Abstract: The Jinbaoshan complex is located in the west margin of the Yangtze Plate, adjacent to the northern part of the Ailaoshan orogenic belt. It contains abundant Pt-Pd resources and is a large magmatic PGE deposit in the Emeishan Large Igneous Province (ELIP). The complex is mainly composed of wehrlites with ore body presented as stratoid or lentoid in wehrlites. Mantle is the most important source of forming the Ni and PGE deposits, thus the study of Ni, Cu and PGE geochemical behavior is important for understanding the genesis of magmatic Ni-Cu-PGE deposits. In this work we determined the PGE and Sr-Nd isotope contents in wehrlites from the Jinbaoshan intrusion. Combined with PGE studies on different series of rocks in the ELIP and research on the Dsul/sil for Ni, Cu and PGE by previous researchers, we suggest that the primitive magma is formed by moderate to high degrees of melting (25%40%), resulting in 12.8 ppb Pd, 9.8 ppb Pt, 0.6 ppb Rh, and 0.7 ppb Ir, close to the contents of the ELIP picrite. The Jinbaoshan intrusion has experienced 10%20% crustal contamination from the Yangtze upper crust during magma evolution. Based on the batch partial melting formula and Dmineral/melt parameters for the PGE, the PGE contents of Jinbaoshan mantle were calculated to be 5.3×10-9 Pd, 7.5×10-9 Pt, 0.75×10-9 Rh, and 1.5×10-9 Ir. Compared to primitive mantle, the mantle of the Jinbaoshan intrusion does not show obvious PGE enrichment. Therefore we may conclude that a large magmatic PGE deposit could be formed by moderate to high degrees of mantle melting accompanied by large scale mixing of magma and sulfides.

Key words: magma source, PGE, partial melting, Jinbaoshan