Detrital zircon U-Pb ages and Hf isotopes of Early-Middle Permian sandstones from the south margin of Xing-Meng orogenic belt and their tectonic significance

In this paper, the authors used the LA-MC-ICP-MS analytical techniques to determine U-Pb ages and Hf isotopic composition of detrital zircons from the Lower Permian Sanmianjing Formation and Middle Permian Elitu Formation in Zhengxiangbai Banner area of Inner Mongolia on the southern margin of the Xing-Meng orogenic belt. Detrital zircon dating of the sandstone of the Sanmianjing Formation yielded three main age populations respectively at 280~369Ma (4 grains), 1800~2271Ma (43 grains, peaked at 1877Ma), and 2507~2711Ma (9 grains), whereas the Elitu Formation displays prominent age groups at 271~371Ma (9 grains), 1258~1395Ma (18 grains, peaked at 1326Ma) and 1695~2454Ma (34 grains, peaked at 1864Ma), respectively. The detrital zircon geochronological and Hf isotopic studies indicate that the Meso-Proterozoic to Neoarchean grains were probably derived from the basement of the North China Craton. The Late Paleozoic zircons exhibit negative ε_Hf(t) values of -5.3~-23.7 and old Hf model ages of 1124~3039Ma. These characteristics show a strong resemblance to the Late Paleozoic igneous zircons from the north margin of the North China Craton, suggesting that the source of the Sanmianjing Formation and Elitu Formation partly came from the North China Craton. Integration of provenance data with regional geological information and magmatic records suggests that no Andean-type active continental margin was generated on the northern margin of the North China Craton during Early to Middle Permian, and the Sanmianjing Formation and Elitu Formation were deposited in an extensional tectonic environment.