黔西南架底金矿床载金黄铁矿的矿物学特征及金的赋存规律研究

Mineralogical characteristics of gold-bearing pyrite and gold occurrence regularity of the Jiadi gold deposit in southwestern Guizhou Province

黔西南地区是中国卡林型金矿的主要产地之一,架底金矿作为黔西南地区近年来在玄武岩中新发现的卡林型金矿床,其金的赋存状态一直备受关注。前人研究表明,含砷黄铁矿是架底金矿的主要载金矿物,然而对架底金矿载金黄铁矿以及金的赋存规律一直缺乏深入的研究。文章结合野外实际调研以及室内显微岩相观察研究,首先对矿区黄铁矿进行了期次的划分;然后利用电子探针微区成分分析方法对不同期次的黄铁矿进行研究,结果显示:架底金矿的黄铁矿中,S、As具有明显的负相关性,Au、As存在一定的相关关系,成矿前黄铁矿与成矿期、成矿后的黄铁矿核部具高S、Fe,低As、Au等相似的特征,成矿期黄铁矿的环带具高As、Au的特征,与成矿后的环带(高As不含Au)相比较具明显差异,两者属于不同的热液事件。据此判断矿区载金黄铁矿的结晶顺序为:草莓状低砷无环带黄铁矿→含砷环带黄铁矿(含金)以及均质无环带的细粒黄铁矿→高砷环带黄铁矿(不含金)。这一结论对架底金矿找矿勘查工作具有一定的指示意义。

Southwestern Guizhou is one of the main producing areas of Carlin-type gold deposits in China. The Jiadi gold deposit is a newly discovered Carlin-type one hosted in basalt in southwestern Guizhou in recent years, and the occurrence state of gold has long been the focus of attention. Previous studies have shown that arsenic-bearing pyrite is the main gold-bearing mineral in the Jiadi gold deposit. However, there has been a lack of in-depth research on the gold-bearing pyrite and the gold occurrence law in the Jiadi gold deposit. Based on the field investigation and indoor microlithographic observation, the pyrites in the mine were divided into different phases first;then, the electronic probe analysis method was used to study the pyrites of different phases. The results show that S and As of pyrite have an obvious negative correlation, and Au and As have a certain positive correlation. Orepredating pyrite, ore-forming pyrite and post-ore pyrite share similarity of high contents of S, Fe and low contents of As, Au. The ring of the ore-forming pyrite has the characteristics of high As and Au, different that of the post-ore pyrite(high As without Au),indicating that two types of pyrites belong to different hydrothermal events. The crystallization sequence of the gold-bearing pyrite in the mine is summarized as follows: Strawberry-like acyclic pyrite of low-arsenic→arsenic, ringing pyrite(containing gold) and homogeneous apyrite fine-grained pyrite→high-arsenic ring pyrite(without gold). This conclusion has certain directive significance for the prospecting and exploration in the Jiadi gold deposit.