The Volatile Compositions And Its Geological Implications Of Xiangshanzhong Cu-Ni Sulfide Deposit In North Xinjiang, China

The copper-nickel deposit of East Tianshan orogenic belt of Xiangshan, Huangshan, and Baixingtan is a product of Neopaleozoic mantle-derived magma events. Xiangshan magmatic deposit is the only copper-nickel sulfide deposit that coexists with titaniferous oxide deposit which bears a completely different mineralization environment, which is of significance for understanding the magmatic mantle source composition, mineralization dynamics, fluid magma composition, metallogenic magma fluid medium environment, redox conditions and sulfur saturation process of Xiangshan deposit. This paper has studied peridotite, pyroxenite and gabbro from the Xiangshan copper-nickel sulfide deposits, including fluid component analysis and carbon isotopic composition analysis to explore the origin of magmatic evolutionary conditions,fluid stream composition and sulfur saturation factor. The main conclusions are listed below:1. The volatile fluids Xiangshan copper-nickel sulfide deposit were mainly released at 200-400, 400-900, and 900-1200 ℃, the average fluid content of which were 59.2, 18054.8 and 2405.5mm3/g respectively. H2O(18369.95mm3/g)is the largest component of the volatiles released. Secondary components are CO2, H2, CO, N2, the content of which were respectively 870.3, 755.0, 240.1, and 160.8mm3/g. H2 O is much higher than Baimazhai Large Igneous Provinces and regions Binchuan samples.2. The total amount of fluid component of each mineral lowers by their precipitation sequence from peridotite(21592.0 mm3 /g), pyroxenite(20948.1 mm3/g) and gabbro(9198.1 mm3/g). Fluid in the mid-magmatic evolution is significantly higher than other periods with an average value of 2056.27 mm3/g. The average content of reducing gas H2(749.8 mm3/g) shows higher values, indicating a reductive environment of magmatic evolution.3. The carbon isotopic composition of CO2 and CH4 for the Copper-Ni deposit in the middle of Xiangshan is related to the origins of the mantle, crust and organic matter. δ13CCO2 and δ13CCH4 of gabbro are significantly lighter than the other two rocks. There is a positive linear correlation between CO2 and carbon isotope values of CO2 emissions。CH4, C2H6 and C3H8 exhibit a positive sequence distribution with the increasing of C. C4H10 and C3H8 appear in reverse order.4. The fluid component of the Copper-Ni deposit in the middle of Xiangshan is characterized by high content of H2 O and alkane carbon isotopic composition of organic thermal cracking formation. It indicates that the magma is originated from the mantle, and in the evolution of the magma, some crust substances are possibly involved. which may derive from ocean sediment organic cleavage. H2 O in the magma maybe originate in ocean subduction plate.5. the recirculation of the subducting plate, in the magma source area of the Copper-Ni deposit in the middle of Xiangshan,provides subduction material and H2 O for the magma,The high H2 O content was conducive to paltial melting. Sulfur saturation mechanism of the Copper-Ni deposit in the middle of Xiangshan maybe is increasing CO2 content causes FeO reduction in the magma, and Si-rich crust contamination,...