The platinum-group element geochemistry in chemical geodynamics

The content ratios of Ru, Rh, Pd, Os, Ir, and Pt noble metal elements are identical to some extent for chondrites and mantle samples, but their contents in mantle samples actually are lower than those in chondrites by about 2 magnitudes, thus the hypothesis of "late veneer" happened during the earth accretion after the core-mantle separation was presented and has become a popular explanation. Heterogeneity in PGE content of the mantle peridotites on scales of ∼ 100 kilometers might be caused by inhomogeneity during the earth accretion, but a more possible explanation is a result of the mantle processes, core-mantle or/and crust-mantle interaction. Partial melting, crystal fractionation of magma (especially segregation of sulfide or metal phases), and fluid (including melt)/rock interaction result in PGE fractionation of mantle peridotites, ophiolites and complex in supersubduction and orogenic zone, and also will be the common mechanisms of generating chromitites and huge-size noble metal deposits.link_to_subscribed_fulltex