SHRIMP U-Pb dating of detrital zircons from the Permian sandstones along the southern and northern margins of Xar Moron River, central inner Mogolia: Implications for provenance and the tectonic evolution of the eastern segment of the Central Asian Orogenic Belt

Abstract

The Xar Moron River fault zone, located in the eastern segment of the Central Asian Orogenic Belt (CAOB), represents the intensely debated final collision zone of the Siberian Craton (SC) and North China Craton (NCC). To determine the tectonic evolution of the eastern segment of the CAOB, we undertook petrography and zircon U-Pb dating of the Huanggangliang and Linxi formations in the Wufendi and Xingfuzhilu areas along the Xar Moron River. Petrographic analysis of Permian sandstones revealed a close relationship between the sedimentary and orogenic sources suggesting short transport distances. A sample from the Huanggangliang Formation yielded detrital zircon U-Pb ages ranging from 2653 Ma to 265 Ma, with three age populations: at 2653 to 2443 Ma, 1935 to 1764 Ma, and 482 to 265 Ma, whereas samples from the Linxi Formation yielded detrital zircon U-Pb ages ranging from 3363 Ma to 257 Ma, with four age populations: at 2705 to 2403 Ma, 2011 to 1203 Ma, 571 to 375 Ma, and 356 to 257 Ma. The age spectrum differences of sandstones on both banks indicate that the Xar Moron River fault zone is the final collision zone of the eastern segment of the CAOB. The sandstone of Huanggangliang Formation yielded a weighted mean age of 265.7 ± 1.5 Ma, suggesting that the main deposition of the Huanggangliang Formation was during the Middle Permian. In addition, a comparison of the youngest age in the sedimentary rocks with U-Pb ages obtained for pyroclastic rock implies that the Linxi Formation formed in the late Permian. The results of our study support the view that the final closure of the eastern segment of Paleo-Asian Ocean (PAO) occurred during late Permian to earliest Triassic times.