The Preliminary Study Of Granitoids In Wushitala, Heshuo Country, Sinkiang, China

The Chinese south Tianshan（South Tianshan for short）orogenic belt lies in themiddle-southern part of the Tianshan orogenic system of the southern North Asia area whichis between the Siberia and Tarim blocks. It is a typical late Paleozoic orogenic belt.SouthTianshan is a late Paleozoic collision zone which was developed from a broad ocean basinbetween the Tarim micro-plate and Kazakhstan micro-plate. In this context, a large volume ofgranitoid plutons formed in the South Tianshan orogenic belt during Late Carboniferous toEarly Permian. Based on predecessors’ researches and detailed field investigations，this papermergers and partitions granite bodies，studies the mineralogy，petrology,geochemistry andZircon U-Pb chronology of Hongshan and Tuogelake granitic Plutons and discusses the causeof the granites,Source area characteristics and Tectonic environments.Gained achievementsare as follows:1、The Hongshan granite pluton is mainly the porphyaceous biotite monzonitic graniteand the medium-coarse grains moyite, mostly belongs to quasi-weakly peraluminous, high-Kcalc-alkaline I-typed granite. By SHRIMP zircon U-Pb dating, it is found that Hongshangranite body was formed in early Permian Epoch (297±3Ma).The residual mineral mainly isamphibole, garnet and little plagioclase and the stress is0.9~1.3GPa in magma source. Underthe post-collision tectonic setting, it is formed by the partial melting of the lower crustalhigh-K andesite regions, and in this process, mantle-derived material makes a littlecontribution.2、The Tuogelake granite pluton is mainly porphyaceous biotite monzonitic granite andmedium-coarse grains moyite granite, mostly belongs to quasi aluminum, Shoshonite seriescalc-alkaline I-typed granite，and also has some characteristics of A-type granite.By SHRIMPzircon U-Pb dating, it is found that Tuogelake monzonite granite was formed in early PermianEpoch (287±3Ma)，and moyite granite was formed in early Permian Epoch (289±4Ma),both belonging to early permian epoch. The residual mineral is mainly amphibole andplagioclase （without garnet）and the stress is less than0.8or1GPa in magma source. Underthe tectonic mechanism of lithospheric thinning in the late post-collision, the mafic magmas upwells, making lower crustal high-K basaltic andesite-andesite materials partial melting,which is the main reason of the rock mass formation.Based on the analysis above，the time of south tianshan study area in the post-collisiontectonic setting is about300~285Ma. This illustrates that the late Paleozoic South TianshanOcean closed at the early Carboniferous and the Tarim plate and Kazakhstan plate collidedinto orogenesis. At the end of the carboniferous(the300Ma or so), the collisional orogenycompleted，and the south tianshan collisional orogenic belt transformed into post-collisiontectonic setting.