The Preliminary Study of the Geochemistry and Tectonic Significance of Late Paleoaoic Granitoids in West Junggar

Abstract: The studied region is located in West Junggar,Toli contry of Tacheng District,Xinjiang of China. Based on the field study, this work has carried out granitoids formed during the Late Paleozoic tectonic environment,formation mechanism and tectonic significance, by analyzing the combination of granite rock types and geochemical characteristics of the West Junggar.The post-collisional magrnatic rocks of late Paleozoic is widespread in the studied areas, The intmsioas formed in 319.6±3.2Ma(Hatu granite) and in 309.4±2.5Ma (Seerdeng granite), the era of the Late Carboniferous. Magmatic rocks in the region consist of A2-type granite and I-type granite. Hatu granite with high silicon, low aluminum, alkali-rich, metaluminous-weakly peraluminous, and poor calcium, low magnesium,10000×Ga/Al ratio was higher, strong enrichment in high field strength elements (HFSE), Sr, Ba strong losses, REE patterns show a typical right-wing plan "seagull-type", etc.These features envinced that granite in Hatu should be typically aluminous A-type granite. Al-A2-type granite discrimination diagrams show that granite in Hatu is the A2-type granite. But about the Serdeng rock, characteristics of mineral rocks, geochemical discrimination diagrams show that the Serdeng rock should be I-type granite rock. In the region that post-colisional I type and A2 type granites after Late Carboniferous provides new evidence for Late Carboniferous crustal material and re-allocation process in the West Junggar regionSeerdeng and Hatu granites formed in a post-collisional extension context. The fomer results from the partial melting of basical substance,the later probably results from femic mineral, with a circumstance of thin continental crust; the underplating of asthenosphere basaltic magma provides the heat enegy for partial melting of the lower crust…
Key words: post-collisional; granite; geochemistry; Tectonic significance; Late Paleozoic; West Jungg

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