-
ARTICLE
Zongyao Rui Richard J. Goldfarb Yumin QiuTaihe Zhou Renyi Chen
Franco Pirajno Grace Yun
Paleozoicearly Mesozoic gold deposits of theXinjiang Autonomous
Region, northwestern China
Received: 23 February 2000 /Accepted: 10 October 2001 /
Published online: 15 January 2002 Springer-Verlag 2002
Abstract The late Paleozoicearly Mesozoic tectonicevolution of
Xinjiang Autonomous Region, northwest-ern China provided a
favorable geological setting for theformation of lode gold deposits
along the sutures be-tween a number of the major Eastern Asia
cratonic
blocks. These sutures are now represented by the AltayShan, Tian
Shan, and Kunlun Shan ranges, with theformer two separated by the
Junggar basin and the lattertwo by the immense Tarim basin. In
northernmostXinjiang, nal growth of the Altaid orogen,
southwardfrom the Angara craton, is now recorded in the remotemid-
to late Paleozoic Altay Shan. Accreted Early toMiddle Devonian
oceanic rock sequences contain typi-cally small, precious-metal
bearing FeCuZn VMSdeposits (e.g. Ashele). Orogenic gold deposits
are wide-spread along the major Irtysh (e.g. Duyolanasayi,
Saidi,Taerde, Kabenbulake, Akexike, Shaerbulake)
andTuergenHongshanzui (e.g. Hongshanzui) fault systems,as well as
in structurally displaced terrane slivers of thewestern Junggar
(e.g. Hatu) and eastern Junggar areas.Geological and
geochronological constraints indicate agenerally Late Carboniferous
to Early Permian episodeof gold deposition, which was coeval with
the nalstages of Altaid magmatism and large-scale,
right-lateraltranslation along older terrane-bounding faults.
TheTian Shan, an exceptionally gold-rich mountain range tothe west
in the Central Asian republics, is only beginningto be recognized
for its gold potential in Xinjiang. In thiseasternmost part to the
range, northerly- and southerly-directed subduction/accretion of
early to mid-Paleozoicand mid- to late Paleozoic oceanic terranes,
respectively,to the Precambrian Yili block (central Tian Shan)
wasassociated with 400 to 250 Ma arc magmatism andCarboniferous
through Early Permian gold-forminghydrothermal events. The more
signicant resulting de-posits in the terranes of the southern Tian
Shan includethe Sawayaerdun orogenic deposit along the
Kyrgyzstanborder and the epithermal and replacement deposits ofthe
Kanggurtag belt to the east in the Chol Tagh range.Gold deposits of
approximately the same age in the Yiliblock include the Axi hot
springs/epithermal depositnear the Kazakhstan border and a series
of small oro-genic gold deposits south of Urumqi (e.g.
Wangfeng).Gold-rich porphyry copper deposits (e.g. Tuwu)
deneimportant new exploration targets in the northern TianShan of
Xinjiang. The northern foothills of the Kunlun
Mineralium Deposita (2002) 37: 393418DOI
10.1007/s00126-001-0243-6
Z. RuiInstitute of Mineral Deposits,Chinese Academy of
Geological Sciences,26 Baiwanzhuang Road, Beijing 100037, P.R.
China
R.J. Goldfarb (&)US Geological Survey, MS 964, Box
25046,Denver Federal Center, Denver, CO 80225, USAE-mail:
[email protected]
R.J. GoldfarbCentre for Global Metallogeny,Dept. of Geology and
Geophysics,University of Western Australia, Crawley, WA 6009,
Australia
Y. QiuCentre for Global Metallogeny,Dept. of Geology and
Geophysics,University of Western Australia, Crawley, WA 6009,
Australia
T. ZhouGreat Central Mines Limited andCentaur Mining and
Exploration Limited,210 Kings Way, South Melbourne, Victoria 3205,
Australia
R. ChenGeological Survey of China,Ministry of Land and Natural
Resources,Beijing 100812, P.R. China
F. PirajnoGeological Survey of Western Australia,100 Plain
Street, East Perth, Western Australia 6004, Australia
G. YunCentre for Global Metallogeny,Dept. of Geology and
Geophysics,University of Western Australia, Crawley, WA 6009,
Australia
Present address: Y. QiuSino Mining Ltd., 7th Floor, Sea Plaza,3A
Xi Xin St., Xian 710004, P.R. China
Present address: Taihe ZhouSino-QZ Group, P.O. Box 2424,Mt.
Waverley, Victoria, 3149 Australia
-
Shan of southern Xinjiang host scattered, small placergold
deposits. Sources for the gold have not been iden-tied, but are
hypothesized to be orogenic gold veinsbeneath the iceelds to the
south. They are predicted tohave formed in the Tianshuihai terrane
during its earlyMesozoic accretion to the amalgamated
TarimQai-damKunlun cratonic block.
Keywords Altay Shan China Gold Tian Shan Xinjiang
Introduction
In recent years, the Chinese government has beenmaking great
eorts to develop the economy of west-ernmost China, which includes
a general policy to ac-celerate mineral exploration. Much of this
work hasbeen focused in the Xinjiang Autonomous Region,
a1.66-million km2 area that comprises the northwesternpart of China
(Fig. 1). For example, since 1986, the 305
Project jointly supported by the Chinese Ministry ofSciences and
Technology, the former Ministry of Geol-ogy and Mineral Resources
(now the Ministry of Landand Mineral Resources), the Chinese
Academy of Sci-ences, and the Xinjiang Uigar Autonomous Region
hasincluded studies on geotectonics, petrology, mineraldeposits,
isotope geology, geochemistry, and geophysicsof Xinjiang.
Geological observations indicate that XinjiangAutonomous Region
is an extremely promising areafrom a minerals exploration
standpoint, with numer-ous, recently-recognized gold deposits and
prospects(Table 1). The northern mountain ranges in the region,the
Altay Shan and Tian Shan, represent easterncontinuations of
eastwest-trending Paleozoic orogenicbelts, which contain signicant
gold resources within
Fig. 1. Location of the Xinjiang Autonomous Region in
north-western China and surrounding provinces and countries.
Theprovince is dominated by two large basins (the Tarim and
Junggar)that are separated by three high-relief mountain ranges
(AltayShan, Tian Shan, and Kunlun Shan)
394
-
Table1.SummaryofgoldresourcesandgeologyofmajorgolddepositsintheXinjiangAutonomousRegion,northwestern
China.Almostallofthegolddepositswereform
edduring
Carboniferousto
PermianorogeniceventswithintheAltayShanandTianShan.Deposittypesaredominatedbyorogenicgolddeposits,butsignicantepithermalsystem
sarealso
present
Region
Deposit
Type
Reserve
(tAu)
Geologically
inferred
re-
source(tAu)
Grade
(g/tAu)
Hostrock
Associated
major
structure
Depositage
AltayShan
Aketishikan
Orogenic
5.1
10
4Devonianphylliteandslate
TuergenHongshanzui
faultsystem
Carboniferous(?)
Hongshanzui
Orogenic
0.51.7
Neoprot.to
Ordovicianphyllite
TuergenHongshanzui
faultsystem
Carboniferous(?)
Duolanasayi
Orogenic
5.3
30
8.3
Devonianphyllite,graywacke,
andcarbonate
Irtysh
faultsystem
LateCarboniferous
EarlyPermian
Saidu
Orogenic
Devonianphyllite,graywacke,
andsiltstone
Irtysh
faultsystem
LateCarboniferous
EarlyPermian
Ashele
VMS
11
Devonianmacvolcanicrocks
Irtysh
faultsystem
EarlyMidDevonian
Akexike
Orogenic
2>5
7EarlyCarboniferousyschand
mac/interm
ediatevolcanicrocks
Irtysh
faultsystem
Carboniferous
Permian(?)
Shaerbuliak
Orogenic
210
3EarlyCarboniferousyschand
mac/interm
ediatevolcanicrocks
Irtysh
faultsystem
LateCarboniferous
Kelasayi
Orogenic
510
6EarlyCarboniferousyschand
mac/interm
ediatevolcanicrocks
Irtysh
faultsystem
Carboniferous
Permian(?)
Tasite
Orogenic
13
5EarlyCarboniferousysch
andshearedgranite
Aermantaifaultsystem
Carboniferous(?)
Buerkesidai
Orogenic
37
6EarlyCarboniferousyschand
interm
ediateto
macdikes
Aermantaifaultsystem
Carboniferous(?)
Kelatongke
Magmatic
NiCu
0.15
LateCarboniferousnoritein
macultramaccomplex
Irtysh
faultsystem
LateCarboniferous
Western
Junggar
QiqiuI(Hatu
district)
Orogenic
13.5
23
7.5
EarlyCarboniferousbasalt
Dalabutefaultsystem
LateCarboniferous
SaertuohaiI
Orogenic
4.26.9
EarlyCarboniferousysch
Dalabutefaultsystem
LateCarboniferous
Baogutu
Orogenic
47
6.5
Mid-Carboniferoustu,some
oreinhornfelsnearLate
Carboniferousgranodiorite
Dalabutefaultsystem
LateCarboniferous
Akesai
CuAuskarn
13
8EarlyCarboniferouslimestone
Wenquanfault
Carboniferous(?)
Eastern
Junggar
Qingshui
Orogenic
0.3
27.3
EarlyCarboniferoustuand
graywacke
Kelameilifaultsystem
Carboniferous
Permian(?)
Nanmingshui
Orogenic
0.2
6.1
EarlyCarboniferousmac
volcanicsandgraywacke
Kelameilifaultsystem
Carboniferous
Permian(?)
Jinshan
Orogenic
1.4
32.2
EarlyCarboniferousmac
volcanicsandgraywacke
Kelameilifaultsystem
Carboniferous
Permian(?)
Adake
Orogenic
0.4
25
MidDevonianvolcaniclastics
Kelameilifaultsystem
Carboniferous
Permian(?)
Jinshangou
Epithermal
0.7
531.2
EarlyCarboniferousandesite
andrhyolite
EarlyCarboniferous
Danjiadi-Su-
angfengshanEpithermal
1.05.0
EarlyCarboniferousfelsicto
interm
ediatevolcanicand
hypabyssalrocks
EarlyCarboniferous(?)
395
-
the Central Asian republics. In Kazakhstan, the AltayShan host
the 13.4 million ounces (Moz) Au Vas-ilkovskoye deposit and the 8
Moz Au Bakyrchikdeposit, as well as other large Caledonian
(earlyPaleozoic) deposits such as Zholymbet, Stepnyak,Aksu, and
Bestyube. In Uzbekistan and Kyrgyzstan,the Tian Shan contain giant
Variscan (late Paleozoic)orebodies at Muruntau (170 Moz Au),
Kalmakyr,(90 Moz Au), Charmitan (>10 Moz Au), and Kumtor(18 Moz
Au), with the latter only 60 km from theXinjiang border (Fig.
1).
