Crystallization and stability of noble metal alloys in the magmatic process

The possibility of existence of noble metal-iron alloys in the magmatic process was estimated on the basis of experimental investigations of noble metal solubility in silicate melts and thermodynamic modeling. It was shown that Fe-Pt and Ir-Ru-Os alloys must be stable in magmatic melts. In contrast, Au-rich alloys cannot be stable in magmatic melts under any conditions. It was shown that the noble metals are incompatible in mineral phases and the bulk analyses of minerals with high contents of platinum-group elements (PGE) that have been reported in the literature can be explained by the contamination of the mineral phases by microinclusions of noble metal alloys. Under certain conditions (low oxygen fugacity and a high concentration of As, Bi, or Sb in the melt), PGE can form liquid compounds with these trace elements, which should facilitate their mobilization by high-temperature fluids. Copyright © 2005 by Pleiades Publishing, Inc.