(1. 中南大学 有色金属成矿预测与地质环境监测教育部重点实验室 地球科学与信息物理学院，长沙 410083；
2. 湖南省有色地质勘查局二总队，湘潭 411102)
摘 要: 包金山金矿位于湖南省双峰金矿带上，根据矿床地质特征将成矿作用划分为变质热液期、岩浆热液期和热液叠加期等3个成矿期，并将岩浆热液期细分为乳白色石英脉阶段(A)、烟灰色石英脉阶段(B)和碳酸盐-石英细脉阶段(C)3个矿化阶段。通过流体包裹体显微测温、包裹体成分分析及氢氧同位素组成分析来研究矿床成矿流体特征，并分析矿床成因。包裹体岩相学研究发现，A、B阶段的石英中发育3类包裹体：气液两相包裹体(I型)、水溶液-CO2包裹体(II型)和纯CO2包裹体(III型)。A阶段发育大量I型包裹体和极少量II型包裹体，均一温度集中于260~380 ℃，盐度为3.12%~15.42%；B阶段发育I型包裹体，II型及III型包裹体明显增多，均一温度集中于250~370 ℃，盐度为2.31%~12.29%。群体包裹体气相成分以H2O和CO2为主，还含有N2、CH4、H2、CO等，液相成分主要为Ca2+、Na+、Mg2+、SO42-、Cl-和NO3-。矿床主成矿期流体属低盐度、中高温、富CO2的Ca2+(Na+、Mg2+)-SO42-(Cl-、NO3-)-H2O-CO2体系，估算成矿压力为70~113 MPa，估算最大成矿深度为4.2km。氢氧同位素分析表明主成矿阶段的流体来源于原生岩浆水。矿床成因类型为变质热液叠加中温岩浆热液充填交代型矿床。
关键字: 流体包裹体；氢氧同位素；成矿流体；矿床成因；包金山金矿
（1. Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring, Ministry of Education, School of Geosciences and Info-Physics, Central South University, Changsha 410083, China;
2. No.2 Team, Hunan Bureau of Nonferrous Metals Geological Exploration, Xiangtan 411102, China）
Abstract:The Baojinshan gold deposit is located in Shuangfeng gold metallogenic belt of Hunan Province. According to geological characteristics of the deposit, three mineralization episodes were identified: metamorphic hydrothermal episode, magmatic hydrothermal episode and hydrothermal superposition episode, and 3 stages were subdivided from magmatic hydrothermal episode, namely milky quartz vein stage (A), smoky quartz vein stage (B) and carbonate-quartz veinlet stage (C). The characteristics of ore-forming fluid and ore genesis were discussed by using the fluid inclusion micro-thermometry, group inclusion composition analysis and H-O isotope analysis. Based on fluid inclusion petrography, three types of fluid inclusions are developed in stages A and B: aqueous inclusion (type I), CO2-aqueous inclusion (type II) and pure CO2 inclusion (type III). Mainly type I and few type II inclusions are present in stage A, having homogenization temperatures at 260-380 ℃, and the salinities ranging from 3.12% to 15.42%. In addition to development of type I inclusions, type II and III inclusions increase significantly in stage B, with homogenization temperatures ranging from 250 ℃ to 370 ℃, salinities are in the range of 2.31%-12.29%. High density of H2O and CO2, followed by N2, CH4, H2 and CO were found as gas compositions in the inclusions. Liquid phase of fluid mainly comprise Ca2+, Na+, Mg2+, SO42-, Cl- and NO3-. Ore-forming fluid of main mineralization episode in Baojinshan gold deposit belongs to low salinity, medium-high temperature, CO2-rich Ca2+(Na+, Mg2+)-SO42-(Cl-, NO3-)-H2O-CO2 system. The calculated metallogenic pressures are in the range of 70-113 MPa, and the maximum estimated mineralization depth is 4.2 km. The result of hydrogen and oxygen isotope analysis shows that ore-forming fluid of main mineralization stage is mainly derived from magmatic fluid. Baojinshan deposit belongs to medium-temperature magmatic hydrothermal filling and metasomatic deposit along with superimposition of metamorphic hydrothermal.
Key words: fluid inclusion; hydrogen and oxygen isotope; ore-forming fluid; genesis; Baojinshan gold deposit
