1. College of Earth Sciences, Jilin University, Changchun 130061, China;
2. Geological Survey Institute of Jilin Province, Changchun 130102, China

In order to study the Early Yanshanian magmatism in central Jilin Province, and delineate the starting time of the subduction of Palaeo-Pacific Plate beneath the Eurasian continent, the authors undertook LA-ICP-MS zircon U-Pb dating and geochemical analysis of Jiangmifeng granodiorite. It shows that the zircon U-Pb age of the granodiorite is 179±1 Ma, which is the product of magmatism in Early Jurassic. The geochemical anal-ysis results indicate that the Jiangmifeng granodiorite has high content of SiO₂, Na₂O, K₂O, Al₂O₃ and TFe₂O₃, but low content of MgO and CaO, belonging to quasi-aluminous, high-potassium calc-alkaline, highly fractionated I-type granite. The granodiorite is enriched in LREEs, LILEs (Rb, K) and HFSEs (Th), depleted in HREEs, LILEs (Ba, Sr) and HFSEs (Nb, Ta, Ti, Zr), with negative Eu anomalies. The formation of the rocks experi-enced the mixing of crustal and mantle materials in the source area to form primary magma and subsequently the mixed magma underwent a two-stage diagenetic process of extensive magmatic differentiation and evolution. Accord-ing to the rock assemblage and spatial distribution of the contemporaneous igneous rocks in adjacent areas, the au -thors suggest that these rocks formed in the back-arc extensional setting which could be related to the subduction of Paleo-Pacific Plate beneath the Eurasian continent.