Geochronology And Geochemistry Of The Cenozoic Intrusives In Eastern South Gangdese, Tibet

The Lhasa terrane,southern Tibet is where the thickest part of the Earth’s crust occurs as a result of the India-Asia collision.This paper reports petrography、zircon U-Pb ages、zircon Hf isotopes and geochemical data of samples collected from the Gangdese batholith,southern Lhasa terrane,reveal the evolution process of rock、the characteristics of magmatic source and the meaning of geodynamic in this region.The εHf(t) of surrounding rock and enclave in Sangri rock are plus, which show that the magmatic source include more mantle to join.Obtains the source of Cenozoic intrusive rocks in the sangri regions is material of crust-mantle mixed source, mainly including mantle-derived,which is the epicontinental potassium calc-alkaline series I-type granite related to the plate collision.The tectonic model is: as the split of India and Gangdese batholith in 45~48Ma,India continue to.subduction of Indian after the continent continue to lower part of Asia lead to magmatic underplating, The melt of enrichment asthenosphere plate under sheet bar not only invade the overlying plate,but also accompanied by the earth’s crust material along the channel into the underthrust plate.And the source of mantle magma by board clips will appear in the upper plate and the subduction plate at the same time.Great heat make the lower crust partial melting,which lead to the formation of felsic magma reservoir,while mafic magma will upwell into the felsic magma reservoir along the gallery with the occurrence of magma mixing.