9706024 Drake This project addresses the geochemistry of highly siderophile elements in silicate systems of Earth's interior. The PIs will carry out an experimental program to investigate the solubility and mineral/melt partitioning behavior of noble siderophile elements. The major scientific goals are to quantify: (1) the geochemical behavior of Re and Os, elements important for chronology and as tracers of planetary evolution; (2) the geochemical behavior of the platinum group elements in general. The PIs will target the Re-Os isotopic system and conduct systematic studies if crystal/melt partitioning of Re and Os. A second approach involves systematic solubility investigations to quantify the chemical controls on highly siderophile element solubilities in lithophile phases. Experiments will be carried out in one-atmosphere gas-mixing furnaces, piston-cylinder apparatus, and multi-anvil apparatus.