Ore genesis of the Xiyi Pb-Zn deposit, western Yunnan province, China: Geologic, fluid inclusion, and isotopic (C-H-O-S-Pb) evidence

摘要: The Xiyi Pb-Zn deposit, located in the Baoshan Block of Sanjiang region western Yunnan, China, contains 1.2 Mt resources. orebodies are hosted by Devonian-Carboniferous limestone, structurally controlled NE-trending fractures, and occur stratiform, vein, lenticular forms. mineral assemblage ores includes sphalerite, galena, pyrite, arsenopyrite, chalcopyrite, marcasite. Calcite, barite, quartz as gangue minerals. Three stages hydrothermal mineralization recognized based on ore textures, crosscutting relationship, assemblages: an early stage sphalerite + galena + calcite (Stage 1), a middle galena + arsenopyrite + calcite ± sphalerite 2), late calcite + pyrite ± barite ± quartz 3). Two types fluid inclusions associated with different ore-forming stages: aqueous hydrocarbon-H2O inclusions. fluids were characterized low temperatures (100 ~ 200 °C), medium salinities (8 ~ 20 wt% NaCleq), densities (1.0 ~ 1.1 g/cm3) contained minor amounts CH4. δDH2O calculated δ18OH2O values Stage 1 calcite range from −89‰ to −103‰ 1.5‰ 5.5‰, respectively, indicating that H2O was derived seawater had reacted organic matter. δ13CPDB δ18OSMOW Stages 3 −5.2‰ 3.2‰ 12.5‰ 20.0‰, respectively. These data plot field between marine carbonate granites close field, suggesting CO2 dissolution sedimentary rocks. pyrite have narrow δ34S (0–3‰), which is lower than Carboniferous Middle-Late Devonian sulfate (+18‰ +23‰). Therefore, because unrelated magmatic activity, sulfur sulfides regional sulfates primarily via reduction at 100 200 °C. lead isotopic compositions very similar those diagenetic host rocks, plotting upper crust Pb evolution curve. Thus, source likely strata. geologic, inclusion, (C-H-O-S-Pb) evidence this study suggests deposit Mississippi Valley-type deposit.