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ORIGINAL PAPER
Mineralogical, stable isotope, and fluid inclusion studiesof
spatially related porphyry Cu and epithermal Au-Temineralization,
Fakos Peninsula, Limnos Island, Greece
Andrew P. Fornadel & Panagiotis Ch. Voudouris &Paul G.
Spry & Vasilios Melfos
Received: 2 February 2011 /Accepted: 26 March 2012 /Published
online: 17 April 2012# Springer-Verlag 2012
Abstract The Fakos porphyry Cu and epithermal Au-Tedeposit,
Limnos Island, Greece, is hosted in a ~20 Ma quartzmonzonite and
shoshonitic subvolcanic rocks that intrudedmiddle Eocene to lower
Miocene sedimentary basementrocks. Metallic mineralization formed
in three stages inquartz and quartz-calcite veins. Early
porphyry-style(Stage 1) metallic minerals consist of pyrite,
chalcopyrite,galena, bornite, sphalerite, molybdenite, and iron
oxides,which are surrounded by halos of potassic and
propyliticalteration. Stage 2 mineralization is composed mostly
ofquartz-tourmaline veins associated with sericitic alterationand
disseminated pyrite and molybdenite, whereas Stage
3,epithermal-style mineralization is characterized by polyme-tallic
veins containing pyrite, chalcopyrite, sphalerite, gale-na,
enargite, bournonite, tetrahedrite-tennantite, hessite,petzite,
altaite, an unknown cervelleite-like Ag-telluride,native Au, and
Au-Ag alloy. Stage 3 veins are spatiallyassociated with sericitic
and argillic alteration. Fluid inclu-sions in quartz from Stage 1
(porphyry-style) mineralizationcontain five types of inclusions.
Type I, liquidvapor inclu-sions, which homogenize at temperatures
ranging from
189.5C to 403.3C have salinities of 14.8 to 19.9 wt. %NaCl
equiv. Type II, liquidvapor-NaCl, Type III liquidvapor-NaCl-XCl2
(where XCl is an unknown chloridephase, likely CaCl2), and Type IV,
liquidvapor-hematiteNaCl homogenize to the liquid phase by
liquidvapor ho-mogenization or by daughter crystal dissolution at
temper-atures of 209.3 to 740.5 C, 267.6 to 780.8 C, and 357.9
to684.2 C, respectively, and, Type V, vapor-rich inclusions.Stage 2
veins are devoid of interpretable fluid inclusions.Quartz from
Stage 3 (epithermal-style) veins contains twotypes of fluid
inclusions, Type I, liquidvapor inclusionsthat homogenize to the
liquid phase (191.6 to 310.0 C)with salinities of 1.40 to 9.73 wt.
% NaCl equiv., and TypeII, vapor-rich inclusions. Mixing of
magmatic fluids withmeteoric water in the epithermal environment is
responsiblefor the dilution of the ore fluids that formed Stage 3
veins.Eutectic melting temperatures of 35.4 to 24.3 C for TypeI
inclusions hosted in both porphyry- and epithermal-styleveins
suggest the presence of CaCl2, MgCl2, and/or FeCl2 inthe
magmatic-hydrothermal fluids. Sulfur isotope values ofpyrite,
galena, sphalerite, and molybdenite range from34S06.82 to 0.82 per
mil and overlap for porphyry andepithermal sulfides, which suggests
a common sulfur sourcefor the two styles of mineralization. The
source of sulfur inthe system was likely the Fakos quartz monzonite
for whichthe isotopically light sulfur isotope values are the
result ofchanges in oxidation state during sulfide deposition
(i.e.,boiling) and/or disproportionation of sulfur-rich
magmaticvolatiles upon cooling. It is less likely that sulfur in
thesulfides was derived from the reduction of seawater sulfateor
leaching of sulfides from sedimentary rocks given theabsence of
primary sulfides in sedimentary rocks in thevicinity of the
deposit. Late-stage barite (34S010.5 permil) is inferred to have
formed during mixing of seawaterwith magmatic ore fluids.
