Study On Late Paleozoic Granites In Hatushan Area Of West Junggar,Xinjiang

The Late Paleozoic is the crucial period of land and ocean transformation of the West Junggar.The Hatushan area is located in the core region of West Junggar,with a lot of Late Paleozoic granites.It is a good research object to explore the regional tectonic evolution and mineralization.In this study,the Tiechanggou pluton,Hatu pluton,Akebasitao pluton,Bieluagaxi pluton,Kuergakexi pluton,and Kushikuduke pluton are taken as the research objects,combined with previous research results,we carried out mineralogy,petrology,geochemistry and chronology research to explore the genesis,provenance and tectonic environment of granite in the survey area,and discussed the relationship between granite and mineralization,and the main achievements are as fellows:1.Large pluton such as Tiechanggou,Hatu,Akebasitao,their lithology are mainly syenite granite,monzonite granite and a small amount of alkali feldspar granite.It is characterized by high Si,alkali-rich,lean Mg,relatively Al-rich,strong loss of Ba,Sr,Eu,P and Ti and obvious negative Eu anomalies.The diagenetic age is concentrated in 309?296Ma,belonging to alkaline weakly peraluminous A₂ type granite;Bieluagaxi,Kuergakexi,Kushikuduke and other small stocks,the lithology are mainly quartz diorite and granodiorite,with moderate Si-rich,Al-rich and enriched large ion philophile elements Rb and Ba,the strong loss of high field strength elements such as Ti,Nb,Ta and heavy rare earth elements Y,Yb and weak positive Eu anomalies.They belong to calcium-alkaline quasily aluminous-weakly peraluminous I type granite,diagenetic age is 322?312Ma.2.Comparing the two granites,it can be seen that the A₂ type granite was formed in the post-orogenic extensional environment,a large amount of mantle-derived material upwelled by the extensional system heated the young crust composed of oceanic crust and island arc,and granitic magma formed by partial melting was formed by separated crystallization;I type granite was formed in the subduction island arc environment.As the oceanic crust subducted to the lower part of the mantle wedge,it caused the subduction fluid and mantle-derived material to invade and upwell,heating the young crust formed by the depleted mantle,and produced by partial melting.3.Two types of granite with different tectonic backgrounds produced in the Late Carboniferous-Early Permian indicate that during their emplacement and diagenesis,the Hatushan area has collided,changing from the subduction island arc environment to the post-orogenic extension environment.However,there are still evidences of Late Carboniferous subduction activity in the South of West Junggar,which shows that the West Junggar is not unified into a post-orogenic environment by collision,but is composed of multiple island arc through multiple stages of collage.Therefore,the main collision time limits in different regions are inconsistent,several ophiolitic mélanges in the southern area of West Junggar juxtaposed with sedimentary rocks and volcanic rocks,which also proves that the West Junggar evolved into a multi-stage collage accretion model in the Late Paleozoic.4.The survey area is located in the Hatu gold belt.Au mineralization potential is good.The proven deposits include Hatu,Beluagaxi,Baobei and other famous gold deposits,the mineralization types are mainly altered rock type and quartz vein type.The age of mineralization is concentrated in the Late Late Carboniferous-Early Early Permian,which is closely related to the Late Paleozoic tectonic magmatism in the area:I type granite has good Au metallogenic potential and is the main source of Au in the survey area;A₂ type of granite has a low Au element content,but provides sufficient heat for the activation and enrichment of the Au element;faults such as Daerbute and Anqi provide channels and seating space for Au element migration and enrichment.