Zircon U-Pb dating of granitic gneiss in Wugong Mountain area, central Qiangtang, Qinghai-Tibet Plateau: age records of Pan-African movement and Indo-China movement

Abstract：Qiangtang basin located in northern Tibetan plateau is a key area in studying the evolution of the Paleo-Tethys Ocean and the boundary of Gondwana and Eurasia, and the age and properties of its basement directly determine the tectonic attribute of southern Qiangtang plate and the range of Gondwana. In this paper, LA-ICP-MS U-Pb dating was carried out for zircons from granitic gneiss inclusions (xenoliths) in Wugong Mountain area, central Qiangtang. The dating results show that granitic gneiss inclusions were formed in late Triassic (209.1±2.8Ma). This age is consistent with the existing research results of the convergence events of Gondwana and Eurasia in central Qiangtang, so the granitic gneiss inclusions are material records of the convergence events of Gondwana and Eurasia. Moreover, the dating results also indicate that granitic gneiss inclusions contain a age record of the end of Pan-African period (464.5±4.8Ma), which is the first age of Pan-African movement found in Qiangtang area, and this age can be compared with ages of large amounts of early Paleozoic granitic rocks in Nujiang area and Baoshan area in western Yunnan, internal Indian plate and Himalayan orogenic belt, suggesting that southern Qiangtang plate has good affinity to Indian plate. All the results obtained by the authors can provide fresh evidence for the study of the properties of Qiangtang basement and the age of the convergence events of Gondwana and Eurasia.