Petrological, mineralogical, fluid
Editorial handling: R. Abart
A. P. Fornadel (*) : P. G. SpryDepartment of Geological and
Atmospheric Sciences,253 Science I, Iowa State University,Ames, IA
50011-3212, USAe-mail: [email protected]
P. C. VoudourisDepartment of Mineralogy-Petrology, University of
Athens,Athens 15784, Greece
V. MelfosDepartment of Mineralogy, Petrology and Economic
Geology,Aristotle University of Thessaloniki,Thessaloniki 54124,
Greece
Miner Petrol (2012) 105:85111DOI 10.1007/s00710-012-0196-8
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inclusion, and sulfur isotope data indicate that the
metallicmineralization at Fakos Peninsula represents an early
por-phyry system that is transitional to a later high- to
intermediate-sulfidation epithermal gold system. This style of
mineralizationis similar to porphyry-epithermal metallic
mineralizationfound elsewhere in northeastern Greece (e.g.,
PagoniRachi, St. Demetrios, St. Barbara, Perama Hill,
Mavrokoryfi,and Pefka).
Introduction
Porphyry- and epithermal-style metallic ore deposits arefound
worldwide and are related to the generation of hy-drous
calc-alkaline and alkaline magmas in convergent tec-tonic regimes
(e.g., Seedorff et al. 2005; Simmons et al.2005). Despite being
geologically distinct, these two typesof ore deposit share a common
elemental metal assemblagethat includes Au, Cu, and S, and they
constitute majorglobal resources of both precious and base metals.
Thetwo styles of deposit are commonly spatially and
temporallyrelated to one another (Arribas 1995; Heinrich et al.
2004).However, epithermal style mineralization invariably
transi-tions to porphyry style mineralization at depth
(Sillitoe1994; Heinrich 2005).
In areas where these two deposit types are spatiallyrelated,
Heinrich (2005) suggested that the epithermal-stylemineralization
formed contemporaneously with porphyry-style mineralization, within
the error of age-dating techni-ques (e.g., Far South East -
Lepanto, Arribas 1995), or that itmay post-date porphyry
mineralization by >1 Ma (e.g.,Colquijirca district, Bendezu et
al. 2003).
Post-orogenic extension and subsequent magmatism innortheastern
Greece and the northern Aegean Sea havegiven rise to a broad
variety of styles of hydrothermalmineralization, which include
Pb-Zn-Ag veins, metamor-phic base metal replacement,
sediment-hosted gold, low-to high-sulfidation epithermal gold,
intrusion-related gold,and porphyry CuMoAu deposits (e.g., Melfos
et al.2002; Marchev et al. 2005; Voudouris 2006; Fornadel etal.
2011). Also documented in the region are deposits, someof economic
importance, which contain both epithermal-and porphyry-style
mineralization (e.g., Kassiteres-Sappesarea with ~1.5 million tons
of Au at grades of up to 18.4 g/t;Voudouris 2006).
Porphyry- and epithermal-style mineralization occurs
inassociation with Miocene volcanism in the northern AegeanSea,
particularly on the islands of Limnos and Lesbos(Voudouris and
Skarpelis 1998; Voudouris and Alfieris2005; Voudouris et al. 2007a,
b). Voudouris and Skarpelis(1998) and Voudouris and Alfieris (2005)
reported Cu-Au(Mo)-bearing porphyry-style mineralization on
FakosPeninsula, Limnos Island, that is spatially related to
epithermal-style Au-Te bearing veins. Although grade andtonnage
information is unknown for this prospect, bulk rockmetal contents
were measured in both an exploration effortby Argosy Mining
(http://www.thefreelibrary.com/Argosy+Mining++Precious+Metals+Program+Extended+into+Greece.-a019029624)
and a study by Voudouris andAlfieris (2005). Samples from these two
studies contain upto 13 ppm Au, 11.3 ppm Ag, 780 ppm Cu, 3500 ppm
Pb,256 ppm Zn, 300 ppm Sb, 26 ppm Bi, 4630 ppm As,83 ppm Mo, and 18
ppm Se. The Argosy Mining study alsonoted As-Sb-Au soil and rock
anomalies, as well as Auanomalies in the sediments of intermittent
streams that drainthe peninsula.
