Zircon SHRIMP ages of Precambrian metamorphic basement rocks and their tectonic significance in the eastern Kunlun Mountains, Qinghai Province, China

Abstract

There are some fragmentary Precambrian basement rocks exposed in the Eastern Kunlun Mountains, which can be divided into two different kinds of basement blocks. The north basement is composed of Archean-Paleoproterozoic Baishahe Group and Mesoproterozoic Xiaomiao Group, and the south basement is composed of Paleoproterozoic-Mesoproterozoic Kuhai Group. The U-Pb SHRIMP age dating to the metamorphic detrital rocks of the Xiaomiao Group in the north basement shows that the provenances of the detrital rocks of the Xiaomiao Group are older than 2 400 Ma. The age dating gives a peak age of about 2 400～2 500Ma, reflecting a metamorphic thermal event in the source area. One detrital zircon yields~(207)Pb/~(206)Pb age of (3 206±14) Ma, showing the existence of Paleoarchean continental nucleus in the source area. The metamorphic zircon and anatectic zircon give an age group of 1 035～(1 074) Ma, showing the principal metamorphism and extensive tectonic-thermal event of the Xiaomiao Group and reflecting the collision event of the north and south blocks during the sealing of the Mesoproterozoic ocean, which is implied by the Qingshuiquan ophiolite. This event is accordant with the formation of the Rodinia supper continent, suggesting that the extensive ductile shearing and anatexis of the basement rocks in the Eastern Kunlun are the representation of the convergence of the Rodinia continent.