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Geological characteristics and mineralization-me tasomati te classification of superlarge Baiganhu tungsten-tin orefield in western Qimantag, East Kunlun Mountains

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... The nature and origin of hydrothermal fluids forming the Baiganhu W-Sn deposit have been the subject of many mineralogical and fluid inclusion studies (Liu et al., 2007;Cao and Lai, 2012;Li et al., 2012;Li et al., 2013;Gao et al., 2014). The source and behavior of the ore-forming elements and whether they were sourced from crustal rocks or magmas, are still poorly understood. ...
... The Baiganhu W-Sn metallogenic belt is located in the western of Qiman Tagh (Fig. 1b), including three deposits at Bashierxi, Baiganhu, and Kekekaerde ( Fig. 2; Li et al., 2006Li et al., , 2012Li et al., , 2013Cao and Lai, 2012;Gao et al., 2014). All the orebodies are hosted in the Mesoproterozoic Xiaomiao Formation of the Jinshuikou Group, and occur on the northwest side of the NE-trending Baiganhua Fault. ...
... The Baiganhu anomaly belt (No. 6) is characterized by a point-like distribution and located in the western segment of the East Kunlun-Qimantag tectonic belt (Fig. 8). This anomalous belt hosts the only large to superlarge tungsten mining field in the East Kunlun region, namely, the Baiganhu W ore field, which consists of four deposits, i.e., Kekekaerde, Baiganhu, Bashierxi, and Awaer (Fig. 5, Table 3) Li et al., 2013). Moreover, this region is a tungsten geochemical block that provides a rich source of ore-forming materials for large W deposits (Xie et al., 2002;Wang et al., 2007b). ...
... 钨锡是中国传统优势矿产资源, 其储量和产量长 期居世界首位, 但由于相关地质找矿工作的投入不足, 加上当前经济社会的快速发展, 目前我国钨锡资源已 显严重不足, 甚至需要从国外进口 [13] . 考虑到钨锡矿产 [14] . 近年来新发现的广 西社洞大型钨钼矿床也是一个与加里东期花岗闪长斑 岩有关的斑岩型、矽卡岩型和石英脉型复合矿床, 该 矿床的发现对华南加里东期钨锡矿床的找矿具有重要 意义 [15] . ...
Article
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Tungsten and tin are important strategic and critical mineral resources, as well as one of China’s most abundant mineral resources. Their distribution is mainly concentrated in the South China block, followed by the Kunlun-Qilian-Qinling-Dabie orogenic belt, the Tianshan-Xingmeng orogenic belt, and the Tibet-Sanjiang orogenic belt. The tungsten and tin resources in South China are mainly concentrated in the Nanling tungsten-tin metallogenic belt, the northern Jiangxi-southern Anhui tungsten metallogenic belt, the Youjiang-Guibei tin metallogenic belt, and the southeast coastal tungsten-tin metallogenic belt. The formation of tungsten and tin deposits in China spans a large period of time, from Proterozoic to Cenozoic, but the Mesozoic Yanshanian mineralization is the most important. There are five main types of primary tungsten-tin deposits in China, namely, porphyry, greisen, skarn, quartz vein, and cassiterite-sulfide. In addition, there are also other types such as altered granite, hydrothermal breccia, and low-temperature hydrothermal vein. Many tungsten-tin deposits are often not of a single genetic type, and multiple mineralization types commonly co-exist in a deposit. Most of the granitoids associated with tungsten mineralization are thought to be S-type granite derived from partial melting of continental crustal materials, while the granitoids associated with tin deposits include I-type and A-type in addition to the S-type granite. Crust-mantle interaction plays an important role in generation of the Sn-bearing granites. Nd-Hf isotope studies show that beside the Sn-bearing granites, some W-bearing granites also have mantle-derived contributions. Whether it is W-bearing or Sn-bearing granite, a highly evolved feature is often more favorable for mineralization. The composite granitoids in South China are closely related to multiple tungsten-tin mineralization. Many tungsten and tin deposits in China are often co-produced with mineralization of other rare metals. According to the combination of ore elements, they mainly include the following three types: W-(Sn)-Be (including Sn-Be), W-(Sn)-Nb-a (including Sn-Nb-Ta), and Sn-Li-Rb-Nb-Ta. All of them are closely related to highly evolved peraluminous granites. The source of ore-forming fluids in most tungsten-tin deposits is closely related to magmatic hydrothermal activity, and some deposits also have characteristics of multi-source fluids. The temperature and salinity of ore-forming fluids vary widely, and the composition of the fluid system is also complex in many cases. Oxygen fugacity plays an important role in the transportation and precipitation of tin, but such an effect on tungsten is still in debate. The formation of many tungsten-tin deposits is generally controlled by a number of factors, such as temperature dropping, fluid mixing, fluid immiscibility, fluid boiling, and water-rock interaction.
