【作者】 王恒涛；

【导师】 杨立强；

【作者基本信息】 中国地质大学(北京) ， 矿物学、岩石学、矿床学， 2012， 硕士

【摘要】 西秦岭阳山金矿是我国已探明资源/储量最大的独立金矿床。本文基于对阳山金矿带系统的岩相学研究，厘定了其金成矿阶段及其矿物世代，进行了流体包裹体显微测温、成分分析和C-H-O同位素研究，探讨了成矿流体的来源与演化以及金元素迁移与富集成矿机理。1、根据含矿细脉和矿石样品的岩相学观察结果，金成矿作用从早到晚可划分为四个阶段：贫矿化石英脉阶段（Ⅰ）、石英-硫化物脉阶段（Ⅱ）、石英-辉锑矿脉阶段（Ⅲ）以及石英-碳酸盐脉阶段（Ⅳ）。2、流体包裹体显微测温和成分分析表明成矿流体为中低温（120℃～320℃）、低盐度（<10%NaCl eqv）、富CO₂流体。Ⅰ阶段成矿流体为H₂O-NaCl-CO₂体系，主要表现为富CO₂包裹体，均一温度集中于260℃～320℃，盐度为0.62%～4.87%NaCl eqv；Ⅱ阶段主要为含CO₂包裹体和水溶液包裹体（CO₂/H₂O比值明显低于Ⅰ阶段，表明此阶段CO₂等挥发份大量逸出），均一温度集中于220℃～280℃，盐度集中在6%～10%NaCl eqv；Ⅲ、Ⅳ阶段仅发育水溶液包裹体，成矿流体已演化为H₂O-NaCl体系，均一温度分别集中于160℃～240℃和120℃～180℃，盐度分别为5%～7%NaCl eqv和2%～7%NaCl eqv。3、成矿流体的C、H、O稳定同位素研究结果表明Ⅰ、Ⅱ阶段成矿流体(δD值为-78‰～-56‰；δ¹⁸OW-SMOW值为5.94‰～13.11‰)以变质流体为主，Ⅲ、Ⅳ阶段成矿流体(δD值为-82‰～-61‰；δ¹⁸OW-SMOW值为4.484‰～6.45‰)中混入大气降水；不同成矿阶段其δ13CCO₂变化不是很大，介于-2.5～-4.1‰之间，也表明成矿流体具有混合来源的特征。4、综合流体包裹体显微测温、成分分析和C-H-O同位素研究，认为金成矿作用主阶段，金主要以硫化物的络合物形式在成矿流体中运移，可能由于压力的剧降，引起CO₂等挥发份大量逸出、pH值升高、温度降低，导致金-硫络合物分解，金及载金矿物（毒砂和黄铁矿）一起沉淀。金成矿作用晚阶段，随着大气降水的加入，发生流体混合，这也可能是引起金-硫络合物大量沉淀和明金出现的主要原因。更多还原

【Abstract】 The Yangshan gold belt is the largest independent gold deposit with huge proved gold resources/reserves. Base on the systematic petrological research, the ore stages and mineral paragenetic sequence were determined, and the microthermometry, composition of the fluid inclusions and the C-H-O isotopes were analyzed, also the origin and evolution of the ore-forming fluids, and the migration and enrichment mechanism of gold resources were discussed in this study.1. According to the petrological observations of the mineralized veinlets and ore samples, the gold mineralization process could be divided into four stages:lean-ore quartz veins stage (Ⅰ), quartz-sulfides stage (Ⅱ), quartz-stibnite stage (Ⅲ), and quartz-calcite veins stage (Ⅳ).2. The results of the microthermometry and composition analysis of the fluid inclusions show that the ore-forming fluid is characterized by medium-low temperature (120～320℃), low salinity (<10.0wt.%NaCl eqv) and CO2-rich. Ore-forming fluids of stage Ⅰ is H2O-NaCl-CO2system, with a lot of CO2-rich inclusions, whose homogenization temperatures vary from260℃to320℃, and salinity between0.62%and4.87%NaCl eqv. The fluid inclusions of stage Ⅱ are CO2-bearing and H2O-solution inclusions, with the homogenization temperatures clustering around220℃～280℃, and the salinity clustering around6%～10%NaCl eqv. The CO2/H2O ratio in stage Ⅱ is obviously lower than that in stage Ⅰ, which probably indicates that the volatile components (CO2) escaped from the ore-forming fluids. All the fluid inclusions of stage Ⅲ and Ⅳ are H2O-solution, with homogenization temperatures clustering around160℃～240℃and120℃～180℃respectively, and salinities clustering around5%～7%NaCl eqv and2%～7%NaCl eqv, respectively.3. The C-H-O isotopes suggest that the ore-forming fluids in the stage Ⅰ and Ⅱ are mainly metamorphic fluids (δD values between-78‰and-56‰; δ18OW-sMOW values between5.94‰and13.11‰). Meanwhile the ore-forming fluids in the stage Ⅲ and Ⅳ are metamorphic fluids which were mixed with meteoric water (δD values between-82‰and-61‰; δ18OW-SMOW values between4.484‰and6.45‰). There is almost no variation of the δ13CCO2values from stage Ⅰ to Ⅳ (range between-2.5‰and-4.1‰), which also shows the characteristics of mixed origin of the ore-forming fluids.4. Based on the results of the microthermometry and composition analysis of the fluid inclusions and the C-H-O isotopes, the migration of gold is mainly in the form of sulfur complexes, and there may be a sudden drop in pressure during the migration-mineralization process, which leads to the escape of CO2and other volatile gases, accompanying by the increase of pH value, causing the decomposition of the sulfur complexes and finally the precipitation with arsenopyrite and pyrite. During the late ore stage, with the addition of meteoric water, the fluid mixing causes the precipitation of sulfur complexes, which may also be the main reason for the present of visible gold.更多还原