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

Zhaishang gold deposit is agiant micro-dissem inated one.Using optical microscope,manual artificial heavy concentrate,electron microprobe and scanning electron microscopy,wetested 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 submicr oscopic gold can befound in gold-bearing minerals as micro-inclusions or isomorphousatoms.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 alogarithmic decreasing trend,while contents of Au and As show alogarithmic increasing trend.Compared with major and trace elements in different pyrites formed in depositional stage and hydrothermal stage,contents of S and Fe change alittle,contents of trace As increase linearly,but contents of Au decrease linearly.