Voudouris and Alfieris (2005) suggested that the
metallicmineralization on Fakos Peninsula, herein called the
Fakosprospect, may define the southern-most extent of theOligocene
to Miocene Serbomacedonian-Rhodope metallo-genic belt, which hosts
porphyry- and epithermal-style min-eralization, and is part of the
Alpine-Balkan-Carpathian-Dinaride metallogenetic and geodynamic
province (Heinrichand Neubauer 2002; Marchev et al. 2005).
The purpose of this contribution is to evaluate the geol-ogy,
mineralogy, and geochemistry (petrochemistry, sulfurisotope, and
fluid inclusion studies) of the Fakos prospectby expanding upon the
mineralogical and petrological stud-ies of Voudouris and Skarpelis
(1998), Voudouris andAlfieris (2005) and Pe-Piper et al. (2009).
The source ofsulfur to the mineralizing system and the
physicochemicalconditions of ore formation, and microthermometric
meas-urements of fluid inclusions trapped in quartz veins fromboth
styles of mineralization elucidate changes in the phys-icochemical
conditions during the formation of metallicmineralization as the
environment transitioned from adeeper porphyry regime to a
shallower epithermal setting.
Geologic setting
Regional geologic setting
In Greece and the northern Aegean Sea, the Hellenideorogen is a
discrete terrane of the Alpine-Himalaya defor-mational belt and
represents a geotectonic link between thesouthern Balkan Peninsula
and Turkey. It formed as a resultof the ongoing Alpine collision
between the African andEurasian plates since the Mesozoic and
caused thrusting andnappe-stacking of three continental blocks
(Apulia, Pelagonia,and Rhodope), as well as the intervening oceanic
crust (Pe-Piper and Piper 2002; Pe-Piper et al. 2009) (Fig.
1).Subduction and duplexing of crust in the region occurredalong a
north-dipping subduction front and the last twohigh-pressure
metamorphic events during collision and crustalthickening have been
dated at 51 and 42 Ma (e.g., Krohe and
86 A.P. Fornadel et al.
-
Mposkos 2001; Kilias et al. 2002; Marchev et al. 2005; Brunand
Sokoutis 2007).
Since the late Tertiary, the Alpine subduction front mi-grated
southwards where it forms the modern Hellenic vol-canic arc
(Marchev et al. 2005). The retreat of thesubduction front gave rise
to ongoing, large-scale regionalextension within the nappe stack,
which occurs in and alongductile shear and detachment zones and, in
a brittle manner,along normal faults. The continental crust in
northeasternGreece has dilated ~100 % since the early Miocene and
isone of the most rapidly extending regions in the world
(e.g.,Dinter 1998; Pe-Piper and Piper 2002). The coupled migra-tion
of the subduction front and large-scale regional exten-sion caused
orogenic collapse and crustal thinning, as wellas the exhumation of
deep-crustal metamorphic core com-plexes (Dinter and Royden 1993;
Kilias et al. 2002).
The geology of northeastern Greece and the northernAegean Sea is
characterized by widespread late Mesozoicto mid-Cenozoic igneous
activity within thrusted crustalblocks that was caused by
subduction-related processesassociated with the Alpine orogeny and
has been ongoing
since the Mesozoic (Pe-Piper and Piper 2002). Igneousrocks of
Mesozoic to Paleogene age are present in theRhodope block; however,
similar rocks are notably absentin the Apulia and Pelagonia blocks
(Pe-Piper et al. 2009).Eocene to Oligocene igneous activity
occurred in theRhodope block and in northwestern Turkey and is
dominatedby the intrusion of calc-alkaline, I-type granitoids into
thetectonically-thickened crust and spatially associated
withcalc-alkaline to shoshonitic volcanic rocks (Fig. 1)
(Pe-Piperand Piper 2002; Dilek and Altunkaynak 2007; Pe-Piper et
al.2009).
