Oxygen isotopes of chondritic components

Hisayoshi Yurimoto, Alexander N. Krot, Byeon Gak Choi, Jerome Aléon, Takuya Kunihiro, Adrian J. Brearley

    Research output: Chapter in Book/Report/Conference proceedingChapter

    107 Citations (Scopus)

    Abstract

    We review the oxygen isotopic compositions of chondrite components (refractory inclusions, chondrules, and matrix) and their inter- and intra- crystalline oxygen isotopic distributions. Primary oxygen isotopic compositions, acquired before planetesimal accretion, are easily disturbed by parent-body processes such as aqueous alternation and thermal metamorphism. Primary or original oxygen isotopic compositions of refractory inclusions (Ca-, Al-rich inclusions and amoeboid olivine aggregates) distribute along a slope-1 line on the three-oxygen isotope diagram over the range of -60‰ < δ 17O ≈ δ18O < +10‰. The variations suggest that oxygen isotopic compositions of the solar nebular gas temporally and spatially varied between 16O-rich and 17O-, 18O-rich during refractory inclusion formation. On the other hand, primary minerals of most chondrules have small isotopic variations and are enriched in 17O and 18O relative to refractory inclusions, suggesting that chondrule formation occurred in 17O-, 18O-rich nebular gas. However, rare 16O-rich chondrules have been found, suggesting some overlap in the timing of formation of chondrules and refractory inclusions in the solar nebula. Oxygen isotopic compositions of matrix grains distribute along the slope-1 line over the same range as refractory inclusions and chondrules. The similarity in oxygen isotopic distributions suggests that matrix was originally a mechanical mixture of nebular dusts co-generated with chondrules and refractory inclusions. Presolar grains with oxygen isotopic compositions that are clearly distinct from those of solar nebular materials are a trace component of chondrite matrices. Based on these oxygen isotopic characteristics, more than 99.5% of the solid materials in the nebula formed locally in the solar nebula, and the remainder formed in interstellar space. The astrophysical setting of chondrite component formation in the early Solar System is also discussed. Refractory inclusions and 16O-rich matrix dusts formed around the inner edge of the solar nebula. On the other hand, most chondrules and 17O-, 18O-rich matrix dusts seem to have formed elsewhere in the solar nebula. Efficient, large-scale radial mixing of the solar nebular materials may have been an essential process in the formation of chondritic planetesimals.

    Original languageEnglish
    Title of host publicationOxygen in the Solar System
    EditorsGlenn MacPherson, David Mittlefehldt, John Jones, Steven Simon
    Pages141-186
    Number of pages46
    DOIs
    Publication statusPublished - Mar 18 2008

    Publication series

    NameReviews in Mineralogy and Geochemistry
    Volume68
    ISSN (Print)1529-6466

    ASJC Scopus subject areas

    • Geochemistry and Petrology

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