摘要
流体包裹体的研究表明,湘西层控金矿床为中低温热液矿床,矿床在弱还原、弱碱性的成矿流体中形成,成矿流体为变质水与建造水混合而成。在流体中金主要以[Au(HS)^-]络离子形式运移,流体温度及pH值的改变是导致金沉淀的主要因素。流体包裹体的研究还揭示,成矿能量主要由雪峰造山作用提供。元素地球化学的研究则证实,湘西元古界是典型的Au-Sb-W含矿建造,它为湘西层控金矿床的形成提供了物质基础。本文的研究显示,湘西层控金矿床的成矿作用是中低温开放体系水、岩反应过程。
Data of mineral assemblages, wall rock alterations and inclusion thermometry suggest that stratabound gold deposits in west Hunan are mesothermalepithermal ones formed in weakly reducing and weakly alkaline media. Ore fluids were mixtures of metamorphic water and formation water, in which An migrated in the form of[Au(HS^-)_2]^-complex ions. Minor element geochemical studies show that Au, Sb and W contents of Proterozoic in west Hunan are obviously higher than their average values in the upper continental crust, and a considerable amount of Au, Sb and W occurs in rocks in a form readily to be activated, suggesting that Proterozoic in west Hunan is a typical Au-Sb-W ore-bearing formation. Studies of regional geology, wall rock alteration and sulfur isotopic geochemistry show that ore-forming substances of stratabound gold deposits in west Hunan came mainly from the Au-Sb-W ore-bearing formation. The authors hold that, under the driving forces of Xuefengian orogeny, formation water of different natures reacted with Proterozoic Au-Sb-W orebearing formation of west Hunan, leading to certain degrees of activation and migration of Au, Sb and W. Driven by regional tectonic stress field, ore-forming fluids rich in metallogenic elements migrated towards and concentrated in the structural dilational zone and then mixed with different quantities of metamorphic water. Pressure reducing and fluid mixture caused obvious variations in such physical-chemical parameters of ore fluids as temperatures and pH values and led to the precipitation of metallogenic elements and correspondingly the formation of Au-Sb-W, Au-Sb and single Au stratabound deposits. The oreforming process of stratabound gold deposits in west Hunan was actually a reaction process between water and rock in an open system of medium-low temperature.
出处
《矿床地质》
CAS
CSCD
北大核心
1992年第1期65-75,共11页
Mineral Deposits
基金
中国科学院矿床地球化学开放实验室
国家自然科学基金委员会联合资助
