黔西南卡林型金矿成矿过程与硅化蚀变的关系探讨

Role of silicification in ore forming process of the Carlin-type gold deposits,southwestern Guizhou Province

作为中国华南"卡林型"金矿的代表之一,贵州省黔西南地区水银洞金矿床广泛发育与成矿关系密切的硅化蚀变,但其在矿床形成过程中的作用还尚不清楚。本文通过对矿区内矿石与围岩的手标本、薄片进行详细观察,同时结合SiO_2与黄铁矿、毒砂含量的关系,将矿区内的硅化蚀变作用初步分为三个阶段,并认为第二阶段偏晚期硅化交代对成矿具积极作用。根据水银洞、太平洞金矿床岩矿石主量元素及金的含量对比分析,发现SiO_2与Au在含量方面没有直接的联系,而SiO_2与CaO,或与CaO+MgO在含量上则呈现明显的负相关关系。结合前人对硅化与金矿化作用形成机制的研究,认为硅化作用的发生绝非矿床形成过程中的一种偶然性,Au在热液中以Au-Si络合物的形式进行活化迁移从本质上决定了在金矿床的形成过程中成矿作用与硅化蚀变之间的紧密联系。而作为矿床形成过程中的非决定性因素,硅化作用的意义在于与去碳酸盐化作用的相互结合为成矿提供了良好的空间,有利于矿质的运移和沉淀。

The Shuiyindong gold deposit,Guizhou province,southwest China,has been regarded as a Carlin- type gold deposit by researchers.Although silicification relates to ore is common in the deposit.it' s not clear about the affect in forming process of the deposit.Based on the detailed observations of hand specimens and thin slices,this paper found out that from early to late,silicification can be separate into three stages and the second stage has a positive effect on the mineralization combine with content relationship between SiO_2 and pyrite or arsenopyrite.In order to make a comparison with content of Au and the result shows that there is no apparent correlation between SiO_2 and Au,whereas there is negative correlation between SiO_2 and CaO or CaO + MgO.We propose that silicification is not a coincidence in the ore forming processes,and a close relationship between mineralization and silicification is reflected by that gold of the hydrothermal solution is main migrated in form of Au- Si complexes.As a non- critical factor,the significance of silicification is providing a good space for mineralization which is benefit for mineral dissolution and precipitation combine with decarbonation.