THE NEOPROTEROZOIC GRANITIC GNEISS IN CHAOMAN FOREST FARM AREA OF DAXINGANLING MOUNTAINS: Zircon U-Pb Dating, Geochemistry and Tectonic Environment

The study on the petrology, geochemistry, genesis and tectonic environment of Neoproterozoic granitic gneiss in Chaoman Forest Farm area of Daxinganling Mountains yields the age of 795.2±4.3 Ma. The granitic gneiss is characterized by high Si, high alkali, rich Ca, Na and K, enrichment of LREEs and depletion of HREEs, with weak negative Eu anomaly and depletion. The magma source area is mainly crust-derived magma, and some mantle-derived magma underplating causes partial melting of rocks in the middle-lower crust, with hybridization of mantle-derived components to form mixed magma. Combined with regional data, the Neoproterozoic granitic gneiss in the study area was formed in a magmatic arc environment related to subduction.