Platinum-group element geochemistry of Cretaceous mafic-ultramafic rocks in the Northern Dabie

Abstract：The contents of platinum group elements (PGE；Ir, Ru, Rh, Pt, Pd) in the Cretaceous mafic-ultramafic rocks of the Northern Dabie have been determined by nickel sulfide fire assay preconcentration, combined with ICP-MS. The PGE abundances for all the twelve samples are low. Primitive mantle-normalized PGE distribution patterns have a positive slope and are slightly depleted in PPGE and strongly depleted in IPGE relative to the primitive mantle with Pd/Ir values far higher than their corresponding mantle ratios. Strong PGE fractionation in the samples is mainly controlled by sulfide phase in the process of low degrees of partial melting of the mantle. Ir occurs in non-sulfide phase such as spinel and possibly also in Os-Ir alloys. The Distribution characteristics of PGE suggest that these mafic-ultramafic rocks are the product of magmatic crystallization differentiation.