... This mid-Paleozoic collision event (Caledonian Orogeny) induced partial melting of the sediments and upper continental crust, and generated the Silurian granite plutons. The CO 2 -rich magmatic fluids sourced from the granitic intrusion formed the Qiman Tagh W-Sn ore belt, which is indicated by the direct spatial relationship between the quartz veins and granite stocks ( Fig. 10b; Li et al., 2006;Li et al., 2013;Gao et al., 2014). In the post ore stages, the fluid inclusions have low salinities and low temperatures, indicating cooling and dilution of the fluids, which is possibly caused by the progressive inflow and mixing of meteoric water (Fig. 10b). ...
Article
The Qiman Tagh W-Sn ore belt is located in the westernmost sector of the East Kunlun Orogen, NW China. It has been recognized as a unique W-Sn belt that formed in the early Paleozoic and related to closure of the Proto-Tethys. To understand the evolution of ore-forming fluids and its relationship with the tectonic setting of East Kunlun Orogen, we report the results obtained from fluid inclusion and H-O isotopic studies of ores and quartz veins for the Qiman Tagh W-Sn ore belt. Mineralization in Qiman Tagh includes four stages characterized by quartz-cassiterite-wolframite assemblage stage 1, quartz ± scheelite assemblage stage 2, quartz-polymetallic sulfides stage 3, and ore-barren veins stage 4. The former two stages are conducive to mineralization, while the latter two stages are less important. The fluid inclusions are distinguished between CO 2-H 2 O (C-type) and NaCl-H 2 O (W-type) in composition, containing a trace of CH 4 , N 2 , C 2 H 6 , SO 2 , and CO 3 2-. Cassiterite and quartz in stage 1, instead of wolframite, contain a great deal of C-type inclusions. All inclusions in minerals of stage 1 yield homogenization temperatures of 230.1-384.1°C (peaking at 310-320°C), with salinities lower than 14.76 wt% NaCl equiv. and bulk densities of 0.63-0.89 g/cm 3. The stage 2 minerals contain both two types of inclusions, yielding homogenization temperatures of 183.4-335.9°C (peaking at 280-290°C), with salinities lower than 14.53 wt% NaCl equiv. and bulk densities of 0.66-0.97 g/cm 3. Fluid inclusions in minerals of stages 3 and 4 are mainly W-type and homogenized at temperatures of 140.6-277.6°C (peaking 210-220°C), and 116.9-255.1°C (peaking 160-170°C), respectively. The H-O isotopic systematics shows that the fluids were dominated by magmatic water in stages 1 and 2, but by meteoric water in stages 3 and 4. Integrating all the geological and geochemical data, we conclude that the fluids forming the Qiman Tagh W-Sn ore belt evolved from granite-derived, CO 2-rich and reducing, to meteoric water-dominated, CO 2-poor and oxidizing. Fluid immiscibility, cooling and interaction with rocks are main mechanisms for metallic deposition.
