v 6 p 342ndash355
Dreher A M Vlach S and Martini S L 1998 Adu-laria associated with epithermal gold veins in theTapajoacutes Mineral Province Paraacute State Northern BrazilRevista Brasileira de Geociecircncias v 28 p 397ndash404
Faraco M T L Carvalho J M A and Klein E L1997 Carta metalogeneacutetica da Proviacutencia Auriacutefera doTapajoacutes in Costa M L and Angeacutelica R S orgsContribuiccedilotildees agrave Geologia da Amazocircnia Beleacutem BrazilFINEPSBG-NO p 423ndash437
Ferreira A L Almeida M E Brito M F L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaJacareacanga (SB21-Y-B) Estados do Paraacute e Amazo-nas escala 1250000 Brasiacutelia Brazil CPRMGeolog-ical Survey of Brazil (CD-ROM)
Goldfarb R J Groves D I and Gardoll S 2001 Oro-genic gold and geologic time A global synthesis OreGeology Reviews v 18 p 1ndash75
Groves D I Goldfarb R J Gebre-Mariam M Hage-mann S and Robert F 1998 Orogenic gold depos-its A proposed classification in the context of theircrustal distribution and relationship to other golddeposit types Ore Geology Reviews v 13 p 7ndash27
Hodgson C J 1989 The structure of shear-related vein-type gold deposits A review Ore Geology Reviews v4 p 231ndash273
Jacobi P 1999 The discovery of epithermal Au-Cu-MoProterozoic deposits in the Tapajoacutes Province BrazilRevista Brasileira de Geociecircncias v 29 p 277ndash279
Jeacutebrak M 1997 Hydrothermal breccias in vein-type oredeposits A review of mechanisms morphology andsize distribution Ore Geology Reviews v 12 p 111ndash134
Juliani C 2001 Metalogecircnese do ouro e metais de baseassociadas com o vulcanismo-plutonismo da porccedilatildeo Wda Proviacutencia Auriacutefera do Tapajoacutes [ext abs] in VIISimpoacutesio de Geologia da Amazocircnia Beleacutem Brazil(CD-ROM)
Kerrich R and Cassidy K F 1994 Temporal relation-ships of lode gold mineralization to accretion magma-tism metamorphism and deformationmdashArchean topresent A review Ore Geology Reviews v 9 p 263ndash310
Klein E L Almeida M E Vasquez M L BahiaR B C Quadros M L E S and Ferreira A L inpress Geologia e recursos minerais da Proviacutencia Min-eral do Tapajoacutes Estados do Paraacute e Amazonas Escala1 500000 Brasiacutelia Brazil CPRMGeological Surveyof Brazil
Klein E L Rosa-Costa L T and Carvalho J M A2000 Fluid inclusion studies at the Patinhas gold-quartz mineralisation Tapajoacutes Gold Province Brazil[abs] in XXXI International Geological Congress Riode Janeiro Brazil (CD-ROM)
Klein E L Santos R A Fuzikawa K and AngeacutelicaR S 2001 Hydrothermal fluid evolution and struc-tural control of the brittle-style Guarim lode-gold min-eralisation Tapajoacutes Province Amazonian CratonBrazil Mineralium Deposita v 36 p 149ndash164
Klein E L and Vasquez M L 2000 Projeto EspecialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Vila Riozinho (SB21-Z-A) Estadodo Paraacute escala 1250000 Brasiacutelia Brazil CPRMGeological Survey of Brazil (CD-ROM)
Klein E L Vasquez M L Santos A and Martins RC 1997 Structural elements of the Maloquinha Intru-sive Suite in Tapajoacutes Mineral Province northern Bra-zil and the emplacement of the plutons [ext abs] inII International Symposium on Granites and Associ-ated Mineralizations ISGAM II Salvador Brazil p313ndash314
Klein E L Vasquez M L Santos A and Rosa-CostaL T 1999 Geologia e controle estrutural das mineral-izaccedilotildees auriacuteferas na Folha Vila Riozinho e NW daFolha Rio Novo Proviacutencia Tapajoacutes [ext abs] in VISimpoacutesio de Geologia da Amazocircnia Manaus Brazil p128ndash131
Lamaratildeo C N DallrsquoAgnol R and Lafon J M 2001Geocronologia e geoquiacutemica das associaccedilotildees vulcacircni-cas e plutocircnicas da regiatildeo de Vila Riozinho ProviacutenciaAuriacutefera do Tapajoacutes [ext abs] in VII Simpoacutesio deGeologia da Amazocircnia Beleacutem Brazil (CD-ROM)
Nunes C M D Juliani C Correcirca-Silva R H Mon-teiro L V S Bettencourt J S Neumann R AlcoverNeto A and Rye R O 2001 Caracterizaccedilatildeo de umsistema epitermal high-sulfidation vulcacircnico pale-oproterozoacuteico da Proviacutencia Auriacutefera do Tapajoacutes Paraacute[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
558 KLEIN ET AL
Ricci P S F Vasquez M L Santos A Klein E LJorge Joatildeo X S and Martins R C 1999 SuiacuteteIntrusiva Creporizatildeo ndash Proviacutencia Tapajoacutes Proposta ecriteacuterios de definiccedilatildeo [ext abs] in VI Simpoacutesio deGeologia da Amazocircnia Manaus Brazil p 519ndash522
Robert F and Poulsen K H 2001 Vein formation anddeformation in greenstone gold deposits in RichardsJ P and Tosdal R M eds Structural controls on oregenesis Reviews in Economic Geology v 14 p 111ndash155
Robert F Poulsen K H and Dubeacute B 1997 Golddeposits and their geological classification in GubinsA G ed Proceedings of Exploration 97 TorontoCanada p 209ndash220
Ronchi L H DallrsquoAgnol R Araujo J C Ribeiro VLamaratildeo C N Borges R M K and Fuzikawa K2001 Fluidos relacionados agraves alteraccedilotildees hidrotermaisno depoacutesito de ouro do Granito Satildeo JorgendashPA [extabs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Rosa-Costa L T and Carvalho J M A 1999 Tipologiade mineralizaccedilotildees auriacuteferas da regiatildeo sul da ProviacutenciaTapajoacutesndashParaacute [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 176ndash179
Santos J O S Groves D I Hartmann L A MouraM A and McNaughton N J 2001 Gold deposits ofthe Tapajoacutes and Alta Floresta Domains Tapajoacutes-Parima orogenic belt Amazon Craton Brazil Minera-lium Deposita v 36 p 279ndash299
Santos J O S Hartmann L A Gaudette H E GrovesD I McNaughton N J and Fletcher I R 2000 Anew understanding of the provinces of the AmazonCraton based on integration of field mapping and U-Pband Sm-Nd geochronology Gondwana Research v 3p 453ndash488
Santos R A 1997 Contribuiccedilatildeo agrave anaacutelise estrutural dejazimentos auriacuteferos do rio Tapajoacutes SW do Paraacute e SEdo Amazonas Garimpos Abacaxis Espiacuterito SantoBom Jesus Goiano Fazenda Pison Ouro Mil SantaIsabel Majestade e Carneirinho Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 1999 Controle estrutural das mineralizaccedilotildees deouro da Proviacutencia Mineral do Tapajoacutes Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 2000 Formation of gold-quartz veins controlledby the strike-slip fault mega-system in Tapajoacutes Min-eral Province Amazon Brazil [abs] in XXXI Interna-tional Geological Congress Rio de Janeiro Brazil(CD-ROM)
Tassinari C C G 1996 O mapa geocronoloacutegico do Craacute-ton Amazocircnico no Brasil Revisatildeo dos dados isotoacutepi-cos Unpubl Tese de Livre Docecircncia Universidade deSatildeo Paulo 139 p
Tassinari C C G and Macambira M J B 1999 Geo-chronological provinces of the Amazonian Craton Epi-sodes v 22 p 174ndash182
Vasquez M L and Klein E L 2000 Projeto especialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Rio Novo (SB21-Z-C) Estado doParaacute escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Vasquez M L Klein E L Macambira M J B SantosA Bahia R B C Ricci P S F and QuadrosM L E S 2000 Geochronology of granitoids maficintrusions and mineralizations of the Tapajoacutes GoldProvincendashAmazonian CratonndashBrazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Vasquez M L Klein E L Quadros M L E S BahiaR B C Santos A Ricci P S F Sachett C RSilva C M G and Macambira M J B 1999 Mag-matismo Uatumatilde na Proviacutencia Tapajoacutesmdashnovos dadosgeocronoloacutegicos [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 471ndash474
Vasquez M L Klein E L and Ricci P S F 2001Granitoacuteides poacutes-colisionais da porccedilatildeo leste da Proviacuten-cia Tapajoacutes [ext abs] in VII Simpoacutesio de Geologia daAmazocircnia Beleacutem Brazil (CD-ROM)
Vearncombe J R 1993 Quartz vein morphology andimplications for formation depth and classification ofArchaean gold-vein deposits Ore Geology Reviews v8 p 407ndash424
550 KLEIN ET AL
TAB
LE 1
Sum
mar
y of
Attr
ibut
es o
f Gol
d D
epos
its o
f the
Sou
ther
n Ta
pajoacute
s Pr
ovin
ce1
No
Cam
p or
dep
osit
(n
umbe
r of
vei
ns)
Stru
ctur
al s
tyle
Inte
rnal
str
uctu
reH
ost r
ock
(s
trat
igra
phic
uni
t)G
angu
e m
iner
alog
yO
re m
iner
alog
yV
ein
orie
ntat
ion
(str
ike
dip)
Sele
cted
ref
eren
ces
1G
oian
o (2
)B
recc
iaC
atac
last
icF
olia
ted
gran
itoi
d (C
IS)
mus
pyN
50E
88S
E N
20W
88
NE
N0E
80E
Sant
os 1
997
2Su
daacuteri
o (4
)F
FV
(plusmn
maf
ic
dike
)M
assi
ve c
atac
last
icG
rani
toid
s (C
CC
)py
N40
-60E
70-
88SE
-N
WR
osa-
Cos
ta a
nd C
arva
lho
199
9
3C
oman
dant
e M
acha
do
(2)
FF
VM
assi
ve c
omb
Fol
iate
d gr
anod
iori
te
(CC
C)
mus
pyN
40E
70S
E a
nd
N50
W6
5SW
Ros
a-C
osta
and
Car
valh
o 1
999
4P
atin
has
Shea
r ve
inM
assi
ve s
hear
edG
rano
dior
ite
(CC
C)
eppy
cpy
N20
E6
8SE
Ros
a-C
osta
and
Car
valh
o 1
999
Kle
in e
t al
200
05
Pau
drsquoA
rco
(3)
FF
VV
einl
ets
sa
ccha
roid
alQ
uart
z-di
orit
ic g
neis
s (C
CC
) m
us k
f c
hl
epcp
y p
yN
30E
65S
EK
lein
et a
l i
n pr
ess
6C
oman
dant
e R
enan
(2)
Shea
r ve
inM
assi
veTo
nali
tic
gnei
ss (
CC
C)
chl
ep
pyN
0-30
E6
088S
EK
lein
et a
l i
n pr
ess
7Ta
uari
FF
VM
assi
veG
rani
toid
(C
IS)
chl
ep
N30
E8
5NW
Kle
in e
t al
in
pres
s8
Our
o M
ilB
recc
ia +
m
afic
dik
eN
etw
orks
Gra
nito
id (
CIS
) +
m
afic
dik
eN
70E
70N
WSa
ntos
199
7
9C
eacuteu A
zul
Bre
ccia
Com
b fi
ber
Gra
nodi
orit
e (C
IS)
qz k
f se
r ep
hem
N70
E8
8SE
Kle
in e
t al
in
pres
s10
Aacutegu
a L
impa
Bre
ccia
Gra
nodi
orit
e (C
IS)
N60
W7
0NE
Kle
in e
t al
in
pres
s11
Roq
ue S
ante
iro
(2)
FF
VM
assi
veTo
nali
tic
gnei
ss (
CC
C)
chl
pyN
45E
75N
WN
40W
88N
EK
lein
et a
l i
n pr
ess
12Ta
boca
lF
FV
Mas
sive
Mon
zogr
anit
e (C
IS)
N70
E8
0NW
Kle
in e
t al
in
pres
s13
Vie
tnam
Shea
r ve
inL
amin
ated
Mon
zogr
anit
e (C
IS)
ser
pyN
70E
75N
WK
lein
et a
l i
n pr
ess
14N
ovo
Vie
tnam
Shea
r ve
inM
assi
ve l
amin
ated
Mon
zogr
anit
e (C
IS)
ser
pyN
55E
80S
EK
lein
et a
l i
n pr
ess
15In
depe
ndecircn
cia
Stoc
kwor
kM
assi
ve v
uggy
Apl
itic
mon
zogr
anit
e (P
IS
CIS
) m
uspy
N45
-80E
10-
60SE
Kle
in e
t al
in
pres
s
16Satilde
o R
aim
undo
LA
RF
Mon
zogr
anit
e (C
IS)
epN
45-6
0E2
5-40
SER
osa-
Cos
ta a
nd C
arva
lho
199
917
Bom
Jes
usF
FV
Lam
inat
edG
rani
toid
(C
IS)
ser
kf
py c
py g
alN
90E
88S
Sant
os 1
997
18B
oa V
ista
Zeacute
Ped
roF
FV
Mon
zogr
anit
e (C
IS)
pyN
70E
80S
ER
osa-
Cos
ta a
nd C
arva
lho
199
918
Boa
Vis
taM
inei
ro-1
Shea
r ve
in +
br
ecci
aM
assi
ve l
amin
ated
Mon
zogr
anit
e (C
IS)
qz s
er c
arb
chl
py c
pyN
30E
88S
EV
asqu
ez a
nd K
lein
200
0
18B
oa V
ista
Min
eiro
-2F
FV
Mas
sive
Mon
zogr
anit
e (C
IS)
chl
ser
ep
pyN
20E
75S
EV
asqu
ez a
nd K
lein
200
018
Boa
Vis
taL
AR
FM
assi
ve s
acch
aroi
dal
Maf
ic v
olca
nic
and
schi
st (
)se
rpy
asp
yN
45-8
0W3
0-45
SWK
lein
et a
l i
n p
ress
Ros
a-C
osta
and
Car
valh
o 1
999
19P
lana
lto
FF
VM
assi
veG
rani
toid
(C
CC
)N
40E
75S
EK
lein
et a
l i
n pr
ess
20B
abil
ocircnia
FF
VM
assi
veM
onzo
gran
ite
(CIS
)se
rpy
N45
W4
5SW
Kle
in e
t al
in
pres
s21
Satildeo
Joseacute
FF
VM
assi
ve s
acch
aroi
dal
Mon
zogr
anit
e (C
IS)
epN
45W
63N
EK
lein
et a
l i
n pr
ess
1 Leg
end
FF
V =
fau
lt-f
ill
vein
CIS
= C
repo
rizatilde
o In
trus
ive
Suit
e C
CC
= C
uiuacute-
Cui
uacute C
ompl
ex P
IS =
Par
auar
i Int
rusi
ve S
uite
mus
= m
usco
vite
ser
= s
eric
ite
ep
= e
pido
te k
f = K
-fel
d-sp
ar c
hl =
chl
orit
e c
arb
= c
arbo
nate
qz
= q
uart
z p
y =
pyr
ite
cpy
= c
halc
opyr
ite
asp
y =
ars
enop
yrit
e g
al =
gal
ena
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 551
the intrusive character of the granitoids Whole-rockgeochemistry (Lamaratildeo et al 2001 Vasquez et al2001) has shown that the Creporizatildeo Suite repre-sents calc-alkaline metaluminous to peraluminousmedium- to high-K arc-related granitoids The REEpatterns show that they are more evolved than theCuiuacute-Cuiuacute granitoids and gneisses U-Pb and Pb-evaporation dating of zircon (Ricci et al 1999Vasquez et al 2000 Santos et al 2000 2001Lamaratildeo et al 2001) indicate crystallization agesbetween 1997 Ma and 1957 Ma This late timingwith respect to the Cuiuacute-Cuiuacute Complex along withthe geochemical characteristics the structural andmetamorphic differences the lack of volcano-sedi-mentary basins associated with the Creporizatildeo gran-itoids and their common association with regionalstrike-slip shear zones led Vasquez et al (2001) toconsider the Creporizatildeo Suite as representing apost-collisional magmatism still related to thedevelopment of the Cuiuacute-Cuiuacute magmatic arc andnot an individual arc (Creporizatildeo arc) as proposedby Santos et al (2001)
Ore mineralogy and wall-rock alteration
Many prospects are still undeveloped and work-ings are restricted to the oxidized (saprolite) zonewhere veins and structures are well preserved buthydrothermal alteration in the immediate host rockis overprinted by secondary processes Henceinformation in these cases is restricted to the veinassemblage and in a few cases to distal alterationwhich can be seen tens or a few hundreds of metersoff of the mineralized zone
Pyrite is the dominant sulfide mineral (Table 1)occurring in most of the deposits in general as dis-seminations filling fractures and cavities in thequartz veins in the contact between vein and hostrock or less commonly forming decimeter-wideaggregates (Fig 6) Chalcopyrite follows pyrite inimportance always occurring in association withpyrite whereas galena and arsenopyrite occur onlylocally
The gangue mineralogy shows little variationwith white mica being the main mineral (followingquartz) present in the quartz veins occurring how-ever in small amounts White mica is also wide-spread in the hydrothermally altered wall rocksoccurring in association with quartz minor amountsof chlorite and scarce carbonate K-feldspar andepidote
Structural controlInvestigation of mesoscopic and macroscopic
features of deposits of the STP showed that they arestrictly structurally controlled in all scalesRegional structures may have played importantroles acting as conduits for mineralizing fluids andcontrolling the distribution of the deposits The goldcamps are located close to or bounded by majorfirst-order faults and shear zones located in low-strain domains between them and rarely withinthese deformation zones (Figs 2 and 3) At campand deposit scales the orientation of the mineral-ized veins is controlled by the orientation andorgeometry of the hosting lower-order structures(Klein et al 1999 Santos 1999 2000)
Structural styles and internal structure
Fault-fill veins This type is by far the most com-mon structural style in STP and in the province as awhole (Klein et al 1999) The deposits consist of asingle quartz vein emplaced in subvertical struc-tures (Fig 4) These are mostly faults with subordi-
FIG 4 Photograph of the surface exposure of a fault-fillvein (outlined by the heavy lines) at Mineiro-2 The hydro-thermal envelope is outlined by the dashed line
552 KLEIN ET AL
nate narrow brittle-ductile shear zones Theirorientations are variable with concentrations ofveins along the N20degndash70degE and N40ndash50W direc-tions The veins are centimeter- to decimeter-thickand consist of milky quartz with minor (lt5) K-feldspar white mica chlorite and sulfide mineralsOccasionally thin extensionalndashoblique quartz toquartzo-feldspathic veinlets occur attached to themain quartz vein (Fig 5) The internal structure ofthe veins is dominantly formed by massive quartz(Fig 6) Laminated saccharoidal and open-spacefilling (comb) textures and hydrothermal brecciasare subordinate A few veins are positioned at thecontact between mafic dikes and the altered countryrock or even cut across the dikes suggesting inthese cases their late timing with respect to thedikes In one situation (Pau DrsquoArco) mineralizationlacks a major quartz vein (only a few discontinuousveinlets are present) and occurs as disseminationsin the hydrothermal zone that surrounds a subverti-cal strike-slip fault
Shear veins In greenstone-hosted deposits shearveins are usually described as fault-fill veinsbecause they occupy faults and the central parts ofshear zones (Hodgson 1989) and because it is con-sidered difficult to define if the veins formed as aresult of displacements along a shear fracture or asthe result of dilation of preexisting shear fractures orductile fabric (eg Robert and Poulsen 2001 and
references therein) In STP shear and fault-fill veinsshare a series of characteristics However in thispaper we prefer to classify them separately at leastfor descriptive purposes because shear veins differfrom fault-fill veins by the fact that they have beenemplaced in ductile-brittle structures (ComandanteRenan Novo Vietnam Fig 5) andor show effects ofductile deformation such as quartz grains withundulose extinction and deformation bands sur-rounded by small recrystallized subgrains (Patin-has) microscopic shear zones (Mineiro-1) andductile fabric either in the vein or in the immediatehost rock (Novo Vietnam) (Fig 5) The internalstructure is chiefly massive to laminated andsheared (Figs 6 and 7) Extensional features suchas breccias and en echelon sulfides (Fig 7) also arepresent
Low- (to moderate-) angle reverse-oblique faultsTwo examples have been observed At the Boa Vistagold field along with fault-fill and breccia veinspresent in several occurrences the main mineraliza-tion consists of a series of subparallel verticallystacked sigmoidal quartz veins (Fig 8A) separatedby hydrothermally altered and strongly foliated hostrock (schist) The veins show variable thicknessfrom a few centimeters up to one meter and strike toN45ordmndash80ordmW dipping 30ordm to 45ordm to the southwestInternally the milky veins show massive to saccha-roidal textures Small amounts of pyrite and minor
FIG 5 Sketch map (plan view) of the shear vein at Novo Vietnam The vein is surrounded by mylonitized wall rockand shows extensional veinlets attached on both sides The vein is massive to laminated and continuous but is formedby discontinuous veinlets (inset) between the two bends
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 553
arsenopyrite are disseminated throughout the veinsand altered wall rock Pyrite occurs filling smallfractures in quartz as well and sericite is presentboth in the vein and in the immediate wall rock
Given the weathered character of the terrainfresh rocks could not be observed in the mineralizedzone and the nature of the host rock could not beconfidently determined A few tens of meters off themineralized zone an undeformed porphyritic maficvolcanic rock crops out The region in turn is dom-inated by granitoids of the Creporizatildeo Suite that isthe host for all other occurrences in the same goldfield The hosting schist may derive from one ofthese two rock types by a combination of intense
deformation and high fluidrock ratios Alterna-tively it may represent a fragment of the metavol-cano-sedimentary sequence of the JacareacangaGroup which has not as yet been recognized in thisportion of the Tapajoacutes Province occurring as mega-xenoliths or roof pendants within the granitoids ofthe Creporizatildeo Suite
In the Satildeo Raimundo deposit mineralizationoccurs in narrow hydrothermal halos envelopinganastomosed shearfault planes in brittle-ductileshear zones (Fig 8B) The hosting shear zones strikeN45ordmndash60ordmE and dip 25ordmndash40ordm SE and the mineralizedzones are up to 2 meters thick (Rosa-Costa and Car-valho 1999) Quartz is generally absent and occurs
FIG 6 A Milky massive quartz with high pyrite contents at Patinhas B Sheared sulfide-poor quartz vein (Patinhas)C Quartz vein with sulfide minerals filling cavities (Novo Vietnam)
FIG 7 Vein structures at Mineiro-1 A Laminated quartz-pyrite veinlet (V) crosscutting the hydrothermally alteredhost rock Alteration is zoned and symmetric (arrows) B Milky massive quartz with extensional fracture filled by sulfideminerals with an en echelon distribution C Hydrothermal breccia formed by quartz (white) and hydrothermally alteredhost rock (grey)
554 KLEIN ET AL
only as small isolated and discontinuous veinletspositioned in the fault planes The host rock is amonzogranite of the Creporizatildeo Suite
Breccia veins Four main occurrences have beenrecorded forming tabular structures of less than 1 min thickness The breccia veins at Ceacuteu Azul andAacutegua Limpa consist of fragments of milky quartzwith angular to rounded shape ranging in size frommm to a few cm (Fig 9) set in a fine-grained red-dish to greenish hydrothermal matrix composed ofquartz feldspar and hematite along with fine-grained sericite and epidote Microscopically dif-ferent quartz fragments show textures such as comband rosettes indicating the shallow emplacement ofthese veins (Dowling and Morrison 1989 Vearn-combe 1993) At Goiano and Ouro Mil the brecciashave less matrix and the quartz fragments are moreangular than in the two other examples
Brecciation occurs also as a minor portion of ashear vein at the Mineiro-1 prospect in the BoaVista gold camp These breccias also differ from theformer by the fact that the angular quartz fragmentsare set in a matrix composed of altered wall rock(Fig 7C)
Stockworks This style has been identified at theIndependecircncia deposit It consists of multidirec-tional quartz veins a few centimeters thick envel-
oped by narrow halos of hydrothermal alterationThe veins are generally widely spaced occurring inan area of ~100 m times tens of meters Locally how-ever they are closely spaced with several individ-ual hydrothermal halos overlapping each otherforming larger areas of hydrothermally altered hostrock The quartz has a milky to smoky characterand shows cavities usually filled by sulfide miner-als Epidote and white mica are common gangueminerals In places large pockets of hydrothermalalteration lacking quartz veins are observed aswell Minor stockworks and networks (the veins as awhole show the same orientation of the veinbrec-cia) occur at Ouro Mil in both margins of the mainbreccia vein (Santos 1997)
Discussion and Concluding Remarks
Gold deposits in the Tapajoacutes Province are hostedin a variety of metamorphic and magmatic rocks InSouthern Tapajoacutes Province (STP) with one excep-tion only orthogneisses of the Cuiuacute-Cuiuacute Complexand orogenic granitoids of the Creporizatildeo Suite areknown hosts for gold Hosting granitoids are domi-nantly monzogranitic in composition whereas theorthogneisses show tonalitic and granodioritic com-positions
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 555
The deposits have been classified in a few struc-tural styles according to the hosting structurestructural regime in which they have been formedand internal structures and textures of the veinsAccordingly fault-fill and shear veins are the domi-nant style followed by subordinate occurrences ofveins hosted in low-angle reverse-oblique faultsbreccia veins and stockworks More than one stylemay occur in the same gold camp and even in a sin-gle deposit
