Geological features and origin of Yangshan supper large gold deposit, Gansu

Yangshan gold deposit is a supper large gold deposit found in recent years.Four discovered ore area of the deposit all occur in Devonian epimetamorphised,phyllite or limestone. Ore bodies being little undulatory forms in plane and veinlike or bedded forms.Pyrite and arsenopyrite are the main metallic minerals which usually contain micrograined native gold(2～3 μm).As,Sb and C contents in the ore are high,and Au show positive correlation with epithermal ore elements such as Ag,As,Hg,Sb.Studies on geology and geochemistry of the deposit show that the host rock is a suite of carbonaceous,siliceous and argillaceous sediments with higher gold content. Gold was primarily enriched during the sedimentary and the later regional metamorphic process.In the early Jurassic period,magmatic and relevant ore fluid activities superposed in the rocks, and gold was enriched further. Therefore,Yangshan gold deposit is a superposed fine disseminated gold deposit.