Chapter
Tungsten and Sn deposits in China are widely distributed in the South China block (i.e., Yangtze craton-Cathaysian block), Himalaya, Tibetan, Sanjiang, Kunlun, Qilian, Qinling, Dabie, and Sulu orogens, and Central Asian orogenic belt. Among these, the South China block hosts the majority of the mineralization with about 73% (9.943 million tonnes WO3) and 85% (6.561 million tonnes Sn) of the country’s total W and Sn resources, respectively. The W resource mainly occurs as skarn (63%), quartz-vein (17%), porphyry (17%), and greisen (3%) Sulu deposits, whereas Sn is present in skarn (81%), quartz veins that are typically tourmaline-bearing (6%), sulfide-rich veins or mantos (5%), greisen (5%), and porphyry (3%) Sulu deposits. The W and Sn mineralization formed during numerous events from Neoproterozoic to Paleocene with a peak in the period from the Middle Jurassic to Early Cretaceous, and with an uneven spatial and temporal distribution pattern. The Neoproterozoic Sn (W) deposits (850–790 Ma) occur on the southern and western margins of the Yangtze craton, the early Paleozoic W(Sn) deposits (450–410 Ma) are mainly distributed in the northern Qilian and the westernmost part of the eastern Kunlun orogens, the late Paleozoic Sn and W deposits (310–280 Ma) are mainly developed in the western part of the Central Asian orogenic belt, the Triassic W and Sn deposits (250–210 Ma) are widely scattered over the whole country, the Early Jurassic to Cretaceous W and Sn deposits (198–80 Ma) mainly occur in eastern China, and the late Early Cretaceous to Cenozoic Sn and W deposits (121–56 Ma) are exposed in the Himalaya-Tibetan-Sanjiang orogen. The petrologic characteristics of W- and Sn-related granitoids in China vary with the associated ore elements and can be divided into the Sn-dominant, W-dominant, W-Cu, and Mo-W (or W-Mo) groups. The granitoids associated with the Sn- and W-dominant magmatic-hydrothermal systems are highly fractionated S- and I-type, high-K calc-alkaline and (or) shoshonitic intrusions that show a metaluminous to peraluminous nature. They exhibit enrichments in F, B, Be, Rb, Nb, and Ta, depletions in Ti, Ca, Sr, Eu, Ba, and Zr, and strongly negative Eu anomalies. The granitoids associated with W-Cu and W-Mo deposits are of a high-K calc-alkaline to shoshonitic nature, metaluminous, depleted in Nb and Ta, and display weakly negative Eu anomalies. Granitoids associated with Sn- and W-dominant deposits are reduced, whereas those linked to W-Cu and Mo-W deposits are relatively more oxidized. The magma sources of W-dominant granitoids are ancient crust, whereas those connected with Sn, Mo-W, and W-Cu deposits are from variable mixing of ancient and juvenile crustal components. The spatial and temporal distribution pattern of W and Sn deposits in China is intimately related to the regional geodynamic evolution. The Neoproterozoic Sn deposits are associated with peraluminous, highly fractionated, and volatile-enriched (boron and fluorine) S-type granites sourced from the melting of an ancient crust in a postcollisional setting related to the assembly of the Rodinia supercontinent. The early Paleozoic W deposits are genetically associated with highly fractionated S-type granites formed during postcollisional events and were derived from the partial melting of a thickened continental crust in the context of Proto-Tethyan assembly. Granitoids associated with late Paleozoic Sn and W deposits were derived from the melting of an ancient and juvenile crust with I-type affinity associated with the closure of the Paleo-Asian Ocean. Although the Triassic W and Sn deposits are related to the assembly of Asian blocks within the Pangea supercontinent, their geologic settings are variable. Those in the South China block and the Himalaya-Tibetan-Sanjiang belt are associated with collision and magma derivation through the partial melting of a thickened continental crust, whereas in the Kunlun-Qilian-Qinling-Dabie-Sulu orogen and the Central Asian orogenic belt, a postcollisional extensional setting dominates. The Early Jurassic (198–176 Ma) W deposits, located in the northern part of northeast China, are associated with highly fractionated I-type granites derived from melting of juvenile crust and emplaced during the subduction of the Mongol-Okhotsk oceanic plate. The extensive group of Middle Jurassic to Cretaceous W and Sn deposits formed at two stages at 170 to 135 and 135 to 80 Ma. The former stage is associated with highly fractionated S- and I-type granites that are the products of partial melting of thickened crust with heat input possibly derived from a slab window associated with the Paleo-Pacific oceanic plate subduction beneath the Eurasian continent. The later stage is closely associated with NNE-trending strike-slip faults along the Eurasian continental margin and is coeval with the formation of rift basins, metamorphic core complexes, and porphyry-epithermal Cu-Au-Ag deposits. These processes, which were instrumental for the formation of a wide range of mineral deposits, can be ascribed to the regional lithospheric thinning and delamination of a thickened lithosphere and thermal erosion in a postsubduction extensional setting. The 121 to 56 Ma Sn deposits in the Himalaya-Tibetan-Sanjiang orogen are associated with S-type granite or I-type granodiorite emplacement in a back-arc extensional setting during Neo-Tethys plate subduction.
