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![Figure 1. (a) Geological map of Xinjiang (modified after [42]). (b)...](publication/362898849/figure/fig1/AS:11431281080607102@1661349525003/a-Geological-map-of-Xinjiang-modified-after-42-b-Simplified-geological-map-of_Q320.jpg)
The Sayashk tin (Sn) deposit is located within the southern part of the Eastern Junggar orogenic belt in Xinjiang Province and forms part of the Kalamaili alkaline granite belt. There are many Sn polymetallic deposits in the area. To constrain the age, genesis, and tectonic setting of the Sayashk tin deposit in the East Junggar region, we conducted...
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... Th and U contents show a good positive correlation, which is consistent with the characteristics of typical magmatic zircons [61][62][63]. The results of zircons from the medium-fine-grained granites and granite porphyry yield a concordia diagram in Figure 7a,b, where the combined data points yield weighted mean 206 Pb/ 238 U ages of 308.2 ± 1.5 Ma (MSWD = 0.68, n = 24) and 310.9 ± 1.5 Ma (MSWD = 0.22, n = 22), respectively. Therefore, we interpret the mean age as the crystallization age of the medium-fine-grained granites and granite porphyry. ...
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... In mineralogy, Type-I arfvedsonite is an important petrogenetic indicator of alkaline magma, which forms in the reducing condition. The Sayashk hydrothermal Sn deposit occurring in the arfvedsonite granite in this area also reflects the low magmatic oxygen fugacity [82]. A large number of metal sulfides and oxides such as pyrrhotite, chalcopyrite, and ilmenite are developed in the graphite orbicules with rarely magnetite content, which also reflects the characteristics of relatively low oxygen fugacity. ...
The Huangyangshan super-large graphite deposit, located in the East Junggar area of the Xinjiang Province, is hosted in and has closely temporal, spatial, and genetic relationships with the Huangyangshan alkaline granites. There are such silicate minerals as amphibole, biotite, pyroxene, and plagioclase occurring in the graphite-bearing granites. The integration of the electron microprobe analysis (EMPA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) enabled us to reveal the physicochemical conditions and evolution process, as well as the relationship of alkaline magmatism with graphite mineralization. The results show that the amphiboles generally have low Al and high Ti, K, Si, and Fe contents, as well as similar rare-earth elements (REEs) patterns and trace element distribution patterns to granites with significantly negative Eu anomalies. In the analyzed samples, primary biotite belongs to Fe-biotite and has characteristics of high Si and Fe and low Al and Mg contents. In the graphite orbicules, the pyroxene phenocrysts develop multiple zonal structures and are characterized by high Si and low Ca and Fe contents. The dominant plagioclase phenocrysts in the graphite orbicules are oligoclase and andesine, with normal and occasionally oscillatory zoning. The calculated crystallization temperature of the pyroxene, amphibole, and primary biotite in graphite orbicules are 840–1012 °C, 681–761 °C, and 658–720 °C, respectively, corresponding with their crystallization order. The pressure and depth calculation results of the amphibole, representing those of the magmatism, are 157–220 Mpa and 5.95–8.32 km, respectively. Both amphibole and biotite crystallized in a reducing environment with extremely low oxygen fugacity. The elemental compositions of these silicates indicate that the Huangyangshan pluton experienced significant mixing of mafic mantle-derived magma and felsic crust-derived magma. The cores of graphite orbicules were formed in a relatively earlier magmatic stage, while the granites and their dioritic enclaves were formed in a later magmatic stage. During magmatism, the mixing of mantle-derived basic magma had an important influence on the evolution and differentiation of the melts. According to the coexisting sulfides with graphite and compositional difference of amphibole and biotite in the granites and graphite ores, the graphite mineralization might be triggered by a magma mixing process.
