Rhenium-Osmium in iron-nickel, sulfide, and phosphide: the possible determination of internal isochrons for iron meteorites

Abstract

For age determinations of specific events in the evolution of iron meteorites, it is essential to obtain a reasonable range of physical-chemical fractionation of Re-Os. The possible stages of iron meteorite evolution that can, in principle, result in Re-Os fractionation include (1) condensation of PGE and of FeNi in the solar nebula; (2) subsequent oxidation of part of the Fe by reaction with S; (3) segregation and partial removal of massive FeS during melting on parent planetesimals; (4) melting followed by fractional crystallization of the metal phase and crystallization of the remaining FeS; (5) element redistribution during subsolidus phase transformations to produce schreibersite sheaves; and, finally, (6) precipitation or exsolution of minor microphases, e.g., rhabdite, at a later stage.