中文摘要：

大坪金矿成矿可分为三个成矿阶段：早期成矿阶段（白钨矿石英脉）、主成矿阶段（团块状多金属硫化物含金石英脉）和晚成矿阶段（碳酸盐石英脉）。本文利用显微测温和拉曼光谱分析了大坪矿脉的流体包裹体特征,结果表明：流体包裹体基本由富液相CO2包裹体和不同CO2/H2O比例的CO2-H2O型包裹体组成,早阶段白钨矿石英脉中同时富含富气相CO2包裹体,主成矿阶段团块状多金属硫化物金矿石中富液相CO2包裹体占明显优势,只有晚成矿阶段碳酸盐石英脉中含有居次要地位的H2O溶液包裹体。流体包裹体中气相组成基本为纯CO2,早阶段者还含少量N2。早阶段CO2-H2O型包裹体的盐度为6.37%-14.64%NaCl,峰值9%-10.5%NaCl,均一温度为299.4-423.7℃,峰值320-380℃,CO2包裹体密度为0.352-0.798g/cm^3,多数在0.64-0.71g/cm^3;主成矿阶段的CO2-H2O型包裹体的盐度在3.70%-14.64%NaCl之间,峰值7.2%-9.0%NaCl,均一温度279.0-406.5℃之间,峰值320-360℃,CO2包裹体密度为0.591-0.843g/cm^3,多数大于0.8g/cm^3;晚成矿阶段CO2-H2O型包裹体的盐度为4.80%-6.54%NaCl,均一温度为287.6-337.1℃。计算表明早阶段成矿压力约为190-440MPa,主阶段成矿压力约为133.5-340.0MPa,相当的成矿深度为5.1-12.9km。这些特征揭示了该矿成矿流体为近临界的高CO2（CO2≥H2O）的中低盐度的CO2-H2O-NaCl体系流体,在成矿过程中基本不存在流体混合,但发生了明显的沸腾和相分离作用。该矿是剪切带控制下的中深中温热液金矿,成矿作用主要是减压沸腾环境下的快速沉淀。结合其它证据,作者认为该矿的成矿流体主体为深源的壳幔混合流体,而不是地壳浅部的大气降水、岩浆水或其混合流体。金在高CO2的成矿流体中可能主要以硫氢络合物形式迁移,矿质沉淀主要与压力速降条件下发生流体的相分离作用相关。

英文摘要：

Mineralization epochs of the Daping gold deposits are divided into three stages： the early stage or scheelite-bearing quartz vein stage, the major stage or massive polymetallic sulphide typed auriferous quartz vein stage and the late stage or carbonate-quartz stage. Fluid inclusions in the various ore veins were studied by using a cooling/heating stage and a Laser Raman spectroscopy, and the results show that the fluid inclusions are dominated by liquid CO2 inclusions and CO2-H2 O inclusions with variable ratios of CO2/ H2O. A lot of gaseous CO2-rich inclusions are found in the early stage scheelite-bearing quartz veins, liquid CO2inclusions are dominanted in the major stage auriferous massive polymetallic sulphide ores, and aqueous inclusions are found only in the late stage carbonate-quartz veins. The gaseous phases in the fluid inclusions are nearly pure CO2, with a little N2 at the early stage. CO2-H2O inclusions in the early stage have salinity of 6.37 % - 14.64 % NaCl with a peak of 9 %-10. 5 % NaCl, homogenization temperature of 299.4-423.7℃ with a peak of 320-380℃,entrapped pressure of about 190-440MPa, and COz inclusions density of 0. 352-0. 798g/cm^3 with a majority of 0. 64-0. 71g/cm^3. CO2-H2O inclusions in the major mineralizing stage possess salinity of 3. 70% - 14. 64% NaCl with a mode of 7. 2%-9. 0% NaCl, homogenization temperature of 279.0-406.5℃ with a mode of 320-360℃, entrapped pressure of 133.5-340.0MPa with corresponding metallogenic depth of about 5.1-12.9km, and CO2 inclusions density of 0. 591-0. 843g/cm^3. The fluid inclusion characteristics indicate that the ore-forming fluid of the Daping mine is a nearly critical CO2-H2 O-NaCl system with high-CO2 content（CO2≥H2O）and low to moderate salinity. Boiling or phase separation without fluid mixing might has occurred during gold mineralization. The Daping mine is a ductile shear zone controlled mesothermal deposit, which was formed by rapid decompression and subsequent boiling and deposition. Combined with other evidences, it