Characteristics And Geological Significance Of The Volcanic Rocks In Upper Jurassic-lower Cretaceous Sangxiu Formation Of The Zhegu Area,south Tibet

Our study area is located between Brahmaputra suture zone and Southern Tibet Detachment System(STDS)in the south of the Qinghai-Tibet Plateau.The Tethys ocean basinin this area is dominated by upper Triassic and Lower Cretaceoussediments.The evolution of the basin was influenced by the collision of Indian continent and Eurasian continent.This study mainly focuses on Upper Jurassic and Lower Cretaceous Sangxiu Group in the Zhegu area,southern Qinghai-Tibet Plateau.field mapping,including field investigationof six important areas,fourcross sections.Then,we divided the Sangxiu Formation three members,and collected 70 samples that were studied using thin section,geochronology and whole-rock geochemistry.The data of this study is mainly from the geological mapping of Wan Zhe ancient Tibet,card bead,Qiong jiang,loose,card fruitareas that I joined.According to the characteristics of the lithologic combination in the measured section of the Sangxiu Group,the Late Jurassic was dominated bysediments of shallow sea.The volcanic rocks as the interlayer of theSangXiu Group yieldzircon U-Pb Concordiaageof 142 ±1 Ma,indicating the age ofcrystallization.Thus,the age further supports thatSangxiu Group isLate Jurassic to Early cretaceous.Based on the geochemical characteristics,we suggest that theJurassictoLower Cretaceous volcanic rocks,is a product of intercontinental rift and derived from mantle with crust contamination.The rock type isalkaline basalt that formed in passive continental margin rift.