Early Miocene volcanism in the northeastern Aegean Seaand
western Turkey occurred to the south of the Mesozoic toearly
Cenozoic igneous activity of the Rhodope block andwas coeval with
large-scale regional extension (Dinter 1998;Pe-Piper and Piper
2002; Pe-Piper et al. 2009). The igneousrocks associated with the
Early Miocene have been definedas a belt of shoshonitic volcanic
rocks (Pe-Piper and Piper2002; Pe-Piper et al. 2009) (Fig. 1). They
originated fromlarge stratovolcanoes in the northeastern Aegean
Sea, theremnants of which are present on the Greek islands of
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AFRICAN PLATE
EURASIAN PLATEVardar suture
Pindos suture
Intra-Pontidesuture
I-Asuture
Black Sea
Hellenicsubduction
zonem
odernsubduction fron
t
Rhodope blockPelagonia blockApulia block
Neogeneaccretionary
prism
Aegean Sea
E 03E 02
32 N
36 N
40 N
+ Aegean shoshonite beltand volcanic centers
Surface traces of Mesozoicocean sutures
Cities
Limnos
Lesbos
Samothraki
Istanbul
N2000 km
Alexandroupolis
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+++++++++++++++++++++++++++++++++++
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+++++++++++++++++++
+++++++++++++++++
+++++++++++++++++++++++++++++++++
++++++++++++++++++++
AFRICAN PLATAA E
EURASIAN PLATAA EVardar sutureVV
Pindos suture
Intra-Pontidesuture
I-Asuture
Black Sea
Hellenicsubduction
zonem
odernsubduction fron
t
Rhodope blockPelagonia blockApulia block
Neogeneaccretionary
prism
Aegean Sea
E03E02
32 N
36 N
40 N
+++++++++++++++++++++ Aegean shoshonite beltand volcanic
centers
Surface traces of Mesozoicocean sutures
Cities
Limnossssssssssssssssss
LesbLesbLesbLesbesLesLesbLesbLesbLesbLeLLesLesbesbesbLesbLesbesbLesbLes
ososososososossosososssosososso
Samoooooooooooooooothrahthrathrathrahrathrathrathrathrathrathrathratthrahhrathrarathrarakikkkikkkikkkkikkkkk
Istanbul
N2000 km
Alexandroupolis
+ +++
+
+++
+++
++
++
Fig. 1 Regional geologicalmap of Greece and the AegeanSea
showing the distribution ofshoshonitic volcanic rocks inthe
northern Aegean Sea, suturezones, and the modern andHellenic
subduction fronts.Modified from Pe-Piper andPiper (2002), Pe-Piper
et al.(2009)
Fakos transitional porphyry Cu to epithermal Au-Te
mineralization 87
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Lesbos, Limnos, and Samothraki, and in western Turkey(Pe-Piper
and Piper 2002; Altunkaynak and Dilek 2006;Pe-Piper et al.
2009).
Several possible causes for such widespread volcanic andplutonic
activity have been proposed, however the mostwidely-accepted
include steepened geothermal gradients as-sociated with mantle
upwelling that was caused by thedetachment and/or roll-back of the
subducting slab (e.g.,Fytikas et al. 1984; de Boorder et al. 1998;
Pe-Piper et al.1998; Kilias and Mountrakis 1998; Melfos et al.
2002), andas crustal thickening due to subduction (e.g., Yilmaz
1990).Due to the style of rare earth element (REE) enrichment,Mg-
and Cr-rich clinopyroxene phenocrysts, and an evolvedSm-Nd isotope
signature for the rocks on Limnos Island, Pe-Piper et al. (2009)
suggested that magmas in the regionincorporated upwelling
asthenospheric mantle due to slabdetachment, which, in turn, caused
melting of metabasalticamphibolites that underplated subducted
continental crust.
Geology of Limnos Island
Limnos Island is predominantly comprised of Paleogeneflysch that
was deposited in a NE-SW trending postorogenicbasin that formed as
a result of normal faulting and exten-sion during postorgenic
collapse of the Rhodope-Sakaryaorogen and comprises the sedimentary
basement (Fig. 2).
The sedimentary rocks were slightly folded due to
regionalcompression prior to the onset of large-scale regional
exten-sion and associated igneous activity (Roussos et al.
1993;Innocenti et al. 1994; Tranos 2009; Brun and Sokoutis
2010)
According to Roussos et al. (1993), the sedimentarybasement
rocks can be delineated into two discrete units,the Upper Unit and
the Lower Unit. The late Eocene to earlyOligocene Lower Unit covers
large parts of the island and iscomposed of siliciclastic
continental slope deposits includ-ing conglomerates, sandstones,
mudstones, claystones, andturbidites (Fig. 2). The early Oligocene
Upper Unit is spa-tially more restricted than the Lower Unit and is
interpretedto have been deposited in a shallower environment than
theLower Unit. The Upper Unit is composed of marine andbrackish
fluviodeltaic sedimentary rocks, including inter-bedded claystones
and sandstones, sandstones, and sandylimestones at the bottom of
the section. Towards its top, theUpper Unit is composed of
terrestrial fluvial sediments,including conglomerates and
sandstones.
