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International Geology Review, 2013Vol. 55, No. 13, 1660–1687, http://dx.doi.org/10.1080/00206814.2013.792500
Two geodynamic–metallogenic events in the Balkhash (Kazakhstan) and the West Junggar(China): Carboniferous porphyry Cu and Permian greisen W-Mo mineralization
Ping Shena*, Hongdi Panb, Wenjiao Xiaoa , Xuanhua Chenc , Seitmuratova Eleonoradd and Yuanchao Shena
aKey Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;bCollege of Earth Sciences, Chang’an University, Xi’an 710054, China; cInstitute of Geomechanics, Chinese Academy of GeologicalSciences, Beijing 100081, China; dLaboratory of Geological Formations, K. Satpaev Institute of Geological Sciences, Almaty 050010,
Kazakhstan
(Accepted 1 April 2013)
This study focuses on the geochronology and elemental and Nd isotopic geochemistry of the Baogutu Cu deposit and thenewly discovered Suyunhe W-Mo deposit in the southern West Junggar ore belt (Xinjiang, China), as well as the geologyof the newly discovered Hongyuan Mo deposit in the southern West Junggar ore belt and the Kounrad, Borly, and AktogaiCu deposits and the East Kounrad, Zhanet, and Akshatau W-Mo deposits in the North Balkhash ore belt (Kazakhstan). Theaim is to compare their petrogenesis, tectonic setting, and mineralization and to determine the relationship between thesouthern West Junggar and North Balkhash ore belts. Based on our newly acquired results, we propose that the Kounrad,Borly, Aktogai, and Baogutu deposits are typical porphyry Cu deposits associated with calc-alkaline magmas and formedin a Carboniferous (327–312 Ma) subduction-related setting. In contrast, the East Kounrad, Zhanet, Akshatau, Suyunhe,and Hongyuan deposits are quartz-vein greisen or greisen W-Mo or Mo deposits associated with alkaline magmas andformed in an early Permian (289–306 Ma) collision-related setting. Therefore, two geodynamic–metallogenic events can bedistinguished in the southern West Junggar and North Balkhash ore belts: (1) Carboniferous subduction-related calc-alkalinemagma – a porphyry Cu metallogenic event – and (2) early Permian collision-related alkaline magma – a greisen W-Mometallogenic event. The North Balkhash ore belt is part of the Kazakhstan metallogenic zone, which can be extended eastwardto the southern West Junggar in China.
Keywords: Porphyry Cu deposits; greisen W-Mo deposits; Balkhash; Kazakhstan; West Junggar; China
1. Introduction
The Central Asian Orogenic Belt (CAOB) is the largestPhanerozoic juvenile crustal growth orogenic belt in theworld, extending 7000 km from west to east and from theSiberian Craton in the north to the Tarim Craton in thesouth (Figure 1A; Sengör et al. 1993; Xiao et al. 2009). Thelate Palaeozoic tectonics of the CAOB was characterizedby continuous subduction, accretion, and collision of vari-ous micro-continental blocks during the formation, evolu-tion, and closure of the Palaeo-Asian Ocean between theSiberian and Tarim cratons (Xiao et al. 2008, 2009; Chenet al. 2010a). It led to the formation of a number of giantore deposits, which formed the Central Asian metallogenicdomain (He and Zhu 2006; Zhu et al. 2007). The porphyryCu and greisen W-Mo deposits are particularly importantin the Central Asian metallogenic domain.
The Balkhash metallogenic belt is world famous forits giant ore deposits. This metallogenic belt consists ofnorth and south zones. In this study, we study the northzone (i.e. the North Balkhash metallogenic belt). The belt
*Corresponding author. Email: [email protected]
begins at the Mointy block in the west and extends east-wards via Sayak to Aktogai in Kazakhstan (Figure 1B). Thebelt includes the Kounrad, Aktogai, and Borly porphyry Cudeposits and East Kounrad, Zhanet, and Akshatau greisenW-Mo deposits, amongst which are both the Kounrad (withCu reserves > 8 Mt) and Aktogai (Cu > 12 Mt), twoworld-famous super-large porphyry Cu deposits. However,the relationship between these deposits has not been givenmuch attention, and whether the belt could be extended tothe West Junggar in China has not been discussed.
The West Junggar metallogenic belt is bounded bythe Altai orogen to the north and by the Ashanti oro-gen to the south, and extends westward to the Balkhashregion in adjacent Kazakhstan and eastward to the JunggarBasin in Xinjiang, China (Figure 1B). This metallogenicbelt includes north and south zones, and in this study,we focused on the south zone (Figure 2). The southernWest Junggar ore belt is famous for its gold depositsand nearly one hundred gold deposits of various sizeshave already been discovered, amongst which is the Hatu
© 2013 Taylor & Francis
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Figure 1. (A) Simplified map of the Central Asia Orogenic Belt (after Xiao et al. 2009). (B) Simplified geotectonic map of the Palaeozoicof Kazakhstan and contiguous China, showing major ore deposits (modified after Abdulin et al. 1996; He et al. 2004; Windley et al. 2007;Xiao et al. 2008 and other sources). The Central Kazakhstan oroclinal bend is reflected by the inward younging of major magmatic arcstowards Lake Balkash.
Note: Cm, Cambrian; O, Ordovician; S, Silurian; D, Devonian; C, Carboniferous; P, Permian; PZ, Palaeozoic; MZ, Mesozoic; CZ,Cenozoic. Subscripts 1, 2, and 3 refer to early, middle, and late.
(with Au > 50 t), one of the largest gold deposits inXinjiang. Recently, its ore potential has been highlighted bythe discovery of the Baogutu porphyry Cu and Hongyuan
Mo deposits in the Kelamay Region and the SuyunheW-Mo deposit in the Barluk Mountains (Figure 2). Thus,the southern West Junggar ore belt includes the porphyry
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Figure 2. Generalized geological map of the West Junggar Region (modified after BGMRXUAR 1993; Shen et al. 2012a).
Cu, quartz vein W-Mo, and Mo deposits and considerablehydrothermal gold deposits. Therefore, it is possible thatthe southern West Junggar ore belt in China may be corre-lated with the North Balkhash ore belt in Kazakhstan. It isnecessary to study and compare the petrogenesis and tec-tonic setting as well as the mineralization types and agesin both the North Balkhash and southern West Junggar orebelts in order to identify the extent of the North Balkhashore belt in Xinjiang, China.
In this work, we study the Kounrad, Borly, and AktogaiCu deposits and the East Kounrad, Zhanet, and AkshatauW-Mo deposits in the North Balkhash (Kazakhstan), theBaogutu Cu deposit and newly discovered Suyunhe W-Moand Hongyuan Mo deposits in southern West Junggar(China), and also present new chemical and Nd isotopicdata and Re-Os isotopic ages for the deposits from thesouthern West Junggar in a bid to (1) compare their min-eralization types, ore-forming ages, ore-bearing magmagenesis, and tectonic setting and (2) determine the relation-ship between the North Balkhash and the southern WestJunggar ore belts and implications for mineralization inCAOB.
2. Geological setting
2.1. West Junggar
The West Junggar terrain is largely composed of Palaeozoicvolcanic arcs in the northern part and accretionary com-plexes in the southern (e.g. Windley et al. 2007; Xiaoet al. 2008; Zhang et al. 2011) that were accreted onto theKazakhstan plate as the Tarim, Kazakhstan, and Siberianplates converged (Chen and Arakawa 2005; Xiao et al.2008).
The southern West Junggar is located between latitudes45◦05′ and 46◦15′ N and longitudes 82◦15′ and 86◦00′ E(Figure 2). It is characterized by northeast-trending faultsand fault-bounded accretionary complexes, which is incontrast to the northern West Junggar where major faultsand fault-bounded blocks are mainly EW oriented (Shenet al. 2012a). The southern West Junggar developedseveral northeast-trending faults including the Barluk,Mayile, and Darbut faults. The documented SuyunheW-Mo deposit occurred in the Barluk Mountains, locatedin the west of the Mayile fault and the documentedBaogutu Cu and Hongyuan Mo deposits occurred in the
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Kelamay Region, located in the east of the Mayile fault(Figure 2).
The Barluk Mountains are located in the westernpart of the southern West Junggar (Figure 2). Fossil-dated Devonian strata occur widely in the BarlukMountains close to the China–Kazakhstan border(Figure 2; BGMRXUAR 1993), and are the volcano-sedimentary strata of the Middle Devonian Barluk andTieliekede Groups. The Barluk Group is composed ofsiltstone, tuff, and minor basalt; the Tieliekede Groupconsists of greywacke, tuffaceous mudstone, and tuffa-ceous siltstone. These Devonian sequences are intrudedby Carboniferous–Permian intrusions in the BarlukMountains. Carboniferous intrusions include peridotite,gabbro, diorite, and quartz diorite stocks, while Permianintrusions include diorite, quartz diorite, and adamellitestocks (BGMRXUAR 1993). Structurally, the BarlukMountains are characterized by the northeast-trendingBarluk fault, although NE- and NW-trending structures arealso present.
The Kelamay Region, located in the eastern part ofthe southern West Junggar, is characterized by the occur-rence of lower Carboniferous volcano-sedimentary strata(Figure 2). There are three early Carboniferous strati-graphic units, from oldest to youngest: the Tailegula,Baogutu, and Xibeikulasi Groups (Shen and Jin 1993).The Tailegula Group consists of a succession of basicvolcanic and volcaniclastic rocks intercalated with chert.The Baogutu Group includes tuffaceous siltstone, silttuff, and felsic tuff, while the Xibeikulasi Group consistsof greywacke. These early Carboniferous sequences areintruded by ore-bearing diorite stocks at about ∼320 Ma(Tang et al. 2009; Shen et al. 2012b) and voluminous bar-ren post-collisional granite batholiths at about ∼310 Ma(Chen and Jahn 2004; Han et al. 2006). The Baogutu andHongyuan intrusions occur in the south of the Darbut fault.
