川滇黔地区天宝山、会泽铅锌矿床成矿流体来源初探:来自流体包裹体及氦氩同位素的证据

Sources of Ore-Forming Fluids from Tianbaoshan and Huize Pb-Zn Deposits in Yunnan-Sichuan-Guizhou Region,Southwest China:Evidence from Fluid Inclusions and He-Ar Isotopes

为限定川滇黔地区大型铅锌矿床成矿流体来源,选择天宝山大型铅锌矿床和会泽超大型铅锌矿床中热液矿物进行流体包裹体及氦氩同位素研究.结果显示:(1)天宝山矿床为中低温、中等盐度流体成矿,成矿流体主要来源于盆地卤水;会泽矿床为中高温、中等盐度流体成矿,成矿流体也主要来源于盆地卤水,但具有不同性质流体混合特征;(2)两矿床硫化物3 He/4 He值范围介于0.02~0.32Ra,证明成矿流体以地壳流体为主,但混有少量(<5.3%)地幔成分,40 Ar/36 Ar值(345.0~1 698.8)表明成矿流体以饱和大气水为主;(3)综合两个矿床地质特征、流体包裹体及氦氩同位素研究认为天宝山矿床和会泽矿床的形成与右江盆地演化及峨眉山大火成岩省的岩浆活动有关.

In order to constrain the source of the ore-forming fluids in large Pb-Zn deposits in the Sichuan-Yunnan-Guizhou region,fluid inclusions and He-Ar isotopes have been analyzed in ore-forming fluids trapped in sulphide minerals from the large Tianbaoshan Pb-Zn deposit and the super large Huize Pb-Zn deposit.The results are summarized as follows：（1）Fluid inclusions in Tianbaoshan deposit have medium-low homogenization temperatures and medium salinities,and ore-forming fluids are mainly derived from basin brine,whereas fluid inclusions in Huize deposit represent high-medium homogenization temperatures and medium salinities,and ore-forming fluids are dominantly derived from basin brine,but with evidence for mixing of different fluids.（2）The values of 3 He/4 He in Tianbaoshan deposit and Huize deposit range from 0.02 to 0.32 Ra（where Ra is the atmospheric value;3 He/4 He= 1.4×10^-6）,indicating that the ore-forming fluids are dominated by continental crust fluids,where as a small but clear mantle helium contribution is present.And the measurements of 40 Ar/36 Ar ratio（345.0-1 698.8）indicate that the ore-forming fluids mainly consist of saturated atmospheric water.（3）Combined with geological features,fluid inclusion trapped in sulphide minerals and He-Ar isotopes,it is concluded that the ore-forming processes of Tianbaoshan deposit and Huize deposit are related to the evolution of Youjiang sedimentary basin and the magmatic activities of the Emeishan large igneous province.