1. College of Earth Sciences, J ilin University, Changchun 130061, China; 2. School of Earth Sciences and Resources, China University of Geosciences (B eijing) , B eijing 100083, China

Element geochemical characteristics of ultramafic-mafic complex rocks in Wuxing show that the primary magma is tholeiitic magma with low Ti and high Mg in content. It derives from the partial melting function of slightly depleted mantle which forms from metasomatic depleted mantle by CO2 -based fluid, and the main residual mineral phases are of garnet, spinel and rutile. The formation and evolution of magma have experienced three stages: �� thermal fluid led to higher partial melting of lithosphere mantle and then formed hypoalkaline basalt with saturated initial sulfur when ascending asthenosphere contacted with the lithosphere mantle; �� the initial magma intruded into the lower crust to form magma chamber, the crystallization of magma p roduced stratiform-like cumulate, including olivine, hypersthene, augite, magnetite, and then formed residual gabbroic magma with the participance of crustalmaterial; �� the residual magma and ore-bearing cumulate intruded upward successively to shape originalmafic complex rocks in Wuxing when the magma chamber cracked. According to the mineralization of Cu-Ni and Pt-Pd deposit, Cu-Ni sulphides were formed by liquation in the late phase of fractional crystallization of magma chamber, and the Pt-Pd mineralization mainly occurred on the p rocess of fluid action after diagenetic stage.