Geological,Geochemical Characteristics Of The Nulasai Copper Deposit,Western Tian Shan,Xinjiang

Nulasai copper deposit is located in the west of Awulale,within western Tianshan of Xinjiang.Nulasai copper deposit has veinlike and strip ore bodies,and they are hosted in the two faults in the mining area and stratum,magmatic rocks and breccias near the faults,ore bodies are controlled by faults obviously.The Wall rock are the Wulang formation basalt,tuff of lower Permian,and Xiaoshansayi formation sand conglomerate of Upper Permian,and granite porphyry and their fault breccia.The ores mainly show massive,banded,vein and disseminated structures and consist of mineral assemblages comprising metallic minerals of chalcocite,bornite,and a small amount of chalcopyrite and pyrite,as well as calcite,barite and a small amount of gypsum.The wall rock alteration mainly are calcitization,baritization chloritization,sericitization,etc,and the alteration zoning is not obvious.According to the research of the petrographic and the characters of geochemistry characteristics inferred that the Mosizaote rock is granite-porphyry,belongs to the peraluminous,calc-alkaline,high-K calc-alkaline I-type granite.The granite porphyry have the relationship with the melting of the carboniferous volcanic rocks.Zircon U-Pb analysis yields the age of granite porphyry is 288.3±3.0Ma,shows the granite porphyry occurs in the Early Permian,formed in a post-collisional extensional stage.The ²⁰⁶Pb/²⁰⁴Pb,²⁰⁷Pb/²⁰⁴Pb,²⁰⁸Pb/²⁰⁴Pb value of sulfide vary from 17.987-18.193,15.516-15.587,and 37.889-38.081,value of?is 9.34-9.47,?is 35.27-36.37,Th/U is3.65-3.72;and the ²⁰⁶Pb/²⁰⁴Pb,²⁰⁷Pb/²⁰⁴Pb,²⁰⁸Pb/²⁰⁴Pb value of granite-porphyry vary from 17.8057-17.9927,15.4914-15.5417,37.6744-37.9489.?is 9.32-9.4,?is 35.17-36.24,Th/U is 3.63-3.73.Sulfide has the similar Rare-Earth element composition to granite-porphyry.These indicate that the metallogenetic materials mainly come from the granite-porphyry magma and has crust mantle mixing charactristics.The sulfide Re-Os isotopic dating shows the isochron age is 281.4±8.1Ma,weighted mean age is 283.5±5.8Ma,displaied Nulasai copper mineralization occurred in the Early Permian,a little later than the age of the granite porphyry.Analysing the geological,geochemical characteristics and combining with previous achievements,the authors think Nulasai copper deposit is a middle-low temperature hydrothermal vein type deposit,and it is formed from granite-porphyry magma intrusion that richs metallogenetic materials related to the melting of the underplated basaltic lower crust.