Geological setting of Xinjiang
Xinjiang is situated with the south-central part of the
Eurasianplate, immediately north of the Himalayan collisional zone
andTibetan plateau. The physiography of Xinjiang is dominated
bythree rugged eastwest- to northwest-trending mountain
rangesseparating large intracontinental foreland basins to the
present-dayIndiaAsia convergence. From north to south, these
features in-clude the Altay Shan, Junggar/Turpan basins, Tian Shan,
Tarimbasin, and Kunlun Shan (Fig. 1). Elevations range from 8,611 m
atQogir Peak on the west side of the Tarim basin and the 7,439
mPobedy Peak in the Tian Shan, to 154 m below sea level at
AidingLake in the Turpan basin.
The region consists of several independent Precambrian
conti-nental blocks that underwent a complex history of dispersion
andreconvergence to Eurasia during the Paleozoic. These include
(I)the composited Yili block (or DjezkazganKirzig unit of Sengorand
Natalin 1996, and also KazakhstanNorth Tian Shan massifof Sokolov
1998) now exposed in the central Tian Shan; (II) theTarim block
that forms a long-lived basin underlying much ofsouthern Xinjiang;
and (III) parts of the Qaidam block extendinginto southeastern
Xinjiang beneath the Qaidam basin (Fig. 1).Paleozoic accretionary
complexes and extensional basins dene thesutures between the
various blocks. These include terranes of theextensive Altaid
orogenic system accreted onto the south side ofthe Angara craton
underlying eastern Russia, those added to boththe north and south
sides of the Yili block, and those that collidedin the Paleozoic
and Mesozoic onto the south side of the Tarimblock. Permian
extensional tectonics formed deep basins within theAltaid orogenic
complex, evolving between the present-day Altayand Tian Shan.
Broad-scale deformation has eected much ofXinjiang during the last
250 million years, with northward-directedcollisions reecting
closure of the Paleo-Tethys and Neo-TethysOceans, and the present
collision with India.
Tarim basin
The Tarim basin covers about one-third of the land area
ofXinjiang (Fig. 1) and is Chinas largest inland basin. The basin
isgenerally recognized to overly the Tarim block, one of the
threemajor cratonic blocks of China, as Precambrian basement is
ex-posed along much of its periphery (Zhang et al. 1984;
Coleman1989). The most extensive exposures occur in the
northeasternTarim basin in the Kuruktagh region (Allen et al.
1992). In addi-tion, a massive magnetic anomaly extending for 1,000
km acrossthe middle of the Tarim basin at latitude 40 provides
evidence ofPrecambrian crystalline rocks generally under 615 km of
youngsedimentary cover and a thin Paleozoic sequence. However,
mag-netic basement in the center of the basin, termed the central
Tarimuplift, is estimated at depths of 48 km or less. The
consistent LateProterozoic and early Paleozoic stratigraphy from
both the northand south margins of the Tarim basin has been used as
an argu-ment that the Tarim was a single coherent cratonic block
since theEarly Proterozoic (Li et al. 1996). The Tarim has been
character-T
able1.(Contd.)
Region
Deposit
Type
Reserve
(tAu)
Geologically
inferred
re-
source(tAu)
Grade
(g/tAu)
Hostrock
Associated
major
structure
Depositage
Eastern
TianShan
Xitan
Epithermal
(high
suldation)
6.4
5.010
Permian(?)andesite
Yamansu
fault
Permian
Kanggurtag
Replacement
10
20
7EarlyCarboniferous
volcaniclastics
Yamansu
fault
LatePermian
Dadonggou
?EarlyCarboniferous
volcaniclastics
Yamansu
fault
Permian(?)
Matoutan
Replacement
20?
10
EarlyCarboniferous
volcaniclastics
Yamansu
fault
LatePermian(?)
XifengshanII
Orogenic(?)
EarlyPermiangranitoid
Tuwu
Porphyry
90
0.16
Mid-Carboniferousgranitoid
Kanggurfault
Mid-Carboniferous
Western
TianShan
Wangfeng
Orogenic
3.1
8.09.0
Silurian-EarlyCarboniferous
granitoids
NorthTianShan
faultsystem
EarlyPermian
Dashankou
Orogenic
12
LateSilurianEarly
Devonianne-grained
clastics
Uncertain
Axi
Epithermal
50
70
5.8
EarlyCarboniferousandesite
andbasalt
Carboniferous
Yierm
and
Hotsprings
EarlyCarboniferousandesite
andbasalt
Carboniferous
Sawayaerdun
Orogenic
100
300
3.05.0
LateSilurianslateandphyllite
PermianTriassic(?)
Bulong
Orogenic
44
LateDevoniangraywacke
andsiltstone
Uncertain
396
-
ized by a complex multi-stage basin evolution throughout the
entirePhanerozoic (Li et al. 1996).
The oldest ages on rocks in the Tarim block of 32633046 Mawere
obtained by UPb dating of zircons from gneisses and am-phibolites
in the northeastern Tarim basin. Other nearby igneousand
metamorphic rocks, as well as those elsewhere around thebasin
margin, have dates that span the Early Proterozoic (Li et al.1996;
Matte et al. 1996). Late Proterozoic rifting along the northernand
southern margin of the Tarim block (Gilder et al. 1991; Li et
al.1996) led to passive margin sedimentation through the
Cambrianand Ordovician. The onset of mid-Paleozoic orogenic events
alongboth margins of the Tarim, continuing into the Mesozoic on
thesouth, resulted in deposition of as much as 12 km of
terrestrialsedimentary rocks during initial formation of the Tarim
basin.Rapid Neogene to Quaternary uplift within the Tian Shan
andKunlun Shan has been responsible for the extensive
sedimentationwithin the Tarim foredeep during the last 20 million
years.
Tian Shan
The Tian Shan range (Fig. 2) is located to the north of the
Tarimbasin with several peaks exceeding 5,000 m in elevation.
Theeastern part of this >2,500-km-long mountain belt trends
eastwest in a 300-km-wide zone across the center of Xinjiang; it
con-tinues westward from China for another 1,000 km
throughKyrgyzstan and Uzbekistan. In China, the range is often
dividedinto the southern and northern Tian Shan provinces, which
sur-round a Precambrian nucleus commonly termed the Yili block
orcentral Tian Shan province. The Chinese Tian Shan can be
con-sidered as having formed the south-central part of the
Altaidorogenic zone, an extensive series of Paleozoic
subductionaccre-
tion complexes added to the Eurasia continent between the
Tarimblock and Angara (Siberia) craton (Sengor and Natalin
1996).
The southern Tian Shan province is composed of early Paleo-zoic
passive margin sequences, which are continuous onto thenorthern
margin of the Tarim Precambrian block. These marinesedimentary
rocks and associated metavolcanic rocks suggest anoceanic basin
existed along that margin in Ordovician and Siluriantimes (Carroll
et al. 1995). The presence of mid-Silurian throughEarly
Carboniferous turbidite-dominant sequences indicates thatthere was
a shift to an active continental margin during the mid-Paleozoic.
Associated mid-Paleozoic volcanic rocks are referred toas part of
the AqishanYamansu arc. It is possible that, during
theDevonianCarboniferous, an ocean basin was being
subductednorthward ahead of the Tarim block and beneath the central
TianShan (Shi et al. 1994; Carroll et al. 1995). Alternatively, a
south-ward-dipping subduction zone may have developed beneath
thenorthern margin of the Tarim micro-continent (Graham 1995). It
is
Fig. 2. Generalized geologic map of the Tian Shan region
incentral Xinjiang after Allen et al. (1992, 1993), Shi et al.
(1994), andCarroll et al. (1995). Two Paleozoic sequences of
allochthonousterranes (northern and southern Tian Shan provinces)
wereamalgamated, partly around the Precambrian Yili block, duringa
complex series of Devonian to Early Permian arc/terranecollisions.
Resulting orogenic (e.g. Wangfeng, Dadonggou, Yuan-baoshan,
Sawayaerdun, Xifengshan, Dashankou, Bulong), replace-ment
(Kanggurtag, Matoutan) and epithermal (e.g. Xitan, Axi)lode gold
deposits are recognized throughout the length of the300-km-wide
orogen that cuts Xinjiang, and signicant potentialexists for the
discovery of additional gold resources in this orogen.The
TuwuYundong deposit is a recently discovered gold-richcopper
porphyry deposit
397
-
clear that, however, no matter what the polarity of the
subduction,the Tarim and Yili blocks were amalgamated in the Late
Devo-nianEarly Carboniferous. Relatively younger dates on
deforma-tion along the western side of the suture may indicate an
oblique,diachronous collision that continued until the end of the
Paleozoic(Chen et al. 1999).
The 500-m-wide QinbulakQawabulak fault of Allen et al.(1992;
also referred to as the Nikolaev line, Central Kazakhstanfault or
the NuratauAtbashi megashear zone in the Central Asianrepublics to
the west) is the site of the Late DevonianEarly Car-boniferous
suture between the Tarim block-southern Tian Shanprovince and the
Yili block (Gao et al. 1998; Fig. 2). It can betraced as far to the
west as the Aral Sea (Allen et al. 1995) and isoften part of an
8-km-wide HPLT assemblage of thrust sheets(Gao et al. 1999). The
giant gold deposits of Central Asia, imme-diately west of Xinjiang,
are all within about 100 km of the suture,and except for Kumtor,
lie within the southern Tian Shan province.The Yili block is
perhaps the easternmost part of the so-calledKazakhstanKyrgyzstan
assemblage, a series of small Precambrianfragments that may have
joined together in the early Paleozoic(Zonenshain et al. 1990).
Alternatively, Shi et al. (1994) claim thatthe Yili block is a
fragment of the Tarim craton that rifted away inthe Early Cambrian
and then re-collided with the craton later in thePaleozoic. The
block pinches out at about longitude 89 and thesuture to the east
of this point is directly between the northern andsouthern Tian
Shan provinces. (We refer to the area in centralXinjiang east of
this longitude as the eastern Tian Shan and that tothe west as the
western Tian Shan within later sections of thispaper.) Migmatitic
basement in one area within the Xinjiang partof the Yili block has
been dated at 14001300 Ma (Allen et al.1992). Ultramac rocks,
interpreted by some workers as ophiolites,follow the suture and may
have been emplaced during obductionassociated with Yili-Tarim block
collision. CarboniferousEarlyPermian carbonate platform facies
cover rocks exposed along thesuture suggest a late Paleozoic
extensional basin formed subsequentto collision (Carroll et al.
1995; Sokolov 1998).
The North Tian Shan fault represents a Late CarboniferousEarly
Permian suture, where rocks of what are now the northernTian Shan
province were subducted below and accreted onto theYili block
(Allen et al. 1993; Gao et al. 1998). The accreted rocks tothe
north of the fault are mainly Devonian to
mid-Carboniferouscalc-alkaline volcanic rocks and ysch (the
Bogda/Turpan terraneof Coleman 1989 or the Kanggur and Bogda arcs
of Pirajno et al.1997), which were separated from the Yili
microcontinent by theNorth Tian Shan sea (Carroll et al. 1995). To
the east, where theYili block is pinched out, south of the Turpan
basin, the NorthTian Shan (or Kanggur) fault separates the northern
and southernTian Shan provinces. As in the southern Tian Shan
province, ul-tramac rocks along the north side of this suture zone
are hy-pothesized to represent obducted oceanic crust.
