摘要
文章总结了产在克拉通和古生代造山带中、受韧性剪切带控制的金矿的重要研究成果。通过对比这两类金矿的地质特征及其成矿作用发生的大地构造背景,探讨形成韧性剪切带型金矿的成矿环境与成矿机制。大型韧性剪切带型金矿一般就位于剪切带的脆_韧性转换位置,成矿作用一般不受围岩性质和变质程度的控制。剪切带既是成矿流体的通道,又是金的沉淀场所。克拉通中韧性剪切带型金矿的成矿模式有两类同构造成矿和构造期后成矿,前者认为变质流体沿韧性剪切带迁移,最终在剪切带中沉淀形成矿床;后者则强调发生在韧性剪切带形成之后的地质过程如岩浆活动等对成矿作用的贡献。
The large_size shear zone related gold deposits are usually located in the transitional part from ductile to brittle deformation. The shear zones served as paths for fluid migration as well as places for gold deposition. The ore_forming processes were not necessarily related to the host rocks and their metamorphic facies. Two models for the ductile_shear zone related gold deposits in old cratons have been proposed, namely the syntectonic model and the post_tectonic model. The former model believes that metamorphic fluids migrated along the shear zones and ultimately deposited gold. The latter model, however, holds that the ore_forming processes related to the geological events took place after the formation of shear zones. In such cases, shear zones served as the fluid pathway and the host of gold deposits. Magmatism played a significant role in some deposits, while in other cases gold formation was not related to any magmatism although granitic bodies might have served as wall rocks of gold_bearing veins. In both cases, the gold_bearing veins mainly occurred in the second_order fractures related to the major shear zones,and the host rocks exerted insignificant effects on the ore_forming processes. The ductile_shear zone related gold deposits in Paleozoic orogenic belt generally had close relations with the evolution of the orogenic belt. The huge Central Asian orogenic belt (including Urals and Tianshan) has complex evolutionary histories, subjected to oceanic crust subduction, formation of island arcs, and continental collisions. This complex orogenic belt is famous for its numerous world_class ductile_shear zone related gold deposits. There is no principal difference between these two types of shear_zone related gold deposits in their modes of occurrence and mineral assemblages. However, they differ apparently from each other in ore_forming mechanism, ore_forming environments, and sources of ore_forming fluids. The shear_zone related gold deposits in the orogenic belt actually resulted from the orogenic process at a definite stage. The ore_forming materials were usually characterized by diversification and might include materials from Lower to Middle crust and upper mantle. The Tiangeer_Wangfeng gold deposit in Middle Tianshan was formed in the Late Paleozoic orogenic belt, occurring as a stage_product in the orogenic processes of the Tianshan Mountains. The shear_zone served as the channel for fluid migration. When gold_bearing ore_forming super_critical fluids moved from the lower crust to shallow levels, the decrease of gold solubility caused gold deposition and thus formed gold deposits.
出处
《矿床地质》
CAS
CSCD
北大核心
2004年第4期509-519,共11页
Mineral Deposits
基金
国家重点基础研究发展规划项目"中国西部中亚型造山与成矿"课题(编号:2001CB409807)资助