The southern West Junggar is characterized bythe occurrence of several ophiolite belts (Figure 2).A Cambrian island arc ophiolite crops out at Tangbale(Jian et al. 2005), together with Ordovician and Siluriansedimentary rocks. Newly discovered Kalamay ophiolitemélanges were formed during the Ordovician (He et al.2007). A Silurian ophiolite is found at Maila (Wang et al.2003), while the Darbut ophiolite belt is Devonian in age(Xu et al. 2006). The youngest reported ophiolite at Maliyahas a Carboniferous age (Dong and Wang 1990). Mostophiolites show contact relationships with the Devonianto lower Carboniferous volcanic–sedimentary strata viafaults.
2.2. North Balkhash
North Balkhash, located in Central and East Kazakhstan,exposes integrated Palaeozoic strata, plutons, and volcanicrocks (Heinhorst et al. 2000; Chen et al. 2010a; Cao
et al. 2012; Figure 1). The strata are divided into threeunits, the first being the Precambrian metamorphic base-ment composed of schist, gneiss, amphibolite, and quartz-feldspathic schist, exposed in the north and west of CentralKazakhstan. This unit is the most prominent unit of theKokchetav Massif in north-central Kazakhstan. The secondunit is Palaeozoic folded sedimentary and metamorphicrocks, which change from assemblages of volcanogenicsilicic, terrigenous clastic, and carbonate rocks in theCambrian and Ordovician, to terrigenous clastic or shallowmarine clastic rocks in the Silurian and Devonian, to vol-canic rocks of dacite and rhyolite intercalated with tuff inthe Carboniferous, and to the basalt-rhyolite and terrestrialvolcanic tuff in the Permian. The third unit is widespreadcover of Mesozoic and Cenozoic sandstone and mudstone.Central and East Kazakhstan display a large oroclinal bendof Palaeozoic foldbelts, which range from Cambrian toOrdovician ages in the outer part to Carboniferous in thecentral part (Popov 1996; He and Zhu 2006; Zhu et al.2007; Figure 1B).
Intrusive rocks emplaced from the Proterozoic toPermian, consisting primarily of late Palaeozoic granitoidrocks. Serykh (1996) subdivided the granitoid series infoldbelts of Central and East Kazakhstan into early or syn-orogenic and late or post-orogenic series. Four series ofvolcanic and intrusive rocks were recognized by Popov(1996): pre-, early, main, and late orogenic. Most of theCu-Mo and Au deposits in the belt are associated withpre-orogenic and early orogenic diorite, granodiorite, andadamellite intrusive rocks. In contrast, stockwork and veinMo deposits and scheelite-bearing W deposits are relatedto main orogenic granite and leucogranite, and polymetal-lic Mo-W-Be-Bi mineralization is accompanied by lateorogenic leucogranitic plutons (Popov 1996; Heinhorstet al. 2000).
There are a number of irregularly distributed remnantsof lower Palaeozoic oceanic crust in Central Kazakhstan.However, in contrast to examples from collisional oro-gens, these ophiolite rocks do not mark interplate suturezones (Sengör et al. 1993) and show geochemical featuresof fore-, back-, or intra-arc oceanic crust (Kröner et al.2007). Ophiolite belts in Central Kazakhstan comprise onlythe topmost layers of palaeo-oceanic crust, especially thedeep-sea sediments and volcanic rocks.
3. Deposit geology
3.1. Porphyry Cu deposits
3.1.1. Baogutu Cu deposit
The Baogutu copper deposit is located about 60 km south-west of Kelamayi City (Figure 2). It contains 630 kt Cumetal at an average grade of 0.28%, 18 kt Mo metal atan average grade of 0.011%, and 14 t Au metal at anaverage grade of 0.1 ppm. Our previous work recognizedtwo mineralized intrusive phases at Baogutu, which are
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the main-stage granular to porphyritic diorites and minorlate-stage diorite porphyries (Shen et al. 2010a, 2010b;Figure 3). They intrude the lower Carboniferous Baogutuand Xibeikulasi groups.
The main-stage diorites host the bulk of the Cu-Au-Mo mineralization at Baogutu. They have been overprintedby three alteration assemblages, including an early potassic(biotite) assemblage that occurs in the centre of the deposit.A propylitic assemblage surrounds the potassic zone con-centrically. Both of these alteration assemblages havebeen overprinted locally by phyllic alteration (Shen et al.2010a, 2010b). Potassic alteration associated with mostCu-Au mineralization is predominant in the diorites andin the wall rocks. Intense phyllic alteration is predomi-nant in the diorites and is associated with most Cu-Momineralization. The dominant disseminated mineraliza-tion (Figure 4A) and lesser amounts of vein stockworks(Figure 4B) occurred in Baogutu. The main mineral assem-blages of the deposit are pyrite, chalcopyrite, pyrrhotite,and molybdenite (Figure 4C).
3.1.2. Kounrad Cu deposit
The Kounrad porphyry Cu deposit is situated 10 km to thenorth of Balkhash City. It lies in the southern part of theTokrausky synclinorium in Central Kazakhstan. Kounradis spatially related to a large massif of silicified volcanicrocks, and it contains more than 8 Mt Cu metal at an aver-age grade of 0.61%, associated with Mo (average grade0.0035%), Au (average grade 0.017 ppm) (Zhukov et al.1997), and a total Cu:Mo ratio of 115:1 (Popov 1996).
Early Carboniferous sedimentary-volcanic unitsoccurred in the Kounrad area and formed a volcanic appa-ratus. The strata include Late Devonian and Carboniferoussedimentary, volcanogenic-sedimentary, and volcanicunits. They are intruded by the Toktay intrusive complexesof Carboniferous age (Figure 5). The Toktay intrusivecomplexes are subdivided into three phases: (1) gabbrodi-orite porphyry, which is a small stock; (2) the main phase,biotite-amphibole granodiorite, porphyritic granodiorite,and granodiorite porphyry; and (3) fine-grained graniteand granite porphyry dikes. The second stock is the mainore-bearing one, which defines an area of mineralizedrocks approximately 1100 m × 800 m.
The Kounrad area is characterized by an irregularelliptical caldera ring-fracture, which is influenced by sev-eral NE–NW-trending faults. The ore-bearing stocks andassociated copper orebodies are controlled by the calderaring-fracture.
Almost all rocks forming the deposit have, to a vari-able extent, been affected by hydrothermal alteration.They can be subdivided into three groups (Kudryavtsev1996): the first is represented by the quartz-sericite andquartz-sericite-diaspore altered rocks that resulted frompost-volcanic hydrothermal activity; the second comprises
quartz-sericite rocks (Figure 4D), propylitic, and the latestquartz-kaolinite argillic alteration that is closely related tothe intrusion of ore-bearing porphyritic granodiorite; thethird is restricted in its occurrence by the late dikes andincludes potassic alteration and mica-quartz-tourmalinealteration. The second alteration is associated with Cu-Mo mineralization (Figures 4D and 4E). Dominant veinstockworks and hydrothermal breccias occur in Kounrad.The main mineral assemblages of the deposit are pyrite,chalcopyrite, chalcocite, and molybdenite.
3.1.3. Borly Cu deposit
The Borly porphyry Cu deposit is situated 60 km to thenorth of Balkhash City and 45 km from the KounradCu deposit. It lies mainly in the southern part of theTokrausky synclinorium, and its Cu reserves amount tosome 600 kt Cu @ 0.34%, associated with Mo (averagegrade 0.11%), Au (average grade 0.03 ppm), Ag (averagegrade 1341 ppm), Re (average grade 0.42 ppm), and Se(average grade 3.01 ppm), with a total Cu:Mo ratio of 50:1(Popov 1996).
The strata in the Borly area include the lowerCarboniferous Karkaralinskaya and upper–middleCarboniferous Keregetass groups. The former is asuite of lithic-crystal tuff, lava, and subvolcanic rocks,while the latter includes a suite of dacite, sometimestrachdacite or andesite-dacite ignimbrite, microlitic tuff,tufflava, lava, and subvolcanic rocks.
The centre of the Borly deposit is the Borlinksyapophysis of the Kyzylzhalsky intrusion. The Borlinksyapophysis contains three phases: (1) quartz diorite, (2) themain phase, biotite amphibole granodiorite (Figure 4G),and (3) light-coloured granite-porphyry. They are cut bya granodiorite stock. The intrusion of that rock bodywas accompanied by intensive cryptoexplosive breccia-tion, hydrothermal alteration, and the formation of quartz-sulphide stockworks. The youngest magmatic assemblageis the alkaline granite porphyry dikes and subvolcanicrocks in the early Permian Zhaksitagalinsky complex(Abdulin et al. 1998).
The Borlinksy apophysis hosts the bulk of the Cu-Mo mineralization (Figures 4H and 4I) at Borly. It hasbeen overprinted by three alteration assemblages: an earlybasic alteration (K-feldspar, chlorite, quartz, epidote), amiddle acidic alteration (quartz, sericite, chlorite, and cal-cite), and a late basic alteration (quartz and calcite). Earlybasic and middle acidic alteration are associated withmost Cu mineralization. The main mineral assemblagesof the deposit are pyrite, chalcopyrite, and molybdenite(Figures 4H and 4I).
3.1.4. Aktogai Cu deposit
The Aktogai porphyry Cu deposit is situated 22 km eastof Aktogai railway station (Figure 6) and contains 12.5 Mt
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Figure 3. (A) Geological map of the Baogutu porphyry Cu deposit showing the intrusion complex. Line WE01 shows the location ofthe section shown in (B), dots indicate the position of drill holes. (B) Geologic cross-section along WE01 showing the host rocks to theBaogutu deposit and the copper ore bodies (Shen et al. 2010a).
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Figure 4. Photographs of ore-bearing rocks and mineralization. Baogutu Cu deposit: (A) disseminated ore in medium-grained dioritewith disseminated chalcopyrite and biotite; (B) vein ore, Q-Cpy veinlets overprinted in the disseminated mineralization in diorite; (C) veinore, Q-Cpy-Mo veins. Kounrad Cu deposit: (D) vein ore, Q-Cpy veinlets overprinted in the disseminated mineralization in granodiorite;(E) disseminated ore with disseminated Mo. Aktogai Cu deposit: (F) disseminated mineralization in granodiorite. Borly Cu deposit: (G)granodiorite; (H) vein ore, Q-Cpy veins; and (I) vein ore, Q-Mo veins. All photographs under natural light.
Note: Q, quartz; Cp, chalcopyrite; Mo, molybdenite.