Article
The Qiman Tagh of the East Kunlun Orogen, NW China, lies within the Tethysides and hosts a largeW–Sn belt associated with the Bashierxi monzogranite. To constrain the origin of the granitic magmatism and its relationship withW–Sn mineralization and the tectonic evolution of the East Kunlun Orogen and the Tethys, we present zircon U–Pb ages and Hf isotopic data, and whole-rock compositional and Sr–Nd–Pb isotopic data of the Bashierxi monzogranite. The granite comprises quartz, K-feldspar, plagioclase, and minor muscovite, tourmaline, biotite, and garnet. It contains high concentrations of SiO2, K2O, and Al2O3, and low concentrations of TiO2 and MgO, indicating a peraluminous high-K calc-alkaline affinity. The rocks are enriched in Rb,U, Pb, and light rare earth elements, and relatively depleted in Eu, Ba, Nb, Sr, P, and Ti, and are classified as S-type granites. Twenty zircon grains yield a weighted mean 238U/206Pb age of 432±2.6 Ma (mean squareweighted deviation=1.3), indicating the occurrence of a middle Silurian magmatic event in the region. Magmatic zircons yield εHf(t) values of −6.7 to 0.7 and corresponding two-stage Hf model ages of 1663–1250 Ma, suggesting that the granite was derived from Mesoproterozoic crust, as also indicated by 207Pb/206Pb ages of 1621–1609 Ma obtained from inherited zircon cores. The inherited zircon cores yield εHf(t) values of 8.3–9.6, which indicate the generation of juvenile crust in the late Paleoproterozoic. Samples of the Bashierxi granite yield high initial 87Sr/86Sr ratios and radiogenic Pb oncentrations, and negative εNd(t) values. Isotopic data from the Bashierxi granite indicate that it was derived from partial melting of ancient (early Paleozoic to Mesoproterozoic) sediments, possibly representing recycled Proterozoic juvenile crust. Middle Silurian granitic magmatism resulted fromcontinental collision following closure of the Proto-Tethys Ocean. The Qiman Tagh represents a Caledonian orogenic belt containing S-type granites and associated W–Sn deposits.
Article
Abundant granitoids are exposed along the East Kunlun orogenic belt (EKOB), and many skarn deposits occur at the contacts between intrusions and strata. One such is the Xiaowolong deposit, a skarn-type tin polymetallic deposit that is temporally and spatially associated with porphyry monzogranite. Tin mineralization is mainly hosted by the skarn. In this study, we reported zircon and cassiterite U–Pb ages, whole-rock geochemistry, and Sr–Nd–Hf isotopic data, and used these to constrain the timing of intrusion and mineralization in the Xiaowolong deposit and identify the origin of the ore-related granites and the link between Sn mineralization and granitic magmatism. Age determinations by LA-ICP-MS U–Pb zircon dating indicated that the porphyry monzogranite formed at 260.0 ± 0.7 Ma. Cassiterite from the ore-bearing skarn yielded a Tera-Wasserburg U–Pb lower intercept age of 258.0 ± 3.7 Ma. These ages suggested that both granitic intrusion and related Sn mineralization in the Xiaowolong deposit were initiated during the Permian (ca. 260 Ma). The porphyry monzogranites had high SiO2 (71.26–73.13 wt%) and Al2O3 (13.84–14.46 wt%) contents, were alkali-enriched (K2O + Na2O = 7.08–7.69 wt%), had A/CNK values that ranged from 1.01 to 1.05, were enriched in light REEs and large ion lithophile elements such as Rb, Th, U and K, were depleted in high field strength elements, and had relatively low Zr, Nb, Y and Ce contents. They thus exhibited the geochemical characteristics of I-type granite. The porphyry monzogranite had consistent negative whole rock ɛNd(t) (−6.8 to −7.1) and magmatic zircon ɛHf(t) values ranging from −7.4 to −1.6, and two-stage Hf model ages ranging from 1393 Ma to 1758 Ma. Detailed elemental and isotopic data demonstrated that the porphyry monzogranite were derived from partial melting of ancient crustal source, and emplacement in a subduction tectonic setting. The Xiaowolong tin mineralization event indicated that the EKOB has great potential for exploration focusing on Permian-Triassic Sn skarn deposits.
