广西八渡金矿床含金硫化物矿物学与地球化学研究

Mineralogy and geochemistry of gold-bearing sulfides in Badu gold deposit,Guangxi Province,China

广西田林县八渡金矿床主要产于辉绿岩侵入体中,广泛发育乳白色石英网脉,蚀变辉绿岩体即为金矿体,具有硅化、粘土化、碳酸盐化和硫化物化等卡林型金矿热液蚀变特征。本文采用电子探针(EPMA)背散射电子图像(BSE)、波谱(WDS)和能谱(EDS)分析技术,对该矿床原生矿石中含金硫化物显微岩相学结构以及主量和微量元素含量和分布规律进行了系统研究,认为金主要是以不可见化学结合态金(Au+)的形式赋存于含砷黄铁矿和毒砂之中。含金硫化物与热液交代形成的金红石密切共生,并保留含钛铁辉石或钛铁矿等矿物的假象,金红石的形成是辉绿岩中含钛铁辉石或钛铁矿热液蚀变的产物,含金硫化物形成所需要的Fe来自辉绿岩中含钛辉石或钛铁矿等矿物的溶解,Fe的硫化物化过程是导致含金硫化物形成的重要机制。

Badu gold deposit mainly occurs within diabase intrusions in Tianlin County, Guangxi Province, China. It hosts within altered gabbro diabase, with intensive barren milky quartz veins and veinlets. The alteration related to mineralization caused silicifieation, argillization, carbonatization and sulfidation of gabbro diabase. In this paper, electron probe microanalysis （EPMA） , baekscattered electron image （BSE）, wavelength dispersive spectrometer （WDS） and energy dispersive spectrometer （EDS） analyses were used to observe petrographic texture and determine element contents and distributions of S, Fe, Au, As and etc. , in gold-bearing sulfides of Badu gold deposit. Results show that gold mainly occurs as invisible chemical bonding （Au^＋） in the forms of arsenian pyrite and arsenopyrite. The gold-bearing sulfides occur with the hydrothermal rutile indicative the products of Ti-bearing elinopyroxene and ilmenite. Iron in sulfide minerals is probably derived from dissolution of Ti-bearing clinopyroxene and ilmenite in the diabase, sulfidized by H2S-rich fluids to precipitate gold-bearing arsenian pyrite and arsenopyrite.