Roughly half of the sedimentary basement on LimnosIsland is
unconformably overlain by Lower Miocene volca-nic rocks of the
Hellenide orogen, which consist of subvol-canic intrusions, lava
flows, and pyroclastic deposits(Fytikas et al. 1980; Innocenti et
al. 1994; Pe-Piper andPiper 2002; Pe-Piper et al. 2009). The
volcanic centers arelocated in the western and southwestern
portions of Limnos
Th Moudros
Katalakon
Myrina
Fakos Peninsula
L. Aliki
AgiosIoannis
Kaminia
RomanouL. Chortarolimni
TownsNLakes
Katalakon Unit: Fakos quartz monzonite
Paleogene SedimentaryBasement
"Therma Unit": Marls and Pyroclastics
Katalakon Unit: Subvolcanic Intrusions
Romanou Unit: Pyroclastics
Myrina Unit: Lava Domes
Agios IoannisSubunit
Th
40 km
40N
3956' N
3952' N
3948' N
22 14' E E '2222E '0122
Area of Study
Fig. 2 Geological map of Limnos Island modified from Innocenti
et al. (1994) and Pe-Piper et al. (2009)
88 A.P. Fornadel et al.
-
Island, and are delineated by domes and lava flows that
areaccompanied by agglomerates. The sedimentary basement
isincreasingly exposed at the surface in the east and northeastof
the island, distal to the volcanic centers (Fig. 2).
The volcanic rocks are divided into three units
(Katalakon,Romanou, and Myrina) on the basis of lithology, age,
andgeographic location (Innocenti et al. 1994). These rocks
areLower Miocene in age (2118 Ma) and demonstrate a calc-alkaline
to shoshonitic affinity (Fytikas et al. 1980, 1984;Innocenti et al.
1994; Pe-Piper and Piper 2002; Pe-Piper etal. 2009).
The lower-most Katalakon unit consists of NW trendingK-rich
andesitic to dacitic lavas. In places, it is interbeddedwith, or
crosscut by, andesitic lava flows, hydrothermalbreccias cemented by
a monomineralic quartz matrix, sills,and E-W trending dikes
(Innocenti et al. 1994; Pe-Piper andPiper 2002). Andesite and
dacite in the Katalakon unityielded whole rock and groundmass K-Ar
ages rangingfrom 21.30.7 to 20.20.2 Ma (Innocenti et al. 1994).This
unit is overlain by the Romanou unit that is composedlargely of
K-rich dacites and latites. At its base, theRomanou unit is
dominated by light-colored lithic- andpumice-rich pyroclastic flows
that are up to 160 m thick. Tothe west and up section, the
pyroclastic flows of the Romanouunit are intercalated with volcanic
breccias, banakitic lavas,airfall tuffs, and terrigenous sediments.
Ignimbrites and ande-sites from the Romanou unit yielded whole rock
K-Ar ages of20.50.9 Ma and 20.20.8, respectively (Fytikas et al.
1980;Innocenti et al. 1994; Pe-Piper and Piper 2002). The
upper-most volcanic unit, the Myrina unit, overlies the Romanouunit
and is composed of K-rich dacite, with lesser amounts ofandesite
and trachyte, which are associated with hydrothermalbreccias
lithologically similar to those in the Katalakon unit,lava flows,
and lahars. Dacites and andesites of the Myrinaunit yielded
groundmass, sanidine, and biotite K-Ar agesranging from 19.30.3 to
17.90.4 Ma (Fytikas et al. 1980;Innocenti et al. 1994; Pe-Piper and
Piper 2002). Both thevolcanic rocks and the sedimentary basement of
LimnosIsland are intermittently overlain by a Pliocene to
recentalluvial sedimentary unit that is composed of
conglomerates,calc-arenites, and sandstones.
