EARLY JURASSIC GRANITES IN FUYUANGOU FOREST FARM OF MOHE COUNTY, NORTHERN DAXINGANLING MOUNTAINS: Chronology, Geochemistry and Tectonic Implications

Through the study of petrography, geochemistry and LA-ICP-MS U-Pb dating of the Early Jurassic granites in Fuyuangou Forest Farm, northern Daxinganling Mountains, the paper discusses their constraints on the regional tectonic evolution. Dominated by monzogranite, the granites are formed in Early Jurassic shown by the zircon dating results of samples. The geochemical analyses reveal that the monzogranite, belonging to high-K calc-alkaline, metaluminous I-type granitoid, is characterized by enrichment of LREEs and LILEs(Rb, K and Ba), and depletion of HREEs and HFSEs (Nb, Ta and P). The primary magma for the monzogranite is derived from partial melting of basaltic lower crust. Combined with the regional data, the emplacement of granites indicates that the Mohe region was still in the tectonic environment of subduction of Mongolia-Okhotsk oceanic plate beneath Erguna Massif during the Early Jurassic Epoch.