Simultaneously,and to the north of the accreting arcs, the
Turkestan (or Junggar)Ocean closed between these arcs that had been
added to the Yiliblock and the more northerly terranes of the
Altaid assemblagethat had been simultaneously accreting to the
Angara craton(Carroll et al. 1990).
Variscan calc-alkaline granite and granodiorite bodies, spreadin
age between 400250 Ma, now outcrop over much of the Yiliblock
(Hopson et al. 1989; Allen et al. 1992). They reect a hugeand still
poorly understood magmatic arc derived from orogenicevents on both
sides of the Yili block. Within the central TianShan along the
southern margin of Kazakhstan, on the north sideof Issyk-Kul Lake
and about 150 km north of the Xinjiangborder, the 100 km2
Talgarskii complex was intruded at 365349 Ma. This complex consists
of riebeckite and hastingsitegranites, and alkaline leucogranites
(Kogarko et al. 1994). If theabsolute dates are correct, they
indicate a region of local exten-sion during the Late DevonianEarly
Carboniferous collisionalevent. Subsequent to the amalgamation of
the Tian Shan belt,Late Permian through Early Triassic extension in
both fore-arcregions (perhaps really a back-arc extension beneath
the Tarimduring the latter southerly subduction) appear to be
marked byalkaline magmatism within both the southern and northern
Tian
Shan. Many of these are a part of Colemans (1989) A-typegranites
of central Asia, a group that obviously also erroneouslylumps in
much of the subduction-related magmatism. Coleman(1989) argues that
isotopic data from these alkaline rocks indicateno Precambrian
basement and magma generation from under-plated oceanic crust.
Altay Shan
The Altay Shan form the remote northern border of
Xinjiang,separating China from Kazakhstan on the northwest, Russia
onthe north, and Mongolia along the northeast (Fig. 3).
Highestelevations include 4,374 m Youyifeng Mt., forming a
boundarypoint between ChinaRussiaMongolia, and 4,362 m
Menghehai-han Mt., which is located about 100 km east of Qinghe in
adjacentMongolia. These mountains in China consist of mainly
latestProterozoic through Carboniferous turbidites with lesser
cherts,basalts, and gabbros. Many of these latter igneous rocks
occur aspieces of dismembered ophiolites emplaced within
mid-Paleozoicmetasedimentary rocks, commonly in association with
blueschistfacies metamorphism. The sedimentary-rock dominant
sequencesrepresent a massive series of Altaid accretionary
complexes (orterranes in some terminology) added to the Angara
cratonthroughout the Paleozoic (Sengor et al. 1993). The ages of
thesedimentary rocks generally get younger to the southwest,
reect-ing the outward growth of the so-called Altay/Sayan
orogen,although Carboniferous and Permian strike-slip events
havetranslated some sequences of older rocks outboard of
morerecently accreted sequences (Sengor et al. 1993). The major
Irtyshshear zone (Fig. 3) separates, what have been termed, the
northernGorny Altay unit from the southern Kalba Narym sector of
theSurgut unit (Sengor et al. 1993; Allen et al. 1995). The
southernmargin of the Surgut unit, dened by the Gornostaev (or
Aer-mantai) shear zone, is mainly unexposed because it is overlain
byPermian and younger rocks of the Junggar basin. These unitsare
possibly similar to the superterrane terminology commonlyused in
Cordilleran tectonics; that is, large allochthonous blockswith some
amalgamation of dierent lithostratigraphic units priorto
accretion.
As with the Tian Shan, Variscan magmatism is also
widespreadthroughout the Altay Shan. In northern China, such arc
magma-tism is found throughout the Altay Shan, but seems most
volu-minous along the China/Mongolia border within the
olderPaleozoic terranes. Most of the calc-alkaline magmatism is
prob-ably the result of Early Carboniferous oblique subduction.
LateCarboniferous to Early Permian post-orogenic right lateral
dis-placement along many terrane sutures, such as the Irtysh
andGornostaev faults, followed by a latest Paleozoic reversal of
shearsense, have complicated recognition of the original
continentalmargin (Sengor et al. 1993). Magmatism mainly changed to
morealkaline in composition during these transtensional events.
Vari-scan alkaline magmatism north of the Irtysh fault is known for
itsassociation with some of the worlds largest pegmatite-type
raremetal (Li, Be, Nb, Ta, Y, Rb, Cs, Zr, and Hf) deposits, some
ofwhich contain gem-grade beryl, within the 450-km-long
TalitskyMongolian Altai belt (Kremenetsky 1996). The magmatic
orescontinue along a northwest trend across adjacent
easternKazakhstan, where they dene the KalbaNarym metallogeniczone
(Malchenko and Ermolov 1996). Regional metamorphicgrade is reported
to show a transition from greenschist in thesoutheastern Altay to
amphibolite and higher grade facies in the
Fig. 3. Generalized geologic map of the Altay Shan region
innorthernmost Xinjiang showing the location of the most
importantlode and placer gold deposits. Northwest-trending regional
faultsystems, mainly separating a complex system of latest
Proterozoicto Carboniferous marine sedimentary and volcanic
rock-dominatedaccreted terranes of the Altaid orogen, provide a
rst-order controlon localization of the lode deposits. Generalized
after Chen et al.(1985)
c
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399
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northwest (Yang et al. 1992), although some of this could reect
abroader contact metamorphism associated with the abundance
ofmagmatism in the northwest. These metamorphosed rocks areoverlain
by unmetamorphosed Permian strata and give whole rockradiogenic
dates of 308267 Ma (Yang et al. 1992), indicative of acessation of
tectonothermal events by late Early Permian.
Permian basins
A series of large basins, the Alakol, Junggar, and Turpan
basins,extend across northern Xinjiang (and western Kazakhstan)
be-tween the Tian Shan and Altay Shan (Fig. 1). The commonly
oil-bearing Permian to Cenozoic basinal strata are as thick as 15
kmalong the southern margin of the Junggar basin (Clayton et
al.1997). The basement to these basins is still debatable (Gao et
al.1998), but many workers now indicate that it likely consists
ofPaleozoic accretionary complexes and magmatic arcs similar
tothose of the southern Altay Shan and northern Tian Shan (Allenet
al. 1995; Allen and Vincent 1997). The basins are widely viewedas
Late Permian to perhaps Early Triassic extensional features(Allen
et al. 1995), although it has also been argued that they didnot
form until the Jurassic (Hendrix et al. 1992). A Late Permianorigin
would temporally overlap with regional sinistral shear mo-tion of
the Eastern European craton relative to the Angara craton,and the
onset of a brief Late Paleozoic episode of alkalic magma-tism
throughout the northern part of central Asia. The Permianand
younger cover rocks overlie the zone marking Late Carbonif-erous
closure of the Turkestan Ocean and the suturing between thetwo
subduction zones of opposite polarity.
Southern Xinjiang
The geologic history along the southern side of the Tarim block
isfairly well understood to the west, but Cenozoic strike-slip
eventsand presence of the Qaidam block and associated
accretionaryprisms make for a very dicult understanding of the
regional ge-ology of southeasternmost Xinjiang. The southern
boundary of theTarim block is recognized by the Kudi suture in the
southwest,which is also referred to as the Kunlun or Tamkaral fault
(Fig. 4).The fault zone separates the 2261 Ma metamorphic rocks of
theTarim block from the 1760 Ma metamorphic rocks of the
Kunlunterrane. It formed during the Silurian as the Tarim block was
un-derthrust beneath the Kunlun terrane. Syn- to
post-collisionalCaledonian calc-alkaline magmatism occurred along
both sides ofthe fault and is dated between about 460 and 380 Ma
(Dewey et al.1988; Matte et al. 1996). Cenozoic strike-slip along
the major andreactivated crustal-scale Altyn TaghKarakash fault
system hasdisplaced part of the Archean and Proterozoic Kunlun
terrane andadjoining rocks of the southern Tarim block, along with
the Cal-edonian arc, hundreds of kilometers to the east to form the
EastKunlun Shan of southeastern Xinjiang (Zhou and Graham 1996).The
Qaidam basin along the northern side of the East KunlunShan, often
termed the Qaidam block, is most probably a piece ofthe Tarim block
that was oset by the Cenozoic IndiaAsia colli-sion.
To the south of the Tarim basin, Paleo-Tethyan oceanic crustwas
thrust northwards underneath the amalgamated TarimQai-dam block and
Kunlun terrane. This led to the successive accretionof the
Tianshuihai and Qiangtang terranes (or northern Tibetblock) in the
Late TriassicEarly Jurassic, Lhasa terrane in the LateJurassic, the
KohistanDras arc in the Late Cretaceous, and Indiaby the early
Tertiary. Only the former of these Tethysides accre-tionary
complexes (see Sengor and Natalin 1996) lies withinXinjiang. The
greenschist facies Permo-Triassic ysch of theTianshuihai terrane
was subducted below and accreted to thesouthern margin of the
Kunlun block along the Altyn Tagh faultzone (Matte et al. 1996), a
structure marking the northernboundary of the Tibetan plateau (Fig.
4). The crustal-scale suturenow is located along some of the high
peaks of the Kunlun Rangethat rise above the Tibetan plateau and,
in the Cenozoic, has been
reactivated as a major sinistral strike-slip system. Anatectic
granitesare scattered along both sides of the suture and their
absolute datesrange between 210 and 180 Ma (Matte et al. 1996). By
about180 Ma, unmetamorphosed Carboniferous to Permian Tethyanrocks
of the Qiangtang terrane, the southernmost rocks exposed
inXinjiang, collided with the southern margin of the
Tianshuihaiterrane along what is now the GozhaLongmu Co fault
zone(Matte et al. 1996).
In the southeastern corner of the Xinjiang province, a few
ad-ditional signicant tectonic units surround the oset East
KunlunShan/Qaidam basin (Fig. 4). The Altyn Tagh Shan are located
onthe north side of the Qaidam block and along the
southeasterncorner of the Tarim basin. Paleozoic ysch and island
arc rocksindicate that the Altyn Tagh Shan were originally part of
the TianShanBei ShanQilian Shan Paleozoic orogenic belt that
cutsacross much of central China (Zhou and Dean 1996). Right
lateraloset along the northeastern extension of the Altyn
TaghKarak-ash fault system has displaced a part of the belt. The
SongpanGanzi terrane, south of the East Kunlun Shan/Qaidam block,
is anearly Mesozoic ysch sequence that denes a large sea
trappedbetween the colliding cratonic blocks of China (Sengor et
al. 1993).It may continue to the west as rocks dened as those of
theTianshuihai terrane and, if so, then if forms the entire
backstop foraccretion of the Qiangtang terrane.
Gold deposits of the Altay Shan
Most gold deposits discovered to date in Xinjiang are inthe
accreted terranes of the Altay Shan, associated witha complex
series of northeasterly-dipping thrust sheets.Both granitoids and
gold deposits in the Altay Shan areultimately associated with
collisional orogenesis alongthe southern side of the Angara craton,
which underliesthe countries to the north. Dong (2000) suggests
that theorogenic gold deposits and prospects of the Altay
Shancluster into eight belts, which are localized by the
mainNW-trending ductile fault zones and lower-order
crossstructures. Our observations favor a more irregularpattern for
the larger deposits (Fig. 3), although thespatial association with
these faults is generally well-supported. The below descriptions
are based upon theexisting literature, extensive eld work in
Xinjiang bythe lead author, and eld visits by two authors (R.G.and
F.P.) to some of the deposits.
