LA-ICP-MS U-Pb Dating of Detrital Zircons and Geological Implications of Linxi Formation in Linxi County, Inner Mongolia

Abstract

The detrital zircon LA-ICP-MS U-Pb dating of the glutenite assemblage with lacking of biological fossils in Linxi County, Inner Mongolia was carried out to clarify the ages and material origin of the coarse clastic rocks and explore the tectonic evolution of the Xar Moron River suture. The detrital zircon ages fall in six groups of ca. (285±4)-(246±4) Ma (peak 264 Ma), (317±5)-(293±4) Ma (peak 310 Ma), (610±10)-(344±6) Ma (peak 423 Ma), (992±14)-(907±13) Ma, (1 467±18)-(1 424±22) Ma,and (1 948±14)-(1 768±16) Ma; besides, there are three zircons with the age of (1 171±17) Ma, (1 238±17) Ma, and (2 443±31) Ma, respectively. Most of the zircons show oscillatory or linear zoning in CL images and high Th/U ratios(>0.1), indicating that they are magmatic origin. We conclude that the depositional age of the coarse-grained clastic rocks is younger than 264 Ma, which should be Upper Permian Linxi Formation. The sedimentary provenance of Linxi Formation in Huichangdi area is mainly from the Jiamusi-Mongolia block with minor from the North China plate, which implies that the North China plate and the Jiamusi-Mongolia block merged in Late Permian at the position of Xar Moron River suture.