GEOLOGICAL CHARACTERISTICS AND GENESIS OF XIAOWANNANSHAN GOLD DEPOSIT IN WESTERN GANSU PROVINCE

Xiaowannanshan gold deposit, controlled by ductile shear zones and higher horizon of D Rock-Formation of Donghuang Group, is a metamorphic-hydrothermal type, occurring in Achaean granitoid-greenstone terrain. The source rocks are mafic volcanic rocks in the greenstone belt. The mineralization fluids are mainly metamorphic hydrothermal fluids. Middle Proterozoic is the main mineralization period. Regional geological background, local geological features, rare element characteristics, S- and Pb-isotopic composition, and fluid inclusions in quartz have been discussed. Based on host strata and rocks, ductile shear structures, wallrock alteration, it is demonstrated that Xiaowannanshan gold deposit should be of metamorphic hydrothermal genesis.