Figure 5. Geological map of the Kounrad porphyry Cu deposit showing the intrusion complex and associated wall rocks (from Zhukovet al. 1997).
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Figure 6. Generalized geological map of the North Balkhash region (modified after Chen et al. 2010a).
Cu metal with an average of 0.3% Cu (Cooke et al. 2005),271 kt Mo metal at an average grade of 0.01%, and 60 tAu metal at a grade of 0.007–0.40 ppm, associated withAg (average grade 1.8 ppm), Re (average grade 0.24 ppm),and Se (average grade 1.8 ppm) (Chen et al. 2010b).
The strata in the Aktogai include the upperCarboniferous–lower Permian Koldarskaya Groupand middle–upper Carboniferous Keregetasskaya Group(Figure 7). The Koldarskaya Group includes a suite ofsedimentary rock, volcano-sedimentary rock, and minor
Figure 7. Geological map of the Aktogai porphyry Cu deposit area showing the Aktogai, Aidarly, and Kyzylkiya Cu deposits (fromZhukov et al. 1997).
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acidic tuffs. The Keregetasskaya Group is a suite ofandesite and minor rhyolite and stone and siltstone. Cu-Momineralization is related to granodiorite porphyry andquartz diorite porphyry (Figure 4F) and other small,shallow, intrusive bodies in the early Carboniferousgranodiorite batholith, covered by Carboniferous–lowerPermian volcano-sedimentary rocks (Figure 7).
Associated hydrothermal alteration consists of silici-fication in the core, K-silicate alteration, quartz-sericitealteration within the stock, and propylitization in the wall-rock. The veinlet disseminated orebody mainly developedin the quartz-sericite alteration. The opaque minerals foundunder the microscope are mainly pyrite, chalcopyrite,molybdenite, and minor pyrrhotite and chalcocite.
3.2. Quartz-vein greisen W-Mo deposits
3.2.1. Suyunhe W-Mo deposit
The Suyunhe W-Mo deposit lies about 80 km southeast ofYumin town (Figure 2). It is a newly discovered W-Modeposit and is under exploration by the local geologicalteam.
Fossil-dated Devonian strata occur widely in theSuyunhe area. They are the volcano-sedimentary strata ofthe Middle Devonian Barluk Group, composed of siltstone,tuff, and minor basalt. The Barluk Group is intruded byCarboniferous–Permian intrusions, which occupy localizeddilatant sites provided by the intersection of NNE- andNEE-trending faults (Figure 8). They include plagiograniteporphyry and granite, based on our microscope observa-tion. The plagiogranite porphyry has a porphyritic texture.
Phenocrysts are plagioclase and quartz and minor biotiteand hornblende; the groundmass exhibits a subhedral tex-ture with plagioclase, quartz, and minor biotite. Granitehas a hypidiomorphic-granular texture and consists of pla-gioclase, microcline, and quartz (Figure 9A). Associatedhydrothermal alteration consists of quartz vein and greisen(quartz-muscovite, Figure 9B) occurring in the granite. Thegranite is associated with W-Mo mineralization.
The orebodies are mainly hosted in the wall rocks(Figure 8), which include tuff and tuffaceous siltstone.The orebodies have vein and lenticular forms and haveno distinct boundaries with country rocks, showing gra-dational contact relationships. The orebodies occupy anarea of 3200 m × 600 m. Five tungsten orebodies,12 molybdenum orebodies, and one tungsten-molybdenumorebody have been recognized in the Suyunhe ore dis-trict. The ore types are W ore, Mo ore, and W-Mo ore(Figures 9C and 9D). The dominant types of ore mineralassemblage are quartz-molybdenite, quartz-scheelite, andquartz-molybdenite-scheelite. Ore minerals mainly includescheelite, molybdenite, and minor chalcopyrite and pyrite.Gangue minerals are mainly quartz, muscovite, sericite,and calcite. The W-Mo mineralizations occur mainly inquartz veins and quartz veinlets.
3.2.2. Hongyuan Mo deposit
The Hongyuan Mo deposit lies about 15 km north ofKelamay City. It is a newly discovered Mo deposit and isunder exploration by the local geological team (Figure 2).The Early Carboniferous Tailegula Group occurs in the
Figure 8. Schematic geological map of the Suyunhe quartz-vein W-Mo deposit (modified from local geological team, 2009).
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Figure 9. Photographs and microphotographs of ore-bearing rocks and ores from the quartz vein-greisen W-Mo deposits in the southernWest Junggar and the North Balkhash ore belts. Suyunhe W-Mo deposit: (A) alkali granite; (B) greisenization alkali granite; (C) Q-Moveins; (L) Q-Sch veins. Hongyuan Mo deposit: (E) porphyritic granite; (F) greisenization porphyritic granite; (G) Q-Ms vein; (H) Q-Movein. East Kounrad W-Mo deposit: (I) alkali granite. Akshatau W-Mo deposit: (J) Q-Mo-Be veins. Zhanet Mo deposit: (K) alkali granite:(L) Q-Mo veins. All photographs taken under natural light except A, B, E, and F, which were taken under transmitted lights.
Note: Pl, plagioclase; Or, K-feldspar; Q, quartz; Mo, molybdenite; Sch, scheelite; Be, beryl.
Hongyuan area and is composed of tuff and tuffa-ceous siltstone intercalated with basic volcanic rocks. TheTailegula Group is intruded by Permian intrusions, includ-ing Kelamay granite pluton and Hongyuan granite stock.The Hongyuan granite stock is associated with Mo miner-alization.
Previous work has suggested that the Hongyuan Modeposit is a porphyry Mo deposit (Li et al. 2012). Basedon our present study, we consider it to be a quartz vein-greisen Mo deposit. The Hongyuan granite stock consistsof granite and porphyritic granite based on our microscopeobservations (Figure 9E). Granite has a hypidiomorphic-granular texture and consists of plagioclase, microcline,and quartz. Porphyritic granite is the same as granite incomposition but has a porphyritic-like texture. The ore-body occurs in the Hongyuan granite stock. In addition,many quartz-muscovite veins occur in the fissures of the
granite (Figure 9G). Greisenization (quartz and muscovite)occurs in the granite stock (Figure 9F), while molybdenitemainly occurs in quartz veins and fissures. The ores containmolybdenite, pyrite, quartz, muscovite, sericite, and veryminor chalcopyrite (Figure 9H).
3.2.3. East Kounrad W-Mo deposit
The East Kounrad W-Mo deposit lies about 11 km east ofthe Kounrad porphyry Cu deposit. It is an underground-mined W-Mo deposit, but the mine is now abandoned. TheEast Kounrad W-Mo deposit has reserves of 200–250 kt,averaging 0.056% Mo.
The East Kounrad W-Mo deposit is associated with thesyenogranite stock (Figure 9I). The ore deposit occurs inendo- and exocontact zones of syenogranite. It is of thequartz vein-greisen type, with the major ore minerals being
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wolframite and molybdenite. W-Mo mineralizations occurmainly in quartz veins and quartz veinlets, and also at thetops of cupolas and in greisens surrounding quartz veins(Burmistrov et al. 1990). The main mineral assemblages ofthe deposit are scheelite, wolframite, molybdenite, apatite,phenakite, beryl, biotite, muscovite, bismite, bismuthinite,calcite, chalcopyrite, ferromolybdite, fluorite, prosopite,helvite, microcline, pyrite, phlogopite, powellite, quartz,rhodochrosite, salite, and topaz.
3.2.4. Akshatau Be-W-Mo deposit
The Akshatau large-sized W-Mo deposit occurs in thesoutheastern part of the Zhaman–Sarysu Anticlinoriumnear its boundary with Toqrau Basin, 150 km fromBalkhash City (Figure 6). It is a disseminated quartz vein-greisen Be-W-Mo deposit and is closely related to the topsof the Carboniferous granite complex in both endocontactsand exocontacts, having resources as follows: 65.5 kt of0.10–0.30% WO3, 17.5 kt of 0.04–0.07% Mo, and 16.0 ktof 0.03–0.07% Be (Yefimov et al. 1990).
The Akshatau deposit occurs within Permianleucogranites of the Akshatau multi-stage complexthat intrude Carboniferous volcanic rocks (Figure 10).The Akshatau multi-stage complex is controlled by linearand circular faulted structures and by the intersectionby structural belts of different trends (Burmistrov et al.1990). The Akshatau deposits are closely related to thetops of ore-forming intrusives in both endo- and exocon-tacts. The greisen bodies consist of root, intermediate,and front zones. Most lie within the intermediate zone,
occurring inside granite cupolas or at their wings andridges of different sizes. Enriched deposits are most easilyfound at the tops of granites in mono-dome structures(Daukeev et al. 2004). The ore-forming process has mainlyundergone two stages and four phases: the first stage isthe pneumatolytic hydrothermal stage, comprising themolybdenite quartz phase (440–340◦C) and a complexrare-metal phase (480–250◦C); the second stage is thereal hydrothermal stage, containing the galena-sphalerite-quartz phase (310–150◦C) and the calcite-fluorite-quartzphase (180–60◦C) (Yefimov et al. 1990). The ores containmolybdenite, wolframite, fluorite, and beryl (Figure 9J).
3.2.5. Zhanet Mo deposit
The Zhanet Mo deposit is a medium-sized quartz vein-greisen Mo deposit located 120 km to the northwest ofBalkhash City (Figure 6). It was first explored in 1948 andwas mined for some time, but at present mining is tem-porarily suspended.
The orebody occurs at the intersection of the Akzhal–Aksoran and Akbastay faults. The network Mo-W min-eralization is associated with syenogranite porphyries.Molybdenite mainly occurs in syenogranite porphyries(Figures 9K and 9L) and in late-stage quartz veins andfissures. In the late-stage quartz veins, molybdenite isassociated with fluorite.
