Figure 34.

Estimating mantle composition using terrestrial peridotites. (a) Ir versus Al₂O₃ for a global suite of variably melt-depleted peridotites. The solid horizontal line represents a regression for all samples with > 2 wt.% Al₂O₃. The intersection of the trend with the estimated range for Al₂O₃ in the primitive mantle, and the associated uncertainties (shaded region) gives an Ir concentration for PM of 3.5 ± 0.4 ng.g⁻¹. (b) Pd/Ir versus Al₂O₃ for a global suite of variably melt-depleted peridotites allow the elemental ratio determination of PM and, consequently estimated abundances of the HSE relative to Ir. The gray band in (b) is Pd/Ir for chondritic meteorites. Methods and data are from Becker et al. (2006) and references therein.