GENETICS, AGES, AND CHEMICAL COMPOSITIONS OF IRON METEORITES

Abstract

Comparison of genetic isotopic compositions of iron meteorites with metal-silicate segregation ages suggests that the isotopic composition of the NC reservoir changed with time. By contrast, no such age-linked changes in the genetic isotopic compositions of iron meteorites from the CC reservoir are observed. Results of comparing bulk planetesimal genetic isotopic compositions with bulk planetesimal siderophile element chemical characteristics indicate that the processes responsible for isotopic heterogeneity in the early Solar System are not discerned by the siderophile element chemical characteristics of planetesimals. Iron meteorite parent bodies from the CC reservoir typically have smaller relative cores and a greater proportion of the Fe content in the mantle, consistent with the CC reservoir being a more oxidized environment, such as the outer Solar System, compared to the NC reservoir. The chemical characteristics of iron meteorite parent bodies, including bulk core FeS/Fe ratios and oxidation states, may form relationships with core formation ages, but whether these characteristics can account for potential differences in the formation ages of NC- and CC-type parent bodies presently cannot be constrained.