Abstract:To address the controversy of the Ershi’erzhan formation sandstone formation ages in the Mohe basin of the northern Da Hinggan Mountains, this study presents an limit to its formation ages using the LA-ICP-MS detrital zircon U-Pb dating in this paper, and discusses its provenance and tectonic setting combined with the geochemistry of major and trace elements. The Zircon U-Pb dating results show that 132 dating date are distributed in the following four periods, 492.3Ma~508.3Ma, 435.5Ma~486.9Ma, 254.2Ma~278.3Ma, 178.1Ma~209.5Ma. It is considered that the formation age of the Ershi’erzhan formation should be middle-late Jurassic combined with the minimum age(178.1Ma) of the zircon and the age of zircon in the East and west of Mohe Basin. The geochemical analysis results show that the REE curves of the Ershi’erzhan formation sandstone are in good agreement with the REE curves of the active continental margin, and are relatively depleted in high field strength elements (Nb and Ta) and large ion lithophile elements (Ba and Sr), and are relatively enriched in high field strength elements (La, Th, Zr, Hf). Based on the analysis of paleocurrent, source rock, zircon dating and trace element characteristics, it is believed that the parent rock of the Ershi’erzhan formation sandstone is mainly from the pre Mesozoic sedimentary metamorphic basement (Xinghuadukou group, Jiageda formation, erguna river formation, etc.) and the intermediate acid igneous rocks.
