【作者】 牛贺才；

【导师】 刘英俊；

【作者基本信息】 南京大学 ， 地球化学， 1991， 博士

【摘要】 湖南益阳——沅陵一带元古界地层中分布着许多金矿床，按其有用元素组合可以分为单Au、Au—Sb、Au—W及Au—Sb—W四类，它们与以漠滨金矿床为代表的产于湘西南、黔东北元古界地层中的金矿床(点)一起构成了湘黔金矿带。 元古界及下部古生界沉积岩、侵入岩及火山岩的岩石学、岩石化学及岩石组合特征表明，在元古代——古生代早期益阳——沅陵一带为大洋板块与扬子板块的聚合部位。板块的聚合作用使区内元古界地层遭受挤压变形，形成线型紧闭的东西向褶皱，并发育同方向的逆冲断裂，为金矿床的形成提供了良好的构造条件。同时，板块的聚合作用也为本区雪峰——加里东期金矿的形成提供了成矿能量。 微量元素地球化学研究揭示，本区元古界地层中Au、Sb、W含量明显高于上部大陆地壳平均值，具有相当数量的Au、Sb、W以易活化的形式赋存于岩石中，这说明本区元古界是典型的Au—Sb—W含矿建造。区域地球化学的研究表明，在矿床外围存在着区域性金亏损，它与矿体及矿化围岩一起构成了金的贫化——富更多还原

【Abstract】 A series of gold deposits occuring in Proterozoic strata in Yiyang-Yuanling region of Hunan Province, can be divided into four categories as follow :Au,Au-Sb,Au-W and Au-Sb-W according to their valuable element association. These deposits as well as the Mobin-type gold deposits occuring in Proterozoic strata in southwest of Hunan province and northeast of Guizhou province form the Hunan-Guizhou gold metallogenic belt.Petrological, petrochemical and rock associative characters of the Proterozoic and lower palaeozoic sedimentary rocks and igneous rocks indicate that Yiyang-Yuanling region is the convergent zone of ocean plate and Yangzi plate in Proterozoic Era to early Palaeozoic Era The convergence which made the Proterozoic strata deformation to form the close linear folds and thrust faults provided the favorable structure conditions for gold deposit, and also provided energy for the formation of the Xuefeng-Caledonian period gold deposits.Trace element geochemistry studies show that Au, Sb and W contents of Proterozoic strata are more than the average vaules of them in the upper continental crust, and most of them exist in rocks with easy activiting forms, so it can be concluded that the Proterozoic strata is a Au-Sb-W associative ore-bearing formation. The regional geochemical studies indicate that thy regional gold-depleted zones occuring in outer area of gold dewposits and the orebodies with their surrounding gold primitive anomalies formed the depletion-enrichment geochemistry conjugate system. This suggests that the gold came from the wallrocks, It can be further demonstrated by the S, C and Pb isotopic studies. Evidence from mineral assemblage, wallrock alteration and mierothermometry of fluid inclusion suggest that the gold deposits in the area belong to middle- to low- temperature deposits. These deposits formed in the weak reducing and alkalic fluids originated from mixture of metamorphic solution and formation water. Au[HS]₂^- was the main migrating form of gold in the fluids, and Au[Cl]₂^- also was the migrating form of gold in minority gold deposits.更多还原