青海双朋西金铜矿床的成矿流体特征及流体来源

通过对双朋西金铜矿床流体包裹体岩相学、测温学及矿石铅、硫同位素等的分析,研究成矿流体性质和演化、成矿流体来源。结果表明:流体包裹体主要为气液两相包裹体,另有少量液相和含子矿物包裹体。包裹体液相成分阳离子以Na+,K+,Ca2+为主,阴离子主要以SO42-,Cl-为主;气相以H2O,CO2为主。均一温度范围为210~370℃和370~460℃,盐度3.0%~6.5%,密度集中于0.600~0.800 g/cm3,压力主要为8.0~20.0 MPa,为中高温、中等盐度、中等密度、中等压力的成矿流体。铅同位素206Pb/204Pb为18.058~18.710,207Pb/204Pb为15.581~15.641,208Pb/204Pb为38.191~38.531,δ(34S)为+3.1×10-3~+6.2×10-3,平均值为+4.42×10-3,成矿流体铅、硫同位素来源为壳幔混合源。

CHARACTERISTICS OF ORE-FORMING FLUID AND GENESIS OF THE SHUANGPENGXI GOLD-COPPER DEPOSITIN QINGHAI PROVINCE

Based on study of the fluid inclusion, thermometry and isotope analyses, the characteristics of ore-forming fluid, fluid evolution and the origin of Shuangpengxi gold-copper deposit were discussed and systematically studied. The results showed that these inclusions are generally consisted of 2 (gas and liquid) phases. and minor liquid and solid sub-mineral phase. The liquid phase includes cations dominated by Na~+,K~+,Ca~2 and ions by SO_4~(2-),Cl~- and gas phase H_2O,CO_2. The homogenization temperature, salinity and density and pressure of the fluid inclusions are medium ones ranged from 210℃ to 460℃,and 3.0% to 6.5%,and 0.600 to 0.800 g/cm~3,and 8.0 to 20.0 MPa, respectively. Analysis of ~(206)Pb/~(204)Pb is in range of 18.058-18.710, ~(207)Pb/~(204)Pb 15.581-15.641, ~(208)Pb/~(204)Pb 38.191-38.531; δ(~(34)S) value +3.1×10~(-3)-+6.2×10~(-3) (average +4.42×10~(-3)) indicating the crust-mantle mixed origin of Pb and S.