南秦岭柞水县冷水沟铜钼金矿床成矿流体、H-O-S同位素特征及成矿作用

冷水沟矿床位于南秦岭山阳-柞水地区,是秦岭地区发现的与复式岩体有关的铜钼金矿床,矿化类型可分为产于岩体内的斑岩型铜钼矿化、产于岩体与碳酸盐岩接触部位矽卡岩型铜矿化和产于斜长角闪岩内的构造蚀变岩型金矿化。流体包裹体研究表明,斑岩型铜钼矿石中发育水溶液包裹体,含少量Na Cl三相包裹体,属中温、中等盐度H2O-Na Cl体系;构造蚀变岩型金矿石中发育气液两相包裹体、含CO2包裹体和CO2包裹体,属中温、中等盐度H2O-CO2-Na Cl体系,显示两种矿石成矿流体类型不同。H-O-S同位素分析表明,斑岩型铜钼矿石成矿流体主要来自岩浆热液,有少量大气降水参与,成矿物质以幔源为主;构造蚀变岩型金矿石成矿流体受建造水或大气降水强烈交代,成矿物质壳源物质为主。成矿流体在演化过程中,流体沸腾是引起铜钼沉淀的重要因素,流体不混溶是引起金沉淀成矿的重要因素。

Features of ore-forming fluids, H-O-S isotopes and mineralization of the Lengshuigou Cu-Mo-Au deposit in Zhashui county, South Qin Ling

The Lengshuigou Cu-Mo-Au deposit is located in the middle of the South Qin Ling orogenic belt, and related with complex intrusive bodies there. The ore types in this region can be divided into three types: porphyry type Cu-Mo occurring in rock bodies, skarn type Cu occurring at the contact zone between intrusive rock and carbonatite, and fracture-altered rock type Au occurring in amphibolite. Study on fluid inclusions shows that there are different types of fluid inclusions in porphyry type Cu-Mo and fracture-altered rock type Au. Masses of aqueous inclusions and a few of NaCl-bearing daughter crystal inclusions occur in porphyry type Cu-Mo. The ore-forming fluid belongs to mesothermal and moderate salinity H2O-NaCl series. Fracture-altered rock type Au contains aqueous two-phase inclusions, i.e. CO2-bearing phase and CO2 phase inclusions, which belong to mesothermal and moderate salinity H2O-CO2-NaCl series. H-O-S isotope compositions show that ore-forming fluids of porphyry Cu-Mo were mainly derived from magmatic water, involved a little meteoric water, and ore-forming material was mainly originated from mantle. The ore-forming fluids of fracture-altered rock type Au roots in metamorphic or meteoric water, and its mineral sources came mainly from crust. Fluid boiling was probably an important factor for Cu-Mo deposition, whereas fluid immiscibility was the key factor for Au deposition during the evolution of inclusions.