摘要
本文以浙江治岭头金矿为例研究蚀变作用过程金的迁移机制。治岭头地区出露由片麻岩类组成的前寒武系变质岩。片麻岩中,金的丰度值平均为11.9ppb,但矿脉两侧片麻岩的金含量平均为4.77ppb。从围岩到矿脉的蚀变带中金含量变化表明在热液蚀变阶段金发生过大量迁移。显然这些片麻岩是金的成矿岩。一般认为金的搬运形式主要是四氯合金络阴离子,过量Cl-有利于形成〔AuCl_4〕络阴离子,它在金的活化和迁移中起着重要作用。
Precambrian gneiss which consists the main metamorphic group in Zhilington area contains11.9 ppb Au in average. However, gold content of the same gneiss adjacent to ore veins remarka-bly decreases consisting only 4.77 ppb in average. This variation shows that a significant amountof gold migrated during the hydrothermal alteration with the surrounding gneiss as source rockof the gold mineralization. It is believed that gold is mainly mobilized and migrated in the form of complex anion ofgold tetrachloride. In acidic condition the role of Cl as a complex ion is much more importantas compared with [HS]^- or S^(2-). Therefore an excess of Cl^- favours the development of [AuCl_4]^-.
关键词
金矿
金
围岩蚀变
活化运移
富集
Wall rock alteration
abundance
activation, migration
hydrothermal genesis
sulphur isotope
