Composition and clues to the origin of refractory metal nuggets extracted from chondritic meteorites

Refractory metal nuggets (RMNs) contain elements, such as Os, Ir, Mo, and Ru, which are predicted to condense from a cooling gas of solar composition simultaneously with CAI-minerals. Berg et al. (2009) identified a large number of RMNs in acid-resistant residues of the Murchison meteorite and suggested that they are pristine condensates. In extending the work of these authors, we have improved the chemical extraction process to enrich the concentration of RMNs in the residue sample and prepared three additional RMN-rich residues from the chondritic meteorites Murchison, Allende, and Leoville. The results show that, while their origin is clearly solar, the compositions in detail of RMNs fro…