Geology And Geochemistry Of Mesozoic Granite In The Gaoligong Tectonic Belt, West Yunnan

Gaoligong tectonic belt, which located between the Tengchong block and Baoshan block, is a branch of Bangonghu-Nujiang tectonic belt. Gaoligong tectonic belt is bounded by the Longchuanjiang and nujiang River valley in the territory of about 450Km length, near 8km width.By observing, Gaoligong tectonic belt and its west side of granite, we can study Gaoligong tectonic belt’s features, tectonic deformation, and the magmatic rock evolution. And further discuss the movement, dynamics and the chronology of the Gaoligong tectonic belt.Gaoligong tectonic belt (Gaoligongshan group), is a series of gneiss, granulite, magmatite and other metamorphic rocks as the main component. Structure deformation, magmatism and metamorphism have occurred frequently in the belt, which are characterized by multi-period tectonic evolution.Geochemical data show that the magmatite is mainly granodioritic-granitic and the classification is a sub-alkaline series. And they exhibit enrichment in light REE and negative Eu-anomaly, which show that they come from Mesoproterozoic granodioritic - granite rock.The oscillatory zoning of zircons in the cathodoluminescence images shows that they experienced simple evolution history. The U-Pb age of the magmatite and the granite west is unanimous (about 112-125Ma), which exhibit that they have the same crystallizing age and metamorphism and deformation of the magmatite may formed later.Gaoligong tectonic belt is consistent with the granite of the northern margin of the Lhasa in age and geochemical characteristics. It suggests that they represent eastern extension of the Gandese belt and the Gaoligong tectonic belt resulted from crustal melting during the southward subduction of the Meso-Teths oceanic lithosphere underneath the Gandese Block.The ductile deformation of Gaoligong tectonic belt is 19-24Ma and 11-14Ma by K-Ar method and the exhumation time of the granite is 5-8Ma by fission track.