五台山区太古宙铁建造型金矿成矿流体性质和成因

The Characteristics and Origin of Ore-forming Fluid of Archean BIF-hosted Gold Deposits in Wutai Mountain Area, SHanxi Province

五台山区铁建造金矿经历初生成矿作用和叠加成矿作用。初生成矿作用形成于变质峰期之后 ,与区域变质作用有关。矿石富含水溶液包裹体。包裹体均一温度 171～ 2 55℃ ,压力 0 .12～ 0 .31GPa。流体成分模式Au -H2 S +NaCl-CO2 -H2 O。氢氧同位素具变质水和雨水双重性 ,流体主要来源于变质热液 ,受雨水混合。叠加成矿作用可能受岩浆活动影响 ,矿石富含CO2 包裹体 ,均一温度 30 6～ 385℃ ,压力 0 .6～ 1.0 5GPa ,流体盐度较高 ,成矿流体可能与岩浆热液有关。

The formation of BIF hosted gold deposits in Wutai mountain area involves two different mineralization processes:primitive mineralization process and superimposed mineralization process. Primitive mineralization occurred after regional peak metamorphism; The main type of fluid inclusion trapped in quartz which comes from ores is aqueous fluid inclusion; The homogenization temperatures of these inclusions are between 171 ℃and 255 ℃,with pressures from 0.12 to 0.31 GPa; The fluids trapped in these inclusions are Au-H 2S+NaCl-CO 2-H 2O-type; Hydrogen and oxygen isotopic data show the characteristic of metamorphic hydrothermal solution mixed with rainwater circling underground. The superimposed mineralization process may be related to latter magmatic activity of carbonatite. The fluid inclusions corresponding to the formation of ore are mainly liquid carbon dioxide type, which derive from magmatic hydrothermal solution, their homogenization temperatures range from 306℃ to 385℃, with pressures of 0.6～ 1.05 GPa and high salinity.