Northern Altay Shan
The lesser mineralized northern Altay area consists of abasement
of Precambrian schists and then Late Prote-rozoic to Ordovician
accretionary sequences, locallyoverlain by rift-related,
mid-Paleozoic volcanic and ne-grained clastic basinal rocks. These
rocks make up muchof the high elevations of the Altay Shan. A zone
of high-angle faults that cuts through the area, collectivelyknown
as the Gorny Altay unit (Sengor et al. 1993),trends WNW and
includes the TuergenHongshanzuifault zone (Fig. 3). Extensive
uplift has exposed base-ment rocks and roots of the Late Devonian
to PermianHalongQinghe (or QingheAltay) magmatic arc. Thearc is
poorly understood, with a wide range of Paleozoic
400
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absolute dates (Wang et al. 1993), but the dominantcalc-alkaline
granitoids typically appear to young fromthe northwest to the
southeast, although many areprobably Early Carboniferous in
age.
Lode ores in the northern Altay have historicallybeen mined in
neighboring Kazakhstan, including the8 Moz Bakyrchik orogenic gold
deposit hosted by mid-Carboniferous metasedimentary rocks (Sokolov
1998).Most of the northernmost Altay gold resources in ad-jacent
Xinjiang are in placer accumulations of theNuoerte region (e.g.
Ayousai, Hongdun, Laojinggou,Xinjinggou, and Akelsala), occurring
within the steepand remote parts of the mountain range. These
placersoccur along many of the streams draining the south sideof
the HalongQinghe arc, which eventually ow intothe large Irtysh
River. Their presence suggests signicantlode gold potential within
the large, mainly Early Car-boniferous, calc-alkaline intrusive
complex. Recently,also a few orogenic gold deposits have been
discoveredhosted in metasedimentary rocks of the northern AltayShan
region, although no large lodes have yet been
found that are clearly spatially associated with
thegranitoids.
The most signicant of the northern Altay orogenicgold deposits
are those of a remote and relatively un-studied gold belt, which
stretches for 200 km along apart of the 500-km-long, NW-trending
and near-verticalTuergenHongshanzui fault. The fault generally
sepa-rates what have been mapped as Early Devonian sedi-mentary and
volcanic basinal rocks to the north fromProterozoic and early
Paleozoic accretionary complexesto the south. It is implied by
OHara et al. (1997) thatsome of the vein host rocks are
metamorphosed toamphibolite and higher grades. The fact that the
olderrocks are located outward (relative to the Angaracraton) of
the younger units reects the complex latePaleozoic strike-slip
events along older suture zones inthe Altay belt, as described by
Sengor et al. (1993).
Typically, 3- to 10-km-wide mineralized zones arelocalized where
NNW- or NE-trending faults intersectthe more regional
TuergenHongshanzui system. Manyof these are the probable sources
for above describedplacer deposits. Among the larger deposits, the
Aketi-shikan deposit (10 t Au resource) is hosted in the
basinalstrata, whereas the Hongshanzui deposit is hosted byolder
greenschist facies metasedimentary rocks of theNeoproterozoic to
Ordovician Habahe Formation. Goldat the Aketishikan deposit occurs
as inclusions withinpyrite and arsenopyrite grains within suldized
sedi-mentary and volcanic rocks. At the Hongshanzuideposit, which
lacks a reported gold resource, mineral-ization occurs along a
NW-tending, ductilebrittle shear.
Fig. 4. Geological and tectonic features of the Kunlun
Shan,southern Xinjiang (modied after Yin et al. 1998). The region
isdened by the northernmost terranes accreted to the Tarim cratonin
early Mesozoic, prior to Cenozoic IndiaAsia collision andresulting
continent-scale strike-slip motion. Poorly documented,but
widespread orogenic gold deposits and resulting placers occuralong
much of the length of the northern Tibet block, havingformed as
terranes of this block were deformed against the TarimblockQaidam
blockKunlun terrane Triassic continental marginbackstop
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The gold, commonly located within sulde grains, oc-curs in
quartz veins and breccias, in stockwork net-works, and is
disseminated in wall rock. In the vicinity ofthe Laojinggou
placers, poorly-documented quartzveins, stockworks, and breccias
are reported to occur inzones as long as 3 km and as wide as 1 km
that cutgranitoids of the HalongQinghe arc (Tan et al. 1994;Liu et
al. 1996). There are no reliable age data for any ofthe gold
occurrences, which probably formed sometimeduring Paleozoic
deformation, perhaps around the timeof the Early Carboniferous
calc-alkaline magmatism orduring slightly later strike-slip. The
fact that the ores arenot found in the unmetamorphosed Late Permian
rockssuggests veining is older than about 260 Ma.
The possibility that some of the gold deposits in thenorthern
Altay Shan are older, perhaps early to mid-Paleozoic in age, also
can not be discounted. Theabundance of gold occurrences continues
to the north-east across the border into the Mongolian Altai.
TheseAuSbW prospects are concentrated within a few tensof
kilometers of the China border and show a strongspatial association
with Caledonian granite and gran-odiorite (Kempe and Belyatsky
2000). Hence, orogenicgold deposits in the Altay Shan may range in
age overmuch of the Paleozoic, with such ages progressivelyyounging
to the southwest and, thus, correlative withoutward growth of the
orogen.
Southern Altay Shan
The NW-striking, NE-dipping Irtysh fault zone (Fig. 3)separates
the Gorny Altay and Surgut units, both Pa-leozoic accretionary
wedges, within the lower elevationsof the southern Altay region.
Much of the fault zone ismarked by the northwesterly-owing Irtysh
River andan extensive belt of ultramac bodies. In places,
my-lonitic zones reach 3 km in width (Sengor et al. 1993).Ductile
deformation along the fault zone ceased by ca.270 Ma (Travin et al.
1998). Orogenic gold, gold-bear-ing magmatic NiCu deposits and
gold-rich volcano-genic massive sulde (VMS) type deposits occur in
thearea, with the former being the most widespread.
The orogenic lode gold deposits are mainly distrib-uted along
the length of the Irtysh fault zone (Fig. 3),likely indicating an
important rst-order control forhydrothermal uid migration. Most of
the importantdeposits occur on second-order faults within about 510
km of the main fault strand. Those deposits to thenorthwest along
the structure, including Duolanasayi,Saidu, Taerde, and
Kabenbulake, cut felsic to interme-diate granitoids, ysch, and
volcaniclastic rocks. Thelargest of these, Duolanasayi (Fig. 5), is
actually madeup of a number of mineralized bodies that occur along
a20-km-long by 10-km-wide zone between the Maerkak-uli and Habahe
second-order faults near the Kazakhstanborder. The lodes cut Middle
Devonian graywacke,phyllite, and carbonate near hornfels associated
with aseries of ca. 290 Ma tonalites (Li et al. 1998). In
places,
granodiorite and plagiogranite dikes, some of which cutand are,
thus, younger than the tonalite, occur as thefootwall or hanging
wall to orebodies. Both the veinsand older parallel dikes are
localized along the lime-stone/clastic rock contacts (Fig. 5). The
gold occursboth in quartz veins and disseminated within
adjacentigneous and metasedimentary country rocks. In additionto a
typical orogenic gold quartzpyritesericitecarbonatechlorite
alteration assemblage, skarn-likecalc-silicate phases occasionally
occur where lodes cutlimestones. Li et al. (1998) report a series
of RbSr dateson uid inclusion waters from quartz veins at
theDuonalasayi and Saidu deposits of between 269 and305 Ma.
Although the meaning of such data may bequestionable, it does hint
at a late Paleozoic ore-formingepisode in the southern Altaids that
is coeval with re-gional right-lateral shearing events. This is
further sup-ported by three KAr dates of ca. 317295 Ma from
theSaidu deposit (Cheng and Rui 1997).
In the same area, along the Irtysh fault zone and onlya few tens
of kilometers from the Kazakhstan border, anumber of small VMS
deposits are hosted in the Early toMiddle Devonian Ashele Formation
(Wang et al. 1998;Wang 1999) of the Gorny Altay unit. The
FeCuZn-bearing suldes occur as laminations, massive bodies,and
stockwork systems between the bimodal, submarinefootwall spilitic
rocks and hanging wall quartzkerato-phyric tu. The approximately 1
million tonne resourceat the Ashele deposit (Fig. 3) grades about
2% com-bined Cu + Zn, along with signicant precious metalgrades of
55 g/t Ag and 1 g/t Au. Locally, higher pre-cious metal grades
correlate with areas of black ore,composed of massive
galenasphaleritechalcopyritebarite (Wang 1999). As with many of the
orogenic golddeposits in the Altay Shan, published absolute dates
formineralization are quite variable, ranging from about373 to 255
Ma (Li et al. 1998). A cluster of SmNd andRbSr dates on volcanic
rocks and massive sulde orescluster near 360 Ma and are interpreted
as the mostprobable age for seaoor hydrothermal activity. This
isrelatively close in time to the widely accepted Early toMiddle
Devonian lithostratigraphy reported for theAshele Formation.
Although the present gold resource at the Asheledeposit is only
about 30,000 oz, the Devonian rocksnorth of the Irtysh fault
present a favorable target forfuture discovery of large
gold-bearing VMS deposits.The belt of precious metal-bearing FeCuZn
depositscontinues to the northwest into adjacent Kazakhstan,where
it includes the Nikolaevskoe, Belousovskoe,Chekmar, and
Snegirikhinskoe deposits (Malchenkoand Ermolov 1996). Deposits of
FeCuAu also con-tinue to the southeast for more than 300 km from
theAshele deposit, where the Qiaoxiahala deposit occurswithin an
ophiolite sequence along the northern side ofthe Irtysh fault zone.
Gold enrichments are recognizedin chalcopyrite and bornite within
massive magnetitebeds within the Middle Devonian Beitashan
Formation(Wang et al. 1999). The presence, however, of a
402
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dominantly oxidized hypogene iron phase in a Phan-erozoic age
deposit and adjacent skarn mineralogysuggest that the Qiaoxiahala
deposit might rather be amagmatic gold system, rather than a part
of the belt ofVMS occurrences.
Along the southern side of the southeastern part ofthe Irtysh
fault zone, the Akexike, Shaerbulake, andKelasayi orogenic gold
deposits occur within EarlyCarboniferous ysch and mac to
intermediate volcanicrocks of the Surgut unit. Mineralization
styles are sim-ilar to those farther northwest along the structure,
andinclude veins, breccias, and disseminated ores. At Sha-erbulake,
the orebodies are hosted by the ysch, whereasat the Akexike deposit
they mainly occur along basalt/tu contacts. In both cases, ductile
shearing within an-ticlinal structures is suggestive of saddle reef
zones,which are well-known common hosts for orogenic golddeposits
in areas such as the Victorian goldelds ofsoutheastern Australia
and the Meguma terrane ofeastern Canada. There are no large
granitoids in thispart of the Surgut unit, although dikes of
various com-positions are widespread. A 292.17.3 Ma RbSr date
on a felsic dike at the Shaerbulake deposit overlaps aPbPb date
from there on arsenopyrite of304.17.4 Ma, which is assumed to be
the age of golddeposition (Li et al. 1998).
