Highly siderophile element and chromium isotopic variations in physically separated components of carbonaceous and ordinary chondrites

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The processes that have enriched and depleted the metal component in various groups of primitive meteorites (chondrites) are still poorly constrained. In addition, the causes of abundance variations of siderophile (iron loving) elements in chondrites are incompletely understood. From comparisons with lithophile elements, it has been known that moderately volatile highly siderophile elements (HSE) in chondrites are at least partly affected by volatile element depletion or addition. Surprisingly, refractory highly siderophile elements also display systematic differences in ordinary and enstatite chondrites compared to carbonaceous chondrites. Fractional condensation in the early solar nebula has been suggested as one possible explanation. The role of solid metal-liquid metal, metal-silicate or sulphide silicate partitioning as additional controls of HSE abundances observed in bulk chondrites remains to be evaluated in a comprehensive way. Here it is proposed to study osmium isotopic compositions, HSE abundances, and major element ratios such as Fe/Ni, Fe/S and Fe/Mg in the same digestion aliquot of separated components of chondrites from different groups. Such data will also facilitate our understanding of the formation and modification processes of chondrite components such as chondrules and matrix.