Fault-fill and shear veins as well as brecciaveins form moderately to steeply dipping tabularbodies that seldom exceed one meter in thicknessand are hosted by strike-slip faults and shear zonesto which they are parallel The vein quartz is domi-nantly massive with laminated saccharoidal andcomb textures occurring subordinately Shearingand cataclasis of the veins is widespread suggest-ing along with other textural and structural evi-dence their positioning in active faults and shearzones or deformation after formation In most casesquartz white mica and pyrite compose the veinmineralogy and along with minor chlorite carbon-ate epidote and K-feldspar they overprint the pri-mary mineralogy of the hosting granitoids and theamphibolite-facies paragenesis of the hostinggneisses
The breccias have likely been produced duringfracture propagation by physical brecciation whichoccurs when the amount of stress exceeds the brittleresistance of the rock by mechanisms such as tec-tonic comminution andor fluid-assisted brecciation(Jeacutebrak 1997) Furthermore they indicate activeseismic slip during mineralization (Robert andPoulsen 2001)
The origin of the large stockwork at Independecircn-cia may be ascribed to hydraulic fracturing occur-ring over a cupola of a small aplitic granitoidrelated to or intruding the regional coarse-grainedmonzogranite of the Creporizatildeo Suite In the latterhypothesis it could be related either to a late-stagepluton of the Creporizatildeo Suite or to a younger grani-toid suite (Parauari) This definition requires geo-chronological support
Deposits and gold camps show strong structuralcontrol at all scales The hosting structures havebeen formed under a dominantly brittle-ductile tobrittle regime and consist of strike slip faults shearfractures intersection and bending of faults andlithological andor lithostratigraphic contactsExtensional fractures have not been characterizedas hosting structures because evidence of displace-
ment andor shearing is virtually always present inthe veins Extensional features are present howeveras en echelon arrays of sulfide minerals and as vein-lets attached to the main longitudinal fault veinsDeposits hosted in granitoids show a more brittlebehavior whereas those hosted in gneisses tend todisplay more ductile features This can result eitherfrom the depth of vein formation or from high fluidrock ratios even in shallow levels of the crust
Formation of deposits occurred in a range ofcrustal depth from mesozonal to epizonal condi-tions as indicated by the internal structure of thequartz veins and by the nature of the hosting struc-tures This is also supported by fluid inclusion stud-ies in a few deposits such as Guarim (Klein et al2001) and Patinhas (Klein et al 2000) both depos-its hosted in gneisses of the Cuiuacute-Cuiuacute ComplexFluid composition is nearly identical but P-T dataalong with textural and structural evidence suggestthat Guarim (outside STP) formed between 4 and 7km whereas Patinhas (within STP) formed at deeperlevels
Hence shear veins and fault-fill veins may beconsidered at least in part and from a structuralview as a single class of structural style with theirdifferences being ascribed to different depths ofemplacement and structural overprint It is not ourintention however to state that all of these veinsformed in a single gold-forming event The issue ofhow many mineralizing events have occurred in theTapajoacutes Province is still unresolved
Santos (1999 2000) studying 23 depositsthroughout the province (including three deposits inSTP) reported a set of characteristics similar tothose we have found in STP He concluded that alldeposits are related to a regional NW-SEndashtrendingstrike-slip fault system and that the orientation of
FIG 9 Breccia vein at Ceacuteu Azul
556 KLEIN ET AL
the lower-order hosting structures is compatiblewith Riedelrsquos system with the direction of the mainstress vector around the E-W direction Orientationsthat do not fit the model may be related to heteroge-neities in the local stress field However nothinghas been said about the timing of this strike-slipsystem in relation to the magmatic metamorphicand tectonic evolution of the province
Coutinho et al (2000) reported model ages thatcluster around 196 Ga and 188 Ga and main-tained that these two ages reflect two mineralizingepochs Santos et al (2001) invoked a single eventat 186 Ga However as stated by Santos et al(2001) the tectonic regime at 186 Ga is brittle Thismodel does not explain the ductile emplacementandor deformed mineralization hosted especially bythe Cuiuacute-Cuiuacute gneisses and by the metavolcano-sedimentary sequences Another (older) mineraliz-ing phase is thus required
We proposed early in this paper that the majorstrike-slip regime that affected the Creporizatildeo Suiteand older units likely occurred between 197 and195 Ga Mineralization hosted in the Cuiuacute-Cuiuacutegneisses (at least in STP) is post-tectonic and post-metamorphic with respect to the host rocks sincehosting structures clearly crosscut the metamorphicbanding and the hydrothermal mineralogy is retro-gressive in relation to the metamorphic paragenesisDeformation affecting the Creporizatildeo granitoids isbrittle-ductile to brittle whereas deformation affect-ing younger granitoids is brittle Thus it is valid toinfer as a working hypothesis that at least in partgold mineralization in STP formed during regionalstrike-slip deformation and emplacement of late-stage plutons of the Creporizatildeo Suite at ~197ndash195Ga a time interval that is in agreement with thatobtained by Coutinho et al (2000) The structuresmay have been reactivated during younger deforma-tional episode(s) and gold deposits may haveformed at this stage as well
The challenge is to decipher which depositsformed at each metallogenic epoch From a struc-tural point of view it is likely that the deposits inSouthern Tapajoacutes Province that have been emplacedat deeper levels of the crust and that show evidenceof plastic deformation (ie the shear veins and thedeposits hosted in low-angle reverse-oblique faultssee Table 1) formed in the older phase Fault-fillveins that occur in association with these deposits inthe same gold camp (eg Boa Vista) probablyformed in the same event The rest of the fault-fillveins (with textures and structures indicating
emplacement in shallow brittle structures associ-ated or not with mafic dikes and showing no associ-ation with shear veins in the same gold camp) aswell as the breccia veins and stockworks may haveformed either in the older or in the younger phaseWe do not have elements to define this Thisrequires much more isotopic data along with addi-tional fluid-inclusion and stable-isotope informationto constrain physico-chemical conditions of golddeposition as well as knowledge of the sources andnature of the mineralizing fluids and the absolutetiming of gold deposition
The attributes shown by the gold deposits in STP(namely the regional structural setting depositstyle vein textures and hydrothermal mineralogy)along with scarce fluid-inclusion data fit with boththe orogenic (magmatic arc-hosted) and intrusion-related models as proposed by Santos et al (2001)the latter sharing characteristics with Korean-typedeposits (Robert et al 1997) as well
Acknowledgments
Alfreu dos Santos (formerly of CPRM) partici-pated in the field work and supervised the TapajoacutesProject His help is acknowledged This is a contri-bution to the project PRONEX-CNPq-FADESP6621031998-0ndashprocess no 4200000
REFERENCES
Almeida M E Brito M F L Ferreira A L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaVila Mamatildee Anatilde (SB21-V-D) Estados do Paraacute e Ama-zonas escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Almeida M E Brito M F L and Macambira M J B1999 Caroccedilal Granite 207Pb206Pb evaporation age inpost-collisional granitoids of Tapajoacutes Gold ProvinceAmazonian region Brazil [abs] in II South AmericanSymposium on Isotope Geology Coacuterdoba ArgentinaActas p 3ndash6
Almeida M E Ferreira A L Brito M F L and Mon-teiro M A S 2001 Evoluccedilatildeo tectono-estrutural daProviacutencia Tapajoacutes com base na geologia das folhas VilaMamatildee Anatilde e Jacareacanga (1250000) regiatildeo limitedos estados do Amazonas e Paraacute in Reis N J andMonteiro M A S orgs Contribuiccedilotildees agrave Geologia daAmazocircnia v 2 Manaus Brazil SBG-NO p 57ndash112
Bahia R B C and Quadros M L E S 2000 Geologiae recursos minerais da Folha Caracol (SB21-X-C)
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 557
Estado do Paraacute Escala 1250000 Brasiacutelia BrazilCPRMGeological Survey of Brazil (CD-ROM)
Cassidy K F Groves D I and McNaughton N J 1998Late-Archean granitoid-hosted lode-gold depositsYilgarn Craton Western Australia Deposit character-istics crustal architecture and implications for oregenesis Ore Geology Reviews v 13 p 65ndash102
Correcirca-Silva R H Juliani C Bettencourt J S NunesC M D and Almeida T I R 2001 Caracterizaccedilatildeode um sistema epitermal low-sulfidation (ou adulaacuteria-sericita) hospedado em vulcacircnicas e vulcanoclaacutesticasdo Grupo Iriri na Proviacutencia auriacutefera do Tapajoacutes (PA)[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Coutinho M G N Santos J O S Fallick A E andLafon J M 2000 Orogenic gold deposits in TapajoacutesMineral Province Amazon Brazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Dowling K and Morrison G 1989 Application ofquartz textures to the classification of gold depositsusing North Queensland examples Economic GeologyMonograph v 6 p 342ndash355
Dreher A M Vlach S and Martini S L 1998 Adu-laria associated with epithermal gold veins in theTapajoacutes Mineral Province Paraacute State Northern BrazilRevista Brasileira de Geociecircncias v 28 p 397ndash404
Faraco M T L Carvalho J M A and Klein E L1997 Carta metalogeneacutetica da Proviacutencia Auriacutefera doTapajoacutes in Costa M L and Angeacutelica R S orgsContribuiccedilotildees agrave Geologia da Amazocircnia Beleacutem BrazilFINEPSBG-NO p 423ndash437
Ferreira A L Almeida M E Brito M F L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaJacareacanga (SB21-Y-B) Estados do Paraacute e Amazo-nas escala 1250000 Brasiacutelia Brazil CPRMGeolog-ical Survey of Brazil (CD-ROM)
Goldfarb R J Groves D I and Gardoll S 2001 Oro-genic gold and geologic time A global synthesis OreGeology Reviews v 18 p 1ndash75
Groves D I Goldfarb R J Gebre-Mariam M Hage-mann S and Robert F 1998 Orogenic gold depos-its A proposed classification in the context of theircrustal distribution and relationship to other golddeposit types Ore Geology Reviews v 13 p 7ndash27
Hodgson C J 1989 The structure of shear-related vein-type gold deposits A review Ore Geology Reviews v4 p 231ndash273
Jacobi P 1999 The discovery of epithermal Au-Cu-MoProterozoic deposits in the Tapajoacutes Province BrazilRevista Brasileira de Geociecircncias v 29 p 277ndash279
Jeacutebrak M 1997 Hydrothermal breccias in vein-type oredeposits A review of mechanisms morphology andsize distribution Ore Geology Reviews v 12 p 111ndash134
Juliani C 2001 Metalogecircnese do ouro e metais de baseassociadas com o vulcanismo-plutonismo da porccedilatildeo Wda Proviacutencia Auriacutefera do Tapajoacutes [ext abs] in VIISimpoacutesio de Geologia da Amazocircnia Beleacutem Brazil(CD-ROM)
Kerrich R and Cassidy K F 1994 Temporal relation-ships of lode gold mineralization to accretion magma-tism metamorphism and deformationmdashArchean topresent A review Ore Geology Reviews v 9 p 263ndash310
Klein E L Almeida M E Vasquez M L BahiaR B C Quadros M L E S and Ferreira A L inpress Geologia e recursos minerais da Proviacutencia Min-eral do Tapajoacutes Estados do Paraacute e Amazonas Escala1 500000 Brasiacutelia Brazil CPRMGeological Surveyof Brazil
Klein E L Rosa-Costa L T and Carvalho J M A2000 Fluid inclusion studies at the Patinhas gold-quartz mineralisation Tapajoacutes Gold Province Brazil[abs] in XXXI International Geological Congress Riode Janeiro Brazil (CD-ROM)
Klein E L Santos R A Fuzikawa K and AngeacutelicaR S 2001 Hydrothermal fluid evolution and struc-tural control of the brittle-style Guarim lode-gold min-eralisation Tapajoacutes Province Amazonian CratonBrazil Mineralium Deposita v 36 p 149ndash164
Klein E L and Vasquez M L 2000 Projeto EspecialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Vila Riozinho (SB21-Z-A) Estadodo Paraacute escala 1250000 Brasiacutelia Brazil CPRMGeological Survey of Brazil (CD-ROM)
Klein E L Vasquez M L Santos A and Martins RC 1997 Structural elements of the Maloquinha Intru-sive Suite in Tapajoacutes Mineral Province northern Bra-zil and the emplacement of the plutons [ext abs] inII International Symposium on Granites and Associ-ated Mineralizations ISGAM II Salvador Brazil p313ndash314
Klein E L Vasquez M L Santos A and Rosa-CostaL T 1999 Geologia e controle estrutural das mineral-izaccedilotildees auriacuteferas na Folha Vila Riozinho e NW daFolha Rio Novo Proviacutencia Tapajoacutes [ext abs] in VISimpoacutesio de Geologia da Amazocircnia Manaus Brazil p128ndash131
Lamaratildeo C N DallrsquoAgnol R and Lafon J M 2001Geocronologia e geoquiacutemica das associaccedilotildees vulcacircni-cas e plutocircnicas da regiatildeo de Vila Riozinho ProviacutenciaAuriacutefera do Tapajoacutes [ext abs] in VII Simpoacutesio deGeologia da Amazocircnia Beleacutem Brazil (CD-ROM)
Nunes C M D Juliani C Correcirca-Silva R H Mon-teiro L V S Bettencourt J S Neumann R AlcoverNeto A and Rye R O 2001 Caracterizaccedilatildeo de umsistema epitermal high-sulfidation vulcacircnico pale-oproterozoacuteico da Proviacutencia Auriacutefera do Tapajoacutes Paraacute[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
558 KLEIN ET AL
Ricci P S F Vasquez M L Santos A Klein E LJorge Joatildeo X S and Martins R C 1999 SuiacuteteIntrusiva Creporizatildeo ndash Proviacutencia Tapajoacutes Proposta ecriteacuterios de definiccedilatildeo [ext abs] in VI Simpoacutesio deGeologia da Amazocircnia Manaus Brazil p 519ndash522
Robert F and Poulsen K H 2001 Vein formation anddeformation in greenstone gold deposits in RichardsJ P and Tosdal R M eds Structural controls on oregenesis Reviews in Economic Geology v 14 p 111ndash155
Robert F Poulsen K H and Dubeacute B 1997 Golddeposits and their geological classification in GubinsA G ed Proceedings of Exploration 97 TorontoCanada p 209ndash220
Ronchi L H DallrsquoAgnol R Araujo J C Ribeiro VLamaratildeo C N Borges R M K and Fuzikawa K2001 Fluidos relacionados agraves alteraccedilotildees hidrotermaisno depoacutesito de ouro do Granito Satildeo JorgendashPA [extabs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Rosa-Costa L T and Carvalho J M A 1999 Tipologiade mineralizaccedilotildees auriacuteferas da regiatildeo sul da ProviacutenciaTapajoacutesndashParaacute [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 176ndash179
Santos J O S Groves D I Hartmann L A MouraM A and McNaughton N J 2001 Gold deposits ofthe Tapajoacutes and Alta Floresta Domains Tapajoacutes-Parima orogenic belt Amazon Craton Brazil Minera-lium Deposita v 36 p 279ndash299
Santos J O S Hartmann L A Gaudette H E GrovesD I McNaughton N J and Fletcher I R 2000 Anew understanding of the provinces of the AmazonCraton based on integration of field mapping and U-Pband Sm-Nd geochronology Gondwana Research v 3p 453ndash488
Santos R A 1997 Contribuiccedilatildeo agrave anaacutelise estrutural dejazimentos auriacuteferos do rio Tapajoacutes SW do Paraacute e SEdo Amazonas Garimpos Abacaxis Espiacuterito SantoBom Jesus Goiano Fazenda Pison Ouro Mil SantaIsabel Majestade e Carneirinho Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 1999 Controle estrutural das mineralizaccedilotildees deouro da Proviacutencia Mineral do Tapajoacutes Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 2000 Formation of gold-quartz veins controlledby the strike-slip fault mega-system in Tapajoacutes Min-eral Province Amazon Brazil [abs] in XXXI Interna-tional Geological Congress Rio de Janeiro Brazil(CD-ROM)
Tassinari C C G 1996 O mapa geocronoloacutegico do Craacute-ton Amazocircnico no Brasil Revisatildeo dos dados isotoacutepi-cos Unpubl Tese de Livre Docecircncia Universidade deSatildeo Paulo 139 p
Tassinari C C G and Macambira M J B 1999 Geo-chronological provinces of the Amazonian Craton Epi-sodes v 22 p 174ndash182
Vasquez M L and Klein E L 2000 Projeto especialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Rio Novo (SB21-Z-C) Estado doParaacute escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Vasquez M L Klein E L Macambira M J B SantosA Bahia R B C Ricci P S F and QuadrosM L E S 2000 Geochronology of granitoids maficintrusions and mineralizations of the Tapajoacutes GoldProvincendashAmazonian CratonndashBrazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Vasquez M L Klein E L Quadros M L E S BahiaR B C Santos A Ricci P S F Sachett C RSilva C M G and Macambira M J B 1999 Mag-matismo Uatumatilde na Proviacutencia Tapajoacutesmdashnovos dadosgeocronoloacutegicos [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 471ndash474
Vasquez M L Klein E L and Ricci P S F 2001Granitoacuteides poacutes-colisionais da porccedilatildeo leste da Proviacuten-cia Tapajoacutes [ext abs] in VII Simpoacutesio de Geologia daAmazocircnia Beleacutem Brazil (CD-ROM)
Vearncombe J R 1993 Quartz vein morphology andimplications for formation depth and classification ofArchaean gold-vein deposits Ore Geology Reviews v8 p 407ndash424
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 551
the intrusive character of the granitoids Whole-rockgeochemistry (Lamaratildeo et al 2001 Vasquez et al2001) has shown that the Creporizatildeo Suite repre-sents calc-alkaline metaluminous to peraluminousmedium- to high-K arc-related granitoids The REEpatterns show that they are more evolved than theCuiuacute-Cuiuacute granitoids and gneisses U-Pb and Pb-evaporation dating of zircon (Ricci et al 1999Vasquez et al 2000 Santos et al 2000 2001Lamaratildeo et al 2001) indicate crystallization agesbetween 1997 Ma and 1957 Ma This late timingwith respect to the Cuiuacute-Cuiuacute Complex along withthe geochemical characteristics the structural andmetamorphic differences the lack of volcano-sedi-mentary basins associated with the Creporizatildeo gran-itoids and their common association with regionalstrike-slip shear zones led Vasquez et al (2001) toconsider the Creporizatildeo Suite as representing apost-collisional magmatism still related to thedevelopment of the Cuiuacute-Cuiuacute magmatic arc andnot an individual arc (Creporizatildeo arc) as proposedby Santos et al (2001)
Ore mineralogy and wall-rock alteration
Many prospects are still undeveloped and work-ings are restricted to the oxidized (saprolite) zonewhere veins and structures are well preserved buthydrothermal alteration in the immediate host rockis overprinted by secondary processes Henceinformation in these cases is restricted to the veinassemblage and in a few cases to distal alterationwhich can be seen tens or a few hundreds of metersoff of the mineralized zone
Pyrite is the dominant sulfide mineral (Table 1)occurring in most of the deposits in general as dis-seminations filling fractures and cavities in thequartz veins in the contact between vein and hostrock or less commonly forming decimeter-wideaggregates (Fig 6) Chalcopyrite follows pyrite inimportance always occurring in association withpyrite whereas galena and arsenopyrite occur onlylocally
The gangue mineralogy shows little variationwith white mica being the main mineral (followingquartz) present in the quartz veins occurring how-ever in small amounts White mica is also wide-spread in the hydrothermally altered wall rocksoccurring in association with quartz minor amountsof chlorite and scarce carbonate K-feldspar andepidote
Structural controlInvestigation of mesoscopic and macroscopic
features of deposits of the STP showed that they arestrictly structurally controlled in all scalesRegional structures may have played importantroles acting as conduits for mineralizing fluids andcontrolling the distribution of the deposits The goldcamps are located close to or bounded by majorfirst-order faults and shear zones located in low-strain domains between them and rarely withinthese deformation zones (Figs 2 and 3) At campand deposit scales the orientation of the mineral-ized veins is controlled by the orientation andorgeometry of the hosting lower-order structures(Klein et al 1999 Santos 1999 2000)
Structural styles and internal structure
Fault-fill veins This type is by far the most com-mon structural style in STP and in the province as awhole (Klein et al 1999) The deposits consist of asingle quartz vein emplaced in subvertical struc-tures (Fig 4) These are mostly faults with subordi-
FIG 4 Photograph of the surface exposure of a fault-fillvein (outlined by the heavy lines) at Mineiro-2 The hydro-thermal envelope is outlined by the dashed line
552 KLEIN ET AL
nate narrow brittle-ductile shear zones Theirorientations are variable with concentrations ofveins along the N20degndash70degE and N40ndash50W direc-tions The veins are centimeter- to decimeter-thickand consist of milky quartz with minor (lt5) K-feldspar white mica chlorite and sulfide mineralsOccasionally thin extensionalndashoblique quartz toquartzo-feldspathic veinlets occur attached to themain quartz vein (Fig 5) The internal structure ofthe veins is dominantly formed by massive quartz(Fig 6) Laminated saccharoidal and open-spacefilling (comb) textures and hydrothermal brecciasare subordinate A few veins are positioned at thecontact between mafic dikes and the altered countryrock or even cut across the dikes suggesting inthese cases their late timing with respect to thedikes In one situation (Pau DrsquoArco) mineralizationlacks a major quartz vein (only a few discontinuousveinlets are present) and occurs as disseminationsin the hydrothermal zone that surrounds a subverti-cal strike-slip fault
Shear veins In greenstone-hosted deposits shearveins are usually described as fault-fill veinsbecause they occupy faults and the central parts ofshear zones (Hodgson 1989) and because it is con-sidered difficult to define if the veins formed as aresult of displacements along a shear fracture or asthe result of dilation of preexisting shear fractures orductile fabric (eg Robert and Poulsen 2001 and
