Sedimentary age and provenance tracing of the Permian Hongquan Formation in the Yantongshan structural belt on the northeastern margin of the Qinghai-Tibet Plateau

Restricted by the absence of reliable fossils, the sedimentary age of the Permian Hongquan Formation which was sporadically exposed in the Yantongshan Fault Belt at the northeastern margin of the Tibetan Plateau has always been under dispute.Besides, due to the lack of reliable sedimentary structures in the Permian Hongquan Formation and outcrops, whether the sediments were sourced from the Ordos Block in the northeast, Alxa Block in the north or Northern Qilian Block in the west is undefined.The sedimentary age and provenance of tuffaceous feldspar sandstone at the bottom of the Permian Hongquan Formation were redefined based on zircon U-Pb dating.The results show that the age spectra of the detrital zircons from the taffaceous feldspathic sandstone yields five age peaks at 264 Ma, 1811 Ma, 1928 Ma, 2348 Ma, and 2465 Ma, among which the zircons with the age of 264 Ma mostly come from tephra deposited during the early stage of the Hongquan Period.Therefore, the sedimentary age of the Hongquan Formation is 264 Ma which can be attributed to the late stage of the Middle Permian to Late Permian.The age spectra of the detrital zircons from the Hongquan Formation have similarity with the age spectra of the basement of the western part of the North China Craton, and significant difference with the age spectra of the basement of the Alxa Block and North Qilian Block.Consequently, it is inferred that the sedimentary materials of the Permian Hongquan Formation should come from the Ordos Block in the northeast.This research not only redefines the sedimentary age of the Hongquan Formation in the arcuate tectonic belt at the northeastern margin of the Tibetan Plateau, but also provides solid evidence for the sedimentary source tracing for the reconstruction of the Permian regional lithofacies palaeogeography.