GEOCHEMISTRY AND GENESIS OF THE NEOARCHEAN METAMORPHIC PLUTONIC ROCKS IN BEIZHEN AREA, LIAONING PROVINCE

The Neoarchean metamorphic plutonic rocks in Beizhen area of Liaoning Province are the oldest crystalline basement in the region. With general metamorphism and deformation of plutons, the structures of protolith have changed. The plutonic rocks can be divided into two rock units of Xiaoqianmaling gneiss complex (Ar₃xqgn^c) and Baichangmen gneiss (Ar₃bgn) according to the characteristics and distribution of rock mass. The SiO₂ content in Ar₃xqgn^c is 59.69%-76.22%. The liquidus temperatures of the two rocks are 720-1024℃ and 776-1024℃ respectively. The Ar₃xqgn^c is characterized by high degree of magmatic differentiation, while Ar₃bgn with high differentiation index (DI) of 68.99-91.68. The Ba/Sr ratios of both rocks are close to each other with approximately parallel right-dipping REE patterns, showing unobvious Eu anomalies with enrichment of LREEs, which indicates that the two rocks are derived from similar material sources.