A few orogenic gold deposits in the Surgut unit occur50100 km
west of Wulonggu Lake to the north of alarge fault zone (Manrak
fault of Allen et al. 1995),which might be a part of the westerly
continuation of thecomplex Aermantai fault system (Fig. 3). Known
as theSawuer district, the deposits are associated with a smallarea
of Devonian and Carboniferous ysch, surroundedby extensive areas of
Permian and younger strata. Mostof the deposits are described as
occurring within theEarly Carboniferous Heishantou Formation. The
oresshow a spatial association to many of the small
Variscangranitoids that are described as both calc-alkaline
andalkaline, and RbSr dates on these rocks range between329 and 314
Ma (He et al. 1994). Quartz veins at theTasite deposit, discovered
more than 50 years ago andrecently having produced about 15,000 oz
Au, arehosted in brittle fault zones near the margins of asheared,
K-feldspar-rich granite. In contrast, at the
Fig. 5a, b. Geology of theDuolanasayi orogenic gold de-posit,
southern Altay Shan.a Regional geology surroundingthe Duolanasayi
gold deposit.The deposit occurs in MiddleDevonian clastic rocks,
andalong their contacts with lime-stone units, within a few
hun-dred meters of hornfelsassociated with 290 Ma tona-lites. b
Detailed geology of themain orebodies at the Duol-anasayi deposit
showing asso-ciation of gold ores with clastic-carbonate rocks
contacts
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Buerkesidai deposit, gold-bearing stockworks occurboth in
carbonaceous ysch and intermediate to macporphyritic dikes.
Potential nickelcoppercobalt resources, grading0.74% Ni and 0.3%
Cu and with precious metal en-richments, occur at the Kelatongke
deposit, about100 km west of Qinghe (Fig. 3). Early
Carboniferousmetasedimentary rocks are intruded by a
NW-trendingbelt of Late Carboniferous macultramac complexes(Li et
al. 1998) that parallel the nearby Irtysh fault. Themagmatic Ni-
and Cu-bearing sulde minerals occurdisseminated in
biotitehornblende olivine norite inthe lower parts of the
complexes. Sulde-rich zones alsoaverage 7.6 g/t Ag and 0.15 g/t Au.
These gabbroic-dominant igneous complexes apparently continue
intoadjacent Kazakhstan, where they include the Au-and PGE-enriched
Checkek deposit (Malchenko andErmolov 1996).
Gold deposits of the western Junggar area
The western Junggar area is characterized by mainlyDevonian to
Early Carboniferous metasedimentaryrocks, oceanic basalts, often
emplaced in ophiolitic se-quences, and some melange (Shen et al.
1996). The area(Fig. 6) is exposed above the Permian Junggar
basinto the east and Alakol basin, in adjacent Kazakhstan, tothe
west. Although rock types and ages are similar tothose of the
northern Altaids, lithologies and major faultzones trend NESW
across the western Junggar areaand are almost orthogonal to those
of the Altaids. Thisis likely the consequence of counterclockwise
rotation ofpart of the vast Altaid accretionary complex during
left-lateral, strike-slip events and basin formation in the
LatePermian (Allen et al. 1995). Limited geochronology,discussed
below, suggests that this tectonism roughlycorrelates with the time
of lode gold formation. It also isthe approximate time of change in
northern Xinjiangfrom calc-alkaline to alkaline magmatism. Jin
andZhang (1993), using a variety of dating methods, de-scribed a
group of 322305 Ma I-type granodiorites andone of 281245 Ma S-type
syenites and alkali granitesthat seem to overlap the transitional
period within thewestern Junggar region.
More than 300 gold deposits and occurrences arerecognized in the
western Junggar area (Shen et al.1996), with the most signicant of
these along thenorthern side of the NE-trending Dalabute fault
zone(Fig. 6) and a total resource of at least 2.5 Moz Au.Unknown
amounts of gold have been mined from oro-genic gold vein deposits
since the Ming Dynasty of themiddle 1300s and extensive amounts of
placer miningoccurred during the Ching dynasty in the early 1800s
inthe Hatu district. Many of the historic and present-daylode
deposits are clustered in a 70-km-long by 20-km-wide corridor,
between the Dalabute and more northerlyAnqi and Hatu rst-order
faults, and extending fromthe Hatu (Qiqiu #1 and #2 deposits) to
Saertuohai
districts (Fig. 7). The regional structures are thought tohave
formed in the Early Carboniferous as NW-trendingthrust zones (Allen
and Vincent 1997), parallel to theIrtysh and other major faults,
within the outwardly-growing Altaid accretionary prism (Fig. 3).
The EarlyCarboniferous lower greenschist facies rocks that hostore
in the districts north of the Dalabute fault are part ofthe
Tailegula Formation (Shen et al. 1996; Fan et al.1998), a series of
coeval intercalated metasedimentaryand metavolcanic lithologies
within part of the late Pa-leozoic accreted margin.
Steeply-dipping, gold-bearingveins and adjacent auriferous
alteration halos occuralong subsidiary faults to the two main
faults, and thesestrike both northeast and in a more discordant
NSdirection (Shen et al. 1996).
The more important orebodies of the Hatu district,forming the 1
Moz Au Qiqiu #1 deposit, are locatedalong the northern side of the
Anqi shear zone, within aca. 330 Ma tholeiitic basalt. The complex
osetting ofmany of the orebodies, including 7 km of
post-Permianstrike-slip between the smaller metasedimentary
rock-hosted Qiqiu #2 deposit and the Qiqiu #1 deposit(Fig. 7),
indicates a signicant amount of post-ore de-formation (Shen et al.
1996). The large Akebasitaobatholith, an alkalic complex with
contradictory UPbages of 256 Ma (Jin and Zhang 1993) and RbSr
datesof 298285 Ma (Li et al. 1998), is located about 6 kmsouthwest
of the district. In addition, mac and graniteporphyry dikes are
widespread within the Hatu golddistrict, and it is uncertain as to
whether these are es-sentially coeval with the alkalic complex
and/or are partof the earlier (ca. 320300 Ma) Variscan
calc-alkalineepisode of magmatism. Two such large, older
calc-alkaline bodies, of granodiorite and quartz
dioritecomposition, occur immediately north of the Hatu fault.
We interpret the occurrences in the Hatu district toclearly be
structurally controlled orogenic gold deposits(e.g. Groves et al.
1998), although some workers havedescribed these as
volcanic-related epithermal gold de-posits (e.g. Shen et al. 1996;
Buckman 2001). Individualquartz veins are generally 100 m along
strike and 0.55 m in width, but, locally, are as large as 380 m by
20 m.In the Qiqiu #1 deposit, the large gold resource is hostedin
27 quartz veins and altered metabasalt host rocks,with grades
ranging between 5 and 10 g/t Au, althoughlocal pockets of much
higher grade are common, typi-cally with abundant visible gold.
Gold grains in the veinsin the hanging wall of the Anqi fault are
variable in size,but may occur as particles more than 1 mm in
diameterwithin the quartz. The deposit has been mined from
the1,434-m level down to the 934-m level, with recovery ofabout
10,00015,000 oz/t Au per year and about250,000 oz mined to date.
Gold:silver ratios are typically21:1, and As, Cu, Sb, and W
enrichments are commonfor most ore zones (Fan et al. 1998). Pyrite
and lesserarsenopyrite are the dominant sulde minerals withinand
adjacent to the veins, with carbonate, sericite, andchlorite also
common in altered wall rocks. The lowergrade (45 g/t Au) Qiqiu #2
deposit is not being mined
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Fig.6.Generalizedgeologicmapofthewestern
Junggarareashowingthelocationofthemostimportantlodegolddeposits,whichareconcentratedintheHatuSaertuohaibelt.The
areaandstructureswithinithavelikelybeenrotatedcounterclockwisefrompositionsoriginallywithintheAltayShan.GeneralizedafterChen
etal.(1985)
405
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and the carbonaceous, volcaniclastic metasedimentaryrock-hosted
ores contain a total resource of 150,000 ozAu in the footwall of
the Anqi fault. Rubidiumstron-tium dates on unspecied material from
two quartz veinsin the Hatu district are 290288 Ma, suggesting
thatveining was slightly younger than adjacent
calc-alkalinemagmatism and perhaps simultaneous with the
morealkalic episode.
A few dierences characterize some of the other golddeposits in
the western Junngar area, although it is likelythat all ores are
part of a single, generally coeval hy-drothermal episode. Many of
the gold occurrences in theSaertuohai district (Fig. 7), about 60
km northeast ofthe Hatu district, occur in shears within NE- to
NNE-striking macultramac ophiolitic slivers along thenorth side of
the Dalabute fault. This reects a chemi-cally favorable trap for
veining adjacent to a major rst-order structure and provides for a
gold-forming scenariovery similar to that in the California Mother
Lode dis-
tricts (Bohlke 1989). A talcmagnesitequartz alterationassemblage
characterizes altered wall rocks within theSaertuohai district,
with vein sulde phases dominatedby pyrite chalcopyrite.
In the Baogutu district, to the south of the Dalabutefault and
40 km southwest of Kelamayi (Fig. 5), tua-ceous conglomerate of the
mid-Carboniferous BaogutuGroup hosts gold ores within a few
kilometers of a seriesof small ca. 320300 Ma hypabyssal
granodiorite stocks(Shen et al. 1996). Many veins cut hornfels
zones sur-rounding the stocks, where relatively competent rockswere
preferentially hydrofractured during uid owevents. The veins are
characterized by common pyrite,arsenopyrite, and
stibnite/berthierite. The occasionalpresence of native bismuth and
native antimony is atypi-cal of orogenic type gold deposits,
perhaps being indica-tive of an overprinting low-temperature
post-ore event.The common occurrence of scoradite in many of
themineralized outcrops is consistent with supergene events.
Fig. 7. Detailed geology of theHatuSaertuohai gold belt
inwestern Junggar. Orogenic golddeposits, known since the1300s, are
spatially associatedwith the HatuDalabute faultsystems. Geology
generalizedfrom Shen et al. (1996), Allenand Vincent (1997),
Chen(1997), Fan et al. (1998), andPirajno (unpublished
eldnotes)
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Gold deposits of the eastern Junggar area
The eastern Junggar area (Fig. 8) is underlain by theeasternmost
exposures of the Late Devonian to LateCarboniferous volcanic arc
and volcanogenic deep ma-rine sedimentary rocks that also
characterized much ofthe Altay Shan. Similar age rocks occur on
both sides ofthe WNW-trending, N-dipping, 10- to
20-km-wide,Kelameili fault zone. The zone separates the
so-calledSurgut unit to the north and JunggaroBalkhagh unit tothe
south (Sengor et al. 1993). The fault itself probablyoriginally
represented a thrusted suture between dierentPaleozoic blocks of
the Altaid sequence, brought to-gether during the Late
Carboniferous to Early Permian
closure of the Junggar Ocean (Carroll et al. 1995). Syn-to
post-kinematic, felsic to intermediate granitoids arescattered on
both sides of the fault, and chromite-bear-ing ultramac bodies
occur along the fault zone. Thesebodies generally are poorly
studied, although a variety ofgranitoids are characterized by KAr
and RbSr datesranging between about 360 and 230 Ma (Chen
1997).Sinistral shear movement was dominant along the faultin the
Late Permian, with associated extension leading toformation of the
Junggar and Turpan basins.
