Geochemical Characteristics And Genesis Of Zhaoxian Gold Deposit In The Jiaodong Peninsula,China

Zhaoxian gold deposit,situated in Jiaoxibei area,a gold deposit concentration zone in Jiaodong Peninsula,Shandong,China,is a new exploration zone which has significant prospecting potential.However,it is weak to learn about the ore genesis.In this paper,based on the geological fact,geochemistry methods are applied to study the source and characteristics of metallogenic materials and ore-forming fluid,some positive result are required.The hydrothermal period of ore formation is considered to include 4 stages:(?)pyrite-quartz-K-feldspar stage,(?)pyrite-quartz-sericite stage,(?)quartz-polymetallic sulfide stage and(?)quartz-carbonate stage.The S/Fe and Fe/(S+As)values of pyrite show that the Zhaoxian gold deposit may form in middle-deep depth,and the lower Co content as well as Au/Ag values indicates that the ore-forming environment may be at low-middle temperature.As the diagrams of Co-Ni and Co-Ni-As shows,the formation of gold deposit was closely related with magmatic and hydrothermal activity and the ore-forming fluid mainly included magmatic fluid and metamorphic water,and thermal groundwater also participated in the metallogenic process.The He-Ar isotope system of fluid inclusion from pyrite suggests that the characteristic of ore-forming fluid is crust and mantle mixing at Au metallogenic stage with the participation of air saturated water while the crust fluid is dominated at the last stage.At Au metallogenic stage,S isotope feature shows that the ?34S values was lower and lower,although the sources of sufur may be different,it showed the characteristic of magmatic sulfur,which indicated that the ore-forming material may originate from Mesozoic granites.The ?34S values are higher at every stage,which may be resulted from the fluid that riched 34S.The ziron U-Pb age of ores is(142±2)Ma,based on the geological fact,the Au metallogenic age is 142?116Ma.In general,under the background of lithospheric thinning and mantle uplifting,magmatic fluid and metamorphic water and so on that carried Au invaded into tensile fractures and Au would rich and mineralize at the right palace.