1. College of Earth Sciences, Jilin University, Changchun 130061, China;
2. Jilin Institute of Geological Survey, Changchun 130061, China

In order to determine the Late Triassic tectonic attribute in the eastern margin of Songnen-Zhangguangcai Range Massif, and delineate the time of the subduction of Palaeo-Pacific Plate underneath the Eurasian continent, LA-ICP-MS zircon U-Pb dating and geochemical analysis of the Xilazigou granodiorite were undertaken. The zircon U-Pb age of the Xilazigou granodiorite is (216±1) Ma that is the product of magmatism in Late Triassic. The geochemical data indicate that the Xilazigou granodiorite belongs to metaluminous, high-potassium calc-alkaline I-type granite, the granites are characterized by high content of SiO₂ and K₂O,low contents of MgO, CaO and Fe₂O₃, enrichment of LREE, relative enrichment in LILE (Rb, Th, U, K) and depletion in HFSE (Nb, Ta, Ti). These characteristics suggest that the Xilazigou granodiorite was derived from partial melting of the lower crustal materials. According to the rock assemblage and spatial distribution of the contemporaneous igneous rocks in adjacent areas, the authors suggest that the Xilazigou granodiorite formed in the post-orogenic extensional setting which could be related to the closure of the Paleo-Asian Ocean, following the subduction of Palaeo-Pacific Plate underneath the Eurasian continent after Late Triassic.