references therein) In STP shear and fault-fill veinsshare a series of characteristics However in thispaper we prefer to classify them separately at leastfor descriptive purposes because shear veins differfrom fault-fill veins by the fact that they have beenemplaced in ductile-brittle structures (ComandanteRenan Novo Vietnam Fig 5) andor show effects ofductile deformation such as quartz grains withundulose extinction and deformation bands sur-rounded by small recrystallized subgrains (Patin-has) microscopic shear zones (Mineiro-1) andductile fabric either in the vein or in the immediatehost rock (Novo Vietnam) (Fig 5) The internalstructure is chiefly massive to laminated andsheared (Figs 6 and 7) Extensional features suchas breccias and en echelon sulfides (Fig 7) also arepresent
Low- (to moderate-) angle reverse-oblique faultsTwo examples have been observed At the Boa Vistagold field along with fault-fill and breccia veinspresent in several occurrences the main mineraliza-tion consists of a series of subparallel verticallystacked sigmoidal quartz veins (Fig 8A) separatedby hydrothermally altered and strongly foliated hostrock (schist) The veins show variable thicknessfrom a few centimeters up to one meter and strike toN45ordmndash80ordmW dipping 30ordm to 45ordm to the southwestInternally the milky veins show massive to saccha-roidal textures Small amounts of pyrite and minor
FIG 5 Sketch map (plan view) of the shear vein at Novo Vietnam The vein is surrounded by mylonitized wall rockand shows extensional veinlets attached on both sides The vein is massive to laminated and continuous but is formedby discontinuous veinlets (inset) between the two bends
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 553
arsenopyrite are disseminated throughout the veinsand altered wall rock Pyrite occurs filling smallfractures in quartz as well and sericite is presentboth in the vein and in the immediate wall rock
Given the weathered character of the terrainfresh rocks could not be observed in the mineralizedzone and the nature of the host rock could not beconfidently determined A few tens of meters off themineralized zone an undeformed porphyritic maficvolcanic rock crops out The region in turn is dom-inated by granitoids of the Creporizatildeo Suite that isthe host for all other occurrences in the same goldfield The hosting schist may derive from one ofthese two rock types by a combination of intense
deformation and high fluidrock ratios Alterna-tively it may represent a fragment of the metavol-cano-sedimentary sequence of the JacareacangaGroup which has not as yet been recognized in thisportion of the Tapajoacutes Province occurring as mega-xenoliths or roof pendants within the granitoids ofthe Creporizatildeo Suite
In the Satildeo Raimundo deposit mineralizationoccurs in narrow hydrothermal halos envelopinganastomosed shearfault planes in brittle-ductileshear zones (Fig 8B) The hosting shear zones strikeN45ordmndash60ordmE and dip 25ordmndash40ordm SE and the mineralizedzones are up to 2 meters thick (Rosa-Costa and Car-valho 1999) Quartz is generally absent and occurs
FIG 6 A Milky massive quartz with high pyrite contents at Patinhas B Sheared sulfide-poor quartz vein (Patinhas)C Quartz vein with sulfide minerals filling cavities (Novo Vietnam)
FIG 7 Vein structures at Mineiro-1 A Laminated quartz-pyrite veinlet (V) crosscutting the hydrothermally alteredhost rock Alteration is zoned and symmetric (arrows) B Milky massive quartz with extensional fracture filled by sulfideminerals with an en echelon distribution C Hydrothermal breccia formed by quartz (white) and hydrothermally alteredhost rock (grey)
554 KLEIN ET AL
only as small isolated and discontinuous veinletspositioned in the fault planes The host rock is amonzogranite of the Creporizatildeo Suite
Breccia veins Four main occurrences have beenrecorded forming tabular structures of less than 1 min thickness The breccia veins at Ceacuteu Azul andAacutegua Limpa consist of fragments of milky quartzwith angular to rounded shape ranging in size frommm to a few cm (Fig 9) set in a fine-grained red-dish to greenish hydrothermal matrix composed ofquartz feldspar and hematite along with fine-grained sericite and epidote Microscopically dif-ferent quartz fragments show textures such as comband rosettes indicating the shallow emplacement ofthese veins (Dowling and Morrison 1989 Vearn-combe 1993) At Goiano and Ouro Mil the brecciashave less matrix and the quartz fragments are moreangular than in the two other examples
Brecciation occurs also as a minor portion of ashear vein at the Mineiro-1 prospect in the BoaVista gold camp These breccias also differ from theformer by the fact that the angular quartz fragmentsare set in a matrix composed of altered wall rock(Fig 7C)
Stockworks This style has been identified at theIndependecircncia deposit It consists of multidirec-tional quartz veins a few centimeters thick envel-
oped by narrow halos of hydrothermal alterationThe veins are generally widely spaced occurring inan area of ~100 m times tens of meters Locally how-ever they are closely spaced with several individ-ual hydrothermal halos overlapping each otherforming larger areas of hydrothermally altered hostrock The quartz has a milky to smoky characterand shows cavities usually filled by sulfide miner-als Epidote and white mica are common gangueminerals In places large pockets of hydrothermalalteration lacking quartz veins are observed aswell Minor stockworks and networks (the veins as awhole show the same orientation of the veinbrec-cia) occur at Ouro Mil in both margins of the mainbreccia vein (Santos 1997)
Discussion and Concluding Remarks
Gold deposits in the Tapajoacutes Province are hostedin a variety of metamorphic and magmatic rocks InSouthern Tapajoacutes Province (STP) with one excep-tion only orthogneisses of the Cuiuacute-Cuiuacute Complexand orogenic granitoids of the Creporizatildeo Suite areknown hosts for gold Hosting granitoids are domi-nantly monzogranitic in composition whereas theorthogneisses show tonalitic and granodioritic com-positions
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 555
The deposits have been classified in a few struc-tural styles according to the hosting structurestructural regime in which they have been formedand internal structures and textures of the veinsAccordingly fault-fill and shear veins are the domi-nant style followed by subordinate occurrences ofveins hosted in low-angle reverse-oblique faultsbreccia veins and stockworks More than one stylemay occur in the same gold camp and even in a sin-gle deposit
Fault-fill and shear veins as well as brecciaveins form moderately to steeply dipping tabularbodies that seldom exceed one meter in thicknessand are hosted by strike-slip faults and shear zonesto which they are parallel The vein quartz is domi-nantly massive with laminated saccharoidal andcomb textures occurring subordinately Shearingand cataclasis of the veins is widespread suggest-ing along with other textural and structural evi-dence their positioning in active faults and shearzones or deformation after formation In most casesquartz white mica and pyrite compose the veinmineralogy and along with minor chlorite carbon-ate epidote and K-feldspar they overprint the pri-mary mineralogy of the hosting granitoids and theamphibolite-facies paragenesis of the hostinggneisses
The breccias have likely been produced duringfracture propagation by physical brecciation whichoccurs when the amount of stress exceeds the brittleresistance of the rock by mechanisms such as tec-tonic comminution andor fluid-assisted brecciation(Jeacutebrak 1997) Furthermore they indicate activeseismic slip during mineralization (Robert andPoulsen 2001)
The origin of the large stockwork at Independecircn-cia may be ascribed to hydraulic fracturing occur-ring over a cupola of a small aplitic granitoidrelated to or intruding the regional coarse-grainedmonzogranite of the Creporizatildeo Suite In the latterhypothesis it could be related either to a late-stagepluton of the Creporizatildeo Suite or to a younger grani-toid suite (Parauari) This definition requires geo-chronological support
Deposits and gold camps show strong structuralcontrol at all scales The hosting structures havebeen formed under a dominantly brittle-ductile tobrittle regime and consist of strike slip faults shearfractures intersection and bending of faults andlithological andor lithostratigraphic contactsExtensional fractures have not been characterizedas hosting structures because evidence of displace-
ment andor shearing is virtually always present inthe veins Extensional features are present howeveras en echelon arrays of sulfide minerals and as vein-lets attached to the main longitudinal fault veinsDeposits hosted in granitoids show a more brittlebehavior whereas those hosted in gneisses tend todisplay more ductile features This can result eitherfrom the depth of vein formation or from high fluidrock ratios even in shallow levels of the crust
Formation of deposits occurred in a range ofcrustal depth from mesozonal to epizonal condi-tions as indicated by the internal structure of thequartz veins and by the nature of the hosting struc-tures This is also supported by fluid inclusion stud-ies in a few deposits such as Guarim (Klein et al2001) and Patinhas (Klein et al 2000) both depos-its hosted in gneisses of the Cuiuacute-Cuiuacute ComplexFluid composition is nearly identical but P-T dataalong with textural and structural evidence suggestthat Guarim (outside STP) formed between 4 and 7km whereas Patinhas (within STP) formed at deeperlevels
Hence shear veins and fault-fill veins may beconsidered at least in part and from a structuralview as a single class of structural style with theirdifferences being ascribed to different depths ofemplacement and structural overprint It is not ourintention however to state that all of these veinsformed in a single gold-forming event The issue ofhow many mineralizing events have occurred in theTapajoacutes Province is still unresolved
Santos (1999 2000) studying 23 depositsthroughout the province (including three deposits inSTP) reported a set of characteristics similar tothose we have found in STP He concluded that alldeposits are related to a regional NW-SEndashtrendingstrike-slip fault system and that the orientation of
FIG 9 Breccia vein at Ceacuteu Azul
556 KLEIN ET AL
the lower-order hosting structures is compatiblewith Riedelrsquos system with the direction of the mainstress vector around the E-W direction Orientationsthat do not fit the model may be related to heteroge-neities in the local stress field However nothinghas been said about the timing of this strike-slipsystem in relation to the magmatic metamorphicand tectonic evolution of the province
Coutinho et al (2000) reported model ages thatcluster around 196 Ga and 188 Ga and main-tained that these two ages reflect two mineralizingepochs Santos et al (2001) invoked a single eventat 186 Ga However as stated by Santos et al(2001) the tectonic regime at 186 Ga is brittle Thismodel does not explain the ductile emplacementandor deformed mineralization hosted especially bythe Cuiuacute-Cuiuacute gneisses and by the metavolcano-sedimentary sequences Another (older) mineraliz-ing phase is thus required
We proposed early in this paper that the majorstrike-slip regime that affected the Creporizatildeo Suiteand older units likely occurred between 197 and195 Ga Mineralization hosted in the Cuiuacute-Cuiuacutegneisses (at least in STP) is post-tectonic and post-metamorphic with respect to the host rocks sincehosting structures clearly crosscut the metamorphicbanding and the hydrothermal mineralogy is retro-gressive in relation to the metamorphic paragenesisDeformation affecting the Creporizatildeo granitoids isbrittle-ductile to brittle whereas deformation affect-ing younger granitoids is brittle Thus it is valid toinfer as a working hypothesis that at least in partgold mineralization in STP formed during regionalstrike-slip deformation and emplacement of late-stage plutons of the Creporizatildeo Suite at ~197ndash195Ga a time interval that is in agreement with thatobtained by Coutinho et al (2000) The structuresmay have been reactivated during younger deforma-tional episode(s) and gold deposits may haveformed at this stage as well
The challenge is to decipher which depositsformed at each metallogenic epoch From a struc-tural point of view it is likely that the deposits inSouthern Tapajoacutes Province that have been emplacedat deeper levels of the crust and that show evidenceof plastic deformation (ie the shear veins and thedeposits hosted in low-angle reverse-oblique faultssee Table 1) formed in the older phase Fault-fillveins that occur in association with these deposits inthe same gold camp (eg Boa Vista) probablyformed in the same event The rest of the fault-fillveins (with textures and structures indicating
emplacement in shallow brittle structures associ-ated or not with mafic dikes and showing no associ-ation with shear veins in the same gold camp) aswell as the breccia veins and stockworks may haveformed either in the older or in the younger phaseWe do not have elements to define this Thisrequires much more isotopic data along with addi-tional fluid-inclusion and stable-isotope informationto constrain physico-chemical conditions of golddeposition as well as knowledge of the sources andnature of the mineralizing fluids and the absolutetiming of gold deposition
The attributes shown by the gold deposits in STP(namely the regional structural setting depositstyle vein textures and hydrothermal mineralogy)along with scarce fluid-inclusion data fit with boththe orogenic (magmatic arc-hosted) and intrusion-related models as proposed by Santos et al (2001)the latter sharing characteristics with Korean-typedeposits (Robert et al 1997) as well
Acknowledgments
Alfreu dos Santos (formerly of CPRM) partici-pated in the field work and supervised the TapajoacutesProject His help is acknowledged This is a contri-bution to the project PRONEX-CNPq-FADESP6621031998-0ndashprocess no 4200000
REFERENCES
Almeida M E Brito M F L Ferreira A L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaVila Mamatildee Anatilde (SB21-V-D) Estados do Paraacute e Ama-zonas escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Almeida M E Brito M F L and Macambira M J B1999 Caroccedilal Granite 207Pb206Pb evaporation age inpost-collisional granitoids of Tapajoacutes Gold ProvinceAmazonian region Brazil [abs] in II South AmericanSymposium on Isotope Geology Coacuterdoba ArgentinaActas p 3ndash6
Almeida M E Ferreira A L Brito M F L and Mon-teiro M A S 2001 Evoluccedilatildeo tectono-estrutural daProviacutencia Tapajoacutes com base na geologia das folhas VilaMamatildee Anatilde e Jacareacanga (1250000) regiatildeo limitedos estados do Amazonas e Paraacute in Reis N J andMonteiro M A S orgs Contribuiccedilotildees agrave Geologia daAmazocircnia v 2 Manaus Brazil SBG-NO p 57ndash112
Bahia R B C and Quadros M L E S 2000 Geologiae recursos minerais da Folha Caracol (SB21-X-C)
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 557
Estado do Paraacute Escala 1250000 Brasiacutelia BrazilCPRMGeological Survey of Brazil (CD-ROM)
Cassidy K F Groves D I and McNaughton N J 1998Late-Archean granitoid-hosted lode-gold depositsYilgarn Craton Western Australia Deposit character-istics crustal architecture and implications for oregenesis Ore Geology Reviews v 13 p 65ndash102
Correcirca-Silva R H Juliani C Bettencourt J S NunesC M D and Almeida T I R 2001 Caracterizaccedilatildeode um sistema epitermal low-sulfidation (ou adulaacuteria-sericita) hospedado em vulcacircnicas e vulcanoclaacutesticasdo Grupo Iriri na Proviacutencia auriacutefera do Tapajoacutes (PA)[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Coutinho M G N Santos J O S Fallick A E andLafon J M 2000 Orogenic gold deposits in TapajoacutesMineral Province Amazon Brazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Dowling K and Morrison G 1989 Application ofquartz textures to the classification of gold depositsusing North Queensland examples Economic GeologyMonograph v 6 p 342ndash355
Dreher A M Vlach S and Martini S L 1998 Adu-laria associated with epithermal gold veins in theTapajoacutes Mineral Province Paraacute State Northern BrazilRevista Brasileira de Geociecircncias v 28 p 397ndash404
Faraco M T L Carvalho J M A and Klein E L1997 Carta metalogeneacutetica da Proviacutencia Auriacutefera doTapajoacutes in Costa M L and Angeacutelica R S orgsContribuiccedilotildees agrave Geologia da Amazocircnia Beleacutem BrazilFINEPSBG-NO p 423ndash437
Ferreira A L Almeida M E Brito M F L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaJacareacanga (SB21-Y-B) Estados do Paraacute e Amazo-nas escala 1250000 Brasiacutelia Brazil CPRMGeolog-ical Survey of Brazil (CD-ROM)
Goldfarb R J Groves D I and Gardoll S 2001 Oro-genic gold and geologic time A global synthesis OreGeology Reviews v 18 p 1ndash75
Groves D I Goldfarb R J Gebre-Mariam M Hage-mann S and Robert F 1998 Orogenic gold depos-its A proposed classification in the context of theircrustal distribution and relationship to other golddeposit types Ore Geology Reviews v 13 p 7ndash27
Hodgson C J 1989 The structure of shear-related vein-type gold deposits A review Ore Geology Reviews v4 p 231ndash273
Jacobi P 1999 The discovery of epithermal Au-Cu-MoProterozoic deposits in the Tapajoacutes Province BrazilRevista Brasileira de Geociecircncias v 29 p 277ndash279
Jeacutebrak M 1997 Hydrothermal breccias in vein-type oredeposits A review of mechanisms morphology andsize distribution Ore Geology Reviews v 12 p 111ndash134
Juliani C 2001 Metalogecircnese do ouro e metais de baseassociadas com o vulcanismo-plutonismo da porccedilatildeo Wda Proviacutencia Auriacutefera do Tapajoacutes [ext abs] in VIISimpoacutesio de Geologia da Amazocircnia Beleacutem Brazil(CD-ROM)
Kerrich R and Cassidy K F 1994 Temporal relation-ships of lode gold mineralization to accretion magma-tism metamorphism and deformationmdashArchean topresent A review Ore Geology Reviews v 9 p 263ndash310
Klein E L Almeida M E Vasquez M L BahiaR B C Quadros M L E S and Ferreira A L inpress Geologia e recursos minerais da Proviacutencia Min-eral do Tapajoacutes Estados do Paraacute e Amazonas Escala1 500000 Brasiacutelia Brazil CPRMGeological Surveyof Brazil
Klein E L Rosa-Costa L T and Carvalho J M A2000 Fluid inclusion studies at the Patinhas gold-quartz mineralisation Tapajoacutes Gold Province Brazil[abs] in XXXI International Geological Congress Riode Janeiro Brazil (CD-ROM)
Klein E L Santos R A Fuzikawa K and AngeacutelicaR S 2001 Hydrothermal fluid evolution and struc-tural control of the brittle-style Guarim lode-gold min-eralisation Tapajoacutes Province Amazonian CratonBrazil Mineralium Deposita v 36 p 149ndash164
Klein E L and Vasquez M L 2000 Projeto EspecialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Vila Riozinho (SB21-Z-A) Estadodo Paraacute escala 1250000 Brasiacutelia Brazil CPRMGeological Survey of Brazil (CD-ROM)
Klein E L Vasquez M L Santos A and Martins RC 1997 Structural elements of the Maloquinha Intru-sive Suite in Tapajoacutes Mineral Province northern Bra-zil and the emplacement of the plutons [ext abs] inII International Symposium on Granites and Associ-ated Mineralizations ISGAM II Salvador Brazil p313ndash314
Klein E L Vasquez M L Santos A and Rosa-CostaL T 1999 Geologia e controle estrutural das mineral-izaccedilotildees auriacuteferas na Folha Vila Riozinho e NW daFolha Rio Novo Proviacutencia Tapajoacutes [ext abs] in VISimpoacutesio de Geologia da Amazocircnia Manaus Brazil p128ndash131
Lamaratildeo C N DallrsquoAgnol R and Lafon J M 2001Geocronologia e geoquiacutemica das associaccedilotildees vulcacircni-cas e plutocircnicas da regiatildeo de Vila Riozinho ProviacutenciaAuriacutefera do Tapajoacutes [ext abs] in VII Simpoacutesio deGeologia da Amazocircnia Beleacutem Brazil (CD-ROM)
Nunes C M D Juliani C Correcirca-Silva R H Mon-teiro L V S Bettencourt J S Neumann R AlcoverNeto A and Rye R O 2001 Caracterizaccedilatildeo de umsistema epitermal high-sulfidation vulcacircnico pale-oproterozoacuteico da Proviacutencia Auriacutefera do Tapajoacutes Paraacute[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
558 KLEIN ET AL
Ricci P S F Vasquez M L Santos A Klein E LJorge Joatildeo X S and Martins R C 1999 SuiacuteteIntrusiva Creporizatildeo ndash Proviacutencia Tapajoacutes Proposta ecriteacuterios de definiccedilatildeo [ext abs] in VI Simpoacutesio deGeologia da Amazocircnia Manaus Brazil p 519ndash522
Robert F and Poulsen K H 2001 Vein formation anddeformation in greenstone gold deposits in RichardsJ P and Tosdal R M eds Structural controls on oregenesis Reviews in Economic Geology v 14 p 111ndash155
Robert F Poulsen K H and Dubeacute B 1997 Golddeposits and their geological classification in GubinsA G ed Proceedings of Exploration 97 TorontoCanada p 209ndash220
Ronchi L H DallrsquoAgnol R Araujo J C Ribeiro VLamaratildeo C N Borges R M K and Fuzikawa K2001 Fluidos relacionados agraves alteraccedilotildees hidrotermaisno depoacutesito de ouro do Granito Satildeo JorgendashPA [extabs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Rosa-Costa L T and Carvalho J M A 1999 Tipologiade mineralizaccedilotildees auriacuteferas da regiatildeo sul da ProviacutenciaTapajoacutesndashParaacute [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 176ndash179
Santos J O S Groves D I Hartmann L A MouraM A and McNaughton N J 2001 Gold deposits ofthe Tapajoacutes and Alta Floresta Domains Tapajoacutes-Parima orogenic belt Amazon Craton Brazil Minera-lium Deposita v 36 p 279ndash299
Santos J O S Hartmann L A Gaudette H E GrovesD I McNaughton N J and Fletcher I R 2000 Anew understanding of the provinces of the AmazonCraton based on integration of field mapping and U-Pband Sm-Nd geochronology Gondwana Research v 3p 453ndash488
Santos R A 1997 Contribuiccedilatildeo agrave anaacutelise estrutural dejazimentos auriacuteferos do rio Tapajoacutes SW do Paraacute e SEdo Amazonas Garimpos Abacaxis Espiacuterito SantoBom Jesus Goiano Fazenda Pison Ouro Mil SantaIsabel Majestade e Carneirinho Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 1999 Controle estrutural das mineralizaccedilotildees deouro da Proviacutencia Mineral do Tapajoacutes Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 2000 Formation of gold-quartz veins controlledby the strike-slip fault mega-system in Tapajoacutes Min-eral Province Amazon Brazil [abs] in XXXI Interna-tional Geological Congress Rio de Janeiro Brazil(CD-ROM)
Tassinari C C G 1996 O mapa geocronoloacutegico do Craacute-ton Amazocircnico no Brasil Revisatildeo dos dados isotoacutepi-cos Unpubl Tese de Livre Docecircncia Universidade deSatildeo Paulo 139 p
Tassinari C C G and Macambira M J B 1999 Geo-chronological provinces of the Amazonian Craton Epi-sodes v 22 p 174ndash182