The ores contain molybdenite, wolframite, topaz, flu-orite, and beryl. The main ore mineral is molybdenite(Figure 9L), which also has high contents of rare-earth andrare elements. Molybdenites occur mainly in Mo-bearing
Lower Carboniferousvolcanic rocks
CarboniferousStage 1 fine – grained
Stage 1 coarse – grained Stage 2 medium –Hydrothermal
quartz rock
Hornfelsed
Greisenization
zone
zone
Stage 2 fine – grainedleucogranite
grained granite
porphyritic granite
porphyritic granite
Carboniferous quartz
subvolcanic rocks
monzonite and granodiorite
Permian Akshatau intrusion complex
Figure 10. Schematic geological map of the Akshatau quartz-vein greisen W-Mo deposit (modified from Daukeev et al. 2004).
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granite-porphyries and in late-stage quartz veins and fis-sures assuming disseminated and veined shapes. In thelate-stage quartz veins, the molybdenites are associ-ated with fluorite. Wall-rock alterations include potassic-alteration (e.g. K-feldspathization, biotitization), pyritiza-tion, greisenization, and epidotization. Pegmatite veinsformed in the late stage.
4. Methods and results
4.1. Methods
4.1.1. Molybdenite Re-Os dating
Previous works have obtained the Re-Os ages ofmolybdenites from the Borly Cu deposit, the East Kounrad,Zhanet, and Akshatau W-Mo deposits in the NorthBalkhash (Chen et al. 2010), and the Baogutu Cu (Shenet al. 2012b) and Hongyuan Mo deposits (Li et al. 2012) insouthern West Junggar. For comparison, in this study,we measured the Re-Os ages of molybdenites from theSuyunhe W-Mo deposit in southern West Junggar.
The five molybdenite samples used for Re-Os isotopedating were collected from the Suyunhe W-Mo deposit.Re-Os isotope dating of the molybdenite samples wasperformed at the Re-Os Isotope Chronology Laboratory,National Research Centre for Geoanalysis. The chemicalseparation and processing processes of Re and Os, as wellas the mass spectrometry technology, have been describedby Du et al. (2004). The isotope ratio was determined usingthe TJA X-series ICP-MS at the National Research Centrefor Geoanalysis. The uncertainties of model ages alsoincluded the uncertainty of the decay constant (1.02%),and the confidence level was also 95%. Ludwig’s (2003)method was used to process the Re and Os isotope datarelating to molybdenites and to obtain the average ages ofRe-Os.
4.1.2. Major and trace elements
Samples used in this paper were petrographically collectedfrom drill cores for chemical analyses at Suyunhe andBaogutu. They are the four granites at Suyunhe and threediorites at Baogutu. Measurements were carried out at theInstitute of Geology and Geophysics, Chinese Academy of
Sciences (CAS) in Beijing. The analytic procedures aresimilar to those described by Shen et al. (2012a). Majorelements were analysed by XRF-1500 Sequential X-rayFluorescence Spectrometry, with wet chemical determina-tion of FeO and loss-on-ignition. A PQ2 Turbo inductivelycoupled plasma mass spectrometer (ICP-MS) was used toanalyse trace elements and REE.
4.1.3. Nd isotopes
The four samples from the Suyunhe and Baogutu depositswere selected for Sm and Nd isotope composition anal-yses. Measurements were carried out at the Institute ofGeology and Geophysics, CAS. Sm and Nd isotope com-positions were analysed according to a procedure simi-lar to that described by Chen et al. (2002). Proceduralblanks were <100 pg for Sm and Nd. The 143Nd/144Ndratios to 146Nd/144Nd = 0.7219. Typical within-run pre-cision (2 σm) for Nd was estimated at ±0.000013.The values measured for the JMC Nd standard were143Nd/144Nd = 0.511937 ± 7 (2 σm, n = 12) during theperiod of data acquisition.
4.2. Results
4.2.1. Molybdenite Re-Os ages
The concentrations of Re and Os and the osmium isotopiccompositions of five samples of the Suyunhe sulphideores are presented in Table 1. Total 187Re and 187Osconcentrations vary from 49 to 113 ppm and from245 to 581 ppb, respectively. The Re-Os model agesof the five molybdenites obtained in the experiment are302.6 ± 4.9 Ma, 304 ± 4.5 Ma, 306.2 ± 5.1 Ma,296.1 ± 4.4 Ma, and 296.5 ± 4.4 Ma, with a mean valueof 300.7 ± 4.1 Ma, which is interpreted as the age ofmolybdenite crystallization during the formation of theSuyunhe W-Mo deposit.
4.2.2. Major and trace elements
Major and trace element concentrations of the studied sam-ples are listed in Table 2 and plotted in Figures 11–13. Forcomparison, data from the Kounrad, Borly, and Aktogai Cu
Table 1. Re-Os isotope composition of molybdenites from the Suyunhe W-Mo deposit in the southern West Junggar ore belt.
Re (μg/g) Normal Os (ng/g) 187Re (μg/g) 187Os (ng/g) Model age (Ma)
Sample no. Weight (g) Measured 2σ Measured 2σ Measured 2σ Measured 2σ Measured 2σ
SyMo-2 0.00635 89.53 0.95 0.031 0.0347 56.27 0.6 284.4 2.5 302.6 4.9SyMo-2 0.01004 95.77 0.92 0.0475 0.213 60.2 0.58 305.6 2.4 304 4.5SyMo-4 0.00558 180.9 2 0.036 0.121 113.7 1.2 581.6 5.5 306.2 5.1ZK03-180 0.00836 78.91 0.73 0.024 0.1344 49.6 0.46 245.2 2.1 296.1 4.4ZK03-159 0.00573 105.3 0.9 0.0835 0.2808 66.19 0.54 327.8 3 296.5 4.4
Note: Uncertainty for the calculated ages is 1.02% at the 95% confidence level.
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Tabl
e2.
Maj
or(w
t.%)
and
trac
eel
emen
t(pp
m)
abun
danc
eof
rock
sfr
omth
eor
e-be
arin
gin
trus
ions
inth
eso
uthe
rnW
estJ
ungg
aran
dN
orth
Bal
khas
hor
ebe
lts.
Dep
osit
Bao
gutu
Kou
nrad
Bor
ly
Sam
ple
ZK
211-
263
ZK
201-
616
ZK
202-
295
BG
T5-
1aB
GT
5-2a
BG
T5-
3aB
GT
5-4a
ZK
211-
60a
ZK
211-
144a
Xh0
8091
0-2(
1)b
Xh0
8091
0-7(
1)b
KoG
25c
1d5d
2d4d
3dX
h080
912
-9(2
)bX
h080
912
-9(3
)b
Roc
kD
iori
teD
iori
teD
iori
teD
iori
teQ
uart
zdi
orit
eD
iori
teD
iori
teD
iori
teD
iori
teA
dam
elli
teP
Qua
rtz
dior
ite
PQ
rano
dior
ite
Qra
nodi
orit
eG
rano
dior
ite
PG
rano
dior
ite
PG
rano
dior
ite
PQ
uart
zdi
orit
eP
Gra
nodi
orit
eP
Gra
nodi
orit
eP
SiO
257
.72
57.1
357
.84
58.9
562
.05
59.9
859
.92
55.6
857
.72
65.2
463
.86
64.4
867
.366
.39
66.1
866
.863
.51
66.5
165
.94
Al 2
O3
15.2
915
.81
16.0
417
.88
15.7
317
.76
18.0
716
.92
17.0
116
.56
16.6
816
.14
16.9
16.5
315
.07
16.8
17.3
216
.81
15.9
8Fe
2O
32.
562.
611.
161.
742.
030.
870.
621.
921.
52.
933.
144.
291.
932.
152.
342
2.39
3.11
2.87
FeO
5.2
5.3
4.2
1.87
3.44
1.64
1.24
4.76
4.55
1.31
2.05
1.69
1.68
2.24
1.83
2.37
1.76
2.16
MgO
4.93
4.16
4.69
4.35
3.91
4.41
4.81
5.01
4.51
1.82
2.53
2.19
1.24
1.79
2.19
1.65
1.92
2.36
1.6
CaO
5.1
7.21
7.45
7.56
5.44
7.52
7.85
7.07
6.94
1.23
3.45
4.38
3.05
2.63
0.92
2.15
3.09
0.61
2.46
Na 2
O3.
424.
075.
044.
414.
164.
464.
753.
874.
034.
713.
394.
114.
33.
845.
394.
634.
632.
243.
28K
2O
2.16
1.03
0.75
0.72
0.65
0.67
0.37
1.4
1.31
2.42
3.15
2.25
2.03
2.11
2.66
2.45
2.67
3.01
2.66
MnO
0.07
0.12
0.08
0.04
0.06
0.03
0.03
0.09
0.08
0.08
0.11
0.08
0.17
0.04
0.06
0.3
0.14
0.06
0.15
TiO
20.
860.
940.
980.
820.
690.
880.
830.
880.
880.
50.
530.
540.
440.
50.
480.
440.
710.
670.
48P
2O
50.
130.
210.
210.
180.
140.
210.
10.
20.
240.
190.
140.
190.
230.
180.
210.
180.
270.
190.
15L
oi2.
391.
331.
451.
131.
221.
10.
951.
510.
895.
012.
690.
891.
572.
311.
040.
911.
26.
274.
34To
tal
99.8
399
.92
99.8
999
.65
99.5
299
.53
99.5
499
.34
99.7
110
210
1.7
99.5
100.
810
0.1
98.7
810
0.1
100.
210
3.6
102.
0M
g#0.
420.
380.
460.
640.
470.
670.
750.
450.
430.
520.
490.
360.
450.
430.
410.
380.
510.
36A
.R.
1.75
1.57
1.65
1.51
1.59
1.51
1.49
1.56
1.57
2.34
1.96
1.90
1.93
1.90
3.03
2.19
2.11
1.86
1.95
Rb
129
34.4
35.2
43.3
14.6
36.4
13.2
40.0
41.2
29.4
93.7
6921
890
.2S
r54
265
563
274
655
970
774
872
273
948
778
660
627
041
4Y
20.6
16.4
17.6
15.1
14.5
15.4
17.4
13.3
14.9
12.1
16.1
11.1
13.2
14.6
Nb
2.74
3.09
3.27
2.48
3.2
2.69
2.69
2.76
2.96
4.81
6.51
87.
377.
43C
s7.
691.
784.
582.
280.
990.
920.
652.
112.
91B
a42
948
626
222
235
424
022
141
141
853
287
752
852
251
5L
a10
.413
.811
.810
.710
.88.
85.