Many small lode gold deposits, and a few placer golddeposits,
stretch along mainly the northeastern side ofthe Kelameili fault
for about 400 km (Fig. 8). Most ofthese are small (
-
Whereas none of these deposits have been dated, it isalmost
certain that they are of late Paleozoic age, beingformed at about
the same time as the larger gold de-posits to the northwest in the
Altay Shan.
In the relative shallowly-exposed Early Carbonifer-ous andesite
of the Batamayineishan Formation, about60 km southwest of the fault
zone and along thenorthern side of the Bogda Shan,
approximately150,000 oz Au are recognized at the Jinshangou
deposit.In contrast to the deposits near the fault zone,
Jin-shangou is a typical epithermal gold deposit locatedwithin a
group of ve calderas distributed along theintersection of two
regional fault systems. Commongangue phases include alunite,
kaolinite, barite, anduorite, all typical of epithermal ores, as
well as themore universally common quartz, albite, sericite,
andcalcite.
In the same formation, near the Mongolian borderand 60 km
northeast of the Kelameili fault zone, theDanjiadiSuangfengshan (or
Twin Peaks) goldsilverprospect (Fig. 8) comprises 12 mineralized
bodiesassociated with felsic to intermediate volcanic and
sub-volcanic bodies. They are again hosted by caldera-related
structures, are enriched in mercury and copper,and locally contain
as much as 125 g/t Ag. The deposit,presently being mined, is
associated with Carboniferousandesite and rhyolite near a contact
with Permian basinll and along the margin of the Turpan basin. The
low-suldation deposit is associated with volcanic domefeatures and
it also is characterized by widespreadauriferous breccias (Wang et
al. 2001).
Gold deposits of the Tian Shan
Most gold deposits recognized in the Tian Shan (Fig. 2)occur
within the eastern Tian Shan (e.g. Xitan, Kang-gurtag, Yuanbaoshan,
Dadonggou, and Xifengshan II),located to the south of the Turpan
basin and in an aridbarren range termed the Chol Tagh, and have
beensuggested to continue to the east into the JinwoziMazhuangshan
gold district of adjacent Gansu prov-ince. This eastwest-trending
Kanggurtag gold belt(Fig. 9), with epithermal deposits and
replacement styledeposits, both probably of magmatic anities and
EarlyPermian age, is located south of the North Tian Shanfault
(also called Kanggur or TuokexunGuozigou faultin places) within
rocks of the AqishanYamansu arc.The arc consists of volcanic rocks
of the Early Carbo-niferous Aqishan and Yamansu Formations, and
gray-wackes of the mid-Carboniferous Kushui Formation,which are
separated by the generally poorly-denedYamansu (or Kushui) fault
(existing data are toocontradictory to distinguish these three
units on Fig. 9).The North Tian Shan fault separates this arc from
thoseof the Kanggur arc to the north, and represents a
LateCarboniferous to Early Permian suture (Ji et al. 1994).Ma et
al. (1997) indicate thrusting within the arcsequence, during
subduction from the north of the
Paleo-Tianshan Ocean, until the end of the Carbonifer-ous, which
was followed by a translational regime alongrst-order faults in the
Permian. Alternatively, this maysimply be the consequences of
oblique TarimYili col-lision throughout the late Paleozoic (Chen et
al. 1999).Either way, the deposits in the Kanggurtag gold beltmight
be located along second-order faults representingdilational zones
that were opened between the eastwest-trending, crustal scale North
Tian Shan fault andKuluketag (also called the Middle Tian
Shan,Shaquanzi, or South Kushui) fault. The latter is locatedabout
75 km to the south of the former, and separatesclastic units from
volcanic units within the southernTian Shan province, which
suggests it too is a likelyterrane boundary. To the north of the
North Tian Shanfault, the recently discovered Tuwu and Yandong
por-phyry copper deposits also contain a signicant
goldresource.
Despite signicant gold resources in the Tian Shan tothe west of
Xinjiang, numerous gold systems have notyet been recognized in the
western Tian Shan of Xinjiangitself. The few important deposits
discovered to dateinclude Wangfeng and Axi in the Yili block,
andSawayaerdun in the southern Tian Shan province; noimportant
deposits are recognized in the northern TianShan province. Although
characterized by exceptionalrelief, the arid conditions in
especially the eastern TianShan have hindered formation of major
placer golddeposits. Only a few small placer deposits are located
inhigh altitude streams near Wangfeng (e.g. Hongkeng,Tiangeer, and
Houxia).
Eastern Tian Shan
Epithermal gold deposits
The Xitan (or Shiyingtan) deposit, which denes thewesternmost
part of the Kanggurtag gold belt, is char-acterized by features
common to many epithermal veindeposits. The ore is hosted in what
is probably aPermian andesite, often brecciated, that overlies a
morewidespread Carboniferous andesitic and dacitic volcanicarc
terrane. A co-magmatic granite porphyry lies be-neath the host
andesite and also outcrops 300 m to thesoutheast of the deposit.
Although only 2 km south ofthe Yamansu ductile shear zone, the
volcanic host rocksshow only brittle features and are
unmetamorphosed.The gold veins occur along what is hypothesized as
thenorthwestern margin of a large caldera with a well-de-veloped
ring dike system (Pirajno et al. 1997). They werediscovered in 1989
during a regional geochemical survey.The total resource is about
200,000 oz Au, of whichabout 30,00035,000 oz have been recovered
since 1993from 510 g/t rock and a large amount of the resource
isawaiting processing in a large stockpile of 15 g/t ma-terial.
Silver has also been recovered, but no other dataare available
other than the fact that the ores average 1:1
408
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Ag:Au. Mining was originally by open pit and is
nowunderground.
Eighteen quartz veins have been identied on thesurface and four
of these are being mined (#1, 3, 4, and5). The largest vein (#3)
averages 20 m in width, is 150-m-long and continues for
100-m-down-dip. The gold-bearing veins consist of cryptocrystalline
and chalce-donic quartz, miarolitic uorite, and platy calcite,
arecommonly crustiform, and contain low salinity, aqueousuid
inclusions that mainly homogenize between150200 C (Feng et al.
2000). Metallic phases are veryrare with pyrite being the most
common sulde mineraland comprising much less than 1% of the
gold-bearingveins. It appears more common in the altered
andesitethan within the veins themselves. Trace amounts
ofarsenopyrite, chalcopyrite, copper oxides, and silversulfosalts
and selenides are also recognized in the veins.Alteration around
the veinlets is zoned from an area of
silicachloritepyrophyllite, through an area of pyritesericite,
and to an outer aureole of chloritecarbonate.Gold grades are
highest where local structures intersectand where the Permian(?)
andesite is highly brecciated.In the #3 vein at Xitan, gold grades
progressivelydecrease from 10 g/t near the surface to 6 g/t at
about100 m depth.
Many of the features of the hydrothermal system ledPirajno et
al. (1997) to rst classify it as a high-sulda-tion epithermal
system. Published absolute dates areimprecise, with reported UPb
and RbSr dates on ex-trusive rocks and tonalite at the Xitan
deposit rangingbetween 293 and 234 Ma, and RbSr isochron ages
forbreccias and veinlets spread between 288 and 244 Ma(Li et al.
1998). Measured d18O quartz values rangingbetween 4.7 and -8.5 per
mil (Feng et al. 2000) areconsistent with a predominantly meteoric
water com-ponent to the ore-forming uids.
Fig. 9. Geology and distribu-tion of epithermal and orogenicgold
deposits within the Kang-gurtag gold belt, eastern TianShan. The
Xitan epithermaldeposit, and Kanggurtag,Matoutan, Yuanbaoshan,
andDadonggou replacement(?)deposits are hosted by a com-plexly
mixed group ofCarboniferous marine sedimen-tary and volcanic rocks.
Figuregeneralized from Pirajno et al.(1997)
409
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Granitoid-related(?) FeCuAu replacement deposits
Other important gold deposits in the Kanggurtag goldbelt appear
to be more deeply-formed iron- and copper-rich, perhaps
granitoid-related gold deposits that appearmainly as massive
replacement bodies in the low meta-morphic grade (probably
prehnitepumpellyite) EarlyCarboniferous volcaniclastic rocks of the
YamansuFormation. The best studied of these is the
Kanggurtagdeposit (also called the Kangguer or #6
Kanggurtagdeposit; Fig. 10), located about 60 km east of
Xitan,which has an approximate 300,000 oz Au resource,about half of
which has been mined to date. The depositwas discovered in 1989
during regional mapping andgeochemical studies. Pirajno et al.
(1997) suggest thatreported sulde zoning at the deposit is
consistent with alow suldation epithermal deposit, although much of
themineralization style appears like that of a deeper, man-to-type
deposit. The Matoutan deposit (also called the#8 Kanggurtag deposit
or perhaps the Yaobashan de-posit), located 5 km east of the
Kanggurtag deposit, hassimilar looking FeCuAu-rich ore and the
mining op-eration appears to be more than double that in size
ofKanggurtag. Access to the Matoutan deposit, as well therelease of
any geologic and resource data, has beenlimited by the local
community at the mine site. How-ever, it is likely that the
combined resource of the twodeposits, which are probably part of
one large mineral-izing system, exceeds 1 Moz Au.
The Kanggurtag deposit occurs as a series of occur-rences within
a 10 5-km area both along and south ofthe Yamansu fault. The
mineralized zones are about5 km southeast of a large Variscan
tonalite stock, and anumber of small granite dikes are reported
within 1 kmof many of the ore zones. Most of the ore at the
Kang-gurtag deposit is localized along three, NE- to
E-striking,steeply N-dipping ductile shear zones within this
area.The largest single zone of continuous mineralizationwithin the
volcanic and subvolcanic rocks of the AqishanFormation is about 200
m along strike, averages 2 m inwidth, and continues down-dip for
>400 m. An un-mineralized 15-m-wide brittleductile shear zone
runsalong the length of the footwall of the mineralized zone.
Termed the #2 orebody, the large ore zone exhibits areplacement
style mineralization that contains most ofthe gold resource. The
ore consists of massive pyrite,chalcopyrite, and magnetite, with
lesser sphalerite, ga-lena, silver sulfosalts, and barite. Hypogene
gypsum isalso present. Gold:silver ratios average 1:5, and the
oreis zoned from gold-rich near the top (1,100-m level) tomore
copper-rich at depth (600-m level). Highest goldgrades often
correlate with the volume of magnetite, andaverage gold grades
decrease from about 9 g/t at thenear surface to 56 g/t at depths of
200 m. Locally,metal concentrations reach 5% Pb, 10% Cu, and 10%Zn.
