Partial melting of H6 ordinary chondrite Kernouvé: Constraints on the effects of reducing conditions on oxidized compositions

Rena L. Ford, Gretchen K. Benedix*, Timothy J. McCoy, Tracy Rushmer

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    12 Citations (Scopus)

    Abstract

    Partial melting experiments at temperatures of 950-1300 °C were conducted on the H6 chondrite Kernouvé under reducing conditions using CO-CO2 gas mixing and graphite-buffered sealed silica tubes to examine the effect of reducing conditions during melting of starting materials that are more oxidized relative to the oxygen fugacity conditions of the experiments. The experiments produced a range of mineralogical and compositional changes. Olivine exhibits significant reduction to compositions of Fa2-5 at temperatures of 1300 °C. In contrast, orthopyroxene exhibits only slight reduction until the highest temperatures. Chromite is sometimes consumed by intruding sulfides, and displays increasingly magnesian compositions ranging as low as Fe/Fe + Mg of 0.1 at a constant Cr/Cr + Al ratio. The compositional changes with increasing temperature reflect a complex set of reactions, including oxidation-reduction. One application of these experiments address whether primitive achondrites could have formed from ordinary chondrite-like precursors by partial melting under reducing conditions. While changes observed in olivine and troilite compositions might support such an idea, differences in oxygen isotopic composition, Cr/Cr + Al in chromite, orthopyroxene compositions, and thermodynamic evidence against reduction during melting of primitive achondrites (Benedix et al. 2005) firmly refute such an idea.

    Original languageEnglish
    Pages (from-to)1399-1414
    Number of pages16
    JournalMeteoritics and Planetary Science
    Volume43
    Issue number8
    Publication statusPublished - Aug 2008

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