610
.014
.115
.921
.718
.526
.219
Ce
22.4
29.3
29.6
29.7
22.9
28.1
16.8
21.2
29.5
31.7
48.1
38.8
59.8
40.8
Pr
3.04
3.9
4.1
4.15
3.2
4.03
2.66
3.18
4.45
4.4
4.99
4.56
5.93
4.58
Nd
13.7
16.9
17.7
18.6
14.9
19.2
13.8
13.1
18.2
17.6
17.7
17.8
21.8
17.7
Sm
3.12
3.69
3.9
3.79
2.77
4.31
3.45
3.15
43.
383.
43.
513.
813.
55E
u0.
891.
291.
231.
210.
921.
271.
140.
981.
180.
850.
890.
910.
890.
83G
d3.
033.
133.
283.
362.
873.
783.
532.
713.
392.
572.
832.
522.
792.
78T
b0.
610.
590.
590.
530.
390.
550.
550.
410.
490.
380.
450.
380.
410.
42D
y3.
633.
143.
462.
912.
53.
093.
162.
422.
841.
992.
422.
012.
172.
23H
o0.
720.
60.
660.
570.
490.
590.
620.
490.
560.
390.
510.
410.
410.
45E
r2.
071.
681.
841.
711.
371.
741.
721.
351.
531.
161.
541.
161.
31.
35T
m0.
340.
250.
30.
220.
210.
240.
270.
20.
220.
160.
220.
160.
190.
19Y
b1.
941.
481.
791.
451.
361.
561.
591.
291.
431.
171.
571.
141.
341.
41L
u0.
330.
270.
310.
230.
210.
230.
230.
190.
210.
170.
250.
150.
210.
21Ta
0.17
0.18
0.22
0.14
0.21
0.15
0.14
0.16
0.21
0.91
1.37
0.8
1.56
1.97
Pb
3.87
5.09
4.87
2.96
2.97
2.98
2.77
4.14
3.86
10.4
16.6
12.7
43.2
19.3
Th
1.89
2.17
1.72
3.29
4.09
1.94
1.58
1.22
2.61
5.14
13.6
7.7
14.4
17.9
U1.
390.
610.
771.
131.
030.
550.
40.
561.
291.
753.
591.
75.
27.
28Z
r50
3636
9413
285
9358
9314
015
685
188
139
Hf
1.73
1.13
1.24
2.61
3.9
2.51
2.71
1.7
2.84
3.52
3.86
2.57
4.54
3.62
(Con
tinu
ed)
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Tabl
e2.
(Con
tinu
ed).
Dep
osit
Akt
ogai
Suy
unhe
Eas
tKou
nrad
Zha
net
Aks
hata
u
Sam
ple
A2-
7-5e
A2-
6e
Xh0
809
19-
5(4)
b
Xh0
809
19-
5(5)
bA
Q7c
AQ
13c
ZK
03-
214
ZK
03-
215
ZK
03-
221
SY
4-1
EK
-1e
Xh0
809
10-
10(1
)bK
oeK
16c
ZH
-2-
10c
Xh0
809
15-
5(3)
b
Xh0
809
15-
5(5)
b
Xh0
809
14-
10(1
)bA
qsK
9cA
QS
G3c
Roc
kG
rano
dior
ite
PG
rano
dior
ite
PG
rano
dior
ite
PA
dam
ell
ite
PPo
rphy
ryst
ock
Gra
noph
yre
Alk
ali
gran
ite
Alk
ali
gran
ite
Alk
ali
gran
ite
Alk
ali
gran
ite
Sye
nogr
anit
eP
Alk
ali
gran
ite
Apl
ite
Sye
nogr
anit
eP
Ada
me
llit
eP
Alk
ali
gran
ite
Alk
ali
gran
ite
Leu
cogr
anit
eL
euco
gran
ite
SiO
269
.00
65.1
67.0
466
.89
68.5
268
.37
77.2
675
.97
75.7
77.9
76.2
76.2
576
.88
73.2
71.6
879
.09
7776
.75
76.9
1A
l 2O
315
.516
.515
.34
16.0
316
.94
16.9
211
.29
11.7
12.4
211
.23
12.7
12.6
412
.44
1314
.17
11.6
212
.24
12.1
512
.41
Fe2
O3
1.87
4.26
1.86
1.38
2.92
2.97
0.63
0.54
0.53
0.46
1.18
0.77
0.64
1.62
0.49
0.24
0.16
0.88
0.34
FeO
0.75
0.92
0.5
0.45
0.65
0.1
0.25
0.56
0.32
0.23
MgO
1.5
1.58
1.45
1.61
0.66
0.9
0.23
0.28
0.33
0.16
0.2
0.12
0.07
0.51
0.49
0.05
0.16
0.1
0.06
CaO
1.42
2.91
1.91
1.63
3.12
2.8
0.85
1.19
0.92
0.63
0.63
0.78
0.57
1.09
2.18
0.48
0.54
0.55
0.8
Na 2
O4.
214.
383.
834.
54.
824.
783.
443.
494.
043.
753.
833.
853.
842.
914.
33.
313.
63.
573.
91K
2O
3.96
2.86
3.65
4.29
3.13
3.65
4.45
4.89
4.47
4.25
4.73
4.58
4.79
5.99
4.88
4.42
5.52
4.96
4.4
MnO
0.02
0.02
0.02
0.02
0.05
0.08
0.03
0.03
0.04
0.02
0.05
0.06
0.03
0.05
0.04
0.02
0.06
0.04
0.03
TiO
20.
430.
570.
440.
480.
320.
370.
130.
140.
150.
090.
170.
160.
10.
270.
310.
080.
120.
140.
09P
2O
50.
180.
240.
180.
190.
110.
120.
030.
030.
040.
020.
040.
020.
010.
050.
050.
010.
010.
020.
02L
oi1.
821.
885.
744.
31.
050.
860.
871
0.56
1.17
0.26
0.62
0.38
0.94
1.84
0.86
0.4
0.51
0.7
Tota
l10
010
0.3
102.
210
2.2
101.
610
1.8
99.7
199
.72
99.8
599
.78
100
100.
199
.899
.610
0.9
100.
510
0.0
99.7
99.7
Mg#
0.60
0.57
0.26
0.32
0.28
0.55
0.27
0.40
0.11
0.35
A.R
.2.
872.
192.
532.
982.
312.
494.
714.
724.
525.
154.
594.
384.
944.
433.
564.
545.
985.
094.
39R
b63
.290
.933
4115
316
616
014
214
418
461
862
664
939
754
3S
r71
892
341
968
054
436
972
.782
.211
771
.186
.849
.522
129
92.9
8.87
4.78
1419
.5Y
9.77
8.25
8.82
9.11
4.8
6.2
23.8
25.8
24.9
17.2
10.9
7.86
4.1
15.9
40.9
13.9
8.95
11.7
11.1
Nb
2.8
3.21
68.
358.
139.
868.
2914
1525
.636
.921
.326
23C
s3
3.47
3.88
3.19
Ba
796
1049
994
934
155
182
303
141
271
2446
325
.719
.834
36.6
La
18.7
21.2
19.8
1710
.713
.613
.113
.614
.88.
2135
.938
.231
.931
.460
.731
.738
.364
.745
.5C
e36
.141
.333
.733
.922
25.5
27.9
29.1
3116
.951
.355
.540
.557
.710
945
49.8
84.2
53.8
Pr
4.45
5.47
4.52
4.33
2.58
2.94
3.32
3.32
3.53
1.98
4.75
5.25
2.61
5.64
9.68
3.8
3.58
5.88
3.44
Nd
16.6
20.1
1717
.110
.711
.812
.112
.212
.37.
1213
.815
.45.
717
26.6
8.35
9.14
14.4
7.5
Sm
2.91
3.62
2.92
3.08
1.92
2.05
2.68
2.77
2.52
1.63
1.86
1.98
0.51
2.76
4.23
1.01
1.23
1.86
0.91
Eu
0.78
0.87
0.83
0.89
0.59
0.57
0.21
80.
220.
320.
180.
320.
280.
070.
530.
50.
060.
120.
180.
09G
d2.
42.
512.
142.
161.
21.
242.
352.
462.
41.
571.
71.
320.
352.
293.
20.
780.
931.
240.
74T
b0.
330.
310.
280.
290.
180.
210.
490.
540.
520.
330.
230.
20.
050.
360.
580.
150.
150.
210.
14D
y1.
751.
551.
461.
450.
871.
053.
23.
373.
32.
241.
431.
080.
42.
293.
850.
990.
941.
321.
01H
o0.
340.
290.
270.
30.
180.
230.
679
0.77
0.74
0.53
0.33
0.23
0.09
0.52
0.94
0.27
0.22
0.3
0.28
Er
0.93
0.75
0.82
0.83
0.51
0.64
2.45
2.75
2.57
1.98
1.01
0.75
0.39
1.73
3.6
1.2
0.83
1.22
1.13
Tm
0.14
0.11
0.11
0.11
0.08
0.1
0.48
0.50
0.49
0.38
0.17
0.12
0.08
0.31
0.73
0.27
0.16
0.22
0.24
Yb
0.94
0.71
0.8
0.78
0.55
0.69
3.47
3.94
3.62
3.01
1.21
1.02
0.74
2.44
6.45
2.56
1.55
2.33
2.44
Lu
0.15
0.11
0.12
0.12
0.08
0.09
0.63
80.
70.
620.
530.
20.
180.
150.
461.
130.
50.
30.
480.
51Ta
0.38
0.46
ndnd
1.95
2.08
1.97
1.41
2.37
1.3
2.73
9.17
3.27
1.8
2.3
Pb
8.06
8.68
8.19
10.2
8.7
11.7
22.3
22.1
19.4
18.5
2620
28.6
21.5
22.7
24.5
2133
.518
.5T
h7.
254.
994.
995.
422.
12
22.6
2220
.920
.118
.39.
5716
.714
.216
.828
25.8
60.1
48.3
U1.
593.
450.
780.
840.
80.
818
.79.
3215
.76.
71.
961.
745.
919
.15.
424.
8534
.39
9.2
Zr
98.5
98.5
4844
133
125
128
112
146
6819
712
010
614
813
7H
f2.
652.
661.
451.
