西藏马攸木金矿富CO_2超临界流体特征及矿床成因探讨

The Characteristics of CO_2-rich Supercritical Fluids and The Genesis Discussion of Mayoum Gold Deposit,Tibet

马攸木金矿床是产于西藏雅鲁藏布江缝合带西段重要的独立岩金矿床。本文通过显微测温分析首次发现该矿床的富CO2流体包裹体具有临界均一的特征,成矿流体属于超临界流体。研究结果表明:成矿流体主要为低盐度的CO2-H2O超临界流体。超临界流体可能是从岩浆出溶的,这种流体萃取了围岩中的金等成矿元素。流体经历了相分离-不均一捕获-跨越临界点-大气降水加入的过程,正是由于成矿流体在跨越临界点时析出部分成矿物质,形成早期矿化体;成矿后期流体与大气降水混合最终导致矿质大量沉淀。

Mayoum Gold deposit is located in the western part of the Brahmaputra suture zone, Tibet, as an important independent rock gold deposit. The present paper first found that the CO2 fluid inclusions have the characteristics of the critical uniform by temperature test. The ore - forming fluids are supercritical fluids~ The results show that the ore - forming fluids are low salinity supercritical CO2 - H2O fluids. Supercritical fluids may exsolute from the magma, and then extract the elements such as gold from the rock. Fluids experienced phase separation, heterogeneity capture, across the critical point, precipitation adding processes. Ore - forming fluids across the critical point precipitate ore - forming elements, and form the early mineralization body. Fluids mix with the precipitation eventually, which lead to mass ore precipitation during the late ore forming stage.