Geological And Geochemical Study Of Baishikuduke Gold Deposit In West Junggar,Xinjiang

The West Junggar area of Xinjiang is rich in mineral resources,Baishikuduke gold deposit is located in the south of West Junggar area,and the gold bearing quartz vein type ore body is controlled by NW faults.The host rocks are tuff and basalt of the lower Carboniferous teragula formation.Silicification,pyritization,sericitization,carbonation and chloritization are developed in the host rocks.The mineralization is closely related to sericitization and pyritization.The ore develops vein,disseminated and breccia structures.The ore textures is relatively complex,including ring texture,inclusion texture,crushing texture and interstitial texture.The main metal minerals are pyrite and arsenopyrite,followed by chalcopyrite,sphalerite,galena,pyrrhotite and natural gold.The intergrowth assemblage of minerals and the relationship between vein bodies indicate that the mineralization includes six stages:Quartz albite stage(?),calcite quartz albite sulfide stage(?),calcite albite quartz arsenopyrite stage(?),quartz albite pyrite stage(?),sericite sulfide stage(?),quartz vein stage(?),in which stage V is the main stage of gold formation Ore stage.From the early to the late stage of mineralization,the content of S and Fe in pyrite decreased and the content of As increased;the content of As in arsenopyrite decreased and the content of S and Fe increased.The As atom percentage of arsenopyrite and Zn/Cd ratio of sphalerite reflect that the temperature and sulfur fugacity of ore-forming fluid decrease with mineralization.The transparent mineral assemblage evolved from calcite to sericite and quartz,and the reaction ore-forming fluid evolved from weak alkaline system to acid system.The change of physicochemical properties of ore-forming fluid is the main cause of gold deposition.The sulfur isotope ?34S value of ore-forming fluid obtained by LA-ICPMS is-1.99‰?7.89‰,indicating that the ore-forming fluid has the characteristics of mantle source sulfur,and the mixing of surrounding rock sulfur leads to the negative migration of sulfur isotope.