Article
The Qiman Tagh of the East Kunlun Orogen, NW China, lies within the Tethysides and hosts a large W–Sn belt associated with the Bashierxi monzogranite. To constrain the origin of the granitic magmatism and its relationship with W–Sn mineralization and the tectonic evolution of the East Kunlun Orogen and the Tethys, we present zircon U–Pb ages and Hf isotopic data, and whole-rock compositional and Sr–Nd–Pb isotopic data of the Bashierxi monzogranite. The granite comprises quartz, K-feldspar, plagioclase, and minor muscovite, tourmaline, biotite, and garnet. It contains high concentrations of SiO2, K2O, and Al2O3, and low concentrations of TiO2 and MgO, indicating a peraluminous high-K calc-alkaline affinity. The rocks are enriched in Rb, U, Pb, and light rare earth elements, and relatively depleted in Eu, Ba, Nb, Sr, P, and Ti, and are classified as S-type granites. Twenty zircon grains yield a weighted mean ²³⁸U/²⁰⁶Pb age of 432 ± 2.6 Ma (mean square weighted deviation = 1.3), indicating the occurrence of a middle Silurian magmatic event in the region. Magmatic zircons yield εHf(t) values of −6.7 to 0.7 and corresponding two-stage Hf model ages of 1663–1250 Ma, suggesting that the granite was derived from Mesoproterozoic crust, as also indicated by ²⁰⁷Pb/²⁰⁶Pb ages of 1621–1609 Ma obtained from inherited zircon cores. The inherited zircon cores yield εHf(t) values of 8.3–9.6, which indicate the generation of juvenile crust in the late Paleoproterozoic. Samples of the Bashierxi granite yield high initial ⁸⁷Sr/⁸⁶Sr ratios and radiogenic Pb concentrations, and negative εNd(t) values. Isotopic data from the Bashierxi granite indicate that it was derived from partial melting of ancient (early Paleozoic to Mesoproterozoic) sediments, possibly representing recycled Proterozoic juvenile crust. Middle Silurian granitic magmatism resulted from continental collision following closure of the Proto-Tethys Ocean. The Qiman Tagh represents a Caledonian orogenic belt containing S-type granites and associated W–Sn deposits.
Article
The newly discovered Baiganhu W-Sn ore district in Qimantag of East Kunlun orogenic belt provides a key window to insight into the W-Sn mineralization in Northwest China. In this paper, the authors present results from the ⁴⁰Ar/³⁹Ar dating of two muscovite samples collected from the ore- bearing quartz veins in the Baiganhu W-Sn ore district, which yielded two ⁴⁰Ar/³⁹Ar plateau ages of 422.7 ± 4.5 Ma and 421.8 ± 2.7 Ma, respectively. These two samples also yielded consistent (within errors) isochronal and inverse isochronal ages of 424 ± 15 Ma and 418 ± 24 Ma, respectively, suggesting that the analytical results are reliable. The new plateau ages show that the mineralization occurred in the Late Silurian, associated with the tectonic- thermal events induced by the closure of Proto-Tethys. The post-subduction continental collision caused the formation of granitic magmas sourced from re- melting of the metalliferous metamorphosed Proterozoic sediments. The W-Sn mineralization resulted by the hydrothermal fluids exsolved from the granitic magmas during their upward emplacement.
