Characteristics, Geochronology Of Lincang Granite In The Southern Lancangjiang, Sanjiang Area And Implication For Tectonics

Lincang granite in the Southern Lancangjiang,Sanjiang area is the important magmatite record of the Paleo-Lancangjiang evolution and collision,The continent-continent or continent-arc collision between Baoshan-Simao Block. Lincang granite is the biggest composite granite batholith that cropped out in Yunnan province,the important element of Tethys tectonic domains.It plays an important role in understanding the tectonic development of Tethys,the precise time for continent-continent collision,bettter understanding the interaction of generation of magmatism and the tectonic evolution of orogenic belt,the machanism of magmatism.We conduct the study on region geology, the basic characteristics of Lincang granite,lithology(lithofacies), zircon LA-ICP-MS U-Pb geochronology, elemental and Sm-Nd,Rb-Sr isotopic geochmistry, to investigate the generation machanism of magmatism and their teetonic settings relative to their generation, to Probe into the closen time of Paleo-Tehtyan Oeean, the interaction of generation machanism of magmatism and the tectonic evolution of orogenic belt.Lincang granite comprises mainly diorite monzonite granite and belongs to the potassium-rich calc-alkali series, with SiO2 67.15-74.6% and K2O/Na2O=1.61-2.63, Lincang granite is peraluminous, with Al2O3>13.12% and A/CNK =1.32-1.89>1.1, show typical S-type granites. The rocksΣREE are high and on the whole relatively rich in LILE but poor in HFSE and shows moderate negative Eu anomalies. According to geochemical characteristics and related discrimination diagrams, it is suggested that Lincang granite should be of S type.The geochronological data of Zircon LA-ICP-MS U-Pb geochronology suggest that Lincang granite were formed at 219.1-198.2Ma, the main formation period from middle Triassic-early Jurassic(T3-J1). Discrimination diagram suggested that Lincang granite were mainly formed in the post-orogenic stage.