Geochemical Characteristics And Genesis Of Gold Deposits Of Xiadian, Shandong

Xiadian gold deposit, which is located at the Northwest Jiaodong, and bounded on the middle of the Zhaoping fault, is a large tectonic alteration gold deposit. Consulting the literatures and earliest formal geological survey, this paper conducts outfield and regional geological survey, ore field geological researches, structure analysis, petrography study, trace element analysis, fluid inclusion tracing, stable isotope analysis and so on, to analysis the relationship between alteration and mineralization, and the ore genesis.By analysis the Geological characteristics of the deposit, author consider that Zhaoping fault controls the form of Xiadian gold deposit. Texture and structure of ores are complexity, sight texture include euhedral crystal-granular, subhedral-allotriomorphic granular texture, metasomatic relict texture, pressure texture, poikilitic texture, emulsion droplet, etc; sight structure, massive structure, disseminated structure, brecciated structure, spotted structure, fine vein structure, vesicular structure. Gold is mainly disseminated in pyrite, aphalerite, galena, chalcopyrite and other sulfides. The alteration types of ore bodies and wall rock are divided into six alteration zones. Combined with the alteration geochemistry, we suggest that there is no direct relationship between K-feldspar and the formation of gold deposit. Silicification and pyrite is the most important factor in the formation f Xiadian gold deposit.Subject to the researches on the occurrence, scale, and grade of the ore body, the component of ore, structure, ore types, alteration types and alteration zoning, Xiadian gold mineralization is divided into two periods and four stages. Analysis of fluid inclusions, including petrography, type, temperature, pressure, salinity, density and characteristics of compositions in the four stages, indicate that, from the early to late stage,(1)the inclusions evolve from the gas+vapor inclusions to the liquid inclusions;(2) temperature, pressure and salinity keep to fall down;(3) Fluid inclusion reflect Xiadian Gold Deposit ore-forming fluid belong to CO2-H2O-NaCl system.The results of hydrogen-oxygen isotope data show that the genesis of ore-forming fluids in the Xiadian gold deposit come from magmatic fluids at the early stage, then mostly the meteoric water. The results of sulfur isotopes show that the sulfur in the Xiadian gold deposit area is inheritable and the sulfur isotope range is between Linglong granite and Jiaodong group, which suggests that the sulfur here apparently comes from the mixing of them. Lead isotopes also show that the genesis of ancient lead had the identical inheritance as sulfur isotopes, and lead isotopic data shows that the genesis of the lead might come from the crust and the mantle.