西藏隆子县恰嘎锑矿床流体包裹体及H、O、S同位素组成特征

Fluid inclusion and H, O, and S isotopic composition of Qiaga stibnite deposit in Longzi County, Tibet

西藏隆子县恰嘎锑矿位于藏南喜马拉雅特提斯造山带的中东部,属藏南江孜-隆子金锑多金属成矿带。综合研究该矿床的石英流体包裹体特征和H-O-S同位素的组成,发现其流体成矿过程包括:黄铁矿-石英阶段发育富液相包裹体(W型),均一温度集中在170～180℃,盐度w(NaCleq)为2.86%～7.17%,成矿压力平均为47.15MPa,成矿深度平均为1.57 km;石英-硫化物阶段主要发育富液相包裹体(W型),其次为CO2-H2O三相包裹体(C型),均一温度位于200～220℃区间,盐度w(NaCleq)为2.20%～5.11%,成矿压力平均为47.46 MPa,成矿深度平均为1.58 km。矿区总体上流体属含微量CO2气体的中低温、低盐度的NaCl-H2O热液体系。H-O和S同位素结果表明存在地幔流体参与成矿,其赋矿浅变质沉积岩地层也为成矿提供了部分成矿流体,以上研究证明,恰嘎锑矿属于多来源流体浅层中低温矿床。

Located in the central-eastern part of the Tethyan Himalayan tectonic belt, the Qiaga stibnite deposit belongs to the Jiangzi-Longzi Au-Sb polymetallic metallogenic belt. Based on the study of fluid inclusions in quartz and isotopic geochemistry of H-O-S analyzed in this study, The authors revealed that the hydrothermal ore-forming process included several stages： the pyrite-quartz assemblage stage, characterized by rich liquid inclusions （.type W）, with homogenization temperatures clustered at 170-180℃, salinities of 2.86%-7.17%, and average pressure of 47.15 MPa, corresponding to the ore-forming depth of 1.57 km; the quartz-sulfide assemblage stage featured mainly by liquid-rich inclusions （type W）; and the third stage containing CO2-H20 three-phase inclusions （type C）, having homogenization temperatures around 200-220℃, salinities of 2.20%-5.11%, and average pressure of 47.46 MPa, corresponding to an ore-forming depth of 1.58 kin. On the whole, the fluid inclusions belong to the NaCl-H2O hydrothermal system of micrco-CO2 gas, medium-low temperature, low salinity. The results of H-O-S isotopic geochemistry shows that the ore-forming fluids originated from the mantle and/or the hosted-metamor- phic sedimentary rocks. This evidence suggests that the Qiaga stibnite deposit belongs to a multiple sources fluid and shallow medium-low temperature deposit.