Zircon U-Pb age, geochemical characteristics and geological significance of the triassic granite in Keerqinyouyizhongqi, Inner Mogolia

Abstract

Based on the Zircon U-Pb dating and geochemical data obtained for the granite in Keerqinyouyizhongqi Inner Mongolia, we discussed the granite types and regional tectonic evolution. The biotite granite and granodiorite are mainly developed in the area. They are enriched in SiO2, Al2O3, and alkali, and belong to high potassium peraluminous calc-alkaline series of S type granite. The rare earth element normalized distribution diagram shows that LREE are highly concentrated, while HREE are relatively depleted with the ratio of LREE/HREE between 3.12 and 16.17, an average of 10.07; the ratio of LaN and YbN is between 2.72 and 28.71, Eu anomaly is moderate negative; enrichment of rock large ion lithophile Rb, K and Pb, depletion of high field strength elements Nb, Ta, Zr, Ce, Ti, the feature of collision type granite. These granitics could be distinguished by their low-Sr and low-Yb based on the geochemical characteristics, which shows that the granitics are likely formed under high pressure. The Zircon U-Pb age (242.6±2.5) Ma, suggests that the paleo Asian Ocean subduction collision occurred in Triassic period, the formation of granite rock mass related to the collision split.