436.
135.
665.
625.
484.
382.
545.
035.
644.
15.
976.
7
Dat
aso
urce
s:a S
hen
etal
.(20
09);
bL
iuet
al.(
2012
);c H
einh
orst
etal
.(20
00);
dK
udry
avts
ev(1
996)
;e Cao
etal
.(20
12).
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] at
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1674 P. Shen et al.
Figure 11. Classification diagrams of samples analysed from the ore-bearing rocks studied. (A) total alkalis versus silica; (B) SiO2 versusK2O; (C) SiO2 versus A.R., A.R. = (Al2O3 + CaO + Na2O + K2O)/(Al2O3 + CaO − Na2O − K2O); (D) SiO2 versus Mg#. (E), (F)discrimination diagrams of I- and A-type granitoids (Whalen et al. 1987).
Note: FG, M + I + S-type fractional granite; OGT, non-fractional M + I + S-type granite; I, fractional I-type granite; S, fractional S-typegranite.
deposits and East Kounrad, Zhanet, and Akshatau W-Modeposits are also listed in Table 2.
The loss on ignition (LOI) for the intrusive rocks inthis study ranges from 0.26 to 6.87 wt.%. All major oxideswere LOI-free normalized before petrogenetic interpreta-tion. The ore-bearing rocks from the porphyry Cu depositsshow a relatively large compositional variation, with SiO2
contents ranging from 55.68 to 69.00 wt.%, straddlingfrom diorite to granodiorite (Table 2; Figure 11A). Theyshow variable K2O contents (0.37–4.29 wt.%) and lowand variable A.R. values (1.49–2.98), with calc-alkalinecharacteristics (Figures 11B and 11C). All samples exhibit
coherent chondrite-normalized (Nakamura 1974) REE pat-terns, characterized by relative enrichment of light rareearth elements (LREE) without Eu anomalies (Figure 12).They also have similar E-MORB-normalized (Sun andMcDonough 1989) trace element patterns, characterizedby a negative Nb anomaly and a positive Sr anomaly,and enrichment in large ion lithophile elements (LILE)(Figure 12). Both the REE pattern and spider variationdiagram are comparable with those of adakites from theAustral Volcanic Zone, which are believed to be derivedfrom partial melting of the subducted oceanic crust (Sternand Kilian 1996; Figure 12).
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International Geology Review 1675
Figure 12. Chondrite normalized (Nakamura 1974) REE distribution and patterns of trace elements normalized (Sun and McDonough1989) to E-MORB for ore-bearing granitoids from porphyry Cu deposits.
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1676 P. Shen et al.
Figure 13. Chondrite normalized (Nakamura 1974) REE distribution and patterns of trace elements normalized (Sun and McDonough1989) to E-MORB for ore-bearing granites from quartz vein-greisen W-Mo deposits.
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International Geology Review 1677
The ore-bearing granites in the quartz vein-greisen W-Mo or Mo deposits have the highest SiO2
(71.68–79.09 wt.%), K2O (4.25–5.99 wt.%), andA.R. values (3.56–5.98) and the lowest MgO con-tents (0.10–0.51 wt.%) among samples of this study(Figures 11A–D). They display alkaline and Fe enrichmentcharacteristics and show an evolutionary trend differentfrom that of ore-bearing granitoids in the porphyry Cudeposits. Granites show LREE enrichment and sub-horizontal HREE patterns, with pronounced negative Euanomalies (Figure 13). Compared with the ore-bearinggranitoids in the Cu deposits, granites have the lowest Srcontent (average 59 ppm) and Sr:Y ratios (average 3.78).The E-MORB normalized trace element variation diagramshows bumpy distribution patterns with pronouncedtroughs at Nb, Sr, Eu, and Ti (Figure 13).
4.2.3. Nd isotopes
Measured and initial (back-calculated to 310 Ma) isotopicratios are reported in Table 3. Nd isotopic analyses forthe ore-bearing intrusions from the Balkhash ore belt inKazakhstan are also given in Table 3. All samples from ore-bearing stocks in Suyunhe and Baogutu intrusions show alimited range in their 143Nd/144Nd ratios (Table 3).
The ore-bearing intrusions in the eastern part of theNorth Balkhash and the southern West Junggar ore beltsshow uniform high εNd(t) values (+4.45 to +5.94), exceptfor one at +2.86. Their Nd model ages are very young TDM
(403–671 Ma; Table 3). Although the ore-bearing rocksfrom the porphyry Cu deposits and quartz vein-greisenW-Mo deposits are different chemically (Figure 11), theyshow little variation in isotopic composition (Figure 14A).Ore-bearing rocks from the Cu and W-Mo deposits inthe western part of the North Balkhash ore belt showslightly varied and low εNd(t) values, ranging from –3.03 to +1.83 except for one at +2.56. Their Nd modelages are old (TDM = 828–1170 Ma, except for two youngerat 572 and 658 Ma; Table 3).
5. Discussion
5.1. Metallogenic ages
For comparison, all U-Pb zircon ages of the ore-bearingintrusions and Re-Os ages of molybdenites from the NorthBalkhash metallogenic belt in Kazakhstan and the south-ern West Junggar metallogenic belt in China are listed inTable 4.
5.1.1. Porphyry Cu mineralization
The Baogutu complex in southern West Junggar consistsof main-stage diorites and minor late-stage diorite por-phyries. Secondary ion mass spectrometry (SIMS) zirconU-Pb ages of the main-stage diorites and late-stage diorite
porphyry are 313.0 ± 2.2 and 312.3 ± 2.2 Ma, respectively(Shen et al. 2012b). Molybdenites formed in the mainstage yielded a Re-Os mean model age of 312.4 ± 1.8 Ma(Shen et al. 2012b). Therefore, a porphyry-type Cu min-eralization event occurred in the late Carboniferous in thesouthern West Junggar ore belt.
The SHARMP zircon U-Pb age of the ore-bearingporphyry is 327.3 ± 2.1 Ma for the Kounrad porphyryCu deposit (Li et al. 2012a). The SHARMP zircon ageon granodiorite is 327.5 ± 1.9 Ma (Li et al. 2012a),and SIMS yielded zircon ages from quartz diorite of328.1 ± 2.1 Ma (Cao et al. 2012) for the Aktogaideposit. The SHARMP zircon U-Pb age of the ore-bearing porphyry is 316.3 ± 0.8 Ma for the Borly deposit(Chen, unpublished), and the Re-Os mean model ageis 315.9 Ma for the Borly porphyry Cu deposit (Chenet al. 2010a). Therefore, a porphyry-type Cu mineralizationevent occurred in the Carboniferous in the North Balkhashore belt.
5.1.2. Greisen W-Mo mineralization
In this study, the average model age of molybdenites is300.7 Ma for the Suyunhe W-Mo deposit in the south-ern West Junggar. The zircon U-Pb age of the ore-bearingporphyry is 302 Ma for the Hongyuan Mo deposit, and themolybdenite Re-Os age is 294.6 Ma (Li et al. 2012b).
The zircon U-Pb age of the ore-bearing porphyry is299.7 ± 2.7 Ma for the East Kounrad deposit (Cao et al.2012), 306 ± 1 Ma (Li et al. 2012a) for the Akshataudeposit, and 304 ± 4 Ma (Li et al. 2012a) for the Zhanetdeposit. The molybdenite Re-Os age is 298.0 Ma for theEast Kounrad W-Mo deposit, 295.0 Ma for the Zhanet Modeposit, and 289.3 Ma for the Akshatau deposit (Chen et al.2010a).
Based on the available data, two epochs of ore forma-tion in the North Balkhash and the southern West Junggarore belts can be recognized: Carboniferous (328–312 Ma)and early Permian (289–300 Ma).
5.2. Petrogenesis
The geochemical data do not define a single evolutionarytrend for the Carboniferous and Permian ore-bearing rocksfrom the North Balkhash to the southern West Junggar(Figures 11–13). Moreover, these rocks have different SiO2
contents but possess similar La/Lu ratios (Figure 15),which is not consistent with differentiation of the sameparental magma. Therefore, these rocks were not derivedfrom fractional crystallization of the same parental magma.
5.2.1. Petrogenesis of the Carboniferous granitoids
Experimental studies demonstrate that Mg# is a usefulindex in discriminating melts purely derived from the crust
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Tabl
e3.
Nd
isot
opic
data
for
the
ore-
bear
ing
intr
usio
nsfr
omth
eso
uthe
rnW
estJ
ungg
aran
dN
orth
Bal
khas
hor
ebe
lts.
Dep
osit
Sam
ple
Roc
ksS
iO2
143N
d/14
4N
d±2
σ(p
pm)
εN
d(t)
TD
M(M
a)D
ata
sour
ces
Kou
nrad
Xh0
8091
0-2(
1)A
dam
elli
tepo
rphy
ry65
.24
0.51
2472
5−0
.07
1090
Liu
etal
.(20
12)
Kou
nrad
Xh0
8091
0-7(
1)Q
uart
zdi
orit
epo
rphy
ry63
.86
0.51
2512
150.
5310
20L
iuet
al.(
2012
)K
ounr
adK
oG25
Gra
nodi
orit
e64
.48
0.51
2257
0.72
828
Hei
nhor
stet
al.(
2000
)B
orly
Xh0
8091
2-9(
2)G
rano
dior
ite
porp
hyry
66.5
10.
5124
358
−0.4
611
50L
iuet
al.(
2012
)B
orly
Xh0
8091
2-9(
3)G
rano
dior
ite
65.9
40.
5125
0210
0.09
1040
Liu
etal
.(20
12)
Akt
ogai
Xh0
8091
9-4(
1)Q
uart
zdi
orit
e64
.27
0.51
2815
85.
5154
0L
iuet
al.(
2012
)A
ktog
aiX
h080
919-
5(4)
Gra
nodi
orit
epo
rphy
ry67
.04
0.51
2731
155.
5367
1L
iuet
al.(
2012
)A
ktog
aiX
h080
919-
5(5)
Ada
mel
lite
porp
hyry
66.8
90.