A ve-stage paragenesis stresses three early stages ofgold, pyrite,
and magnetite, followed by barren basemetal and carbonate-rich
hydrothermal events (Ji et al.1994; Li et al. 1998).
Quartz veins at Kanggurtag dened a much smallerpart of the
resource, occurring in a discontinuous belt forabout 1 km in
length, 500 m north of the #2 orebody.Termed the #1 orebody, the
quartz vein-hosted ore wasmined out in 1995. The low-suldation
epithermalquartz veins contain chlorite, sericite, carbonate,
andbarite gangue, with pyrite and arsenopyrite as the mainsulde
mineral phases (i.e., 525% of the vein volume).
The area surrounding the Kanggurtag and Matoutandeposits appears
highly prospective for the discovery ofadditional lode gold
deposits. Weathered fragments ofquartz vein material are scattered
over an area of per-haps 20 by 2 km, from just west of Kanggurtag
to alarge saline lake east of Matoutan. Much of the quartzlooks
barren of metals, is often chalcedonic or waxy, butnonetheless
indicates the presence of an extensive hy-drothermal system. Late
Paleozoic marble outcrops inthe eastern part of the area and
suggests an additionalpotential for FeCuAu skarn deposits.
Numerous RbSr dates bracket volcanoclastic hostrock deposition
to between ca. 300 and 280 Ma, and aUPb date on the nearby tonalite
is 275 Ma (Li et al.1998). The RbSr method was also used to suggest
thatore formation occurred near the end of this magmaticepisode
and/or some 2030 million years later duringLate Permian (Li et al.
1998). Stable isotope measure-ments range between 11.3 and 17.7 per
mil for d18O ofore-bearing quartz (stages not specied), 53 to 61
permil for dD of uid inclusion waters in the quartz, and0.9 to +3.3
per mil for d34S of suldes from the veins.These data can not
distinguish between a magmatic ormetamorphic uid and sulfur source,
but they do pro-vide little support for signicant meteoric water
withinthe hydrothermal systems at Kanggurtag.
Along the same shear system and 25 km east of theKanggurtag
deposit, the Dadonggou occurrence (Fig. 9)was discovered about 10
years ago. The geological set-ting and host rocks are the same as
at Kanggurtag, butthe strike of the shear system is NWW at the
Dadong-gou occurrence. Granodiorite and plagiogranite dykes,as long
as 3 km and as wide as 100 m, parallel the mainYamansu fault and
the auriferous shear system. Synki-nematic, concordant quartz veins
are widespread, com-monly 10- to 20-m-long and 20- to 30-cm-wide,
but theyare barren. A later stage of slightly discordant quartz
K-feldspar and albite veins, contains 510% suldeminerals,
dominantly pyrite, and averages about 12 g/tAu.
The Kanggurtag gold belt is often shown to continuefar to the
east along the Tian Shan, where a monzog-ranite pluton hosts the
Xifengshan II gold occurrence.The relatively undeformed quartz
veins contain gold,pyrite, and chalcopyrite. Li et al. (1998) claim
a RbSrage of 284 Ma for the host granitoid and 272 Ma age
formineralization (RbSr on uid inclusions in quartz)at the
Xifengshan II occurrence. If reliable, these datasuggest a
relatively consistent Permian age forgold deposition across the
eastern Tian Shan withinXinjiang.
410
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Fig. 10. Local geology of theKanggurtag gold deposit, east-ern
Tian Shan, in a plan viewand b cross section. Althoughshowing many
characteristics ofan orogenic gold deposit,reported downward
zoningfrom Au-, to AuCu-, and thento PbZn-rich veins is
moreconsistent with many epither-mal deposits
411
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The deposits along the western edge of adjacentGansu province,
including the Jinwozi (or Gold Nest;Fig. 2) and 210 deposits, are
often also described as apart of the Kanggurtag gold belt (e.g.
Pirajno et al.1997). However, these gold deposits are hosted
byDevonian metasedimentary rocks and Permo-Triassicplutons of the
Bei Shan, located to the east of theRuoqiangXingxingxia fault,
which marks the eastern-most edge of the Tian Shan. The plutons,
which are cutby widespread gold-bearing quartz veins, have Pb
zircondates as young as 241 Ma (Ji et al. 1994; Ji and Xue1996),
requiring veining to be post-Permian. The BeiShan is likely a part
of the Qilian Shan, which was right-laterally oset sometime in the
Mesozoic and/or Ceno-zoic (Zhou and Graham 1996). Gold deposits
within thewesternmost part of the Qilian Shan are Triassic in
age(Mao et al. 2000), and we suggest that these deposits inthe Bei
Shan may be an oset part of this gold provinceand unrelated to ores
of the Kanggurtag gold belt.
Gold-bearing porphyry deposits
A series of porphyry copper deposits, some gold-bear-ing, were
discovered in 1993 during regional mapping inthe northeastern Tian
Shan and are located about 80 kmsouthwest of the town of Hami (Fig.
2). They are pres-ently being drilled and studied by the No. 1
GeologicalTeam of the Xinjiang Bureau of Geology and
MineralResources. The deposits are located about 13 km northof the
North Tian Shan (or Kanggur fault) and arehosted by intrusions into
the Early to mid-Carbonifer-ous intermediate to mac volcaniclastic
rocks of theKanggur arc. The No. 1 Geological Team reports
theintrusive rocks to be of Permian age, whereas a con-icting RbSr
whole rock date of 370 Ma on the Tuwudeposit host intrusion (Rui,
unpublished data) wouldsuggest the country rocks must also be older
than theiroften accepted Carboniferous age. The most reliable
ageestimate is probably a new ReOs isochron date of322.72.5 Ma for
seven molybdenite samples from thedeposit (Du et al. 2001).
Initial reports by the No. 1 Geological Team indicatethat the
Tuwu porphyry deposit contains about 3 mil-lion tons of copper at a
cuto grade of 0.2% Cu. Inaddition, the deposit is estimated to
contain 3 millionozof Au at an average grade of 0.16 g/t, and also
sig-nicant amounts of silver. Stockwork-hosted and dis-seminated
sulde minerals, in the porphyritic andgranod- ioritic host
intrusion, are mainly pyrite andchalcopyrite, with lesser bornite.
Biotite is closely asso-ciated with the main ore zones, but
K-feldspar is absent.Surrounding alteration zones are dominated by
massivesilicication, outward to a quartzsericite zone,
thensericitekaolinite, and nally an epidote-rich outer halo.Other
deposits in this porphyry copper belt, includingChihu, Tuwu East,
Yandong, and Linglong, are evenless well-studied. Gold grades of
0.11 g/t are reportedfor Yandong, where
chalcopyritemagnetitebiotite-rich
ore zones are hosted by a subvolcanic diorite. Smallepithermal
gold veins are also reported to be widespreadthroughout this region
of the eastern Tian Shan.
Western Tian Shan
Orogenic gold deposits
The Wangfeng deposit (Fig. 2), and adjacent smallerprospects
(e.g. Saridala, Nalongxiaer, and Babagesayi),are located slightly
more than 100 km southwest of thecity of Urumqi. These small
orogenic gold occurrencesare restricted to the NW-striking
Bingdaban orShenglidaban mylonitized shear zone, which
separatesProterozoic to Ordovician, and perhaps
Silurian,orthogneiss, schist, and marble from mainly
EarlyCarboniferous granitoids, within the northern part ofthe Yili
block (or central Tian Shan). The shear zoneparallels, and is only
35 km south of, the deep-crustalNorth Tian Shan fault zone (locally
called theHongwuyueqiao fault) and thus may be a related strandof
this major suture zone.
The Wangfeng deposit was discovered in 1988 andmining began in
1998 on two of nineteen recognizedorebodies, each comprised of
numerous quartz veins andveinlets in the hanging wall of the
Bingdaban fault.Presently, an 80,000 oz Au resource is being mined
fromthe northwest-striking and near vertical #12 ore zone.The zone
consists of two distinct and parallel, 0.6- to0.8-m-wide and
1,300-m-long orebodies that are about10 m apart. To date, less than
1,000 oz Au have beenrecovered. The orebodies appear as silicied,
ductileshear zones, with typically 12% pyrite and pyrrhotite(?)in
the gold-bearing veinlets. Although the average goldgrade is 5 g/t,
there is a strong zonation from 18 g/t nearthe top of #12 down to
1.4 g/t at the lowest levels of theorebodies.
Dates on the intrusive host rocks range from a UPbzircon date on
biotite granite of 437 Ma to a RbSr dateof 310 Ma on mylonitized
plagiogranite, whereas a RbSr date on unspecied material (uid
inclusion waters?)from an auriferous vein was calculated at 277 Ma
(Li etal. 1998). The questionable date on the ore materialwould
suggest a roughly similar time to gold mineral-ization in the
eastern Tian Shan. The signicance of thehost rock dates are
uncertain; they might reect a broadSilurian through Permian
magmatic evolution in thecentral Tian Shan, as suggested by Allen
et al. (1992).Geochemical studies (Chen et al. 2000) suggest
miner-alization may have formed at
-
southeast-trending brittleductile shear zone, which isexposed
over a length of almost 2 km and a width of300 m in the mine area.
The auriferous quartz containsminor pyrite, with common sericite
and ankerite inore-hosting, altered Late Silurian to Early
Devonianmetamorphosed clastic rocks. Average grades fromvarious
orebodies range between 13 g/t Au, but locallyreach multiple
ounces. No important intrusions arelocated in the vicinity of the
Dashankou deposit,although Variscan bodies are recognized
regionally(Jingwen Mao 2001, personal communication).
The Sawayaerdun gold deposit (Fig. 11), along theChinaKyrgyzstan
border, is the largest recognizedorogenic gold deposit in Xinjiang,
with >3 Moz of goldand a geologically inferred resource of at
least 10 MozAu. This deposit within the eastern Kokshaal area of
thesouthern Tian Shan province is hosted by Late Silurianslates and
carbonaceous phyllites. The mid-Paleozoicrocks are part of a
complex sequence of allochthonousslices, with thrusting having
occurred during Variscancollisions (Biske and Shilov 1998).
Gold mineralization at Sawayaerdun is localizedover a 70-km-long
by 50- to 600-m-wide zone betweentwo regional faults, perhaps
sutures between a series ofaccreted oceanic terranes. In this belt
of highly tect-onized metasedimentary rock, economic gold grades
of35 g/t most commonly occur as widespread dissemi-nations. Quartz,
sericite, siderite, calcite, and chloriteare commonly associated
with the gold. Pyrite, pyr-rhotite, and arsenopyrite are the main
ore-associatedsuldes, with less common stibnite, chalcopyrite,
gale-na, sphalerite, and marcasite. Except for a few smallmac
dikes, no igneous rocks have been recognized inthis gold-rich zone.
Fluid inclusions mainly homogenizeat two modes of 155220 and 260290
C, and containabundant CO2 and signicant CH4 and N2 (Ye et
al.1999). Fluid inclusion waters from ore-related gangueat the
Sawayaerdun deposit have dD values of 59 to84 per mil, and d34S
data for sulde minerals rangebetween about 3 and +1 per mil. Many
of thesefeatures, including a probable Permo-Triassic age
offormation, led Ye et al. (1999) to suggest that thedeposit is
very similar to the immense Muruntaudeposit, located farther to the
west in the southern TianShan province.
