Study On Petrography,Mineralogy And Genesis Of Baixintan Cu–Ni Sulfide Deposits In Xinjiang

Eastern Tianshan is cover with most Ni-Cu bearing mafic-ultramafic intrusions in Kangguer ductile shear belt and its adjacent areas,where is an important Cu-Ni-PGE ore-concentrated area.Different from previous studies,which mainly focused on the eastern and central parts of this belt,and Dacaotan of the parts of this belt are not found in the exploration of ore body with economic value.This paper is focus on Baixintan which is the only Ni-Cu sulfide deposit on the western part of the belt which attract broad attention by geologists.Chronology,the structural regularity of controlling rock and controlling orebody,,lithogenesis,metallogenic characteristics have been done about Baixintan intrusion.but the petrography and mineralogy has done little.The paper focusing on systematic petrography,mineral petrography,mineral crystallochemistry,combine with geochemistry to discuss the scientific problems of metallogenic geology,petrology,mineralogy,geochemical,magmatic origin,mother magmatic composition,and tectonic background of this intrusion.The following are the main results:(1)The petrographic composition of Baixintan intrusion are Peridotite facies,Olive norite facies,Gabbro facies.The main rock-forming minerals are olivine,orthopyroxene,clinopyroxene,amphibole and plagioclase.we obtain the development sequences of minerals is olivine?orthopyroxene?clinopyxene ?plagioclase?amphibole?(2)The results of olive norite zircon U-Pb age was 284.8 ±0.91 Ma,which shows that the formation age of Baixintan intrusion was early Permian.the age and the obtained within other mafic-ultramafic intrusion is consistent,which was at the peak period of Permian in east tianshan area?(3)The content of Mg O is about 9.93wt%,and the content of Fe O is about 9.29 wt% in the parent magma,which suggest that it belongs to basaltic magma through olivine crystallization differentiation.(4)The magma temperatures is 1006.7 to 1394.41 ?,the mean temperature is 1207.55?.The pressure is about 3.2kbar.The oxygen fugacity is ~QFM+1.(5)Further demonstrates the east tianshan copper nickel ore rock formed in the environment after the collision extend,magma source area is affected by subduction event transform partial melting of mantle metasomatism,melting and after collision extend under the background of lithosphere delamination and asthenosphere upwelling.