The Geological And Geochemical Characteristics And Formation Age Study Of The Luomahu Rock Group Galashan Rock Group In Greater Hinggan Mountains Tekelaier

The Greater Khingan Mountains Luomahu Rock Group has been regarded as a Precambrian metamorphic basement of Xing'an block for a long time. In recent years, with the large amount of accurate isotope data and the availability of fossil data, it has been shown that the Lomahu Rock Group is later than the Neoproterozoic- Early Cambrian, possibly the Ordovician- Silurian, the chronology of the progress of the geological significance of the Loma Rock Group put forward new constraints.The author relies on the "Geological and Mineral Resources Survey of the Inner Mongolia 1? 50000 Tekelaier, Wubaqi, Kewoni, Xinliuzhan" in the project of the China Geological Survey, The paper analyzes the petrology, petrographic geochemistry, and chronology of the Galashan Formation of the Lamahu Rock Group, which is exposed in the Tekelaier Mountains of the Greater Khingan Mountains. The results show that the Galashan Formation is composed of amphibolite, leptynite, schist and gneiss, The main body of the original rock is a set of clastic rocks, and the volcanic rocks are locally clipped. The metamorphic degree generally reaches the high greenschist facies-amphibolite facies. The REE assemblage model is characterized by the enrichment of light rare earths, the depletion of heavy rare earths, the REE curve is a right- lean curve of light rare earth enrichment, and the negative Eu anomaly characteristics. Trace elements with Th, U, K, Nd obvious enrichment and Ba, Nb, Ta, Sr, P, and Ti obvious depleted characteristics. In this study, the detrital zircon isotopic ages of 449-946 Ma were obtained in the two-mica monzonitic gneiss of the Galashan Formation of the Lamahu Rock Group, indicating that the Galashan Formation formed late In the Neoproterozoic- Early Cambrian, the minimum peak age(449±5Ma) indicates that the upper limit of deposition is not earlier than the Ordovician.With the comprehensive geochemical tectonic environment discriminant analysis, it is considered that the Galashan Formation of Luomahu Rock Group is mainly formed in the tectonic setting of the Duobaoshan continent island arc.