Faults and joints occur in both the igneous and sedimen-tary
rocks, and gentle to open folds occur in the sedimentarybasement
rocks (Roussos et al. 1993; Innocenti et al. 1994;Tranos 2009). The
axes of these folds trend E-W and WSW-ENE and gently plunge (~11)
to the WSW (Tranos 2009).Folding does not affect the Miocene
volcanic rocks.
Faults are pervasive throughout the island (up to 7 km long)and
occur in three dominant orientations, NE-SW, ENE-WSW,and E-W. Minor
populations of faults are oriented NNESSW(N10E to N30E) and NWSE to
NNWSSE (Tranos 2009).These different orientations led Tranos (2009)
to conclude thatfive discrete regional-scale deformational events
were
responsible for the faulting. Faults and associated
deformation-al features crosscut both the sedimentary basement and
theoverlying volcanic rocks.
Geology of the Fakos area
The Fakos prospect occurs in an area topographically de-fined by
two large hills, the western Tourlida Hill and theeastern
Petrospitos Hill, both of which are ~300 m in eleva-tion. Their
prominence is controlled by subvolcanic intru-sions that were
emplaced into the sedimentary host rocks(Fig. 3). The sedimentary
basement on Fakos Peninsula iscomposed largely of medium-grained
quartz-rich sandstonesand claystones that were silicified by
hydrothermal fluids(Fig. 4a). Finely disseminated sulfides are
pervasive in thesesandstones.
The sedimentary basement rocks were intruded and over-lain by
the oldest plutonic rocks and volcanic rocks foundon Limnos Island,
which are comprised of andesitic lavaflows, tuffs, and
trachyandestic subvolcanic intrusions of thesouthern-most exposures
of the Katalakon unit (Fig. 3). Atthe north end of Fakos Peninsula,
there is a small outcrop ofpyroclastic rock of the Romanou unit
(Roussos et al. 1993;Innocenti et al. 1994; Pe-Piper and Piper
2002; Voudouris2006; Pe-Piper et al. 2009). Based on the
classificationscheme of Le Bas et al. (1986), the extrusive rocks
onFakos Peninsula range from shoshonitic andesites (latites),to
trachyandesites, and trachytes (Innocenti et al. 1994;Voudouris
2006; Pe-Piper et al. 2009).
Towards the central part of Fakos Peninsula, the extrusiveand
sedimentary basement rocks were intruded by a subvol-canic
microporphyrytic quartz monzonite (the Fakos quartzmonzonite)
(Voudouris and Alfieris 2005; Voudouris 2006;Pe-Piper et al. 2009)
(Fig. 3). Pe-Piper et al. (2009) suggestedthat the Fakos quartz
monzonite is genetically related to theemplacement of other
subvolcanic intrusions of the Katalakonunit due to its age,
chemistry, and proximity to the Katalakonunit instrusives.
Late-stage, E-W trending, alkaline dikeswarms crosscut the Fakos
quartz monzonite and the adjacentrocks (Roussos et al. 1993;
Voudouris and Skarpelis 1998; Pe-Piper and Piper 2002; Voudouris
2006; Kamvisis 2010)(Fig. 4b).
Much of the southwestern portion of Limnos Island wassubjected
to hydrothermal alteration along fault zones(Papoulis and
Tsolis-Katagas 2008). Four discrete zones ofhydrothermal alteration
have been identified based on claymineralogy: smectite, illite,
halloysite, and kaolinite-dickitezones. However, the smectite and
illite zones are uncommon(Papoulis and Tsolis-Katagas 2008).
The Fakos Peninsula, like the rest of Limnos Island, iscrosscut
by many major NE-SW and ENE-WSW-trendingfaults. These structures
controlled the emplacement of thesubvolcanic bodies and facilitated
the flow of magmatic-
Fakos transitional porphyry Cu to epithermal Au-Te
mineralization 89
-
hydrothermal fluids that were responsible for the
metallicmineralization (Voudouris 2006; Tranos 2009). The
Fakosquartz monzonite and adjacent host rocks were locally
sub-jected to intense hydrothermal alteration (Voudouris
andAlfieris 2005; Voudouris 2006; Papoulis and Tsolis-Katagas2008).
