(1. 中南大學(xué) 有色金屬成礦預(yù)測(cè)與地質(zhì)環(huán)境監(jiān)測(cè)教育部重點(diǎn)實(shí)驗(yàn)室 地球科學(xué)與信息物理學(xué)院，長(zhǎng)沙 410083；
2. 湖南省有色地質(zhì)勘查局二總隊(duì)，湘潭 411102)
摘 要: 包金山金礦位于湖南省雙峰金礦帶上，根據(jù)礦床地質(zhì)特征將成礦作用劃分為變質(zhì)熱液期、巖漿熱液期和熱液疊加期等3個(gè)成礦期，并將巖漿熱液期細(xì)分為乳白色石英脈階段(A)、煙灰色石英脈階段(B)和碳酸鹽-石英細(xì)脈階段(C)3個(gè)礦化階段。通過(guò)流體包裹體顯微測(cè)溫、包裹體成分分析及氫氧同位素組成分析來(lái)研究礦床成礦流體特征，并分析礦床成因。包裹體巖相學(xué)研究發(fā)現(xiàn)，A、B階段的石英中發(fā)育3類(lèi)包裹體：氣液兩相包裹體(I型)、水溶液-CO2包裹體(II型)和純CO2包裹體(III型)。A階段發(fā)育大量I型包裹體和極少量II型包裹體，均一溫度集中于260~380 ℃，鹽度為3.12%~15.42%；B階段發(fā)育I型包裹體，II型及III型包裹體明顯增多，均一溫度集中于250~370 ℃，鹽度為2.31%~12.29%。群體包裹體氣相成分以H2O和CO2為主，還含有N2、CH4、H2、CO等，液相成分主要為Ca2+、Na+、Mg2+、SO42-、Cl-和NO3-。礦床主成礦期流體屬低鹽度、中高溫、富CO2的Ca2+(Na+、Mg2+)-SO42-(Cl-、NO3-)-H2O-CO2體系，估算成礦壓力為70~113 MPa，估算最大成礦深度為4.2km。氫氧同位素分析表明主成礦階段的流體來(lái)源于原生巖漿水。礦床成因類(lèi)型為變質(zhì)熱液疊加中溫巖漿熱液充填交代型礦床。
關(guān)鍵字: 流體包裹體；氫氧同位素；成礦流體；礦床成因；包金山金礦
（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
