FIGURE 1 Elemental mantle abundances relative to carbonaceous chondrite. The stair-step depletion pattern is a function of the affinity of each group of elements for iron; thus, lithophile elements, which have no affinity for iron, occur at the chondrite concentration level in the terrestrial mantle, whereas the PGE, Re, and Au, which are "iron-loving elements," are depleted by two orders of magnitude relative to chondritic meteorites. The uniform depletion of these highly siderophile elements cannot be modelled by metallic melt-silicate melt partition coefficients determined at 1 bar pressure. The use of high-pressure metallic melt-silicate melt partition coefficients can reconcile the abundance of Pd (Righter et al. 2007) but not that of Pt (Ertel et al. 2006). FIGURE ADAPTED FROM DRAKE AND RIGHTER (2002) AND COTTRELL ANDWALKER (2006)