新疆东准噶尔南明水金矿床成矿流体特征：流体包裹体及氢氧同位素证据

新疆东准噶尔南明水金矿床位于卡拉麦里成矿带东段，矿体受NW—NWW向韧-脆性断裂控制，赋矿围岩为下石炭统姜巴斯套组的浅变质海相火山碎屑-沉积岩。以流体包裹体和氢、氧同位素为研究手段，查明了矿床成矿流体性质、来源及其演化特征与金成矿的关系。其热液成矿过程可划分早、中、晚3个阶段，石英中原生包裹体主要有CO2-H2O包裹体、水溶液包裹体和纯CO2包裹体3种类型。早阶段石英中以CO2-H2O包裹体和纯CO2包裹体为主，均一温度变化于257~339 ℃，盐度为04%~22%；中阶段石英中3种类型包裹体均发育，CO2-H2O包裹体和水溶液包裹体均一温度为196~361 ℃，盐度为04%~60%；晚阶段石英中仅见水溶液包裹体，均一温度相对较低，为174~252 ℃，盐度为14%~32%。由CO2-H2O包裹体计算的早、中阶段捕获压力分别为214~371 MPa、236~397 MPa，对应的成矿深度分别为81~140 km、89~150 km。成矿流体由早、中阶段的CO2-H2O-NaCl±CH4体系演化至晚阶段贫CO2的H2O-NaCl体系，成矿温度和流体密度呈逐渐降低趋势，盐度变化不大。流体包裹体和氢、氧同位素研究表明，主成矿阶段成矿流体主要来源于变质水，CO2-H2O-NaCl流体的不混溶是导致Au富集成矿的重要机制，南明水金矿属于中深成造山型金矿床。

Characteristics of Ore forming Fluids of the Nanmingshui Gold Deposit in the East Junggar,Xinjiang: Evidences from Fluid Inclusions and H O Isotopes

The Nanmingshui gold deposit is located in the eastern part of the Kalamaili metallogenic belt. Its ore bodies, controlled by the NW—NWW trending ductile brittle faults, are hosted in epimetamorphic marine volcaniclastic sedimentary rocks of the Lower Carboniferous Jiangbasitao Formation. Based on the studies of fluid inclusions and hydrogen and oxygen isotopic geochemistry, the properties, source and evolution of ore forming fluids are discussed in this paper. The ore forming process can be divided into three metallogenic stages including the early, middle and late stages. Three types of fluid inclusions that include CO2 H2O, H2O NaCl and pure CO2 inclusions are identified in the quartz of the Nanmingshui gold deposit. The early stage quartz mainly contains CO2 H2O and pure CO2 inclusions with homogenization temperatures and salinities ranging from 257 ℃ to 339 ℃ and 04% to 22%. All three types of inclusions are trapped in the middle(main) stage quartz. The homogenization temperatures and salinities of CO2 H2O and H2O NaCl inclusions vary from 196 ℃ to 361 ℃ and 04% to 60%. Only H2O NaCl inclusions are found in the late stage quartz with relatively lower homogenization temperatures clustering at 174 ℃ to 252 ℃. Meanwhile, the salinities of H2O NaCl inclusions vary from 14% to 32%. According to the estimation from CO2 H2O inclusions, the minimum trapping pressures for early and middle stages are 214 MPa to 371 MPa and 236 MPa to 397 MPa, respectively, corresponding to the metallogenic depths of 81 km to 140 km and 89 km to 150 km, respectively. The studies of fluid inclusions in different metallogenic stages indicate that the metallogenetic temperatures and fluid densities show a decreasing trend, as the ore forming fluids are evolved from CO2 H2O NaCl±CH4 system in the early and middle stages to H2O NaCl system in the late stage. Fluid inclusions and hydrogen and oxygen isotopic studies show that the ore forming fluids of the main metallogenic stage were dominantly originated from metamorphic water. The immiscibility of CO2 H2O NaCl fluids is an important mechanism that leads to the gold precipitation and enrichment. The genesis of the Nanmingshui gold deposit is a mesozonal to hypozonal orogenic gold deposit.