Article
The Baiganhu W–Sn orefield in the southeastern Xinjiang Uygur Autonomous Region is associated with Caledonian S-type syenogranites and metasediments of the Paleoproterozoic Jinshuikou Group. Four types of garnets have been identified in the orefield using petrographic and major and trace element data. Grt-I garnets are generally present as inclusions within magmatic quartz in the syenogranites, with end-member formulas of Sps45–53Alm46–53Adr0–1Grs0–1Prp0–1 and rare earth element (REE) patterns that are enriched in heavy REE (HREE) and contain strong negative Eu anomalies. Grt-II garnets are associated with tourmaline and quartz and occur in interstices between feldspars within the syenogranites. In general, the Grt-II garnets have end-member formulae (Sps64–70Alm29–34Adr0–1Grs0–2Prp0) and REE patterns that are similar to the Grt-I garnets although they are more spessartine-rich and contain higher concentrations of HREE. Grt-III garnets coexist with clinopyroxenes and Mo-rich scheelites within skarns developed along the syenogranite and marble contact. Their compositions are Adr62–88Grs1–18Sps3–12Alm0–8Pyr0 and they have relatively flat REE patterns with no negative Eu anomalies. Grt-IV garnets are present as massive aggregates that are often cross-cut by Mo-poor scheelite-bearing calcite veins. Their end-member formulas are Adr4–22Grs62–73Sps5–16Alm2–10Pyr0 and they have slightly domed REE patterns without negative Eu anomalies. Both Grt-III and Grt-IV garnets contain lower concentrations of the HREE (2–3 and 4–32 ppm, respectively) than Grt-I and Grt-II garnets (682–1352 ppm with Y = 1558–2159 ppm, and 6051–12831 ppm with Y =9663–13333 ppm, respectively).
Article
Baiganhu tungsten-tin ore field is located in Ruoqiang County, Xinjiang. It is in the west of Qimantage mountain, East Kunlun and consists of four deposits of Baiganhu, Kekekaerde, Bashierxi and Awaer. These deposits are spatially associated with the Caledonian Bashierxi Magmatic Series. With particular focus on the Baiganhu deposit, we conducted detailed studies on the petrology, geochronology and geochemistry of the causative granite and discuss its characteristics, genetic type and the relationship with W-Sn mineralization. The causative granite is syenogranite based on slice identification. LA-MC-ICP-MS zircon U-Pb dating reveals that the syenogranite was emplaced at 413.6 ± 2.4Ma (MSWD = 0.36, n = 30). Our and previously published ages and geochemical data of the plutons in the Baiganhu area together show that the S-type granites and A-type granites are coexisting in Bashierxi Magmatic Series and they were formed in a post-collisional setting during the Middle Silurian-Early Devonian (433∼413Ma). Baiganhu syenogranite contains magmatic garnets and muscovites and the values of A/CNK and A/NK are in the range of 1.07 ∼ 1.11 and 1.45 ∼ 1.49, respectively, with a relatively low zircon saturated temperature and high field strength elements (HFSEs) content. Thus this plu ton is peraluminous and high-K calc-alkaline S-type granite. It formed during the late stage of Bashierxi Magmatic Series and has a closely genetic connection with the tungsten-tin mineralization. We suggest that more attention should be payed to the buried or apophysis-like syenogranite during the further exploration for tungsten-tin in this area. Whereas the monzogranite and alkali feldspar granite contain hornblendes and biotites which penetrate in the interstices between magmatic feldspar and quartz or even enclave magmatic quartz. They have relatively high K2O content (5.25% ∼6.29%), with A/CNK ranging from 0.92 to 1.02, thus belong to metaluminous or weakly peraluminous shoshonite series. Their zircon saturated temperature (866 ∼ 917°C), all alkali content (8.30% ∼ 9.69%), Σ REE content (200×10-6-413×10-6) and HFSEs content such as Zr, Nb, Ce and Y (Zr + Nb + Ce + Y =556 × 10-6 -1006 × 10-6) all are obviously high thus belong to the shoshonite series A-type granites. It is inferred that rare and rare earth element mineralization related to A-type granite may be found in the Baiganhu and adjacent region.
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