Geochemical Characteristics and Geological Significance of Granites in Eastern Songliao Basin

LA–ICP–MS dating and trace REE geochemical analysis of biotite–bearing granites in the eastern part of Songliao basin and the western part of Zhangguangcai range are carried out to explore their diagenetic age and environment in this paper . The sample zircon oscillatory growth zone is obvious, and the Th/U ratio is big, indicating that it belongs to magmatic origin. The ages of zircon U–Pb dating are （179.3±1.5）Ma; （177.5±1.4）Ma, belonging to the end of Early Jurassic. Light rare earth elements have obvious fractionation, heavy rare earth elements have no obvious fractionation, and Eu and Ce elements have positive anomalies. The sample was formed in the subduction and accumulation environment of the plate. The formation of granites in the two regions is mainly controlled by partial melting. The two dikes have the duality of crust and mantle, may have mantle contamination. Based on the statistics of the ages of the granites in the Greater Khingan Mountains, Songliao basin and Zhangguangcai range, it is found that the granites in Zhangguangcai range were formed earlier than those in Songliao basin. Validate the previous speculation that the ancient Pacific plate and the Mongolia–Okhotsk ocean plate have double subduction and delamination.