甘肃岷县寨上特大型金矿次显微金的赋存状态研究

Occurrence of Submicro Gold in a Super-Large-Sized Gold Deposit in Zhaishang of Min County,Gansu Province

寨上金矿是一微细浸染型超大型金矿床。通过光学显微镜、人工重砂、电子探针、扫描电镜等显微测试手段对寨上矿区主要载金矿物进行分析测试得出:黄铁矿、白钨矿是最主要的载金矿物之一,石英、褐铁矿、辉铜矿是次要的载金矿物,方解石、菱铁矿、重晶石等不含金。由于受检测手段所限,在含金黄铁矿、白钨矿、石英等矿物中未发现独立金颗粒,所以寨上金矿次显微金呈微包裹体形式存在于载金矿物中或呈类质同象替代的原子形式存在。通过研究主要载金矿物黄铁矿中Au、As的关系得出:Au与As呈正相关关系;从具有增生环带结构黄铁矿的内核向增生体S、Fe呈对数下降趋势,Au、As呈对数上升趋势。对比沉积期、热液期形成的黄铁矿主量、微量元素得出S、Fe变化不大,微量As呈线性递增,而Au呈线性递减。

Zhaishang gold deposit is a giant micro-disseminated one. Usmg opucai microscope, manual artificial heavy concentrate, electron microprobe and scanning electron microscopy, we tested major gold- bearing minerals in Zhaishang deposit. Pyrite and scheelite are the most important gold-bearing minerals. Quartz, limonite, and chalcocite are the secondary gold-bearing minerals. Calcite, siderite, barite and other minerals do not contain any gold. Because of detection limitation, the gold particles are not found independently in pyrite, scheelite, quartz, and other minerals. So it is believed that submicroscopic gold can be found in gold-bearing minerals as micro-inclusions or isomorphous atoms. Contents of Au and As in pyrite are positively correlated. From kernel to proliferation in pyrite with proliferative structure, contents of S and Fe show a logarithmic decreasing trend, while contents of Au and As show a logarithmic increasing trend. Compared with major and trace elements in different pyrites formed in depositional stage and hydrothermal stage, contents of S and Fe change a little, contents of trace As increase linearly, but contents of Au decrease linearly.