5127
3810
5.44
661
Liu
etal
.(20
12)
Akt
ogai
AQ
1Po
rphy
riti
cG
rano
dior
ite
64.1
0.51
2538
5.58
498
Hei
nhor
stet
al.(
2000
)A
ktog
aiA
Q3
Gra
nodi
orit
e61
.05
0.51
248
4.45
603
Hei
nhor
stet
al.(
2000
)A
ktog
aiA
Q4
Gra
nite
69.7
20.
5125
295.
4150
8H
einh
orst
etal
.(20
00)
Akt
ogai
AQ
7Po
rphy
ryst
ock
68.5
20.
5123
992.
8667
2H
einh
orst
etal
.(20
00)
Akt
ogai
AQ
13G
rano
phyr
e68
.37
0.51
2556
5.94
403
Hei
nhor
stet
al.(
2000
)A
ktog
aiV
E9
73.3
50.
5128
545.
360
0K
röne
ret
al.(
2008
)B
aogu
tuB
GT
5-1
Dio
rite
58.9
50.
5128
59
4.31
522
She
net
al.(
2009
)B
aogu
tuB
GT
5-2
Qua
rtz
dior
ite
62.0
50.
5128
810
4.86
525
She
net
al.(
2009
)B
aogu
tuB
GT
5-3
Dio
rite
59.9
80.
5128
611
4.42
537
She
net
al.(
2009
)B
aogu
tuB
GT
5-4
Dio
rite
59.9
20.
5129
410
6.01
618
She
net
al.(
2009
)B
aogu
tuZ
K20
1-61
6Q
uart
zdi
orit
e57
.13
0.51
258
114.
0650
3T
his
stud
yB
aogu
tuZ
K20
2-29
5D
iori
te57
.84
0.51
261
135.
8545
7T
his
stud
yE
astK
ounr
adX
h080
910-
10(1
)A
lkal
igra
nite
76.2
50.
5125
0912
1.83
1020
Liu
etal
.(20
12)
Eas
tKou
nrad
Koe
K16
Apl
ite
76.8
80.
5123
411.
6257
2H
einh
orst
etal
.(20
00)
Zha
net
Xh0
8091
5-5(
3)A
dam
elli
tepo
rphy
ry71
.68
0.51
2526
151.
5799
9L
iuet
al.(
2012
)Z
hane
tX
h080
915-
5(5)
Alk
alig
rani
te79
.09
0.51
2529
92.
5699
2L
iuet
al.(
2012
)A
ksha
tau
Xh0
8091
4-9(
1)gr
anod
iori
te70
.33
0.51
2424
10−1
.06
1160
Liu
etal
.(20
12)
Aks
hata
uX
h080
914-
10(1
)A
lkal
igra
nite
770.
5124
725
1.11
1080
Liu
etal
.(20
12)
Aks
hata
uX
h080
914-
10(2
)G
rano
dior
ite
69.6
10.
5124
195
−0.8
111
70L
iuet
al.(
2012
)A
ksha
tau
Aqs
K9
Leu
cogr
anit
e76
.75
0.51
229
0.75
658
Hei
nhor
stet
al.(
2000
)A
ksha
tau
AQ
SG
3L
euco
gran
ite
76.9
10.
5120
97−3
.03
1010
Hei
nhor
stet
al.(
2000
)S
uyun
heZ
K03
-215
Alk
alig
rani
te75
.97
0.51
2812
103.
3954
4T
his
stud
yS
uyun
heZ
K03
-221
Alk
alig
rani
te75
.70.
5128
314
3.74
525
Thi
sst
udy
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International Geology Review 1679
Figure 14. (A) εNd(t) versus SiO2; (B) Nd isotopic evolution and Nd isotope data of the ore-bearing rocks. The early to middleProterozoic crust is from Hu et al. (2000).
from those involved in the mantle. Melts from basalticlower crust are characterized by low Mg# (<0.4), whereasthose with Mg# >0.4 can only be obtained with a man-tle component involved (Rapp and Watson 1995). Allore-bearing rocks from the North Balkhash and the south-ern West Junggar have relatively high Mg# (0.36–0.75)(Figure 11D; Table 2), indicating the involvement of man-tle components. In detail, the Kounrad and Borly depositshave relatively low Mg# (0.36–0.52), while the Baogutuand Aktogai have variable and high Mg# (0.38–0.75),indicating more involvement of mantle components.
The Kounrad and Borly deposits have low and negativeεNd(t) (–0.46 to +0.72; Table 3), indicating the involve-ment of the old continental crust of Central Kazakhstan,
whereas the Aktogai and Baogutu have high and posi-tive εNd(t) (+4.45 to +5.94; Table 3), suggesting theinvolvement of the juvenile lower crust (Rapp and Watson1995).
The ore-bearing rocks have high Sr:Y ratios (aver-age = 52), low Y (average = 13 ppm), and high Ba andSr contents (average = 490 and = 613 ppm, respectively),which are comparable to those of modern adakites (Defantet al. 1991; Figure 16). In detail, the Aktogai intrusionexhibits comparable geochemical characteristics to thoseof modern adakites (Figure 16). However, the other intru-sions exhibit some distinct geochemical characteristics. Forexample, compared with adakites, these intrusions haveslightly low and variable Sr:Y ratios (Figure 16). They also
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Table 4. U-Pb zircon ages of the ore-bearing intrusions and Re-Os ages of molybdenites from the southern West Junggar and NorthBalkhash ore belts.
Deposits Ore-bearing intrusions U-Pb ages (Ma) Data sources Re-Os ages (Ma) Data sources
Porphyry Cu depositsBaogutu Diorite 313.0 ± 2.2 Shen et al. (2012) 312.4 ± 1.8 Shen et al. (2012)
Diorite porphyry 312.3 ± 2.2 Shen et al. (2012)Kounrad Adamellite porphyry 327.3 ± 2.1 Li et al. (2012a)Borly Granodiorite 316.3 ± 0.8 Chen (unpublished) 315.9 Chen et al. (2010)Aktogai Granodiorite 327.5 ± 1.9 Li et al. (2012a)
Quartz dioriteporphyry
328.1 ± 2.1 Cao et al. (2012)
Quartz vein-greisen W-Mo depositsSuyunhe Alkali granite 300.7 ± 4.1 This studyHongyuan Granite 302 Li et al. (2012b) 294.6 Li et al. (2012b)East Kounrad Syenogranite 299.7 ± 2.7 Cao et al. (2012) 298.0 Chen et al. (2010)Akshatau Alkali granite 306 ± 1 Chen (unpublished) 289.3 Chen et al. (2010)Zhanet Adamellite porphyry 304 ± 4 Chen (unpublished) 295.0 Chen et al. (2010)
contain high MgO and low SiO2 contents (Figure 11) rel-ative to the adakites (Defant et al. 1991). The above datademonstrate that these intrusions have a genetic affinitybetween the typical adakites and diorites occurring in thenormal arc. In the Sr:Y versus Y diagram (Defant andDrummond 1993) and the (La:Yb)n versus Ybn diagram(Defant and Drummond 1990), the translation field fromadakite to normal arc is plotted (Figure 16).
In the Zr:Nb–Zr diagram, partial melting and frac-tional crystallization show different evolutionary trends(Figure 15B). The ore-bearing rocks in Aktogai andBaogutu display trends comparable to those of the partialmelting process. The ore-bearing rocks in Kounrad andBorly show a transitional evolutionary trend from partialmelting to fractional crystallization.
Based on these results, we propose that the melt of theore-bearing rocks at Aktogai is a product of partial melt-ing of an oceanic slab, while the melt of the ore-bearingrocks at Baogutu could be a product of partial melting ofan oceanic slab and later interaction with the mantle dur-ing ascent, whereas the melt of the ore-bearing rocks atKounrad and Borly is a product of partial melting of anoceanic slab with the involvement of the old continentalcrust of Central Kazakhstan during ascent.
5.2.2. Petrogenesis of the Permian granites
Permian granites in this study are characterized by alkaliand Fe enrichment; they are alkali granites. In the Suyunhe(the southern West Junggar), because of their high εNd(t)values (+3.39 to +3.74; Table 3), the alkali granites areconsidered to have been derived from a juvenile lowercrust. This conclusion is supported by their Nd model ages,ranging from 525 to 544 Ma (Table 3), which are similar tothe age of ophiolites in the West Junggar (Xu et al. 2006;He et al. 2007).
In the East Kounrad, Akshatau, and Zhanet in theNorth Balkhash, the alkali granites have low and negativeεNd(t) (–3.03 to +2.56; Table 3), indicating the signifi-cant involvement of the old continental crust of CentralKazakhstan. This conclusion is supported by their Ndmodel ages ranging from 992 to 1170 Ma, except for twoat 572 and 658 Ma (Table 3).
All alkali granites show variable Zr contents but lessvariable Zr:Nb ratios, indicating a clear fractional crys-tallization trend (Figure 15B). The pronounced negativeEu and Sr anomalies (Figure 13) suggest fractionation ofplagioclase and alkali-feldspar.
Based on these results, we propose that the precursormagma of the alkali granite in the southern West Junggarwas possibly derived from a juvenile lower crust, followedby the fractional crystallization process, and the magmaof the alkali granites in the North Balkhash was possi-bly derived from a mixture of the old continental crust ofCentral Kazakhstan and the juvenile lower crust, followedby the fractional crystallization process.
5.3. Tectonic setting
5.3.1. The basement nature
As the early to middle Proterozoic crust has considerablyenriched isotopic composition (εNd(t) ≤ 8; Hu et al. 2000;Chen and Arakawa 2005), incorporation of even smallamounts of the old continental components in the sourcewould markedly change isotopic composition.
Most local geologists in Kazakhstan believe in anancient continental precursor of Central Kazakhstan(‘Kazakhstan micro-continent’) (e.g. Glukhan and Serykh1996; Popov 1996). In contrast, Heinhorst et al. (2000) andKröner et al. (2008) interpreted the Central Kazakhstanbasement as a juvenile continental crust in the Phanerozoic
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Figure 15. (A) SiO2 versus La:Lu diagram showing that ore-bearing rocks from the Cu and W-Mo deposits have similar La:Lu ratios; (B)Zr:Nb–Zr diagram showing that ore-bearing granitoids from porphyry Cu deposits are controlled by partial melting, whereas ore-bearinggranites from quartz vein-greisen W-Mo deposits are dominated by fractional crystallization. Symbols are the same as in Figure 14.
based on positive εNd(t) (0 to +5.5). Similarly, someauthors (e.g. Wu 1987) propose that the West Junggarterrane is a micro-continent with Precambrian basement,while others (Feng et al. 1989; Carroll et al. 1990) sug-gest that it represents trapped Palaeozoic oceanic crust andarc complexes. Chen and Arakawa (2005) conclude that itshould be dominated by juvenile crust in the Palaeozoicbased on the high εNd(t).