Vasquez M L and Klein E L 2000 Projeto especialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Rio Novo (SB21-Z-C) Estado doParaacute escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Vasquez M L Klein E L Macambira M J B SantosA Bahia R B C Ricci P S F and QuadrosM L E S 2000 Geochronology of granitoids maficintrusions and mineralizations of the Tapajoacutes GoldProvincendashAmazonian CratonndashBrazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Vasquez M L Klein E L Quadros M L E S BahiaR B C Santos A Ricci P S F Sachett C RSilva C M G and Macambira M J B 1999 Mag-matismo Uatumatilde na Proviacutencia Tapajoacutesmdashnovos dadosgeocronoloacutegicos [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 471ndash474
Vasquez M L Klein E L and Ricci P S F 2001Granitoacuteides poacutes-colisionais da porccedilatildeo leste da Proviacuten-cia Tapajoacutes [ext abs] in VII Simpoacutesio de Geologia daAmazocircnia Beleacutem Brazil (CD-ROM)
Vearncombe J R 1993 Quartz vein morphology andimplications for formation depth and classification ofArchaean gold-vein deposits Ore Geology Reviews v8 p 407ndash424
552 KLEIN ET AL
nate narrow brittle-ductile shear zones Theirorientations are variable with concentrations ofveins along the N20degndash70degE and N40ndash50W direc-tions The veins are centimeter- to decimeter-thickand consist of milky quartz with minor (lt5) K-feldspar white mica chlorite and sulfide mineralsOccasionally thin extensionalndashoblique quartz toquartzo-feldspathic veinlets occur attached to themain quartz vein (Fig 5) The internal structure ofthe veins is dominantly formed by massive quartz(Fig 6) Laminated saccharoidal and open-spacefilling (comb) textures and hydrothermal brecciasare subordinate A few veins are positioned at thecontact between mafic dikes and the altered countryrock or even cut across the dikes suggesting inthese cases their late timing with respect to thedikes In one situation (Pau DrsquoArco) mineralizationlacks a major quartz vein (only a few discontinuousveinlets are present) and occurs as disseminationsin the hydrothermal zone that surrounds a subverti-cal strike-slip fault
Shear veins In greenstone-hosted deposits shearveins are usually described as fault-fill veinsbecause they occupy faults and the central parts ofshear zones (Hodgson 1989) and because it is con-sidered difficult to define if the veins formed as aresult of displacements along a shear fracture or asthe result of dilation of preexisting shear fractures orductile fabric (eg Robert and Poulsen 2001 and
references therein) In STP shear and fault-fill veinsshare a series of characteristics However in thispaper we prefer to classify them separately at leastfor descriptive purposes because shear veins differfrom fault-fill veins by the fact that they have beenemplaced in ductile-brittle structures (ComandanteRenan Novo Vietnam Fig 5) andor show effects ofductile deformation such as quartz grains withundulose extinction and deformation bands sur-rounded by small recrystallized subgrains (Patin-has) microscopic shear zones (Mineiro-1) andductile fabric either in the vein or in the immediatehost rock (Novo Vietnam) (Fig 5) The internalstructure is chiefly massive to laminated andsheared (Figs 6 and 7) Extensional features suchas breccias and en echelon sulfides (Fig 7) also arepresent
Low- (to moderate-) angle reverse-oblique faultsTwo examples have been observed At the Boa Vistagold field along with fault-fill and breccia veinspresent in several occurrences the main mineraliza-tion consists of a series of subparallel verticallystacked sigmoidal quartz veins (Fig 8A) separatedby hydrothermally altered and strongly foliated hostrock (schist) The veins show variable thicknessfrom a few centimeters up to one meter and strike toN45ordmndash80ordmW dipping 30ordm to 45ordm to the southwestInternally the milky veins show massive to saccha-roidal textures Small amounts of pyrite and minor
FIG 5 Sketch map (plan view) of the shear vein at Novo Vietnam The vein is surrounded by mylonitized wall rockand shows extensional veinlets attached on both sides The vein is massive to laminated and continuous but is formedby discontinuous veinlets (inset) between the two bends
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 553
arsenopyrite are disseminated throughout the veinsand altered wall rock Pyrite occurs filling smallfractures in quartz as well and sericite is presentboth in the vein and in the immediate wall rock
Given the weathered character of the terrainfresh rocks could not be observed in the mineralizedzone and the nature of the host rock could not beconfidently determined A few tens of meters off themineralized zone an undeformed porphyritic maficvolcanic rock crops out The region in turn is dom-inated by granitoids of the Creporizatildeo Suite that isthe host for all other occurrences in the same goldfield The hosting schist may derive from one ofthese two rock types by a combination of intense
deformation and high fluidrock ratios Alterna-tively it may represent a fragment of the metavol-cano-sedimentary sequence of the JacareacangaGroup which has not as yet been recognized in thisportion of the Tapajoacutes Province occurring as mega-xenoliths or roof pendants within the granitoids ofthe Creporizatildeo Suite
In the Satildeo Raimundo deposit mineralizationoccurs in narrow hydrothermal halos envelopinganastomosed shearfault planes in brittle-ductileshear zones (Fig 8B) The hosting shear zones strikeN45ordmndash60ordmE and dip 25ordmndash40ordm SE and the mineralizedzones are up to 2 meters thick (Rosa-Costa and Car-valho 1999) Quartz is generally absent and occurs
FIG 6 A Milky massive quartz with high pyrite contents at Patinhas B Sheared sulfide-poor quartz vein (Patinhas)C Quartz vein with sulfide minerals filling cavities (Novo Vietnam)
FIG 7 Vein structures at Mineiro-1 A Laminated quartz-pyrite veinlet (V) crosscutting the hydrothermally alteredhost rock Alteration is zoned and symmetric (arrows) B Milky massive quartz with extensional fracture filled by sulfideminerals with an en echelon distribution C Hydrothermal breccia formed by quartz (white) and hydrothermally alteredhost rock (grey)
554 KLEIN ET AL
only as small isolated and discontinuous veinletspositioned in the fault planes The host rock is amonzogranite of the Creporizatildeo Suite
Breccia veins Four main occurrences have beenrecorded forming tabular structures of less than 1 min thickness The breccia veins at Ceacuteu Azul andAacutegua Limpa consist of fragments of milky quartzwith angular to rounded shape ranging in size frommm to a few cm (Fig 9) set in a fine-grained red-dish to greenish hydrothermal matrix composed ofquartz feldspar and hematite along with fine-grained sericite and epidote Microscopically dif-ferent quartz fragments show textures such as comband rosettes indicating the shallow emplacement ofthese veins (Dowling and Morrison 1989 Vearn-combe 1993) At Goiano and Ouro Mil the brecciashave less matrix and the quartz fragments are moreangular than in the two other examples
Brecciation occurs also as a minor portion of ashear vein at the Mineiro-1 prospect in the BoaVista gold camp These breccias also differ from theformer by the fact that the angular quartz fragmentsare set in a matrix composed of altered wall rock(Fig 7C)
Stockworks This style has been identified at theIndependecircncia deposit It consists of multidirec-tional quartz veins a few centimeters thick envel-
oped by narrow halos of hydrothermal alterationThe veins are generally widely spaced occurring inan area of ~100 m times tens of meters Locally how-ever they are closely spaced with several individ-ual hydrothermal halos overlapping each otherforming larger areas of hydrothermally altered hostrock The quartz has a milky to smoky characterand shows cavities usually filled by sulfide miner-als Epidote and white mica are common gangueminerals In places large pockets of hydrothermalalteration lacking quartz veins are observed aswell Minor stockworks and networks (the veins as awhole show the same orientation of the veinbrec-cia) occur at Ouro Mil in both margins of the mainbreccia vein (Santos 1997)
Discussion and Concluding Remarks
Gold deposits in the Tapajoacutes Province are hostedin a variety of metamorphic and magmatic rocks InSouthern Tapajoacutes Province (STP) with one excep-tion only orthogneisses of the Cuiuacute-Cuiuacute Complexand orogenic granitoids of the Creporizatildeo Suite areknown hosts for gold Hosting granitoids are domi-nantly monzogranitic in composition whereas theorthogneisses show tonalitic and granodioritic com-positions
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 555
The deposits have been classified in a few struc-tural styles according to the hosting structurestructural regime in which they have been formedand internal structures and textures of the veinsAccordingly fault-fill and shear veins are the domi-nant style followed by subordinate occurrences ofveins hosted in low-angle reverse-oblique faultsbreccia veins and stockworks More than one stylemay occur in the same gold camp and even in a sin-gle deposit
Fault-fill and shear veins as well as brecciaveins form moderately to steeply dipping tabularbodies that seldom exceed one meter in thicknessand are hosted by strike-slip faults and shear zonesto which they are parallel The vein quartz is domi-nantly massive with laminated saccharoidal andcomb textures occurring subordinately Shearingand cataclasis of the veins is widespread suggest-ing along with other textural and structural evi-dence their positioning in active faults and shearzones or deformation after formation In most casesquartz white mica and pyrite compose the veinmineralogy and along with minor chlorite carbon-ate epidote and K-feldspar they overprint the pri-mary mineralogy of the hosting granitoids and theamphibolite-facies paragenesis of the hostinggneisses
The breccias have likely been produced duringfracture propagation by physical brecciation whichoccurs when the amount of stress exceeds the brittleresistance of the rock by mechanisms such as tec-tonic comminution andor fluid-assisted brecciation(Jeacutebrak 1997) Furthermore they indicate activeseismic slip during mineralization (Robert andPoulsen 2001)
The origin of the large stockwork at Independecircn-cia may be ascribed to hydraulic fracturing occur-ring over a cupola of a small aplitic granitoidrelated to or intruding the regional coarse-grainedmonzogranite of the Creporizatildeo Suite In the latterhypothesis it could be related either to a late-stagepluton of the Creporizatildeo Suite or to a younger grani-toid suite (Parauari) This definition requires geo-chronological support
Deposits and gold camps show strong structuralcontrol at all scales The hosting structures havebeen formed under a dominantly brittle-ductile tobrittle regime and consist of strike slip faults shearfractures intersection and bending of faults andlithological andor lithostratigraphic contactsExtensional fractures have not been characterizedas hosting structures because evidence of displace-
ment andor shearing is virtually always present inthe veins Extensional features are present howeveras en echelon arrays of sulfide minerals and as vein-lets attached to the main longitudinal fault veinsDeposits hosted in granitoids show a more brittlebehavior whereas those hosted in gneisses tend todisplay more ductile features This can result eitherfrom the depth of vein formation or from high fluidrock ratios even in shallow levels of the crust
Formation of deposits occurred in a range ofcrustal depth from mesozonal to epizonal condi-tions as indicated by the internal structure of thequartz veins and by the nature of the hosting struc-tures This is also supported by fluid inclusion stud-ies in a few deposits such as Guarim (Klein et al2001) and Patinhas (Klein et al 2000) both depos-its hosted in gneisses of the Cuiuacute-Cuiuacute ComplexFluid composition is nearly identical but P-T dataalong with textural and structural evidence suggestthat Guarim (outside STP) formed between 4 and 7km whereas Patinhas (within STP) formed at deeperlevels
Hence shear veins and fault-fill veins may beconsidered at least in part and from a structuralview as a single class of structural style with theirdifferences being ascribed to different depths ofemplacement and structural overprint It is not ourintention however to state that all of these veinsformed in a single gold-forming event The issue ofhow many mineralizing events have occurred in theTapajoacutes Province is still unresolved
Santos (1999 2000) studying 23 depositsthroughout the province (including three deposits inSTP) reported a set of characteristics similar tothose we have found in STP He concluded that alldeposits are related to a regional NW-SEndashtrendingstrike-slip fault system and that the orientation of
FIG 9 Breccia vein at Ceacuteu Azul
556 KLEIN ET AL
the lower-order hosting structures is compatiblewith Riedelrsquos system with the direction of the mainstress vector around the E-W direction Orientationsthat do not fit the model may be related to heteroge-neities in the local stress field However nothinghas been said about the timing of this strike-slipsystem in relation to the magmatic metamorphicand tectonic evolution of the province
Coutinho et al (2000) reported model ages thatcluster around 196 Ga and 188 Ga and main-tained that these two ages reflect two mineralizingepochs Santos et al (2001) invoked a single eventat 186 Ga However as stated by Santos et al(2001) the tectonic regime at 186 Ga is brittle Thismodel does not explain the ductile emplacementandor deformed mineralization hosted especially bythe Cuiuacute-Cuiuacute gneisses and by the metavolcano-sedimentary sequences Another (older) mineraliz-ing phase is thus required
We proposed early in this paper that the majorstrike-slip regime that affected the Creporizatildeo Suiteand older units likely occurred between 197 and195 Ga Mineralization hosted in the Cuiuacute-Cuiuacutegneisses (at least in STP) is post-tectonic and post-metamorphic with respect to the host rocks sincehosting structures clearly crosscut the metamorphicbanding and the hydrothermal mineralogy is retro-gressive in relation to the metamorphic paragenesisDeformation affecting the Creporizatildeo granitoids isbrittle-ductile to brittle whereas deformation affect-ing younger granitoids is brittle Thus it is valid toinfer as a working hypothesis that at least in partgold mineralization in STP formed during regionalstrike-slip deformation and emplacement of late-stage plutons of the Creporizatildeo Suite at ~197ndash195Ga a time interval that is in agreement with thatobtained by Coutinho et al (2000) The structuresmay have been reactivated during younger deforma-tional episode(s) and gold deposits may haveformed at this stage as well
The challenge is to decipher which depositsformed at each metallogenic epoch From a struc-tural point of view it is likely that the deposits inSouthern Tapajoacutes Province that have been emplacedat deeper levels of the crust and that show evidenceof plastic deformation (ie the shear veins and thedeposits hosted in low-angle reverse-oblique faultssee Table 1) formed in the older phase Fault-fillveins that occur in association with these deposits inthe same gold camp (eg Boa Vista) probablyformed in the same event The rest of the fault-fillveins (with textures and structures indicating
emplacement in shallow brittle structures associ-ated or not with mafic dikes and showing no associ-ation with shear veins in the same gold camp) aswell as the breccia veins and stockworks may haveformed either in the older or in the younger phaseWe do not have elements to define this Thisrequires much more isotopic data along with addi-tional fluid-inclusion and stable-isotope informationto constrain physico-chemical conditions of golddeposition as well as knowledge of the sources andnature of the mineralizing fluids and the absolutetiming of gold deposition
The attributes shown by the gold deposits in STP(namely the regional structural setting depositstyle vein textures and hydrothermal mineralogy)along with scarce fluid-inclusion data fit with boththe orogenic (magmatic arc-hosted) and intrusion-related models as proposed by Santos et al (2001)the latter sharing characteristics with Korean-typedeposits (Robert et al 1997) as well
Acknowledgments
Alfreu dos Santos (formerly of CPRM) partici-pated in the field work and supervised the TapajoacutesProject His help is acknowledged This is a contri-bution to the project PRONEX-CNPq-FADESP6621031998-0ndashprocess no 4200000
REFERENCES
Almeida M E Brito M F L Ferreira A L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaVila Mamatildee Anatilde (SB21-V-D) Estados do Paraacute e Ama-zonas escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Almeida M E Brito M F L and Macambira M J B1999 Caroccedilal Granite 207Pb206Pb evaporation age inpost-collisional granitoids of Tapajoacutes Gold ProvinceAmazonian region Brazil [abs] in II South AmericanSymposium on Isotope Geology Coacuterdoba ArgentinaActas p 3ndash6
Almeida M E Ferreira A L Brito M F L and Mon-teiro M A S 2001 Evoluccedilatildeo tectono-estrutural daProviacutencia Tapajoacutes com base na geologia das folhas VilaMamatildee Anatilde e Jacareacanga (1250000) regiatildeo limitedos estados do Amazonas e Paraacute in Reis N J andMonteiro M A S orgs Contribuiccedilotildees agrave Geologia daAmazocircnia v 2 Manaus Brazil SBG-NO p 57ndash112
Bahia R B C and Quadros M L E S 2000 Geologiae recursos minerais da Folha Caracol (SB21-X-C)
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 557
Estado do Paraacute Escala 1250000 Brasiacutelia BrazilCPRMGeological Survey of Brazil (CD-ROM)
Cassidy K F Groves D I and McNaughton N J 1998Late-Archean granitoid-hosted lode-gold depositsYilgarn Craton Western Australia Deposit character-istics crustal architecture and implications for oregenesis Ore Geology Reviews v 13 p 65ndash102
Correcirca-Silva R H Juliani C Bettencourt J S NunesC M D and Almeida T I R 2001 Caracterizaccedilatildeode um sistema epitermal low-sulfidation (ou adulaacuteria-sericita) hospedado em vulcacircnicas e vulcanoclaacutesticasdo Grupo Iriri na Proviacutencia auriacutefera do Tapajoacutes (PA)[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Coutinho M G N Santos J O S Fallick A E andLafon J M 2000 Orogenic gold deposits in TapajoacutesMineral Province Amazon Brazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Dowling K and Morrison G 1989 Application ofquartz textures to the classification of gold depositsusing North Queensland examples Economic GeologyMonograph v 6 p 342ndash355
Dreher A M Vlach S and Martini S L 1998 Adu-laria associated with epithermal gold veins in theTapajoacutes Mineral Province Paraacute State Northern BrazilRevista Brasileira de Geociecircncias v 28 p 397ndash404
Faraco M T L Carvalho J M A and Klein E L1997 Carta metalogeneacutetica da Proviacutencia Auriacutefera doTapajoacutes in Costa M L and Angeacutelica R S orgsContribuiccedilotildees agrave Geologia da Amazocircnia Beleacutem BrazilFINEPSBG-NO p 423ndash437
Ferreira A L Almeida M E Brito M F L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaJacareacanga (SB21-Y-B) Estados do Paraacute e Amazo-nas escala 1250000 Brasiacutelia Brazil CPRMGeolog-ical Survey of Brazil (CD-ROM)
Goldfarb R J Groves D I and Gardoll S 2001 Oro-genic gold and geologic time A global synthesis OreGeology Reviews v 18 p 1ndash75
Groves D I Goldfarb R J Gebre-Mariam M Hage-mann S and Robert F 1998 Orogenic gold depos-its A proposed classification in the context of theircrustal distribution and relationship to other golddeposit types Ore Geology Reviews v 13 p 7ndash27
Hodgson C J 1989 The structure of shear-related vein-type gold deposits A review Ore Geology Reviews v4 p 231ndash273
Jacobi P 1999 The discovery of epithermal Au-Cu-MoProterozoic deposits in the Tapajoacutes Province BrazilRevista Brasileira de Geociecircncias v 29 p 277ndash279
Jeacutebrak M 1997 Hydrothermal breccias in vein-type oredeposits A review of mechanisms morphology andsize distribution Ore Geology Reviews v 12 p 111ndash134
Juliani C 2001 Metalogecircnese do ouro e metais de baseassociadas com o vulcanismo-plutonismo da porccedilatildeo Wda Proviacutencia Auriacutefera do Tapajoacutes [ext abs] in VIISimpoacutesio de Geologia da Amazocircnia Beleacutem Brazil(CD-ROM)
Kerrich R and Cassidy K F 1994 Temporal relation-ships of lode gold mineralization to accretion magma-tism metamorphism and deformationmdashArchean topresent A review Ore Geology Reviews v 9 p 263ndash310
Klein E L Almeida M E Vasquez M L BahiaR B C Quadros M L E S and Ferreira A L inpress Geologia e recursos minerais da Proviacutencia Min-eral do Tapajoacutes Estados do Paraacute e Amazonas Escala1 500000 Brasiacutelia Brazil CPRMGeological Surveyof Brazil
Klein E L Rosa-Costa L T and Carvalho J M A2000 Fluid inclusion studies at the Patinhas gold-quartz mineralisation Tapajoacutes Gold Province Brazil[abs] in XXXI International Geological Congress Riode Janeiro Brazil (CD-ROM)
Klein E L Santos R A Fuzikawa K and AngeacutelicaR S 2001 Hydrothermal fluid evolution and struc-tural control of the brittle-style Guarim lode-gold min-eralisation Tapajoacutes Province Amazonian CratonBrazil Mineralium Deposita v 36 p 149ndash164
Klein E L and Vasquez M L 2000 Projeto EspecialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Vila Riozinho (SB21-Z-A) Estadodo Paraacute escala 1250000 Brasiacutelia Brazil CPRMGeological Survey of Brazil (CD-ROM)
Klein E L Vasquez M L Santos A and Martins RC 1997 Structural elements of the Maloquinha Intru-sive Suite in Tapajoacutes Mineral Province northern Bra-zil and the emplacement of the plutons [ext abs] inII International Symposium on Granites and Associ-ated Mineralizations ISGAM II Salvador Brazil p313ndash314
Klein E L Vasquez M L Santos A and Rosa-CostaL T 1999 Geologia e controle estrutural das mineral-izaccedilotildees auriacuteferas na Folha Vila Riozinho e NW daFolha Rio Novo Proviacutencia Tapajoacutes [ext abs] in VISimpoacutesio de Geologia da Amazocircnia Manaus Brazil p128ndash131
Lamaratildeo C N DallrsquoAgnol R and Lafon J M 2001Geocronologia e geoquiacutemica das associaccedilotildees vulcacircni-cas e plutocircnicas da regiatildeo de Vila Riozinho ProviacutenciaAuriacutefera do Tapajoacutes [ext abs] in VII Simpoacutesio deGeologia da Amazocircnia Beleacutem Brazil (CD-ROM)
Nunes C M D Juliani C Correcirca-Silva R H Mon-teiro L V S Bettencourt J S Neumann R AlcoverNeto A and Rye R O 2001 Caracterizaccedilatildeo de umsistema epitermal high-sulfidation vulcacircnico pale-oproterozoacuteico da Proviacutencia Auriacutefera do Tapajoacutes Paraacute[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
558 KLEIN ET AL
