Geochemical Characteristics And Genesis Of Hongshi Gold Deposit,East Tianshan,Xinjiang

The Eastern Tianshan Mountains in Xinjiang are located in the southern margin of the Central Asian orogenic belt,between the Junggar Basin in the north and the Tarim Basin in the south.The Hongshi gold deposit is an important result of gold prospecting and exploration in the East Tianshan area,located in the central and western part of the Kanggur-Huangshan ductile shear zone.The ore bodies are mainly hosted in the alkaline feldspar granite of the Gandun Formation of the Lower Carboniferous.Based on the study of regional metallogenic geological background and geological characteristics of the deposit,the relationship between ore-controlling factors?strata,structures,magmatic rocks?and mineralization is analyzed by means of lithofacies,metallogenic facies,geochemistry,Hf isotope analysis and fluid inclusion study,and discussed the magmatism,metallogenic dynamic background and metallogenic mechanism of Hongshi gold deposit,Providing new information for prospecting and exploration of Hongshi gold deposit in the eastern Tianshan Mountains in Xinjiang.The main knowledge and achievements are as follows:?1?In this paper,the SIMS zircon U-Pb age of granite in the deep part of the Hongshi gold deposit is 334.0?+3.4 Ma?.The crysta llization age of the host rock body is in the middle and late Early Carboniferous,and the metallogenic age of the Hongshi gold deposit is later than that of the diagenesis.?2?The petrogeochemical data show that the deep rock mass of Hongshi gold deposit is characterized by high silicon and alkali,and is a series of high potassium calc-alkaline-potassium basaltic rocks.The rocks are rich in large ion lithophile elements such as Rb,K and Pb,and relatively deplete high field strength elements such as Nb,Ta,Ti and P.With slight Eu anomaly?Eu/Eu*=0.6¹.16?,the fractionation of rare earth elements is not obvious and LREE is slightly enriched.Zircon epsilon Hf?t?value of alkaline feldspar granite?+3.1⁺15.6?is positive.Combining with Mg^#?8.38-47.85?,it is determined that the granitic source area of Hongshi gold deposit is the neogenic lower crustal material,and some mantle material is added at the same time.?3?Quartz fluid inclusions in quartz veins of Hongshi gold deposit are mainly liquid-rich and gas-rich?CO₂?inclusions.Combined with previous studies on hydrogen and oxygen isotopes,it is shown that the early evolution stage of ore-forming fluids is high temperature and reductive magmatic fluids,while in the late stage,a small amount of meteoric water is mixed,and the ore-forming fluids are medium-low temperature and low salinity mixed fluids.?4?Comprehensive regional tectonic evolution,chronology,geochemistry and isotope studies show that the East Tianshan Mountains entered the post-collision extension stage since the Permian,and the Kanggur-Huangshan ductile shear zone experienced strong right-strike-slip shear and uplift.Combined with the formation time of Hongshi gold deposit and the right-strike-slip shear time of shear zones,the occurrence of shear zones has a good coupling.Right strike-slip shearing is the main cause of formation of Hongshi gold deposit.