Based on our newly acquired data, together with otheravailable data, we propose that the West Junggar and theeastern part of the North Balkhash share the basement ofthe juvenile crust; in contrast, the basement of the westernpart of the North Balkhash is Precambrian basement withjuvenile crust.
In this study, the available data (Heinhorst et al. 2000;Kröner et al. 2008; Shen et al. 2009, 2012b; Tang et al.2009; Chen et al. 2010a; Li et al. 2012a, 2012b) and ournewly acquired isotopic data for the Carboniferous andPermian ore-bearing intrusions in the North Balkhash andthe southern West Junggar show variable isotopic signa-tures. The Carboniferous and Permian ore-bearing rocksfrom the West Junggar and the eastern part of the NorthBalkhash have very similar positive initial εNd(t) values of+2 to +6 and depleted mantle model ages in the range of403–672 Ma. As shown in Figure 14B, they plot betweenthe boundaries for the juvenile crust and depleted mantle.Therefore, we conclude that the basement of the southernWest Junggar and the eastern North Balkhash should be
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Figure 16. (A) Diagram of Sr:Y versus Y (Defant and Drummond 1993); (B) diagram of (La:Yb)n versus Ybn (Defant and Drummond1990) for ore-bearing granitoids in porphyry Cu deposits. Symbols are the same as in Figure 14.
dominated by juvenile crust formed in the early to middlePalaeozoic and that Precambrian basement must be veryminor, if any.
The Carboniferous and Permian ore-bearing intrusionsin the western part of the North Balkhash plot in both juve-nile and Precambrian crusts (Figure 14B). Contributionsfrom Precambrian crust are remarkable. Therefore, thebasement in the western part of the North Balkhash hasboth Precambrian basement and juvenile crust.
5.3.2. Carboniferous tectonic setting
Confirming the rock series to which they belong is veryimportant to help discriminate the tectonic setting of
the intrusive rocks. In the SiO2 versus K2O diagram(Figure 11B), samples from the Baogutu plot in low-K tholeiite and medium-K calc-alkaline fields, indicatinga transitional character from calc-alkaline to tholeiite.Calc-alkaline rocks are typical constituents of island arcs,whereas tholeiitic rocks may be associated with emerg-ing island arcs (e.g. Miyashiro 1974), mid-ocean ridges,and backarc-basin spreading centres (e.g. Gill 1976). TheBaogutu intrusive rocks are enriched moderately in LREEand have E-MORB-like Nb:Yb ratios (Figure 17). Thusit is very likely that the Baogutu dioritic rocks formedin an immature island arc. All samples from the Aktogaiplot in the high-K calc-alkaline field (Figure 11B). Theyhave a transitional character from calc-alkaline to alkaline
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Figure 17. Th:Yb–Nb:Yb diagram (Pearce and Peate 1995; Sayit and Goncouglu 2009) for ore-bearing granitoids in porphyry Cudeposits. Symbols are the same as in Figure 14.
(Figures 11C and 11D). Alkaline rocks are typical con-stituents of mature island arcs. Since the Aktogai intrusiverocks are highly enriched in LREE and have OIB-likeNb:Yb ratios (Figure 17), the Aktogai intrusive rocks haveformed in a mature island arc. In addition, since all rocksfrom the Baogutu and Aktogai have high εNd(t) (+4.35 to+6.01), the Baogutu and Aktogai intrusive rocks haveformed in an inter-oceanic island arc.
Samples from the Kounrad and Borly plot in high-K and medium-K calc-alkaline fields (Figure 11B). Theyare enriched in LREE and have OIB-like Nb:Yb ratios(Figure 17). In addition, since they have low and negativeεNd(t) (–0.46 to +0.72), the Kounrad and Borly rocks formin an arc setting with a transitional characteristic from acontinental to an inter-oceanic arc.
5.3.3. Permian tectonic setting
From the late Carboniferous to Permian, the Palaeo-AsianOcean began to close and the plate collided with theSiberian plate (Xiao et al. 2008, 2009). The Balkhash andthe West Junggar entered the collision stage, giving rise toextensive granite magmatism. All samples plot in the high-K calc-alkaline field (Figure 11B) and the alkaline field(Figure 11C), indicating that they are alkali granites. Mostalkali granites plot in the I-type granite field (Figures 11Eand 11F). The Permian granites show negative Eu anoma-lies and comparatively high HREE abundances in the REEpatterns and negative Sr anomalies in the spidergrams(Figure 13). In the Rb versus Y + Nb tectonic discrim-ination diagram for granites (Figure 18), the granites ofthe Suyunhe in the southern West Junggar fall into thepost-collisional granites field, while the granites of the East
Kounrad, Zhanet, and Akshatao in Balkhash plot in the syn-collisional granites and volcanic arc granites fields. Thesegeochemical signatures suggest that the granites formed inan arc–continental collision to post-collisional setting.
6. Geodynamic–metallogenic evolution
6.1. Carboniferous geodynamic–metallogenic event
The Kounrad, Borly, and Aktogai in the North Balkhashand Baogutu in the southern West Junggar are typi-cal porphyry Cu deposits formed in the Carboniferous(328–312 Ma). They are characterized by stronglyhydrothermal alteration and widely disseminated vein-let mineralization. Their ore-bearing magma is thesubduction-related calc-alkaline magma with adakite fea-tures and formed in the magma arc setting during theCarboniferous. In detail, the Baogutu Cu deposit formedin an immature island arc and the Aktogai Cu depositformed in a mature island arc, whereas the Kounrad andBorly Cu deposits formed in a transitional arc setting.Therefore, the southern West Junggar and the eastern partof the North Balkhash belong to an inter-oceanic islandarc, and the western part of the North Balkhash is a tran-sitional arc from a continental arc to an inter-oceanic arcduring the Carboniferous (Figure 19). Simultaneously withthe intrusion of these adakites, volatile matter in remnantmagma became saturated, resulting in micro-stockwork-shaped fracturing of porphyry envelopes and countryrocks. The super-saline fluids released during the early-stage magmatic crystallization produced areal dissemi-nated mineralization in the early stage. Ore fluids generatedin the late stage produced sulphide-quartz veinlets andstockworks.
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Figure 18. Rb versus Y + Nb diagram (Pearce et al. 1984) for ore-bearing granite in quartz vein-greisen W-Mo deposits.
Note: ORG, ocean ridge granites; Post-ColG, post-collisional granites; Syn-ColG, syn-collisional granites; VAG, volcanic arc granites;WPG, within-plate granites. Symbols are the same as in Figure 14.
Figure 19. Sketch showing the evolution of geodynamic setting and related magma and ore deposits in the West Junggar and NorthBalkhash. (A), (B) Production of island arc responding to slab subduction and associated calc-alkaline magma and porphyry Cu depositsin the Carboniferous. (C), (D) Accretion of the island arc to the western margin of the Kazakhstan plate in the late Carboniferous (Fenget al. 1989). Following the accretion–collision processes, the alkali granite magma and related quartz vein-greisen W-Mo or Mo depositsform in the early Permian.
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6.2. Permian geodynamic–metallogenic event
The East Kounrad, Zhanet, and Akshatao in the NorthBalkhash and Suyunhe and Hongyuan in the southern WestJunggar are typical quartz vein-greisen W-Mo deposits andformed in the early Permian (289–300 Ma). They are char-acterized by greisen alteration and related vein mineraliza-tion. The ore-bearing granitic magma is collision-relatedalkaline magma. Therefore, during the early Permian, theNorth Balkhash and the southern West Junggar enteredthe collision stage, giving rise to extensive alkaline granitemagmatism, causing W and Mo mineralization (Figure 19).The tectonic transition from Carboniferous subduction toPermian collision could be key to the formation of thegreisen W-Mo deposits in the North Balkhash and thesouthern West Junggar.
The geodynamic–metallogenic events occurred in theNorth Balkhash and the southern West Junggar terraneslike the Lachlan fold belt of Australia and the Appalachianorogen of North America (Blevin and Chappell 1995;Samson et al. 1995). These terranes have a similarmetallogenic spectrum to the North Balkhash and thesouthern West Junggar. The large-scale processes associ-ated with subduction and collision are probably the mostfavourable environments for the generation of magmatic–hydrothermal ore deposits.
7. Conclusions
(1) Two types of mineralization can be distinguishedin the southern West Junggar ore belt in north-west China and the North Balkhash ore belt inKazakhstan: the porphyry Cu deposits (Baogutu,Kounrad, Borly, and Aktogai) and quartz vein-greisen W-Mo deposits (Suyunhe, Hongyuan, EastKounrad, Zhanet, and Akshatao).
(2) Based on available data, two epochs of oreformation can be recognized: Carboniferous(328–312 Ma) and early Permian (300–289 Ma).Carboniferous porphyry Cu deposits are associatedwith calc-alkaline magma with adakite affinity andPermian quartz vein-greisen W-Mo deposits areassociated with alkali magma.
(3) Porphyry Cu deposits formed in a transitional arc(from continental arc to inter-oceanic arc) and aninter-oceanic arc, the latter having a westward mat-uration trend (i.e. from an immature island arc(Baogutu) to a mature island arc (Aktogai)). Quartzvein-greisen W-Mo deposits formed in a collisionto post-collision setting.
(4) Two geodynamic–metallogenic events can bedistinguished: subduction-related calc-alkalinemagma-porphyry Cu mineralization and collision-related alkaline magma-quartz vein-greisen W-Momineralization.
AcknowledgementsThis work was granted by the Innovative Project of theChinese Academy of Sciences (KZCX-EW-LY02), NationalInternational Cooperation in Science and Technology project(2010DFB23390), National Science Fund (41272109, 40972064,41230207, 40725009, 41190071, 41190072), and National305 Project (2011BAB06B01).
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