Ricci P S F Vasquez M L Santos A Klein E LJorge Joatildeo X S and Martins R C 1999 SuiacuteteIntrusiva Creporizatildeo ndash Proviacutencia Tapajoacutes Proposta ecriteacuterios de definiccedilatildeo [ext abs] in VI Simpoacutesio deGeologia da Amazocircnia Manaus Brazil p 519ndash522
Robert F and Poulsen K H 2001 Vein formation anddeformation in greenstone gold deposits in RichardsJ P and Tosdal R M eds Structural controls on oregenesis Reviews in Economic Geology v 14 p 111ndash155
Robert F Poulsen K H and Dubeacute B 1997 Golddeposits and their geological classification in GubinsA G ed Proceedings of Exploration 97 TorontoCanada p 209ndash220
Ronchi L H DallrsquoAgnol R Araujo J C Ribeiro VLamaratildeo C N Borges R M K and Fuzikawa K2001 Fluidos relacionados agraves alteraccedilotildees hidrotermaisno depoacutesito de ouro do Granito Satildeo JorgendashPA [extabs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Rosa-Costa L T and Carvalho J M A 1999 Tipologiade mineralizaccedilotildees auriacuteferas da regiatildeo sul da ProviacutenciaTapajoacutesndashParaacute [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 176ndash179
Santos J O S Groves D I Hartmann L A MouraM A and McNaughton N J 2001 Gold deposits ofthe Tapajoacutes and Alta Floresta Domains Tapajoacutes-Parima orogenic belt Amazon Craton Brazil Minera-lium Deposita v 36 p 279ndash299
Santos J O S Hartmann L A Gaudette H E GrovesD I McNaughton N J and Fletcher I R 2000 Anew understanding of the provinces of the AmazonCraton based on integration of field mapping and U-Pband Sm-Nd geochronology Gondwana Research v 3p 453ndash488
Santos R A 1997 Contribuiccedilatildeo agrave anaacutelise estrutural dejazimentos auriacuteferos do rio Tapajoacutes SW do Paraacute e SEdo Amazonas Garimpos Abacaxis Espiacuterito SantoBom Jesus Goiano Fazenda Pison Ouro Mil SantaIsabel Majestade e Carneirinho Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 1999 Controle estrutural das mineralizaccedilotildees deouro da Proviacutencia Mineral do Tapajoacutes Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 2000 Formation of gold-quartz veins controlledby the strike-slip fault mega-system in Tapajoacutes Min-eral Province Amazon Brazil [abs] in XXXI Interna-tional Geological Congress Rio de Janeiro Brazil(CD-ROM)
Tassinari C C G 1996 O mapa geocronoloacutegico do Craacute-ton Amazocircnico no Brasil Revisatildeo dos dados isotoacutepi-cos Unpubl Tese de Livre Docecircncia Universidade deSatildeo Paulo 139 p
Tassinari C C G and Macambira M J B 1999 Geo-chronological provinces of the Amazonian Craton Epi-sodes v 22 p 174ndash182
Vasquez M L and Klein E L 2000 Projeto especialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Rio Novo (SB21-Z-C) Estado doParaacute escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Vasquez M L Klein E L Macambira M J B SantosA Bahia R B C Ricci P S F and QuadrosM L E S 2000 Geochronology of granitoids maficintrusions and mineralizations of the Tapajoacutes GoldProvincendashAmazonian CratonndashBrazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Vasquez M L Klein E L Quadros M L E S BahiaR B C Santos A Ricci P S F Sachett C RSilva C M G and Macambira M J B 1999 Mag-matismo Uatumatilde na Proviacutencia Tapajoacutesmdashnovos dadosgeocronoloacutegicos [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 471ndash474
Vasquez M L Klein E L and Ricci P S F 2001Granitoacuteides poacutes-colisionais da porccedilatildeo leste da Proviacuten-cia Tapajoacutes [ext abs] in VII Simpoacutesio de Geologia daAmazocircnia Beleacutem Brazil (CD-ROM)
Vearncombe J R 1993 Quartz vein morphology andimplications for formation depth and classification ofArchaean gold-vein deposits Ore Geology Reviews v8 p 407ndash424
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 553
arsenopyrite are disseminated throughout the veinsand altered wall rock Pyrite occurs filling smallfractures in quartz as well and sericite is presentboth in the vein and in the immediate wall rock
Given the weathered character of the terrainfresh rocks could not be observed in the mineralizedzone and the nature of the host rock could not beconfidently determined A few tens of meters off themineralized zone an undeformed porphyritic maficvolcanic rock crops out The region in turn is dom-inated by granitoids of the Creporizatildeo Suite that isthe host for all other occurrences in the same goldfield The hosting schist may derive from one ofthese two rock types by a combination of intense
deformation and high fluidrock ratios Alterna-tively it may represent a fragment of the metavol-cano-sedimentary sequence of the JacareacangaGroup which has not as yet been recognized in thisportion of the Tapajoacutes Province occurring as mega-xenoliths or roof pendants within the granitoids ofthe Creporizatildeo Suite
In the Satildeo Raimundo deposit mineralizationoccurs in narrow hydrothermal halos envelopinganastomosed shearfault planes in brittle-ductileshear zones (Fig 8B) The hosting shear zones strikeN45ordmndash60ordmE and dip 25ordmndash40ordm SE and the mineralizedzones are up to 2 meters thick (Rosa-Costa and Car-valho 1999) Quartz is generally absent and occurs
FIG 6 A Milky massive quartz with high pyrite contents at Patinhas B Sheared sulfide-poor quartz vein (Patinhas)C Quartz vein with sulfide minerals filling cavities (Novo Vietnam)
FIG 7 Vein structures at Mineiro-1 A Laminated quartz-pyrite veinlet (V) crosscutting the hydrothermally alteredhost rock Alteration is zoned and symmetric (arrows) B Milky massive quartz with extensional fracture filled by sulfideminerals with an en echelon distribution C Hydrothermal breccia formed by quartz (white) and hydrothermally alteredhost rock (grey)
554 KLEIN ET AL
only as small isolated and discontinuous veinletspositioned in the fault planes The host rock is amonzogranite of the Creporizatildeo Suite
Breccia veins Four main occurrences have beenrecorded forming tabular structures of less than 1 min thickness The breccia veins at Ceacuteu Azul andAacutegua Limpa consist of fragments of milky quartzwith angular to rounded shape ranging in size frommm to a few cm (Fig 9) set in a fine-grained red-dish to greenish hydrothermal matrix composed ofquartz feldspar and hematite along with fine-grained sericite and epidote Microscopically dif-ferent quartz fragments show textures such as comband rosettes indicating the shallow emplacement ofthese veins (Dowling and Morrison 1989 Vearn-combe 1993) At Goiano and Ouro Mil the brecciashave less matrix and the quartz fragments are moreangular than in the two other examples
Brecciation occurs also as a minor portion of ashear vein at the Mineiro-1 prospect in the BoaVista gold camp These breccias also differ from theformer by the fact that the angular quartz fragmentsare set in a matrix composed of altered wall rock(Fig 7C)
Stockworks This style has been identified at theIndependecircncia deposit It consists of multidirec-tional quartz veins a few centimeters thick envel-
oped by narrow halos of hydrothermal alterationThe veins are generally widely spaced occurring inan area of ~100 m times tens of meters Locally how-ever they are closely spaced with several individ-ual hydrothermal halos overlapping each otherforming larger areas of hydrothermally altered hostrock The quartz has a milky to smoky characterand shows cavities usually filled by sulfide miner-als Epidote and white mica are common gangueminerals In places large pockets of hydrothermalalteration lacking quartz veins are observed aswell Minor stockworks and networks (the veins as awhole show the same orientation of the veinbrec-cia) occur at Ouro Mil in both margins of the mainbreccia vein (Santos 1997)
Discussion and Concluding Remarks
Gold deposits in the Tapajoacutes Province are hostedin a variety of metamorphic and magmatic rocks InSouthern Tapajoacutes Province (STP) with one excep-tion only orthogneisses of the Cuiuacute-Cuiuacute Complexand orogenic granitoids of the Creporizatildeo Suite areknown hosts for gold Hosting granitoids are domi-nantly monzogranitic in composition whereas theorthogneisses show tonalitic and granodioritic com-positions
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 555
The deposits have been classified in a few struc-tural styles according to the hosting structurestructural regime in which they have been formedand internal structures and textures of the veinsAccordingly fault-fill and shear veins are the domi-nant style followed by subordinate occurrences ofveins hosted in low-angle reverse-oblique faultsbreccia veins and stockworks More than one stylemay occur in the same gold camp and even in a sin-gle deposit
Fault-fill and shear veins as well as brecciaveins form moderately to steeply dipping tabularbodies that seldom exceed one meter in thicknessand are hosted by strike-slip faults and shear zonesto which they are parallel The vein quartz is domi-nantly massive with laminated saccharoidal andcomb textures occurring subordinately Shearingand cataclasis of the veins is widespread suggest-ing along with other textural and structural evi-dence their positioning in active faults and shearzones or deformation after formation In most casesquartz white mica and pyrite compose the veinmineralogy and along with minor chlorite carbon-ate epidote and K-feldspar they overprint the pri-mary mineralogy of the hosting granitoids and theamphibolite-facies paragenesis of the hostinggneisses
The breccias have likely been produced duringfracture propagation by physical brecciation whichoccurs when the amount of stress exceeds the brittleresistance of the rock by mechanisms such as tec-tonic comminution andor fluid-assisted brecciation(Jeacutebrak 1997) Furthermore they indicate activeseismic slip during mineralization (Robert andPoulsen 2001)
The origin of the large stockwork at Independecircn-cia may be ascribed to hydraulic fracturing occur-ring over a cupola of a small aplitic granitoidrelated to or intruding the regional coarse-grainedmonzogranite of the Creporizatildeo Suite In the latterhypothesis it could be related either to a late-stagepluton of the Creporizatildeo Suite or to a younger grani-toid suite (Parauari) This definition requires geo-chronological support
Deposits and gold camps show strong structuralcontrol at all scales The hosting structures havebeen formed under a dominantly brittle-ductile tobrittle regime and consist of strike slip faults shearfractures intersection and bending of faults andlithological andor lithostratigraphic contactsExtensional fractures have not been characterizedas hosting structures because evidence of displace-
ment andor shearing is virtually always present inthe veins Extensional features are present howeveras en echelon arrays of sulfide minerals and as vein-lets attached to the main longitudinal fault veinsDeposits hosted in granitoids show a more brittlebehavior whereas those hosted in gneisses tend todisplay more ductile features This can result eitherfrom the depth of vein formation or from high fluidrock ratios even in shallow levels of the crust
Formation of deposits occurred in a range ofcrustal depth from mesozonal to epizonal condi-tions as indicated by the internal structure of thequartz veins and by the nature of the hosting struc-tures This is also supported by fluid inclusion stud-ies in a few deposits such as Guarim (Klein et al2001) and Patinhas (Klein et al 2000) both depos-its hosted in gneisses of the Cuiuacute-Cuiuacute ComplexFluid composition is nearly identical but P-T dataalong with textural and structural evidence suggestthat Guarim (outside STP) formed between 4 and 7km whereas Patinhas (within STP) formed at deeperlevels
Hence shear veins and fault-fill veins may beconsidered at least in part and from a structuralview as a single class of structural style with theirdifferences being ascribed to different depths ofemplacement and structural overprint It is not ourintention however to state that all of these veinsformed in a single gold-forming event The issue ofhow many mineralizing events have occurred in theTapajoacutes Province is still unresolved
Santos (1999 2000) studying 23 depositsthroughout the province (including three deposits inSTP) reported a set of characteristics similar tothose we have found in STP He concluded that alldeposits are related to a regional NW-SEndashtrendingstrike-slip fault system and that the orientation of
FIG 9 Breccia vein at Ceacuteu Azul
556 KLEIN ET AL
the lower-order hosting structures is compatiblewith Riedelrsquos system with the direction of the mainstress vector around the E-W direction Orientationsthat do not fit the model may be related to heteroge-neities in the local stress field However nothinghas been said about the timing of this strike-slipsystem in relation to the magmatic metamorphicand tectonic evolution of the province
Coutinho et al (2000) reported model ages thatcluster around 196 Ga and 188 Ga and main-tained that these two ages reflect two mineralizingepochs Santos et al (2001) invoked a single eventat 186 Ga However as stated by Santos et al(2001) the tectonic regime at 186 Ga is brittle Thismodel does not explain the ductile emplacementandor deformed mineralization hosted especially bythe Cuiuacute-Cuiuacute gneisses and by the metavolcano-sedimentary sequences Another (older) mineraliz-ing phase is thus required
We proposed early in this paper that the majorstrike-slip regime that affected the Creporizatildeo Suiteand older units likely occurred between 197 and195 Ga Mineralization hosted in the Cuiuacute-Cuiuacutegneisses (at least in STP) is post-tectonic and post-metamorphic with respect to the host rocks sincehosting structures clearly crosscut the metamorphicbanding and the hydrothermal mineralogy is retro-gressive in relation to the metamorphic paragenesisDeformation affecting the Creporizatildeo granitoids isbrittle-ductile to brittle whereas deformation affect-ing younger granitoids is brittle Thus it is valid toinfer as a working hypothesis that at least in partgold mineralization in STP formed during regionalstrike-slip deformation and emplacement of late-stage plutons of the Creporizatildeo Suite at ~197ndash195Ga a time interval that is in agreement with thatobtained by Coutinho et al (2000) The structuresmay have been reactivated during younger deforma-tional episode(s) and gold deposits may haveformed at this stage as well
The challenge is to decipher which depositsformed at each metallogenic epoch From a struc-tural point of view it is likely that the deposits inSouthern Tapajoacutes Province that have been emplacedat deeper levels of the crust and that show evidenceof plastic deformation (ie the shear veins and thedeposits hosted in low-angle reverse-oblique faultssee Table 1) formed in the older phase Fault-fillveins that occur in association with these deposits inthe same gold camp (eg Boa Vista) probablyformed in the same event The rest of the fault-fillveins (with textures and structures indicating
emplacement in shallow brittle structures associ-ated or not with mafic dikes and showing no associ-ation with shear veins in the same gold camp) aswell as the breccia veins and stockworks may haveformed either in the older or in the younger phaseWe do not have elements to define this Thisrequires much more isotopic data along with addi-tional fluid-inclusion and stable-isotope informationto constrain physico-chemical conditions of golddeposition as well as knowledge of the sources andnature of the mineralizing fluids and the absolutetiming of gold deposition
The attributes shown by the gold deposits in STP(namely the regional structural setting depositstyle vein textures and hydrothermal mineralogy)along with scarce fluid-inclusion data fit with boththe orogenic (magmatic arc-hosted) and intrusion-related models as proposed by Santos et al (2001)the latter sharing characteristics with Korean-typedeposits (Robert et al 1997) as well
Acknowledgments
Alfreu dos Santos (formerly of CPRM) partici-pated in the field work and supervised the TapajoacutesProject His help is acknowledged This is a contri-bution to the project PRONEX-CNPq-FADESP6621031998-0ndashprocess no 4200000
REFERENCES
Almeida M E Brito M F L Ferreira A L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaVila Mamatildee Anatilde (SB21-V-D) Estados do Paraacute e Ama-zonas escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Almeida M E Brito M F L and Macambira M J B1999 Caroccedilal Granite 207Pb206Pb evaporation age inpost-collisional granitoids of Tapajoacutes Gold ProvinceAmazonian region Brazil [abs] in II South AmericanSymposium on Isotope Geology Coacuterdoba ArgentinaActas p 3ndash6
Almeida M E Ferreira A L Brito M F L and Mon-teiro M A S 2001 Evoluccedilatildeo tectono-estrutural daProviacutencia Tapajoacutes com base na geologia das folhas VilaMamatildee Anatilde e Jacareacanga (1250000) regiatildeo limitedos estados do Amazonas e Paraacute in Reis N J andMonteiro M A S orgs Contribuiccedilotildees agrave Geologia daAmazocircnia v 2 Manaus Brazil SBG-NO p 57ndash112
Bahia R B C and Quadros M L E S 2000 Geologiae recursos minerais da Folha Caracol (SB21-X-C)
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 557
Estado do Paraacute Escala 1250000 Brasiacutelia BrazilCPRMGeological Survey of Brazil (CD-ROM)
Cassidy K F Groves D I and McNaughton N J 1998Late-Archean granitoid-hosted lode-gold depositsYilgarn Craton Western Australia Deposit character-istics crustal architecture and implications for oregenesis Ore Geology Reviews v 13 p 65ndash102
Correcirca-Silva R H Juliani C Bettencourt J S NunesC M D and Almeida T I R 2001 Caracterizaccedilatildeode um sistema epitermal low-sulfidation (ou adulaacuteria-sericita) hospedado em vulcacircnicas e vulcanoclaacutesticasdo Grupo Iriri na Proviacutencia auriacutefera do Tapajoacutes (PA)[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Coutinho M G N Santos J O S Fallick A E andLafon J M 2000 Orogenic gold deposits in TapajoacutesMineral Province Amazon Brazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Dowling K and Morrison G 1989 Application ofquartz textures to the classification of gold depositsusing North Queensland examples Economic GeologyMonograph v 6 p 342ndash355
Dreher A M Vlach S and Martini S L 1998 Adu-laria associated with epithermal gold veins in theTapajoacutes Mineral Province Paraacute State Northern BrazilRevista Brasileira de Geociecircncias v 28 p 397ndash404
Faraco M T L Carvalho J M A and Klein E L1997 Carta metalogeneacutetica da Proviacutencia Auriacutefera doTapajoacutes in Costa M L and Angeacutelica R S orgsContribuiccedilotildees agrave Geologia da Amazocircnia Beleacutem BrazilFINEPSBG-NO p 423ndash437
Ferreira A L Almeida M E Brito M F L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaJacareacanga (SB21-Y-B) Estados do Paraacute e Amazo-nas escala 1250000 Brasiacutelia Brazil CPRMGeolog-ical Survey of Brazil (CD-ROM)
Goldfarb R J Groves D I and Gardoll S 2001 Oro-genic gold and geologic time A global synthesis OreGeology Reviews v 18 p 1ndash75
Groves D I Goldfarb R J Gebre-Mariam M Hage-mann S and Robert F 1998 Orogenic gold depos-its A proposed classification in the context of theircrustal distribution and relationship to other golddeposit types Ore Geology Reviews v 13 p 7ndash27
Hodgson C J 1989 The structure of shear-related vein-type gold deposits A review Ore Geology Reviews v4 p 231ndash273
Jacobi P 1999 The discovery of epithermal Au-Cu-MoProterozoic deposits in the Tapajoacutes Province BrazilRevista Brasileira de Geociecircncias v 29 p 277ndash279
Jeacutebrak M 1997 Hydrothermal breccias in vein-type oredeposits A review of mechanisms morphology andsize distribution Ore Geology Reviews v 12 p 111ndash134
Juliani C 2001 Metalogecircnese do ouro e metais de baseassociadas com o vulcanismo-plutonismo da porccedilatildeo Wda Proviacutencia Auriacutefera do Tapajoacutes [ext abs] in VIISimpoacutesio de Geologia da Amazocircnia Beleacutem Brazil(CD-ROM)
Kerrich R and Cassidy K F 1994 Temporal relation-ships of lode gold mineralization to accretion magma-tism metamorphism and deformationmdashArchean topresent A review Ore Geology Reviews v 9 p 263ndash310
Klein E L Almeida M E Vasquez M L BahiaR B C Quadros M L E S and Ferreira A L inpress Geologia e recursos minerais da Proviacutencia Min-eral do Tapajoacutes Estados do Paraacute e Amazonas Escala1 500000 Brasiacutelia Brazil CPRMGeological Surveyof Brazil
Klein E L Rosa-Costa L T and Carvalho J M A2000 Fluid inclusion studies at the Patinhas gold-quartz mineralisation Tapajoacutes Gold Province Brazil[abs] in XXXI International Geological Congress Riode Janeiro Brazil (CD-ROM)
Klein E L Santos R A Fuzikawa K and AngeacutelicaR S 2001 Hydrothermal fluid evolution and struc-tural control of the brittle-style Guarim lode-gold min-eralisation Tapajoacutes Province Amazonian CratonBrazil Mineralium Deposita v 36 p 149ndash164
Klein E L and Vasquez M L 2000 Projeto EspecialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Vila Riozinho (SB21-Z-A) Estadodo Paraacute escala 1250000 Brasiacutelia Brazil CPRMGeological Survey of Brazil (CD-ROM)
Klein E L Vasquez M L Santos A and Martins RC 1997 Structural elements of the Maloquinha Intru-sive Suite in Tapajoacutes Mineral Province northern Bra-zil and the emplacement of the plutons [ext abs] inII International Symposium on Granites and Associ-ated Mineralizations ISGAM II Salvador Brazil p313ndash314
Klein E L Vasquez M L Santos A and Rosa-CostaL T 1999 Geologia e controle estrutural das mineral-izaccedilotildees auriacuteferas na Folha Vila Riozinho e NW daFolha Rio Novo Proviacutencia Tapajoacutes [ext abs] in VISimpoacutesio de Geologia da Amazocircnia Manaus Brazil p128ndash131
Lamaratildeo C N DallrsquoAgnol R and Lafon J M 2001Geocronologia e geoquiacutemica das associaccedilotildees vulcacircni-cas e plutocircnicas da regiatildeo de Vila Riozinho ProviacutenciaAuriacutefera do Tapajoacutes [ext abs] in VII Simpoacutesio deGeologia da Amazocircnia Beleacutem Brazil (CD-ROM)
Nunes C M D Juliani C Correcirca-Silva R H Mon-teiro L V S Bettencourt J S Neumann R AlcoverNeto A and Rye R O 2001 Caracterizaccedilatildeo de umsistema epitermal high-sulfidation vulcacircnico pale-oproterozoacuteico da Proviacutencia Auriacutefera do Tapajoacutes Paraacute[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
558 KLEIN ET AL
Ricci P S F Vasquez M L Santos A Klein E LJorge Joatildeo X S and Martins R C 1999 SuiacuteteIntrusiva Creporizatildeo ndash Proviacutencia Tapajoacutes Proposta ecriteacuterios de definiccedilatildeo [ext abs] in VI Simpoacutesio deGeologia da Amazocircnia Manaus Brazil p 519ndash522
Robert F and Poulsen K H 2001 Vein formation anddeformation in greenstone gold deposits in RichardsJ P and Tosdal R M eds Structural controls on oregenesis Reviews in Economic Geology v 14 p 111ndash155