Recent subsidence of Fakos Peninsula is inferred tohave occurred as
a result of extension along en echelon normalfaults.
Samples and analytical methods
Major oxide and trace element (including REE) composi-tions of
31 samples of igneous and sedimentary rock relatedto the metallic
mineralization were obtained from ACMEAnalytical Laboratory,
Vancouver, Canada, (Acme methods4A and 4B) using inductively
coupled plasma (ICP)-emis-sion spectrometry (ES) and ICP-mass
spectrometry (MS),respectively, after the samples were subjected to
lithiummetaborate-tetraborate fusion and dilute nitric acid
digestion.Loss on ignition was obtained by measuring the mass
differ-ence of each sample prior to and subsequent to roasting
at1000C. Total carbon and sulfur were measured be Lecoanalysis.
Base metal (Cu, Pb, and Zn) and precious metalcontents were
ascertained by dissolution of samples in aqua
regia followed by ICP-MS analysis. Standards used byACME
Analytical are accurate to within 2 percent for majorelements and 5
ppm for trace elements. The whole rockgeochemical results of
selected samples are given in Table 1.
Sixty surface samples were collected of igneous andsedimentary
rocks that host metal-bearing quartz veins forpetrographic, fluid
inclusion, stable isotope, and electronmicroprobe studies. Thin and
polished thin sections of hostrocks and metal-bearing veins were
studied with a polariz-ing microscope at Iowa State University, and
a JEOL JSM5600 scanning electron microprobe equipped with back-
Alunitic
Silicic
Sericitic / Argillic
Potassic / Propylitic
TourlidaHill
PetrospitasHill
TourlidaHill
PetrospitasHill
Katalakon Unit: Fakos quartz monzonite
Paleogene SedimentaryBasement
Katalakon Unit: Subvolcanic intrusions
Faults
N
0.50 km
Primitive Roads
B
3949' N
22 10' E
A
Fig. 3 a Geological map of the study area on Fakos Peninsula
showing trends of local faults and, b Approximate extent of the
hydrothermalalteration zones superimposed onto the local
geology
Fig. 4 a Silicified sandstones that form the basement on Fakos
Pen-insula. In places, the bedding is obliterated by intense
hydrothermalalteration. b Dark-colored alkalic dike that crosscuts
the Fakos quartzmonzonite. c and d Quartz stockworks surrounded by
potassicallyaltered host rock associated with porphyry-style
mineralization. eFakos quartz monzonite pervasively altered by
K-feldspar and magne-tite. f Large-scale quartz vein system
trending roughly EW that isspatially associated with
epithermal-style polymetallic mineralization.g and h
Quartz-tourmaline veins associated with sericitic alteration.
iSericitically altered monzonite breccia cemented by tourmaline.
jQuartz-calcite-telluride veinlet associated with Stage 3
epithermalmineralization. k Potassically altered Fakos quartz
monzonite. l Alu-nitic alteration with native sulfur. m Quartz vein
system developedacross Fakos Peninsula with alunitic-silicic
lithocap visible in thebackground. n Vuggy-silica alteration
showing silica deposition intohollows
b
90 A.P. Fornadel et al.
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Fakos transitional porphyry Cu to epithermal Au-Te
mineralization 91
-
Table1
Whole-rockchem
istry
Sam
ple
AF-4
AF-21A
AF-75
AF-76
AF-84
AF-99
AF-101
PP-LM45*
PP-LM48*
PP-LM50*
AF-8
AF-21b
AF-5
AF-14
AF-15
AF-16
AF-17
AF-25
AF-27
AF-34
AF-47
AF-64A
AF-64B
Lithology
qmz
qmz
qmz
qmz
qmz
qmz
qmz
qmz
qmz
qmz
dike
dike
dkqm
zss
ssss
ssss
ssss
ssss
ss
SiO
2(wt.%)
60.58
58.71
69.73
62.31
66.92
65.57
61.83
59.7
60.2
58.4
57.51
59.25
59.48
82.85
88.06
76.42
72.21
84.87
89.24
78.17
74.96
81.82
74.53
TiO
20.74
0.75
0.4
0.7
0.52
0.46
0.64
0.78
0.79
0.84
0.82
0.64
0.56
0.33
0.27
0.27
0.74
0.33