The distribution of platinum and palladium metals in iron meteorites and in the metal phase of ordinary chondrites

Abstract

The concentrations of Ru, Rh, Pd, Ir, and Pt have been determined spectrographically in twenty-four iron meteorites and in the metal phase of five ordinary chondrites. It was found that most iron meteorites fall into three distinct groups with regard to the Ru and Rh concentrations and into three groups with regard to the Ir and Pt concentrations, each Ir-Pt group corresponding to one of the Ru-Rh groups. Correlations are observed between these Ir-Pt and Ru-Rh groups on the one hand, and the Ga-Ge groups found by previous workers on the other, but the relationships are by no means clear-cut. Compared with Ru, Ir, and Pt, Pd was found to vary over a relatively small range. The metal phases of all chondrites studied are chemically identical with the iron meteorites of the largest Ru-Rh and the largest Ir-Pt group, namely the Ru-Rh group which contains about 6 ppm Ru and 1.5 ppm Rh, and the Ir-Pt group which contains about 2 ppm Ir and 7 ppm Pt. The following atomic abundances (Si = 10^6) of Ru, Rh, Pd, Ir, and Pt have been derived from our data: Ru Rh Pd Ir Pt Based on metal phase of high-iron-group chondrites 1.66 0.27 1.05 0.40 1.22 Based on iron meteorites, assuming they constitute 10%of mean meteoritic matter 1.44 0.23 0.52 0.31 0.89 These values generally agree within a factor of less than 2 with the abundances calculated by recent workers.

Files

Additional details