Robert F Poulsen K H and Dubeacute B 1997 Golddeposits and their geological classification in GubinsA G ed Proceedings of Exploration 97 TorontoCanada p 209ndash220
Ronchi L H DallrsquoAgnol R Araujo J C Ribeiro VLamaratildeo C N Borges R M K and Fuzikawa K2001 Fluidos relacionados agraves alteraccedilotildees hidrotermaisno depoacutesito de ouro do Granito Satildeo JorgendashPA [extabs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Rosa-Costa L T and Carvalho J M A 1999 Tipologiade mineralizaccedilotildees auriacuteferas da regiatildeo sul da ProviacutenciaTapajoacutesndashParaacute [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 176ndash179
Santos J O S Groves D I Hartmann L A MouraM A and McNaughton N J 2001 Gold deposits ofthe Tapajoacutes and Alta Floresta Domains Tapajoacutes-Parima orogenic belt Amazon Craton Brazil Minera-lium Deposita v 36 p 279ndash299
Santos J O S Hartmann L A Gaudette H E GrovesD I McNaughton N J and Fletcher I R 2000 Anew understanding of the provinces of the AmazonCraton based on integration of field mapping and U-Pband Sm-Nd geochronology Gondwana Research v 3p 453ndash488
Santos R A 1997 Contribuiccedilatildeo agrave anaacutelise estrutural dejazimentos auriacuteferos do rio Tapajoacutes SW do Paraacute e SEdo Amazonas Garimpos Abacaxis Espiacuterito SantoBom Jesus Goiano Fazenda Pison Ouro Mil SantaIsabel Majestade e Carneirinho Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 1999 Controle estrutural das mineralizaccedilotildees deouro da Proviacutencia Mineral do Tapajoacutes Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 2000 Formation of gold-quartz veins controlledby the strike-slip fault mega-system in Tapajoacutes Min-eral Province Amazon Brazil [abs] in XXXI Interna-tional Geological Congress Rio de Janeiro Brazil(CD-ROM)
Tassinari C C G 1996 O mapa geocronoloacutegico do Craacute-ton Amazocircnico no Brasil Revisatildeo dos dados isotoacutepi-cos Unpubl Tese de Livre Docecircncia Universidade deSatildeo Paulo 139 p
Tassinari C C G and Macambira M J B 1999 Geo-chronological provinces of the Amazonian Craton Epi-sodes v 22 p 174ndash182
Vasquez M L and Klein E L 2000 Projeto especialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Rio Novo (SB21-Z-C) Estado doParaacute escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Vasquez M L Klein E L Macambira M J B SantosA Bahia R B C Ricci P S F and QuadrosM L E S 2000 Geochronology of granitoids maficintrusions and mineralizations of the Tapajoacutes GoldProvincendashAmazonian CratonndashBrazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Vasquez M L Klein E L Quadros M L E S BahiaR B C Santos A Ricci P S F Sachett C RSilva C M G and Macambira M J B 1999 Mag-matismo Uatumatilde na Proviacutencia Tapajoacutesmdashnovos dadosgeocronoloacutegicos [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 471ndash474
Vasquez M L Klein E L and Ricci P S F 2001Granitoacuteides poacutes-colisionais da porccedilatildeo leste da Proviacuten-cia Tapajoacutes [ext abs] in VII Simpoacutesio de Geologia daAmazocircnia Beleacutem Brazil (CD-ROM)
Vearncombe J R 1993 Quartz vein morphology andimplications for formation depth and classification ofArchaean gold-vein deposits Ore Geology Reviews v8 p 407ndash424
554 KLEIN ET AL
only as small isolated and discontinuous veinletspositioned in the fault planes The host rock is amonzogranite of the Creporizatildeo Suite
Breccia veins Four main occurrences have beenrecorded forming tabular structures of less than 1 min thickness The breccia veins at Ceacuteu Azul andAacutegua Limpa consist of fragments of milky quartzwith angular to rounded shape ranging in size frommm to a few cm (Fig 9) set in a fine-grained red-dish to greenish hydrothermal matrix composed ofquartz feldspar and hematite along with fine-grained sericite and epidote Microscopically dif-ferent quartz fragments show textures such as comband rosettes indicating the shallow emplacement ofthese veins (Dowling and Morrison 1989 Vearn-combe 1993) At Goiano and Ouro Mil the brecciashave less matrix and the quartz fragments are moreangular than in the two other examples
Brecciation occurs also as a minor portion of ashear vein at the Mineiro-1 prospect in the BoaVista gold camp These breccias also differ from theformer by the fact that the angular quartz fragmentsare set in a matrix composed of altered wall rock(Fig 7C)
Stockworks This style has been identified at theIndependecircncia deposit It consists of multidirec-tional quartz veins a few centimeters thick envel-
oped by narrow halos of hydrothermal alterationThe veins are generally widely spaced occurring inan area of ~100 m times tens of meters Locally how-ever they are closely spaced with several individ-ual hydrothermal halos overlapping each otherforming larger areas of hydrothermally altered hostrock The quartz has a milky to smoky characterand shows cavities usually filled by sulfide miner-als Epidote and white mica are common gangueminerals In places large pockets of hydrothermalalteration lacking quartz veins are observed aswell Minor stockworks and networks (the veins as awhole show the same orientation of the veinbrec-cia) occur at Ouro Mil in both margins of the mainbreccia vein (Santos 1997)
Discussion and Concluding Remarks
Gold deposits in the Tapajoacutes Province are hostedin a variety of metamorphic and magmatic rocks InSouthern Tapajoacutes Province (STP) with one excep-tion only orthogneisses of the Cuiuacute-Cuiuacute Complexand orogenic granitoids of the Creporizatildeo Suite areknown hosts for gold Hosting granitoids are domi-nantly monzogranitic in composition whereas theorthogneisses show tonalitic and granodioritic com-positions
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 555
The deposits have been classified in a few struc-tural styles according to the hosting structurestructural regime in which they have been formedand internal structures and textures of the veinsAccordingly fault-fill and shear veins are the domi-nant style followed by subordinate occurrences ofveins hosted in low-angle reverse-oblique faultsbreccia veins and stockworks More than one stylemay occur in the same gold camp and even in a sin-gle deposit
Fault-fill and shear veins as well as brecciaveins form moderately to steeply dipping tabularbodies that seldom exceed one meter in thicknessand are hosted by strike-slip faults and shear zonesto which they are parallel The vein quartz is domi-nantly massive with laminated saccharoidal andcomb textures occurring subordinately Shearingand cataclasis of the veins is widespread suggest-ing along with other textural and structural evi-dence their positioning in active faults and shearzones or deformation after formation In most casesquartz white mica and pyrite compose the veinmineralogy and along with minor chlorite carbon-ate epidote and K-feldspar they overprint the pri-mary mineralogy of the hosting granitoids and theamphibolite-facies paragenesis of the hostinggneisses
The breccias have likely been produced duringfracture propagation by physical brecciation whichoccurs when the amount of stress exceeds the brittleresistance of the rock by mechanisms such as tec-tonic comminution andor fluid-assisted brecciation(Jeacutebrak 1997) Furthermore they indicate activeseismic slip during mineralization (Robert andPoulsen 2001)
The origin of the large stockwork at Independecircn-cia may be ascribed to hydraulic fracturing occur-ring over a cupola of a small aplitic granitoidrelated to or intruding the regional coarse-grainedmonzogranite of the Creporizatildeo Suite In the latterhypothesis it could be related either to a late-stagepluton of the Creporizatildeo Suite or to a younger grani-toid suite (Parauari) This definition requires geo-chronological support
Deposits and gold camps show strong structuralcontrol at all scales The hosting structures havebeen formed under a dominantly brittle-ductile tobrittle regime and consist of strike slip faults shearfractures intersection and bending of faults andlithological andor lithostratigraphic contactsExtensional fractures have not been characterizedas hosting structures because evidence of displace-
ment andor shearing is virtually always present inthe veins Extensional features are present howeveras en echelon arrays of sulfide minerals and as vein-lets attached to the main longitudinal fault veinsDeposits hosted in granitoids show a more brittlebehavior whereas those hosted in gneisses tend todisplay more ductile features This can result eitherfrom the depth of vein formation or from high fluidrock ratios even in shallow levels of the crust
Formation of deposits occurred in a range ofcrustal depth from mesozonal to epizonal condi-tions as indicated by the internal structure of thequartz veins and by the nature of the hosting struc-tures This is also supported by fluid inclusion stud-ies in a few deposits such as Guarim (Klein et al2001) and Patinhas (Klein et al 2000) both depos-its hosted in gneisses of the Cuiuacute-Cuiuacute ComplexFluid composition is nearly identical but P-T dataalong with textural and structural evidence suggestthat Guarim (outside STP) formed between 4 and 7km whereas Patinhas (within STP) formed at deeperlevels
Hence shear veins and fault-fill veins may beconsidered at least in part and from a structuralview as a single class of structural style with theirdifferences being ascribed to different depths ofemplacement and structural overprint It is not ourintention however to state that all of these veinsformed in a single gold-forming event The issue ofhow many mineralizing events have occurred in theTapajoacutes Province is still unresolved
Santos (1999 2000) studying 23 depositsthroughout the province (including three deposits inSTP) reported a set of characteristics similar tothose we have found in STP He concluded that alldeposits are related to a regional NW-SEndashtrendingstrike-slip fault system and that the orientation of
FIG 9 Breccia vein at Ceacuteu Azul
556 KLEIN ET AL
the lower-order hosting structures is compatiblewith Riedelrsquos system with the direction of the mainstress vector around the E-W direction Orientationsthat do not fit the model may be related to heteroge-neities in the local stress field However nothinghas been said about the timing of this strike-slipsystem in relation to the magmatic metamorphicand tectonic evolution of the province
Coutinho et al (2000) reported model ages thatcluster around 196 Ga and 188 Ga and main-tained that these two ages reflect two mineralizingepochs Santos et al (2001) invoked a single eventat 186 Ga However as stated by Santos et al(2001) the tectonic regime at 186 Ga is brittle Thismodel does not explain the ductile emplacementandor deformed mineralization hosted especially bythe Cuiuacute-Cuiuacute gneisses and by the metavolcano-sedimentary sequences Another (older) mineraliz-ing phase is thus required
We proposed early in this paper that the majorstrike-slip regime that affected the Creporizatildeo Suiteand older units likely occurred between 197 and195 Ga Mineralization hosted in the Cuiuacute-Cuiuacutegneisses (at least in STP) is post-tectonic and post-metamorphic with respect to the host rocks sincehosting structures clearly crosscut the metamorphicbanding and the hydrothermal mineralogy is retro-gressive in relation to the metamorphic paragenesisDeformation affecting the Creporizatildeo granitoids isbrittle-ductile to brittle whereas deformation affect-ing younger granitoids is brittle Thus it is valid toinfer as a working hypothesis that at least in partgold mineralization in STP formed during regionalstrike-slip deformation and emplacement of late-stage plutons of the Creporizatildeo Suite at ~197ndash195Ga a time interval that is in agreement with thatobtained by Coutinho et al (2000) The structuresmay have been reactivated during younger deforma-tional episode(s) and gold deposits may haveformed at this stage as well
The challenge is to decipher which depositsformed at each metallogenic epoch From a struc-tural point of view it is likely that the deposits inSouthern Tapajoacutes Province that have been emplacedat deeper levels of the crust and that show evidenceof plastic deformation (ie the shear veins and thedeposits hosted in low-angle reverse-oblique faultssee Table 1) formed in the older phase Fault-fillveins that occur in association with these deposits inthe same gold camp (eg Boa Vista) probablyformed in the same event The rest of the fault-fillveins (with textures and structures indicating
emplacement in shallow brittle structures associ-ated or not with mafic dikes and showing no associ-ation with shear veins in the same gold camp) aswell as the breccia veins and stockworks may haveformed either in the older or in the younger phaseWe do not have elements to define this Thisrequires much more isotopic data along with addi-tional fluid-inclusion and stable-isotope informationto constrain physico-chemical conditions of golddeposition as well as knowledge of the sources andnature of the mineralizing fluids and the absolutetiming of gold deposition
The attributes shown by the gold deposits in STP(namely the regional structural setting depositstyle vein textures and hydrothermal mineralogy)along with scarce fluid-inclusion data fit with boththe orogenic (magmatic arc-hosted) and intrusion-related models as proposed by Santos et al (2001)the latter sharing characteristics with Korean-typedeposits (Robert et al 1997) as well
Acknowledgments
Alfreu dos Santos (formerly of CPRM) partici-pated in the field work and supervised the TapajoacutesProject His help is acknowledged This is a contri-bution to the project PRONEX-CNPq-FADESP6621031998-0ndashprocess no 4200000
REFERENCES
Almeida M E Brito M F L Ferreira A L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaVila Mamatildee Anatilde (SB21-V-D) Estados do Paraacute e Ama-zonas escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Almeida M E Brito M F L and Macambira M J B1999 Caroccedilal Granite 207Pb206Pb evaporation age inpost-collisional granitoids of Tapajoacutes Gold ProvinceAmazonian region Brazil [abs] in II South AmericanSymposium on Isotope Geology Coacuterdoba ArgentinaActas p 3ndash6
Almeida M E Ferreira A L Brito M F L and Mon-teiro M A S 2001 Evoluccedilatildeo tectono-estrutural daProviacutencia Tapajoacutes com base na geologia das folhas VilaMamatildee Anatilde e Jacareacanga (1250000) regiatildeo limitedos estados do Amazonas e Paraacute in Reis N J andMonteiro M A S orgs Contribuiccedilotildees agrave Geologia daAmazocircnia v 2 Manaus Brazil SBG-NO p 57ndash112
Bahia R B C and Quadros M L E S 2000 Geologiae recursos minerais da Folha Caracol (SB21-X-C)
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 557
Estado do Paraacute Escala 1250000 Brasiacutelia BrazilCPRMGeological Survey of Brazil (CD-ROM)
Cassidy K F Groves D I and McNaughton N J 1998Late-Archean granitoid-hosted lode-gold depositsYilgarn Craton Western Australia Deposit character-istics crustal architecture and implications for oregenesis Ore Geology Reviews v 13 p 65ndash102
Correcirca-Silva R H Juliani C Bettencourt J S NunesC M D and Almeida T I R 2001 Caracterizaccedilatildeode um sistema epitermal low-sulfidation (ou adulaacuteria-sericita) hospedado em vulcacircnicas e vulcanoclaacutesticasdo Grupo Iriri na Proviacutencia auriacutefera do Tapajoacutes (PA)[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Coutinho M G N Santos J O S Fallick A E andLafon J M 2000 Orogenic gold deposits in TapajoacutesMineral Province Amazon Brazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Dowling K and Morrison G 1989 Application ofquartz textures to the classification of gold depositsusing North Queensland examples Economic GeologyMonograph v 6 p 342ndash355
Dreher A M Vlach S and Martini S L 1998 Adu-laria associated with epithermal gold veins in theTapajoacutes Mineral Province Paraacute State Northern BrazilRevista Brasileira de Geociecircncias v 28 p 397ndash404
Faraco M T L Carvalho J M A and Klein E L1997 Carta metalogeneacutetica da Proviacutencia Auriacutefera doTapajoacutes in Costa M L and Angeacutelica R S orgsContribuiccedilotildees agrave Geologia da Amazocircnia Beleacutem BrazilFINEPSBG-NO p 423ndash437
Ferreira A L Almeida M E Brito M F L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaJacareacanga (SB21-Y-B) Estados do Paraacute e Amazo-nas escala 1250000 Brasiacutelia Brazil CPRMGeolog-ical Survey of Brazil (CD-ROM)
Goldfarb R J Groves D I and Gardoll S 2001 Oro-genic gold and geologic time A global synthesis OreGeology Reviews v 18 p 1ndash75
Groves D I Goldfarb R J Gebre-Mariam M Hage-mann S and Robert F 1998 Orogenic gold depos-its A proposed classification in the context of theircrustal distribution and relationship to other golddeposit types Ore Geology Reviews v 13 p 7ndash27
Hodgson C J 1989 The structure of shear-related vein-type gold deposits A review Ore Geology Reviews v4 p 231ndash273
Jacobi P 1999 The discovery of epithermal Au-Cu-MoProterozoic deposits in the Tapajoacutes Province BrazilRevista Brasileira de Geociecircncias v 29 p 277ndash279
Jeacutebrak M 1997 Hydrothermal breccias in vein-type oredeposits A review of mechanisms morphology andsize distribution Ore Geology Reviews v 12 p 111ndash134
Juliani C 2001 Metalogecircnese do ouro e metais de baseassociadas com o vulcanismo-plutonismo da porccedilatildeo Wda Proviacutencia Auriacutefera do Tapajoacutes [ext abs] in VIISimpoacutesio de Geologia da Amazocircnia Beleacutem Brazil(CD-ROM)
Kerrich R and Cassidy K F 1994 Temporal relation-ships of lode gold mineralization to accretion magma-tism metamorphism and deformationmdashArchean topresent A review Ore Geology Reviews v 9 p 263ndash310
Klein E L Almeida M E Vasquez M L BahiaR B C Quadros M L E S and Ferreira A L inpress Geologia e recursos minerais da Proviacutencia Min-eral do Tapajoacutes Estados do Paraacute e Amazonas Escala1 500000 Brasiacutelia Brazil CPRMGeological Surveyof Brazil
Klein E L Rosa-Costa L T and Carvalho J M A2000 Fluid inclusion studies at the Patinhas gold-quartz mineralisation Tapajoacutes Gold Province Brazil[abs] in XXXI International Geological Congress Riode Janeiro Brazil (CD-ROM)
Klein E L Santos R A Fuzikawa K and AngeacutelicaR S 2001 Hydrothermal fluid evolution and struc-tural control of the brittle-style Guarim lode-gold min-eralisation Tapajoacutes Province Amazonian CratonBrazil Mineralium Deposita v 36 p 149ndash164
Klein E L and Vasquez M L 2000 Projeto EspecialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Vila Riozinho (SB21-Z-A) Estadodo Paraacute escala 1250000 Brasiacutelia Brazil CPRMGeological Survey of Brazil (CD-ROM)
Klein E L Vasquez M L Santos A and Martins RC 1997 Structural elements of the Maloquinha Intru-sive Suite in Tapajoacutes Mineral Province northern Bra-zil and the emplacement of the plutons [ext abs] inII International Symposium on Granites and Associ-ated Mineralizations ISGAM II Salvador Brazil p313ndash314
Klein E L Vasquez M L Santos A and Rosa-CostaL T 1999 Geologia e controle estrutural das mineral-izaccedilotildees auriacuteferas na Folha Vila Riozinho e NW daFolha Rio Novo Proviacutencia Tapajoacutes [ext abs] in VISimpoacutesio de Geologia da Amazocircnia Manaus Brazil p128ndash131
Lamaratildeo C N DallrsquoAgnol R and Lafon J M 2001Geocronologia e geoquiacutemica das associaccedilotildees vulcacircni-cas e plutocircnicas da regiatildeo de Vila Riozinho ProviacutenciaAuriacutefera do Tapajoacutes [ext abs] in VII Simpoacutesio deGeologia da Amazocircnia Beleacutem Brazil (CD-ROM)
Nunes C M D Juliani C Correcirca-Silva R H Mon-teiro L V S Bettencourt J S Neumann R AlcoverNeto A and Rye R O 2001 Caracterizaccedilatildeo de umsistema epitermal high-sulfidation vulcacircnico pale-oproterozoacuteico da Proviacutencia Auriacutefera do Tapajoacutes Paraacute[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
558 KLEIN ET AL
Ricci P S F Vasquez M L Santos A Klein E LJorge Joatildeo X S and Martins R C 1999 SuiacuteteIntrusiva Creporizatildeo ndash Proviacutencia Tapajoacutes Proposta ecriteacuterios de definiccedilatildeo [ext abs] in VI Simpoacutesio deGeologia da Amazocircnia Manaus Brazil p 519ndash522
Robert F and Poulsen K H 2001 Vein formation anddeformation in greenstone gold deposits in RichardsJ P and Tosdal R M eds Structural controls on oregenesis Reviews in Economic Geology v 14 p 111ndash155
Robert F Poulsen K H and Dubeacute B 1997 Golddeposits and their geological classification in GubinsA G ed Proceedings of Exploration 97 TorontoCanada p 209ndash220
Ronchi L H DallrsquoAgnol R Araujo J C Ribeiro VLamaratildeo C N Borges R M K and Fuzikawa K2001 Fluidos relacionados agraves alteraccedilotildees hidrotermaisno depoacutesito de ouro do Granito Satildeo JorgendashPA [extabs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Rosa-Costa L T and Carvalho J M A 1999 Tipologiade mineralizaccedilotildees auriacuteferas da regiatildeo sul da ProviacutenciaTapajoacutesndashParaacute [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 176ndash179
Santos J O S Groves D I Hartmann L A MouraM A and McNaughton N J 2001 Gold deposits ofthe Tapajoacutes and Alta Floresta Domains Tapajoacutes-Parima orogenic belt Amazon Craton Brazil Minera-lium Deposita v 36 p 279ndash299
Santos J O S Hartmann L A Gaudette H E GrovesD I McNaughton N J and Fletcher I R 2000 Anew understanding of the provinces of the AmazonCraton based on integration of field mapping and U-Pband Sm-Nd geochronology Gondwana Research v 3p 453ndash488
Santos R A 1997 Contribuiccedilatildeo agrave anaacutelise estrutural dejazimentos auriacuteferos do rio Tapajoacutes SW do Paraacute e SEdo Amazonas Garimpos Abacaxis Espiacuterito SantoBom Jesus Goiano Fazenda Pison Ouro Mil SantaIsabel Majestade e Carneirinho Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 1999 Controle estrutural das mineralizaccedilotildees deouro da Proviacutencia Mineral do Tapajoacutes Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 2000 Formation of gold-quartz veins controlledby the strike-slip fault mega-system in Tapajoacutes Min-eral Province Amazon Brazil [abs] in XXXI Interna-tional Geological Congress Rio de Janeiro Brazil(CD-ROM)
Tassinari C C G 1996 O mapa geocronoloacutegico do Craacute-ton Amazocircnico no Brasil Revisatildeo dos dados isotoacutepi-cos Unpubl Tese de Livre Docecircncia Universidade deSatildeo Paulo 139 p
Tassinari C C G and Macambira M J B 1999 Geo-chronological provinces of the Amazonian Craton Epi-sodes v 22 p 174ndash182
