Comparison Study On Genesis And Features Of The Cu-Ni Sulfide Deposits In Eastern Tianshan Area, Xinjiang Province

There widely distribute mafic-ultra mafic magmatic plutons with Cu-Nisulfide mineralization in Eastern Tianshan area, North Xinjiang Province, whichhas been one of the key magmatic Cu-Ni sulfide mineralized zones in China. Inthis study, the author focuses on10respective mafic-ultra mafic intrusions locatedin Eastern Tianshan area, including Huangshan, Huangshandong, Xiangshan, Hulu,Tulaergen, Tudun, Baishiquan, Shixi Cu-Ni mineralized plutons and Qiatekaermafic dyke, then, further discusses the magmatic source, evolution andmineralization of these10typical mafic-ultra mafic intrusions, based on thesystematic research on their geology, petrology and, mineralogy, geochemistry andgeochronology. It exhibits that the mafic-ultra mafic intrusions with Cu-Ni sulfidemineralization can be subdivided into two structural systems: one is controlled byKangguer deep faults and its derived secondary faults. The other is controlled byAqikuduke-Shaquanzi deep faults and its derived secondary faults. Themineralization of these9mafic-ultra mafic intrusions can be further divided intosegregation-type deposits (including Huangshan, Huangshandong and Tudun) andvolcanic channel-type deposits (including Hulu, Xiangshan, Tulaergen, Baishiqianand Tianyu). It’s noted that the Xianshan deposit contains both copper-nickelmineralization and vanadium-titanium mineralization, where the former one is alitter younger then later one. In these Cu-Ni sulfide deposits, their mineralizedpetrology contains pyroxenite-peridotite, olivine-pyroxenite, peridotite, pyroxenite,gabbro, metal minerals contains chalcopyrite, pyrrhotite, pentlandite etc. There aresome early-stage vanadium-titanium magnetite minerals distributed in theXiangshan deposits, furthermore, there are Argentian pentlandite solid solutionbearing in the chalcopyrite in Hulu deposit, where the Ag contents was reportedthe highest one in the Argentian pentlandites all over the world. Each copper-nickel sulfide mineralized mafic-ultra mafic intrusions was derived from high-Mg,low-PGE and water-enriched parent magma, which was probably from PGE-depleted, arc-volcano mantle source, or contaminated by oceanic crust. Theprimary magma of the mineralized mafic-ultra mafic intrusions located in theKangguer deep faults and its derived secondary faults belt was relatively higher- degree mantle melting than what located in the Aqikuduke-Shaquanzi deep faultsand its derived secondary faults belt. According to their geochemical analysis andcalculation, the curst contamination degrees of these mafic-ultra mafic intrusionswere characterized as that Huangshan, Hulu and Tulaergen mineralized mafic-ultramafic intrusions (about10-20%or more) higher than Huangshandong, Xiangshan,Tudun, Baishiquan, Shixi and Qiatekaer mafic-ultra mafic intrusions (about10%),while Tianyu mafic-ultra mafic intrusion experienced lowest curst contaminationdegree (about1-5%). Though the crustal contamination in the early evolution stageof the mafic magma was the most popular mechanism to generate sulfur saturationin these Cu-Ni sulfide deposits, there also multi-type other mechanisms togenerate sulfur saturation in different deposits, including (1) the sulfur saturationin Huangshan deposit was generated by high-degree crustal contamination in thelater evolutional stage of the mafic magma, which experienced olivine fractionalcrystallization in early evolutional stage,(2) the sulfur saturation in Huangshandeposit was probably controlled by the accession of the external hydrothermalfluids,(3) the sulfur saturation in Xiangshan deposit was affected by the mixing ofyounger mama and (4) the sulfur saturation in Tulaergen deposit was probablyaffected multi-stage pulse magmatic activities with different crustal contamination.