College of Earth Sciences, Jilin University, Changchun 130061, China

The authors analyzed zircon geochronological data and geochemical data of Zhushan metagabbro from Yilan, eastern Heilongjiang to determine their age, petrogenesis and tectonic setting. Zircons from metagabbro are euhedral-subhedral in shape with typical striation absorption features and high Th/U ratios (0.20~0.86), implying their magmatic origin. LA-ICP-MS zircon U-Pb dating shows that Zhushan metagabbro from Yilan formed during Late Permian with age of (256±3)Ma. The geochemical characteristics show that these metagabbros are low in silicon and high in magnesium, iron, aluminum and calcium. The rocks are enriched in LREEs and LILEs (Rb, Ba), and depleted in HREEs and HFSEs (Nb, Ta, Zr, Hf and Ti). Combined with the regional geological data, it is proposed that Zhushan metagabbro was derived from a mantle wedge that had been metasomatized by subducted slab-derived fluids. Its formation was probably related to the subduction of a paleo-oceanic plate, which implies that the collision between the Jiamusi Massif and the Songnen Massif may have not happened before Late Permian.