GEOCHRONOLOGY AND GEOCHEMISTRY OF THE GRANITE PORPHYRY IN TEGEWULA AREA OF XIN BARAG YOUQI, INNER MONGOLIA

The study on the petrology, geochemistry, genesis and tectonic environment of the granite porphyry in Tegewula area of Daxinganling Mountains show that the age of the rock is 145.9±1.2 Ma, formed in the late Early Cretaceous. The granite porphyry is rich in silicon, alkali and aluminum, belonging to the quasi aluminous-aluminous high-potassium calc-alkaline series. The mineral assemblage and geochemical characteristics show that the granite porphyry is highly differentiated I-type granite, with enriched LILEs (Rb, Th and U) and LREEs (La, Ce and Pr), and obvious negative Eu anomaly, indicating the geochemical characteristics of crust-derived magma or magma mixed with crustal materials. It is concluded that the granite porphyry in Tegewula area was formed in a post-orogenic extensional environment, which may be related to the delamination of thickened continental crust after the closure of Mongolia-Okhotsk suture zone.