On the Kyrgyzstan side of the border, where a con-tinuation of
the ores bodies within Early and MiddleDevonian phyllite is known
as the Savoyardy deposit,there is a zoning of mineralized veins
(United Nations1998). A central zone of arsenopyrite-rich quartz
veinsgrades 6.5 g/t Au and is reported to also contain about10% Pb.
Surrounding polymetallic veins average 4.5%Sb, 4.5% Pb, and 41.5
g/t Ag. This suggests a district-wide metallogeny similar to that
in areas such as CoeurdAlene (Idaho, USA), Keno Hill (Yukon,
Canada), andCobar (NSW, Australia), where adjacent gold- and
base-metal-rich epigenetic veins may reect metal leachingfrom a
variety of geochemically-distinct metasedimen-tary units.
A few hundred kilometers northeast of the Sawy-aerdun deposit,
the Bulong deposit is hosted by LateDevonian clastic rocks. A
series of parallel quartz veinscontains gold in minor pyrite, with
associated chlorite,sericite, and carbonate minerals in altered
wall rock.Mining of these veins began in the mid-1990s. Late-stage,
barren quartzbarite veins are also extensivewithin the Bulong
deposit. Fluid inclusions from thegold-bearing quartz are CO2-rich
(Jingwen Mao 2001,personal communication).
Epithermal gold deposits
The 1.6 Moz Au Axi deposit is the most importantepithermal gold
deposit in Xinjiang. It is located about80 km north of Yining and
less than 100 km from theKazakhstan border (Fig. 2). The deposit
was discoveredduring regional mapping in 1988 and has producedabout
250,000 oz Au and an unspecied amount of sil-ver since mining began
in 1995. Mining is presently byopen pit, but future underground
development is plan-ned. The Axi deposit occurs in an Early
Carboniferousvolcanic eld that is located in the cover sequence to
theYili block, which is dominated by Proterozoic carbonatesequences
and OrdovicianSilurian clastic and carbon-ate rocks. The closest
known Variscan granitoid to Axi
Fig. 11. Local geology of the still poorly studied
Sawyaerdundeposit near the ChinaKyrgyzstan border. A geologically
inferredresource of >10 Moz Au occurs in quartz veins hosted by
LateSilurian slates and carbonaceous phyllites
413
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is 15 km to the northeast, although rare synvolcanicdikes occur
in the deposit area. Many other small goldand leadzinc vein
occurrences are also associated withthe volcanic system, although
only the small Tawobiekedeposit is also being mined.
The Axi deposit is hosted by Early Carboniferousporphyritic
andesite of the Dahalajunshan Formation(Fig. 12) to the south of
the North Tian Shan fault.These host rocks represent part of the
late Paleozoic arcsuperimposed on the Precambrian Yili block
duringcollision of the Kunggar arc (or North Tian Shan arc)from the
north (Gao et al. 1998). Volcanic pipe-likefeatures are associated
with NW- to N-trending base-ment faults (Wang and Wang 1995). Liu
et al. (1996)indicate an association of the Axi deposit with
volcanicring structures. The deposit is divided into a northernand
southern part, each of which is about 500-m-long.The auriferous
quartz in the northern part is commonlychalcedonic, sinter-like,
and laminated, often showing avariety of colors among the
laminations that reectsignicant dierences in trace element
chemistry. Muchof the northern orebody is jasperoidal and there is
somebrecciation. The quartz and metals were likely precipi-tated at
very shallow levels and, in part, in a hot springs
environment. The nearby Yiermand gold occurrence isalso
suggested to have formed in a hot springs envi-ronment within rocks
of the Dahalajunshan Formation(Zhai et al. 1999). The southern
orebody at Axi is morediuse, with extensive silicication and
stockworking,rather than discreet veins. Brecciation is much
moreextensive.
Fine-grained pyrite is the most common suldemineral in the Axi
deposit. Arsenopyrite and scoraditeare also common minor
constituents of the ores. Liuet al. (1996) also note the occurrence
of rare, ne-grained tetrahedrite, chalcopyrite, and galena, and
seri-cite, siderite, and calcite, along with silica, are the
maingangue phases. Propylitic, argillic, and phyllic
alterationzones surround the orebodies. The deposit averages5.7 g/t
Au, with slightly higher grades in the north partand local
concentrations of 150 g/t Au, and exhibits aAu:Ag ratio of 1:2. Ore
uids were low salinity and oreformation temperatures between 135
and 200 C (Liuet al. 1996).
An auriferous basal conglomerate at the Axi deposit(Fig. 12)
occurs in the overlying, late Early to mid-Carboniferous intertidal
sedimentary rocks of the Aq-alhe Formation (Liu et al. 1996). This
may representaccumulations of gold eroded from older
epithermalquartz veins at Axi, although the intertidal
environmentis an unlikely setting for such a conglomerate.
Perhaps,however, this is some type of coastal-margin, wave-formed
bar or channel-ll accumulation.
The age of mineralization at Axi is unclear. Li et al.(1998)
report a series of RbSr and 40Ar/39Ar dates on
Fig. 12. a Local geology map and b cross section of the
Axiepithermal gold deposit. The epithermal veins are hosted
alongfaults in volcanic breccia within the Early Carboniferous
Dahala-junshan Formation. Additional gold resources are contained
in anoverlying auriferous conglomerate of the Aqalhe
Formation.Figure generalized from Liu et al. (1996)
414
-
quartz veins that range between 344 and 301 Ma. Theoldest date
agrees well with the hypothesized geneticassociation between Early
Carboniferous volcanism andepithermal gold deposition. The Late
Carboniferousdates are younger than the volcanic rock host
sequences,but are not inconsistent with other magmatism in thispart
of the Yili block that continued until the end of theCarboniferous
(Gao et al. 1998; Li et al. 1998).
Gold deposits of the Kunlun Shan
The Kunlun Shan, along the southern margin of theTarim basin,
have relatively little recognized gold re-sources. However, small
paleo-terrace and bench typeplacer gold deposits are scattered
along the northernfoothills of the Kunlun Shan for more than 1,000
km.These occurrences extend from Hetian in the west,across all
Xinjiang, and into Qinghai province in theeast. In addition, broad
areas with extremely anomalousgold values in stream sediments have
been identiedthroughout the western Kunlun Shan (Minco Miningand
Metals Corp News Release, 21 May 1997).
The source for much of this gold is the high peaks ofthe Kunlun
Shan, reaching 6,2007,600 m in Xinjiang,where dicult access has
prevented signicant explora-tion for lode sources. Because much of
this remotecountry is covered by extensive ice and snow, nding
thesources for the anomalies and placer accumulations willcontinue
to be dicult. It is likely, however, that sourcelodes are orogenic
gold deposits located in the upliftedysch of the Tianshuihai
terrane. These deposits theo-retically could have formed during
hydrothermal eventsthat would have occurred during Late Triassic to
EarlyJurassic (i.e. Indosinian time), greenschist facies
meta-morphism and magmatism within the metasedimentaryrocks as they
collided with the Precambrian TarimQaidamKunlun nucleus. The small
Wulonggou, Tanj-ianshan, Qinglonggou, Kaihuangbei, Dongdatan,
andDachang orogenic gold occurrences in the easternKunlun Shan (Yu
et al. 1998; Cui et al. 2000), where therange extends into adjacent
Qinghai province, are likelya part of the belt that has contributed
to the placers.Orebodies at the Wulonggou deposit cut granitoids
asyoung as early Mesozoic (Yu et al. 1999) and, therefore,provide
support for a post-Paleozoic origin for lode golddeposits in the
Kunlun Shan. Absolute dates of ca. 160200 Ma, using RbSr and KAr
methods on ore-relatedminerals, conrm a Jurassic timing (Qian et
al. 2000;Wang and Hu 2000).
Synthesis of gold metallogeny of Xinjiang
The mountain ranges of Xinjiang are favorable for theoccurrence
of Variscan (late Paleozoic) or Indosinian(early Mesozoic)
gold-bearing orogenic, epithermal, re-placement and VMS deposits.
The former gold deposittype may be associated with economic placer
accumu-
lations, especially in the northernmost Altay Shan andthe
northern foothills to the Kunlun Shan. Good de-posit-scale maps of
the deposits and main districts arenotably lacking. Almost no
well-documented ore depositstudies exist in the western literature
that describe indi-vidual deposits over this vast part of China.
There is afair amount of geochronology, uid inclusion
microth-ermometry, and stable isotope studies within the Chi-nese
literature, but the general contradictory nature ofmuch of the data
make these dicult to evaluate. Nev-ertheless, combining (1)
preliminary eld examination ofsome of these deposits by some of us,
(2) the publishedcharacteristics of many of the deposits as
described inthe Chinese literature, and (3) our evaluation of
thespatial distribution of the gold resources, allows for abetter
understanding of the gold resources in Xinjiang.
Late Paleozoic terrane accretion and collisional oro-genesis of
early to mid-Paleozoic marine sequencesbetween Precambrian blocks
provided a tectonic envi-ronment highly favorable for the formation
of orogeniclode gold deposits. Growth of the Altaid
complexthroughout the Paleozoic included formation of oro-genic
gold deposits that young to the southwest within agrowing
continental margin. Latest hydrothermal eventsof the orogen led to
the development of gold vein sys-tems in the Early
Carboniferous(?), and perhaps earliertimes in northernmost
Xinjiang, and in the southern-most part of the Altay Shan and
adjacent areas nowsurrounding the Junggar basin in the Late
Carbonifer-ous and Early Permian. Overlapping the nal stages
ofAltaid orogenesis, and likely elsewhere along the samenorthern
Paleo-Tethys Ocean continental margin,Permian translation of
terranes accreted in the mid-Paleozoic was also associated with
localized orogenicgold-vein formation in the southern Tian Shan.
Therestriction of orogenic gold deposits in the Chinese TianShan to
the Sawyaerdun deposit and the area south ofUrumqi may reect the
predominance of unfavorableshallow crustal rocks in the eastern
Tian Shan and thelimited exploration in the rugged alpine country
of thewestern part of the mountain range. The occurrence ofthe
Kumtor deposit in the latter, very close to theXinjiang border,
further identies this as an area that isextremely permissive for
the discovery of importantorogenic gold deposits. Continued
collisions in the earlyMesozoic, to the south of the Tarim basin,
led todevelopment of the youngest gold lodes in Xinjiang,localized
in the mainly inaccessible high elevations of theKunlun Shan.
The recognition of epithermal gold deposits as old asPaleozoic
and within areas of extensive regional uplift isexceptional and of
great scientic and economic interest.These include small epithermal
deposits in the southernAltay Shan, the Early Carboniferous Axi
deposit in thecentral Tian Shan, the Early(?) Permian Xitan deposit
inthe southern Tian Shan, and Early Carboniferous (?)Jinshangou
deposit in the East Junggar area. Whereasmany deeper types of gold
deposits are cla