西藏冈底斯东段帮浦铜多金属矿床成矿流体特征

为了探讨西藏冈底斯斑岩铜矿带帮浦铜多金属矿床流体的来源及演化过程,对矿体中的石英斑晶、辉钼矿石英脉、铅锌矿石英脉及方解石脉中所含的流体包裹体进行了岩相学、显微测温和激光拉曼探针以及硫同位素研究。结果表明:与成矿有关的流体包裹体可以分为富气相包裹体、富液相包裹体、含子晶多相包裹体3个类型。流体包裹体的均一温度、盐度及密度测定值均可分为两个区间,分别为300~350℃、390~440℃,6.96~11.63 wt%NaCl、16.76~23.7wt%NaCl及1.05~1.15g/cm3、0.40~1.00 g/cm3。含石盐子晶包裹体所对应的盐度范围是39.38~56.1wt%NaCl。激光拉曼光谱分析表明,含子晶流体包裹体中子矿物为石盐、黄铜矿、白铁矿等,气相包裹体和液相包裹体中气相中含有CO2。石英斑晶与辉钼矿石英脉中低密度气相包裹体与高密度液相包裹体、高盐度含子晶包裹体共生,其均一温度范围一致,但盐度相差较大,指示成矿流体有不混溶作用或沸腾作用,成矿流体来自于岩浆的出熔,金属硫化物直接来源于岩浆;而铅锌矿石英脉与两种不同性质流体的混合作用有关。

Ore-forming fluid characteristics of Bangpu copper polymetal deposit,Eastern Gangdese

In order to investigate the origin and evolution of ore-forming fluid in Bangpu copper polymetallic deposit in Gangdese porphyry copper belt in Tibet, fluid inclusions from quartz of porphyry and molybdenite-bearing veins and Pb-Zn veins and calcite from calcite-bearing veins are studied by petrography, microthermometry, laser Raman microprobe and sulfur isotope methods. The results showed that： fluid inclusions can be divided into gas-rich inclusions , liquid-rich inclusions, sub-crystalline muhiphase inclusions; homogenization temperature, salinity and density can be divided into two intervals, 300 - 350℃, 390 - 440 ℃, 6.96 - 11.63 wt% NaCl, 16.76 23.7wt% NaCl and 1.05 to 1.15 g/cm3, 0.40 - 1.00 g/era3 respectively. Salinity of halite-bearing inclusions are 39.38 - 56.1wt% NaCl. Raman spectroscopy showed the mineral in fluid inclusions containing halite, chalcopyrite, marcasite, etc., CO2 is contained in gas phase of inclusions. The coexistence of low_density gas_rich inclusions, high_density liquid_rich inclusions and high_salinity halite-bearing inclusions with striking salinity differences in the same range of homogenization temperatures in the quartz phenocryst, molybdenite-quartz veins, is attributed to the immiscible separation of fluids, boiling of magma or mixing of fluids, ore-forming fluid exsolution from the magma. The Pb-Zn quartz maybe formed by mixing of two fluids of different nature.