Study Of Ore-forming Fluid In Gold Deposits Of Zhaoping Fault Zone, Shandong Province

The Linglong gold deposit, Xiejiagou gold deposit, Dayingezhuang gold deposit and Xiadian gold deposit are four representational deposits occurred in Zhaoping fault of Shandong province, which are controlled and influenced by Zhaoping fault. According to the comparison of the four typical deposits, this paper mainly discussed the fluid character and gold source on the viewpoint of ore-forming fluid. Main conclusions as following:(1) The fluid inclusions in four deposits can be divided into three types: Type-Ⅰ, NaCl-H2O inclusions; Type-Ⅱ, CO2-bearing fluid inclusions and Type-Ⅲ, Daughter-mineral-bearing multiphase inclusions.(2) The thermodynamics and composition study of fluid inclusions show that the ore-forming fluid is typically mesothermal, low salinity, low density and rich-CO2 fluid with reductibility.(3) The geochemical studies indicated that magmatic hydrothermal from depth was the main ore-forming fluid in the early and middle stages, meanwhile other kinds of fluids from different host rocks also joined to provide mineralization, and in the late stage much meteoric water infiltrated and joined the ore-forming process as the fluid system opening, ore deposits were differently influenced by meteoric water because of structures and geological characters in different areas.(4) The ore metal source of gold deposits in Zhaoping fault -zone had polygenetic characters, primary gold which mainly sourced from mantle entered the crust in the process of crust-mantle interchange, and the Mesozoic magmatic rocks also provided the main ore metal sources directly for ore-forming, especially the vein rocks(acidic-intermedinte vein rocks) acted as an important part.(5) The ore types of Zhaoping fault gold deposit-zone are different because of the difference of ore-forming environment, ore-forming fluid filled in the fissures and mainly formed quartz vein type deposits in brittle fracture area; the gold-rich fluid alternated with host rocks and mainly formed altered rock type deposits in the depth facies of the fault because the less open of ore-forming environment.