The Early Paleozoic magmatism in Qiangtang, northern Tibet and its geological significance

The Qiangtang early Paleozoic magmatism and its tectonic evolution are of great significance for the study of the early evolution of the Qinghai-Tibet Plateau and the basement properties and structures of the Qiangtang basin. This paper systematically summarizes the spatial and temporal distribution characteristics and chronological framework of the Early Paleozoic magmatic rocks in the Qiangtang region of northern Tibet, and preliminarily discusses the constraints of the Early Paleozoic tectonic-magmatic events and the tectonic evolution in the northern margin of Gondwana and the basement properties of the Qiangtang Basin on the Qinghai-Tibet Plateau. The results show that the magma records with metagabbro, metabasalt, andesite, granite, metarhyolite and granitic gneisses as the main rock assemblages developed in Riwan Chaka, Duguer, Gemuri, and Bensongco areas in central Qiangtang. The results of regional geological survey and chronology indicate that the Qiangtang had experienced a strong Early Paleozoic episodic magmatism, which can be subdivided into 5 stages, namely ~500 Ma, ~482 Ma, ~474 Ma, ~455 Ma and ~438 Ma respectively. In reference to previous geochemical and isotopic data, we preliminary speculate the Early Paleozoic magmatism in central Qiangtang may be a result of lithospheric extension on the northern margin of Gondwana after Pan-African orogenic movement. They constitute the Early Paleozoic crystalline basement of Southern Qiangtang-Baoshan Plate. The magmatic records play an importont role in constrainting the northern continental margin of Gondwana in the Qinghai-Tibet Plateau.