GENETIC TYPE CHARACTERISTICS AND EXPLORATION OF GOLD DEPOSIT IN BEISHAN AREA, GANSU PROVINCE

There occurs a lot of gold deposits which belong to three genetic types:ductile shear zone-type,magmatic-hydrothermal type and marine-volcanic type.Source materials of gold deposits in the area are derived mainly from the metamorphic rocks,Variscan intermediate-acid intrusive rock,and marine volcanic rocks and sub-volcanic rocks of Carboniferous system.Except the metamorphic rocks and volcanic rocks of Carboniferous system,there is little selectivity of stratigraphic time for gold deposit to occur.Ore fluid of magmatic-hydrothermal type and marine-volcanic type gold deposits is drawn mainly from magmatic water,but one of ductile shear zone-type from magmatic water and dynamic metamorphic hydrothermal solution.The study of structure controls of gold deposits shows that tectonics and regional structure control the distribution of ore bearing rock series,secondary structure controls the distribution of ore forming rock mass and mineralization belts.The ore-hosting structures are ductile shear zone,low angle faults,and fractures in the magmatitic mass.And most of gold deposit in the area fromed mainly in late Paleozoic era.The prospective places for gold deposit are Xiaoxigong and its peripheral area,Baidunzi Shibandun area,Jinwozi Zhaobishan area,Shijinpo -Nanjintan area,Mazhuangshan -Nanjinshan area and Gubaiquan Laojinchang area.