Vasquez M L and Klein E L 2000 Projeto especialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Rio Novo (SB21-Z-C) Estado doParaacute escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Vasquez M L Klein E L Macambira M J B SantosA Bahia R B C Ricci P S F and QuadrosM L E S 2000 Geochronology of granitoids maficintrusions and mineralizations of the Tapajoacutes GoldProvincendashAmazonian CratonndashBrazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Vasquez M L Klein E L Quadros M L E S BahiaR B C Santos A Ricci P S F Sachett C RSilva C M G and Macambira M J B 1999 Mag-matismo Uatumatilde na Proviacutencia Tapajoacutesmdashnovos dadosgeocronoloacutegicos [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 471ndash474
Vasquez M L Klein E L and Ricci P S F 2001Granitoacuteides poacutes-colisionais da porccedilatildeo leste da Proviacuten-cia Tapajoacutes [ext abs] in VII Simpoacutesio de Geologia daAmazocircnia Beleacutem Brazil (CD-ROM)
Vearncombe J R 1993 Quartz vein morphology andimplications for formation depth and classification ofArchaean gold-vein deposits Ore Geology Reviews v8 p 407ndash424
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 555
The deposits have been classified in a few struc-tural styles according to the hosting structurestructural regime in which they have been formedand internal structures and textures of the veinsAccordingly fault-fill and shear veins are the domi-nant style followed by subordinate occurrences ofveins hosted in low-angle reverse-oblique faultsbreccia veins and stockworks More than one stylemay occur in the same gold camp and even in a sin-gle deposit
Fault-fill and shear veins as well as brecciaveins form moderately to steeply dipping tabularbodies that seldom exceed one meter in thicknessand are hosted by strike-slip faults and shear zonesto which they are parallel The vein quartz is domi-nantly massive with laminated saccharoidal andcomb textures occurring subordinately Shearingand cataclasis of the veins is widespread suggest-ing along with other textural and structural evi-dence their positioning in active faults and shearzones or deformation after formation In most casesquartz white mica and pyrite compose the veinmineralogy and along with minor chlorite carbon-ate epidote and K-feldspar they overprint the pri-mary mineralogy of the hosting granitoids and theamphibolite-facies paragenesis of the hostinggneisses
The breccias have likely been produced duringfracture propagation by physical brecciation whichoccurs when the amount of stress exceeds the brittleresistance of the rock by mechanisms such as tec-tonic comminution andor fluid-assisted brecciation(Jeacutebrak 1997) Furthermore they indicate activeseismic slip during mineralization (Robert andPoulsen 2001)
The origin of the large stockwork at Independecircn-cia may be ascribed to hydraulic fracturing occur-ring over a cupola of a small aplitic granitoidrelated to or intruding the regional coarse-grainedmonzogranite of the Creporizatildeo Suite In the latterhypothesis it could be related either to a late-stagepluton of the Creporizatildeo Suite or to a younger grani-toid suite (Parauari) This definition requires geo-chronological support
Deposits and gold camps show strong structuralcontrol at all scales The hosting structures havebeen formed under a dominantly brittle-ductile tobrittle regime and consist of strike slip faults shearfractures intersection and bending of faults andlithological andor lithostratigraphic contactsExtensional fractures have not been characterizedas hosting structures because evidence of displace-
ment andor shearing is virtually always present inthe veins Extensional features are present howeveras en echelon arrays of sulfide minerals and as vein-lets attached to the main longitudinal fault veinsDeposits hosted in granitoids show a more brittlebehavior whereas those hosted in gneisses tend todisplay more ductile features This can result eitherfrom the depth of vein formation or from high fluidrock ratios even in shallow levels of the crust
Formation of deposits occurred in a range ofcrustal depth from mesozonal to epizonal condi-tions as indicated by the internal structure of thequartz veins and by the nature of the hosting struc-tures This is also supported by fluid inclusion stud-ies in a few deposits such as Guarim (Klein et al2001) and Patinhas (Klein et al 2000) both depos-its hosted in gneisses of the Cuiuacute-Cuiuacute ComplexFluid composition is nearly identical but P-T dataalong with textural and structural evidence suggestthat Guarim (outside STP) formed between 4 and 7km whereas Patinhas (within STP) formed at deeperlevels
Hence shear veins and fault-fill veins may beconsidered at least in part and from a structuralview as a single class of structural style with theirdifferences being ascribed to different depths ofemplacement and structural overprint It is not ourintention however to state that all of these veinsformed in a single gold-forming event The issue ofhow many mineralizing events have occurred in theTapajoacutes Province is still unresolved
Santos (1999 2000) studying 23 depositsthroughout the province (including three deposits inSTP) reported a set of characteristics similar tothose we have found in STP He concluded that alldeposits are related to a regional NW-SEndashtrendingstrike-slip fault system and that the orientation of
FIG 9 Breccia vein at Ceacuteu Azul
556 KLEIN ET AL
the lower-order hosting structures is compatiblewith Riedelrsquos system with the direction of the mainstress vector around the E-W direction Orientationsthat do not fit the model may be related to heteroge-neities in the local stress field However nothinghas been said about the timing of this strike-slipsystem in relation to the magmatic metamorphicand tectonic evolution of the province
Coutinho et al (2000) reported model ages thatcluster around 196 Ga and 188 Ga and main-tained that these two ages reflect two mineralizingepochs Santos et al (2001) invoked a single eventat 186 Ga However as stated by Santos et al(2001) the tectonic regime at 186 Ga is brittle Thismodel does not explain the ductile emplacementandor deformed mineralization hosted especially bythe Cuiuacute-Cuiuacute gneisses and by the metavolcano-sedimentary sequences Another (older) mineraliz-ing phase is thus required
We proposed early in this paper that the majorstrike-slip regime that affected the Creporizatildeo Suiteand older units likely occurred between 197 and195 Ga Mineralization hosted in the Cuiuacute-Cuiuacutegneisses (at least in STP) is post-tectonic and post-metamorphic with respect to the host rocks sincehosting structures clearly crosscut the metamorphicbanding and the hydrothermal mineralogy is retro-gressive in relation to the metamorphic paragenesisDeformation affecting the Creporizatildeo granitoids isbrittle-ductile to brittle whereas deformation affect-ing younger granitoids is brittle Thus it is valid toinfer as a working hypothesis that at least in partgold mineralization in STP formed during regionalstrike-slip deformation and emplacement of late-stage plutons of the Creporizatildeo Suite at ~197ndash195Ga a time interval that is in agreement with thatobtained by Coutinho et al (2000) The structuresmay have been reactivated during younger deforma-tional episode(s) and gold deposits may haveformed at this stage as well
The challenge is to decipher which depositsformed at each metallogenic epoch From a struc-tural point of view it is likely that the deposits inSouthern Tapajoacutes Province that have been emplacedat deeper levels of the crust and that show evidenceof plastic deformation (ie the shear veins and thedeposits hosted in low-angle reverse-oblique faultssee Table 1) formed in the older phase Fault-fillveins that occur in association with these deposits inthe same gold camp (eg Boa Vista) probablyformed in the same event The rest of the fault-fillveins (with textures and structures indicating
emplacement in shallow brittle structures associ-ated or not with mafic dikes and showing no associ-ation with shear veins in the same gold camp) aswell as the breccia veins and stockworks may haveformed either in the older or in the younger phaseWe do not have elements to define this Thisrequires much more isotopic data along with addi-tional fluid-inclusion and stable-isotope informationto constrain physico-chemical conditions of golddeposition as well as knowledge of the sources andnature of the mineralizing fluids and the absolutetiming of gold deposition
The attributes shown by the gold deposits in STP(namely the regional structural setting depositstyle vein textures and hydrothermal mineralogy)along with scarce fluid-inclusion data fit with boththe orogenic (magmatic arc-hosted) and intrusion-related models as proposed by Santos et al (2001)the latter sharing characteristics with Korean-typedeposits (Robert et al 1997) as well
Acknowledgments
Alfreu dos Santos (formerly of CPRM) partici-pated in the field work and supervised the TapajoacutesProject His help is acknowledged This is a contri-bution to the project PRONEX-CNPq-FADESP6621031998-0ndashprocess no 4200000
REFERENCES
Almeida M E Brito M F L Ferreira A L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaVila Mamatildee Anatilde (SB21-V-D) Estados do Paraacute e Ama-zonas escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Almeida M E Brito M F L and Macambira M J B1999 Caroccedilal Granite 207Pb206Pb evaporation age inpost-collisional granitoids of Tapajoacutes Gold ProvinceAmazonian region Brazil [abs] in II South AmericanSymposium on Isotope Geology Coacuterdoba ArgentinaActas p 3ndash6
Almeida M E Ferreira A L Brito M F L and Mon-teiro M A S 2001 Evoluccedilatildeo tectono-estrutural daProviacutencia Tapajoacutes com base na geologia das folhas VilaMamatildee Anatilde e Jacareacanga (1250000) regiatildeo limitedos estados do Amazonas e Paraacute in Reis N J andMonteiro M A S orgs Contribuiccedilotildees agrave Geologia daAmazocircnia v 2 Manaus Brazil SBG-NO p 57ndash112
Bahia R B C and Quadros M L E S 2000 Geologiae recursos minerais da Folha Caracol (SB21-X-C)
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 557
Estado do Paraacute Escala 1250000 Brasiacutelia BrazilCPRMGeological Survey of Brazil (CD-ROM)
Cassidy K F Groves D I and McNaughton N J 1998Late-Archean granitoid-hosted lode-gold depositsYilgarn Craton Western Australia Deposit character-istics crustal architecture and implications for oregenesis Ore Geology Reviews v 13 p 65ndash102
Correcirca-Silva R H Juliani C Bettencourt J S NunesC M D and Almeida T I R 2001 Caracterizaccedilatildeode um sistema epitermal low-sulfidation (ou adulaacuteria-sericita) hospedado em vulcacircnicas e vulcanoclaacutesticasdo Grupo Iriri na Proviacutencia auriacutefera do Tapajoacutes (PA)[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Coutinho M G N Santos J O S Fallick A E andLafon J M 2000 Orogenic gold deposits in TapajoacutesMineral Province Amazon Brazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Dowling K and Morrison G 1989 Application ofquartz textures to the classification of gold depositsusing North Queensland examples Economic GeologyMonograph v 6 p 342ndash355
Dreher A M Vlach S and Martini S L 1998 Adu-laria associated with epithermal gold veins in theTapajoacutes Mineral Province Paraacute State Northern BrazilRevista Brasileira de Geociecircncias v 28 p 397ndash404
Faraco M T L Carvalho J M A and Klein E L1997 Carta metalogeneacutetica da Proviacutencia Auriacutefera doTapajoacutes in Costa M L and Angeacutelica R S orgsContribuiccedilotildees agrave Geologia da Amazocircnia Beleacutem BrazilFINEPSBG-NO p 423ndash437
Ferreira A L Almeida M E Brito M F L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaJacareacanga (SB21-Y-B) Estados do Paraacute e Amazo-nas escala 1250000 Brasiacutelia Brazil CPRMGeolog-ical Survey of Brazil (CD-ROM)
Goldfarb R J Groves D I and Gardoll S 2001 Oro-genic gold and geologic time A global synthesis OreGeology Reviews v 18 p 1ndash75
Groves D I Goldfarb R J Gebre-Mariam M Hage-mann S and Robert F 1998 Orogenic gold depos-its A proposed classification in the context of theircrustal distribution and relationship to other golddeposit types Ore Geology Reviews v 13 p 7ndash27
Hodgson C J 1989 The structure of shear-related vein-type gold deposits A review Ore Geology Reviews v4 p 231ndash273
Jacobi P 1999 The discovery of epithermal Au-Cu-MoProterozoic deposits in the Tapajoacutes Province BrazilRevista Brasileira de Geociecircncias v 29 p 277ndash279
Jeacutebrak M 1997 Hydrothermal breccias in vein-type oredeposits A review of mechanisms morphology andsize distribution Ore Geology Reviews v 12 p 111ndash134
Juliani C 2001 Metalogecircnese do ouro e metais de baseassociadas com o vulcanismo-plutonismo da porccedilatildeo Wda Proviacutencia Auriacutefera do Tapajoacutes [ext abs] in VIISimpoacutesio de Geologia da Amazocircnia Beleacutem Brazil(CD-ROM)
Kerrich R and Cassidy K F 1994 Temporal relation-ships of lode gold mineralization to accretion magma-tism metamorphism and deformationmdashArchean topresent A review Ore Geology Reviews v 9 p 263ndash310
Klein E L Almeida M E Vasquez M L BahiaR B C Quadros M L E S and Ferreira A L inpress Geologia e recursos minerais da Proviacutencia Min-eral do Tapajoacutes Estados do Paraacute e Amazonas Escala1 500000 Brasiacutelia Brazil CPRMGeological Surveyof Brazil
Klein E L Rosa-Costa L T and Carvalho J M A2000 Fluid inclusion studies at the Patinhas gold-quartz mineralisation Tapajoacutes Gold Province Brazil[abs] in XXXI International Geological Congress Riode Janeiro Brazil (CD-ROM)
Klein E L Santos R A Fuzikawa K and AngeacutelicaR S 2001 Hydrothermal fluid evolution and struc-tural control of the brittle-style Guarim lode-gold min-eralisation Tapajoacutes Province Amazonian CratonBrazil Mineralium Deposita v 36 p 149ndash164
Klein E L and Vasquez M L 2000 Projeto EspecialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Vila Riozinho (SB21-Z-A) Estadodo Paraacute escala 1250000 Brasiacutelia Brazil CPRMGeological Survey of Brazil (CD-ROM)
Klein E L Vasquez M L Santos A and Martins RC 1997 Structural elements of the Maloquinha Intru-sive Suite in Tapajoacutes Mineral Province northern Bra-zil and the emplacement of the plutons [ext abs] inII International Symposium on Granites and Associ-ated Mineralizations ISGAM II Salvador Brazil p313ndash314
Klein E L Vasquez M L Santos A and Rosa-CostaL T 1999 Geologia e controle estrutural das mineral-izaccedilotildees auriacuteferas na Folha Vila Riozinho e NW daFolha Rio Novo Proviacutencia Tapajoacutes [ext abs] in VISimpoacutesio de Geologia da Amazocircnia Manaus Brazil p128ndash131
Lamaratildeo C N DallrsquoAgnol R and Lafon J M 2001Geocronologia e geoquiacutemica das associaccedilotildees vulcacircni-cas e plutocircnicas da regiatildeo de Vila Riozinho ProviacutenciaAuriacutefera do Tapajoacutes [ext abs] in VII Simpoacutesio deGeologia da Amazocircnia Beleacutem Brazil (CD-ROM)
Nunes C M D Juliani C Correcirca-Silva R H Mon-teiro L V S Bettencourt J S Neumann R AlcoverNeto A and Rye R O 2001 Caracterizaccedilatildeo de umsistema epitermal high-sulfidation vulcacircnico pale-oproterozoacuteico da Proviacutencia Auriacutefera do Tapajoacutes Paraacute[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
558 KLEIN ET AL
Ricci P S F Vasquez M L Santos A Klein E LJorge Joatildeo X S and Martins R C 1999 SuiacuteteIntrusiva Creporizatildeo ndash Proviacutencia Tapajoacutes Proposta ecriteacuterios de definiccedilatildeo [ext abs] in VI Simpoacutesio deGeologia da Amazocircnia Manaus Brazil p 519ndash522
Robert F and Poulsen K H 2001 Vein formation anddeformation in greenstone gold deposits in RichardsJ P and Tosdal R M eds Structural controls on oregenesis Reviews in Economic Geology v 14 p 111ndash155
Robert F Poulsen K H and Dubeacute B 1997 Golddeposits and their geological classification in GubinsA G ed Proceedings of Exploration 97 TorontoCanada p 209ndash220
Ronchi L H DallrsquoAgnol R Araujo J C Ribeiro VLamaratildeo C N Borges R M K and Fuzikawa K2001 Fluidos relacionados agraves alteraccedilotildees hidrotermaisno depoacutesito de ouro do Granito Satildeo JorgendashPA [extabs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Rosa-Costa L T and Carvalho J M A 1999 Tipologiade mineralizaccedilotildees auriacuteferas da regiatildeo sul da ProviacutenciaTapajoacutesndashParaacute [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 176ndash179
Santos J O S Groves D I Hartmann L A MouraM A and McNaughton N J 2001 Gold deposits ofthe Tapajoacutes and Alta Floresta Domains Tapajoacutes-Parima orogenic belt Amazon Craton Brazil Minera-lium Deposita v 36 p 279ndash299
Santos J O S Hartmann L A Gaudette H E GrovesD I McNaughton N J and Fletcher I R 2000 Anew understanding of the provinces of the AmazonCraton based on integration of field mapping and U-Pband Sm-Nd geochronology Gondwana Research v 3p 453ndash488
Santos R A 1997 Contribuiccedilatildeo agrave anaacutelise estrutural dejazimentos auriacuteferos do rio Tapajoacutes SW do Paraacute e SEdo Amazonas Garimpos Abacaxis Espiacuterito SantoBom Jesus Goiano Fazenda Pison Ouro Mil SantaIsabel Majestade e Carneirinho Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 1999 Controle estrutural das mineralizaccedilotildees deouro da Proviacutencia Mineral do Tapajoacutes Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 2000 Formation of gold-quartz veins controlledby the strike-slip fault mega-system in Tapajoacutes Min-eral Province Amazon Brazil [abs] in XXXI Interna-tional Geological Congress Rio de Janeiro Brazil(CD-ROM)
Tassinari C C G 1996 O mapa geocronoloacutegico do Craacute-ton Amazocircnico no Brasil Revisatildeo dos dados isotoacutepi-cos Unpubl Tese de Livre Docecircncia Universidade deSatildeo Paulo 139 p
Tassinari C C G and Macambira M J B 1999 Geo-chronological provinces of the Amazonian Craton Epi-sodes v 22 p 174ndash182
Vasquez M L and Klein E L 2000 Projeto especialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Rio Novo (SB21-Z-C) Estado doParaacute escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Vasquez M L Klein E L Macambira M J B SantosA Bahia R B C Ricci P S F and QuadrosM L E S 2000 Geochronology of granitoids maficintrusions and mineralizations of the Tapajoacutes GoldProvincendashAmazonian CratonndashBrazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Vasquez M L Klein E L Quadros M L E S BahiaR B C Santos A Ricci P S F Sachett C RSilva C M G and Macambira M J B 1999 Mag-matismo Uatumatilde na Proviacutencia Tapajoacutesmdashnovos dadosgeocronoloacutegicos [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 471ndash474
Vasquez M L Klein E L and Ricci P S F 2001Granitoacuteides poacutes-colisionais da porccedilatildeo leste da Proviacuten-cia Tapajoacutes [ext abs] in VII Simpoacutesio de Geologia daAmazocircnia Beleacutem Brazil (CD-ROM)
Vearncombe J R 1993 Quartz vein morphology andimplications for formation depth and classification ofArchaean gold-vein deposits Ore Geology Reviews v8 p 407ndash424
556 KLEIN ET AL
the lower-order hosting structures is compatiblewith Riedelrsquos system with the direction of the mainstress vector around the E-W direction Orientationsthat do not fit the model may be related to heteroge-neities in the local stress field However nothinghas been said about the timing of this strike-slipsystem in relation to the magmatic metamorphicand tectonic evolution of the province
Coutinho et al (2000) reported model ages thatcluster around 196 Ga and 188 Ga and main-tained that these two ages reflect two mineralizingepochs Santos et al (2001) invoked a single eventat 186 Ga However as stated by Santos et al(2001) the tectonic regime at 186 Ga is brittle Thismodel does not explain the ductile emplacementandor deformed mineralization hosted especially bythe Cuiuacute-Cuiuacute gneisses and by the metavolcano-sedimentary sequences Another (older) mineraliz-ing phase is thus required
We proposed early in this paper that the majorstrike-slip regime that affected the Creporizatildeo Suiteand older units likely occurred between 197 and195 Ga Mineralization hosted in the Cuiuacute-Cuiuacutegneisses (at least in STP) is post-tectonic and post-metamorphic with respect to the host rocks sincehosting structures clearly crosscut the metamorphicbanding and the hydrothermal mineralogy is retro-gressive in relation to the metamorphic paragenesisDeformation affecting the Creporizatildeo granitoids isbrittle-ductile to brittle whereas deformation affect-ing younger granitoids is brittle Thus it is valid toinfer as a working hypothesis that at least in partgold mineralization in STP formed during regionalstrike-slip deformation and emplacement of late-stage plutons of the Creporizatildeo Suite at ~197ndash195Ga a time interval that is in agreement with thatobtained by Coutinho et al (2000) The structuresmay have been reactivated during younger deforma-tional episode(s) and gold deposits may haveformed at this stage as well
The challenge is to decipher which depositsformed at each metallogenic epoch From a struc-tural point of view it is likely that the deposits inSouthern Tapajoacutes Province that have been emplacedat deeper levels of the crust and that show evidenceof plastic deformation (ie the shear veins and thedeposits hosted in low-angle reverse-oblique faultssee Table 1) formed in the older phase Fault-fillveins that occur in association with these deposits inthe same gold camp (eg Boa Vista) probablyformed in the same event The rest of the fault-fillveins (with textures and structures indicating
emplacement in shallow brittle structures associ-ated or not with mafic dikes and showing no associ-ation with shear veins in the same gold camp) aswell as the breccia veins and stockworks may haveformed either in the older or in the younger phaseWe do not have elements to define this Thisrequires much more isotopic data along with addi-tional fluid-inclusion and stable-isotope informationto constrain physico-chemical conditions of golddeposition as well as knowledge of the sources andnature of the mineralizing fluids and the absolutetiming of gold deposition
The attributes shown by the gold deposits in STP(namely the regional structural setting depositstyle vein textures and hydrothermal mineralogy)along with scarce fluid-inclusion data fit with boththe orogenic (magmatic arc-hosted) and intrusion-related models as proposed by Santos et al (2001)the latter sharing characteristics with Korean-typedeposits (Robert et al 1997) as well
Acknowledgments
Alfreu dos Santos (formerly of CPRM) partici-pated in the field work and supervised the TapajoacutesProject His help is acknowledged This is a contri-bution to the project PRONEX-CNPq-FADESP6621031998-0ndashprocess no 4200000
REFERENCES
Almeida M E Brito M F L Ferreira A L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaVila Mamatildee Anatilde (SB21-V-D) Estados do Paraacute e Ama-zonas escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Almeida M E Brito M F L and Macambira M J B1999 Caroccedilal Granite 207Pb206Pb evaporation age inpost-collisional granitoids of Tapajoacutes Gold ProvinceAmazonian region Brazil [abs] in II South AmericanSymposium on Isotope Geology Coacuterdoba ArgentinaActas p 3ndash6
Almeida M E Ferreira A L Brito M F L and Mon-teiro M A S 2001 Evoluccedilatildeo tectono-estrutural daProviacutencia Tapajoacutes com base na geologia das folhas VilaMamatildee Anatilde e Jacareacanga (1250000) regiatildeo limitedos estados do Amazonas e Paraacute in Reis N J andMonteiro M A S orgs Contribuiccedilotildees agrave Geologia daAmazocircnia v 2 Manaus Brazil SBG-NO p 57ndash112
Bahia R B C and Quadros M L E S 2000 Geologiae recursos minerais da Folha Caracol (SB21-X-C)
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 557
Estado do Paraacute Escala 1250000 Brasiacutelia BrazilCPRMGeological Survey of Brazil (CD-ROM)
Cassidy K F Groves D I and McNaughton N J 1998Late-Archean granitoid-hosted lode-gold depositsYilgarn Craton Western Australia Deposit character-istics crustal architecture and implications for oregenesis Ore Geology Reviews v 13 p 65ndash102
Correcirca-Silva R H Juliani C Bettencourt J S NunesC M D and Almeida T I R 2001 Caracterizaccedilatildeode um sistema epitermal low-sulfidation (ou adulaacuteria-sericita) hospedado em vulcacircnicas e vulcanoclaacutesticasdo Grupo Iriri na Proviacutencia auriacutefera do Tapajoacutes (PA)[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Coutinho M G N Santos J O S Fallick A E andLafon J M 2000 Orogenic gold deposits in TapajoacutesMineral Province Amazon Brazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Dowling K and Morrison G 1989 Application ofquartz textures to the classification of gold depositsusing North Queensland examples Economic GeologyMonograph v 6 p 342ndash355
Dreher A M Vlach S and Martini S L 1998 Adu-laria associated with epithermal gold veins in theTapajoacutes Mineral Province Paraacute State Northern BrazilRevista Brasileira de Geociecircncias v 28 p 397ndash404
Faraco M T L Carvalho J M A and Klein E L1997 Carta metalogeneacutetica da Proviacutencia Auriacutefera doTapajoacutes in Costa M L and Angeacutelica R S orgsContribuiccedilotildees agrave Geologia da Amazocircnia Beleacutem BrazilFINEPSBG-NO p 423ndash437
Ferreira A L Almeida M E Brito M F L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaJacareacanga (SB21-Y-B) Estados do Paraacute e Amazo-nas escala 1250000 Brasiacutelia Brazil CPRMGeolog-ical Survey of Brazil (CD-ROM)
Goldfarb R J Groves D I and Gardoll S 2001 Oro-genic gold and geologic time A global synthesis OreGeology Reviews v 18 p 1ndash75
Groves D I Goldfarb R J Gebre-Mariam M Hage-mann S and Robert F 1998 Orogenic gold depos-its A proposed classification in the context of theircrustal distribution and relationship to other golddeposit types Ore Geology Reviews v 13 p 7ndash27
Hodgson C J 1989 The structure of shear-related vein-type gold deposits A review Ore Geology Reviews v4 p 231ndash273
Jacobi P 1999 The discovery of epithermal Au-Cu-MoProterozoic deposits in the Tapajoacutes Province BrazilRevista Brasileira de Geociecircncias v 29 p 277ndash279
Jeacutebrak M 1997 Hydrothermal breccias in vein-type oredeposits A review of mechanisms morphology andsize distribution Ore Geology Reviews v 12 p 111ndash134
Juliani C 2001 Metalogecircnese do ouro e metais de baseassociadas com o vulcanismo-plutonismo da porccedilatildeo Wda Proviacutencia Auriacutefera do Tapajoacutes [ext abs] in VIISimpoacutesio de Geologia da Amazocircnia Beleacutem Brazil(CD-ROM)
Kerrich R and Cassidy K F 1994 Temporal relation-ships of lode gold mineralization to accretion magma-tism metamorphism and deformationmdashArchean topresent A review Ore Geology Reviews v 9 p 263ndash310
Klein E L Almeida M E Vasquez M L BahiaR B C Quadros M L E S and Ferreira A L inpress Geologia e recursos minerais da Proviacutencia Min-eral do Tapajoacutes Estados do Paraacute e Amazonas Escala1 500000 Brasiacutelia Brazil CPRMGeological Surveyof Brazil
Klein E L Rosa-Costa L T and Carvalho J M A2000 Fluid inclusion studies at the Patinhas gold-quartz mineralisation Tapajoacutes Gold Province Brazil[abs] in XXXI International Geological Congress Riode Janeiro Brazil (CD-ROM)
Klein E L Santos R A Fuzikawa K and AngeacutelicaR S 2001 Hydrothermal fluid evolution and struc-tural control of the brittle-style Guarim lode-gold min-eralisation Tapajoacutes Province Amazonian CratonBrazil Mineralium Deposita v 36 p 149ndash164
Klein E L and Vasquez M L 2000 Projeto EspecialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Vila Riozinho (SB21-Z-A) Estadodo Paraacute escala 1250000 Brasiacutelia Brazil CPRMGeological Survey of Brazil (CD-ROM)
Klein E L Vasquez M L Santos A and Martins RC 1997 Structural elements of the Maloquinha Intru-sive Suite in Tapajoacutes Mineral Province northern Bra-zil and the emplacement of the plutons [ext abs] inII International Symposium on Granites and Associ-ated Mineralizations ISGAM II Salvador Brazil p313ndash314
Klein E L Vasquez M L Santos A and Rosa-CostaL T 1999 Geologia e controle estrutural das mineral-izaccedilotildees auriacuteferas na Folha Vila Riozinho e NW daFolha Rio Novo Proviacutencia Tapajoacutes [ext abs] in VISimpoacutesio de Geologia da Amazocircnia Manaus Brazil p128ndash131
Lamaratildeo C N DallrsquoAgnol R and Lafon J M 2001Geocronologia e geoquiacutemica das associaccedilotildees vulcacircni-cas e plutocircnicas da regiatildeo de Vila Riozinho ProviacutenciaAuriacutefera do Tapajoacutes [ext abs] in VII Simpoacutesio deGeologia da Amazocircnia Beleacutem Brazil (CD-ROM)
Nunes C M D Juliani C Correcirca-Silva R H Mon-teiro L V S Bettencourt J S Neumann R AlcoverNeto A and Rye R O 2001 Caracterizaccedilatildeo de umsistema epitermal high-sulfidation vulcacircnico pale-oproterozoacuteico da Proviacutencia Auriacutefera do Tapajoacutes Paraacute[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
558 KLEIN ET AL
Ricci P S F Vasquez M L Santos A Klein E LJorge Joatildeo X S and Martins R C 1999 SuiacuteteIntrusiva Creporizatildeo ndash Proviacutencia Tapajoacutes Proposta ecriteacuterios de definiccedilatildeo [ext abs] in VI Simpoacutesio deGeologia da Amazocircnia Manaus Brazil p 519ndash522
Robert F and Poulsen K H 2001 Vein formation anddeformation in greenstone gold deposits in RichardsJ P and Tosdal R M eds Structural controls on oregenesis Reviews in Economic Geology v 14 p 111ndash155
Robert F Poulsen K H and Dubeacute B 1997 Golddeposits and their geological classification in GubinsA G ed Proceedings of Exploration 97 TorontoCanada p 209ndash220
Ronchi L H DallrsquoAgnol R Araujo J C Ribeiro VLamaratildeo C N Borges R M K and Fuzikawa K2001 Fluidos relacionados agraves alteraccedilotildees hidrotermaisno depoacutesito de ouro do Granito Satildeo JorgendashPA [extabs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Rosa-Costa L T and Carvalho J M A 1999 Tipologiade mineralizaccedilotildees auriacuteferas da regiatildeo sul da ProviacutenciaTapajoacutesndashParaacute [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 176ndash179
Santos J O S Groves D I Hartmann L A MouraM A and McNaughton N J 2001 Gold deposits ofthe Tapajoacutes and Alta Floresta Domains Tapajoacutes-Parima orogenic belt Amazon Craton Brazil Minera-lium Deposita v 36 p 279ndash299
Santos J O S Hartmann L A Gaudette H E GrovesD I McNaughton N J and Fletcher I R 2000 Anew understanding of the provinces of the AmazonCraton based on integration of field mapping and U-Pband Sm-Nd geochronology Gondwana Research v 3p 453ndash488
Santos R A 1997 Contribuiccedilatildeo agrave anaacutelise estrutural dejazimentos auriacuteferos do rio Tapajoacutes SW do Paraacute e SEdo Amazonas Garimpos Abacaxis Espiacuterito SantoBom Jesus Goiano Fazenda Pison Ouro Mil SantaIsabel Majestade e Carneirinho Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 1999 Controle estrutural das mineralizaccedilotildees deouro da Proviacutencia Mineral do Tapajoacutes Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 2000 Formation of gold-quartz veins controlledby the strike-slip fault mega-system in Tapajoacutes Min-eral Province Amazon Brazil [abs] in XXXI Interna-tional Geological Congress Rio de Janeiro Brazil(CD-ROM)
Tassinari C C G 1996 O mapa geocronoloacutegico do Craacute-ton Amazocircnico no Brasil Revisatildeo dos dados isotoacutepi-cos Unpubl Tese de Livre Docecircncia Universidade deSatildeo Paulo 139 p
Tassinari C C G and Macambira M J B 1999 Geo-chronological provinces of the Amazonian Craton Epi-sodes v 22 p 174ndash182
Vasquez M L and Klein E L 2000 Projeto especialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Rio Novo (SB21-Z-C) Estado doParaacute escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Vasquez M L Klein E L Macambira M J B SantosA Bahia R B C Ricci P S F and QuadrosM L E S 2000 Geochronology of granitoids maficintrusions and mineralizations of the Tapajoacutes GoldProvincendashAmazonian CratonndashBrazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Vasquez M L Klein E L Quadros M L E S BahiaR B C Santos A Ricci P S F Sachett C RSilva C M G and Macambira M J B 1999 Mag-matismo Uatumatilde na Proviacutencia Tapajoacutesmdashnovos dadosgeocronoloacutegicos [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 471ndash474
Vasquez M L Klein E L and Ricci P S F 2001Granitoacuteides poacutes-colisionais da porccedilatildeo leste da Proviacuten-cia Tapajoacutes [ext abs] in VII Simpoacutesio de Geologia daAmazocircnia Beleacutem Brazil (CD-ROM)
Vearncombe J R 1993 Quartz vein morphology andimplications for formation depth and classification ofArchaean gold-vein deposits Ore Geology Reviews v8 p 407ndash424
GNEISS- AND GRANITOID-HOSTED GOLD MINERALIZATION 557
Estado do Paraacute Escala 1250000 Brasiacutelia BrazilCPRMGeological Survey of Brazil (CD-ROM)
Cassidy K F Groves D I and McNaughton N J 1998Late-Archean granitoid-hosted lode-gold depositsYilgarn Craton Western Australia Deposit character-istics crustal architecture and implications for oregenesis Ore Geology Reviews v 13 p 65ndash102
Correcirca-Silva R H Juliani C Bettencourt J S NunesC M D and Almeida T I R 2001 Caracterizaccedilatildeode um sistema epitermal low-sulfidation (ou adulaacuteria-sericita) hospedado em vulcacircnicas e vulcanoclaacutesticasdo Grupo Iriri na Proviacutencia auriacutefera do Tapajoacutes (PA)[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Coutinho M G N Santos J O S Fallick A E andLafon J M 2000 Orogenic gold deposits in TapajoacutesMineral Province Amazon Brazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Dowling K and Morrison G 1989 Application ofquartz textures to the classification of gold depositsusing North Queensland examples Economic GeologyMonograph v 6 p 342ndash355
Dreher A M Vlach S and Martini S L 1998 Adu-laria associated with epithermal gold veins in theTapajoacutes Mineral Province Paraacute State Northern BrazilRevista Brasileira de Geociecircncias v 28 p 397ndash404
Faraco M T L Carvalho J M A and Klein E L1997 Carta metalogeneacutetica da Proviacutencia Auriacutefera doTapajoacutes in Costa M L and Angeacutelica R S orgsContribuiccedilotildees agrave Geologia da Amazocircnia Beleacutem BrazilFINEPSBG-NO p 423ndash437
Ferreira A L Almeida M E Brito M F L and Mon-teiro M A S 2000 Projeto Especial Proviacutencia Min-eral do Tapajoacutes Geologia e recursos minerais da FolhaJacareacanga (SB21-Y-B) Estados do Paraacute e Amazo-nas escala 1250000 Brasiacutelia Brazil CPRMGeolog-ical Survey of Brazil (CD-ROM)
Goldfarb R J Groves D I and Gardoll S 2001 Oro-genic gold and geologic time A global synthesis OreGeology Reviews v 18 p 1ndash75
Groves D I Goldfarb R J Gebre-Mariam M Hage-mann S and Robert F 1998 Orogenic gold depos-its A proposed classification in the context of theircrustal distribution and relationship to other golddeposit types Ore Geology Reviews v 13 p 7ndash27
Hodgson C J 1989 The structure of shear-related vein-type gold deposits A review Ore Geology Reviews v4 p 231ndash273
Jacobi P 1999 The discovery of epithermal Au-Cu-MoProterozoic deposits in the Tapajoacutes Province BrazilRevista Brasileira de Geociecircncias v 29 p 277ndash279
Jeacutebrak M 1997 Hydrothermal breccias in vein-type oredeposits A review of mechanisms morphology andsize distribution Ore Geology Reviews v 12 p 111ndash134
Juliani C 2001 Metalogecircnese do ouro e metais de baseassociadas com o vulcanismo-plutonismo da porccedilatildeo Wda Proviacutencia Auriacutefera do Tapajoacutes [ext abs] in VIISimpoacutesio de Geologia da Amazocircnia Beleacutem Brazil(CD-ROM)
Kerrich R and Cassidy K F 1994 Temporal relation-ships of lode gold mineralization to accretion magma-tism metamorphism and deformationmdashArchean topresent A review Ore Geology Reviews v 9 p 263ndash310
Klein E L Almeida M E Vasquez M L BahiaR B C Quadros M L E S and Ferreira A L inpress Geologia e recursos minerais da Proviacutencia Min-eral do Tapajoacutes Estados do Paraacute e Amazonas Escala1 500000 Brasiacutelia Brazil CPRMGeological Surveyof Brazil
Klein E L Rosa-Costa L T and Carvalho J M A2000 Fluid inclusion studies at the Patinhas gold-quartz mineralisation Tapajoacutes Gold Province Brazil[abs] in XXXI International Geological Congress Riode Janeiro Brazil (CD-ROM)
Klein E L Santos R A Fuzikawa K and AngeacutelicaR S 2001 Hydrothermal fluid evolution and struc-tural control of the brittle-style Guarim lode-gold min-eralisation Tapajoacutes Province Amazonian CratonBrazil Mineralium Deposita v 36 p 149ndash164
Klein E L and Vasquez M L 2000 Projeto EspecialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Vila Riozinho (SB21-Z-A) Estadodo Paraacute escala 1250000 Brasiacutelia Brazil CPRMGeological Survey of Brazil (CD-ROM)
Klein E L Vasquez M L Santos A and Martins RC 1997 Structural elements of the Maloquinha Intru-sive Suite in Tapajoacutes Mineral Province northern Bra-zil and the emplacement of the plutons [ext abs] inII International Symposium on Granites and Associ-ated Mineralizations ISGAM II Salvador Brazil p313ndash314
Klein E L Vasquez M L Santos A and Rosa-CostaL T 1999 Geologia e controle estrutural das mineral-izaccedilotildees auriacuteferas na Folha Vila Riozinho e NW daFolha Rio Novo Proviacutencia Tapajoacutes [ext abs] in VISimpoacutesio de Geologia da Amazocircnia Manaus Brazil p128ndash131
Lamaratildeo C N DallrsquoAgnol R and Lafon J M 2001Geocronologia e geoquiacutemica das associaccedilotildees vulcacircni-cas e plutocircnicas da regiatildeo de Vila Riozinho ProviacutenciaAuriacutefera do Tapajoacutes [ext abs] in VII Simpoacutesio deGeologia da Amazocircnia Beleacutem Brazil (CD-ROM)
Nunes C M D Juliani C Correcirca-Silva R H Mon-teiro L V S Bettencourt J S Neumann R AlcoverNeto A and Rye R O 2001 Caracterizaccedilatildeo de umsistema epitermal high-sulfidation vulcacircnico pale-oproterozoacuteico da Proviacutencia Auriacutefera do Tapajoacutes Paraacute[ext abs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
558 KLEIN ET AL
Ricci P S F Vasquez M L Santos A Klein E LJorge Joatildeo X S and Martins R C 1999 SuiacuteteIntrusiva Creporizatildeo ndash Proviacutencia Tapajoacutes Proposta ecriteacuterios de definiccedilatildeo [ext abs] in VI Simpoacutesio deGeologia da Amazocircnia Manaus Brazil p 519ndash522
Robert F and Poulsen K H 2001 Vein formation anddeformation in greenstone gold deposits in RichardsJ P and Tosdal R M eds Structural controls on oregenesis Reviews in Economic Geology v 14 p 111ndash155
Robert F Poulsen K H and Dubeacute B 1997 Golddeposits and their geological classification in GubinsA G ed Proceedings of Exploration 97 TorontoCanada p 209ndash220
Ronchi L H DallrsquoAgnol R Araujo J C Ribeiro VLamaratildeo C N Borges R M K and Fuzikawa K2001 Fluidos relacionados agraves alteraccedilotildees hidrotermaisno depoacutesito de ouro do Granito Satildeo JorgendashPA [extabs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Rosa-Costa L T and Carvalho J M A 1999 Tipologiade mineralizaccedilotildees auriacuteferas da regiatildeo sul da ProviacutenciaTapajoacutesndashParaacute [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 176ndash179
Santos J O S Groves D I Hartmann L A MouraM A and McNaughton N J 2001 Gold deposits ofthe Tapajoacutes and Alta Floresta Domains Tapajoacutes-Parima orogenic belt Amazon Craton Brazil Minera-lium Deposita v 36 p 279ndash299
Santos J O S Hartmann L A Gaudette H E GrovesD I McNaughton N J and Fletcher I R 2000 Anew understanding of the provinces of the AmazonCraton based on integration of field mapping and U-Pband Sm-Nd geochronology Gondwana Research v 3p 453ndash488
Santos R A 1997 Contribuiccedilatildeo agrave anaacutelise estrutural dejazimentos auriacuteferos do rio Tapajoacutes SW do Paraacute e SEdo Amazonas Garimpos Abacaxis Espiacuterito SantoBom Jesus Goiano Fazenda Pison Ouro Mil SantaIsabel Majestade e Carneirinho Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 1999 Controle estrutural das mineralizaccedilotildees deouro da Proviacutencia Mineral do Tapajoacutes Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 2000 Formation of gold-quartz veins controlledby the strike-slip fault mega-system in Tapajoacutes Min-eral Province Amazon Brazil [abs] in XXXI Interna-tional Geological Congress Rio de Janeiro Brazil(CD-ROM)
Tassinari C C G 1996 O mapa geocronoloacutegico do Craacute-ton Amazocircnico no Brasil Revisatildeo dos dados isotoacutepi-cos Unpubl Tese de Livre Docecircncia Universidade deSatildeo Paulo 139 p
Tassinari C C G and Macambira M J B 1999 Geo-chronological provinces of the Amazonian Craton Epi-sodes v 22 p 174ndash182
Vasquez M L and Klein E L 2000 Projeto especialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Rio Novo (SB21-Z-C) Estado doParaacute escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Vasquez M L Klein E L Macambira M J B SantosA Bahia R B C Ricci P S F and QuadrosM L E S 2000 Geochronology of granitoids maficintrusions and mineralizations of the Tapajoacutes GoldProvincendashAmazonian CratonndashBrazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Vasquez M L Klein E L Quadros M L E S BahiaR B C Santos A Ricci P S F Sachett C RSilva C M G and Macambira M J B 1999 Mag-matismo Uatumatilde na Proviacutencia Tapajoacutesmdashnovos dadosgeocronoloacutegicos [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 471ndash474
Vasquez M L Klein E L and Ricci P S F 2001Granitoacuteides poacutes-colisionais da porccedilatildeo leste da Proviacuten-cia Tapajoacutes [ext abs] in VII Simpoacutesio de Geologia daAmazocircnia Beleacutem Brazil (CD-ROM)
Vearncombe J R 1993 Quartz vein morphology andimplications for formation depth and classification ofArchaean gold-vein deposits Ore Geology Reviews v8 p 407ndash424
558 KLEIN ET AL
Ricci P S F Vasquez M L Santos A Klein E LJorge Joatildeo X S and Martins R C 1999 SuiacuteteIntrusiva Creporizatildeo ndash Proviacutencia Tapajoacutes Proposta ecriteacuterios de definiccedilatildeo [ext abs] in VI Simpoacutesio deGeologia da Amazocircnia Manaus Brazil p 519ndash522
Robert F and Poulsen K H 2001 Vein formation anddeformation in greenstone gold deposits in RichardsJ P and Tosdal R M eds Structural controls on oregenesis Reviews in Economic Geology v 14 p 111ndash155
Robert F Poulsen K H and Dubeacute B 1997 Golddeposits and their geological classification in GubinsA G ed Proceedings of Exploration 97 TorontoCanada p 209ndash220
Ronchi L H DallrsquoAgnol R Araujo J C Ribeiro VLamaratildeo C N Borges R M K and Fuzikawa K2001 Fluidos relacionados agraves alteraccedilotildees hidrotermaisno depoacutesito de ouro do Granito Satildeo JorgendashPA [extabs] in VII Simpoacutesio de Geologia da AmazocircniaBeleacutem Brazil (CD-ROM)
Rosa-Costa L T and Carvalho J M A 1999 Tipologiade mineralizaccedilotildees auriacuteferas da regiatildeo sul da ProviacutenciaTapajoacutesndashParaacute [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 176ndash179
Santos J O S Groves D I Hartmann L A MouraM A and McNaughton N J 2001 Gold deposits ofthe Tapajoacutes and Alta Floresta Domains Tapajoacutes-Parima orogenic belt Amazon Craton Brazil Minera-lium Deposita v 36 p 279ndash299
Santos J O S Hartmann L A Gaudette H E GrovesD I McNaughton N J and Fletcher I R 2000 Anew understanding of the provinces of the AmazonCraton based on integration of field mapping and U-Pband Sm-Nd geochronology Gondwana Research v 3p 453ndash488
Santos R A 1997 Contribuiccedilatildeo agrave anaacutelise estrutural dejazimentos auriacuteferos do rio Tapajoacutes SW do Paraacute e SEdo Amazonas Garimpos Abacaxis Espiacuterito SantoBom Jesus Goiano Fazenda Pison Ouro Mil SantaIsabel Majestade e Carneirinho Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 1999 Controle estrutural das mineralizaccedilotildees deouro da Proviacutencia Mineral do Tapajoacutes Brasiacutelia BrazilCPRMGeological Survey of Brazil (unpubl report)
______ 2000 Formation of gold-quartz veins controlledby the strike-slip fault mega-system in Tapajoacutes Min-eral Province Amazon Brazil [abs] in XXXI Interna-tional Geological Congress Rio de Janeiro Brazil(CD-ROM)
Tassinari C C G 1996 O mapa geocronoloacutegico do Craacute-ton Amazocircnico no Brasil Revisatildeo dos dados isotoacutepi-cos Unpubl Tese de Livre Docecircncia Universidade deSatildeo Paulo 139 p
Tassinari C C G and Macambira M J B 1999 Geo-chronological provinces of the Amazonian Craton Epi-sodes v 22 p 174ndash182
Vasquez M L and Klein E L 2000 Projeto especialProviacutencia Mineral do Tapajoacutes Geologia e recursosminerais da Folha Rio Novo (SB21-Z-C) Estado doParaacute escala 1250000 Brasiacutelia Brazil CPRMGeo-logical Survey of Brazil (CD-ROM)
Vasquez M L Klein E L Macambira M J B SantosA Bahia R B C Ricci P S F and QuadrosM L E S 2000 Geochronology of granitoids maficintrusions and mineralizations of the Tapajoacutes GoldProvincendashAmazonian CratonndashBrazil [abs] in XXXIInternational Geological Congress Rio de JaneiroBrazil (CD-ROM)
Vasquez M L Klein E L Quadros M L E S BahiaR B C Santos A Ricci P S F Sachett C RSilva C M G and Macambira M J B 1999 Mag-matismo Uatumatilde na Proviacutencia Tapajoacutesmdashnovos dadosgeocronoloacutegicos [ext abs] in VI Simpoacutesio de Geologiada Amazocircnia Manaus Brazil p 471ndash474
Vasquez M L Klein E L and Ricci P S F 2001Granitoacuteides poacutes-colisionais da porccedilatildeo leste da Proviacuten-cia Tapajoacutes [ext abs] in VII Simpoacutesio de Geologia daAmazocircnia Beleacutem Brazil (CD-ROM)
Vearncombe J R 1993 Quartz vein morphology andimplications for formation depth and classification ofArchaean gold-vein deposits Ore Geology Reviews v8 p 407ndash424
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