Insights into the origin of carbonaceous chondrite organics from their triple oxygen isotope composition

Romain Tartese, Marc Chaussidon, Andrey Gurenko, Frédéric Delarue, Francois Robert

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    Abstract

    Dust grains of organic matter were the main reservoir of C and N in the forming Solar System and are thus considered to be an essential ingredient for the emergence of life. However, the physical environment and the chemical mechanisms at the origin of these organic grains are still highly debated. In this study, we report high-precision triple oxygen isotope composition for insoluble organic matter isolated from three emblematic carbonaceous chondrites, Orgueil, Murchison, and Cold Bokkeveld. These results suggest that the O isotope composition of carbonaceous chondrite insoluble organic matter falls on a slope 1 correlation line in the triple oxygen isotope diagram. The lack of detectable mass-dependent O isotopic fractionation, indicated by the slope 1 line, suggests that the bulk of carbonaceous chondrite organics did not form on asteroidal parent bodies during low-temperature hydrothermal events. On the other hand, these O isotope data, together with the H and N isotope characteristics of insoluble organic matter, may indicate that parent bodies of different carbonaceous chondrite types largely accreted organics formed locally in the protosolar nebula, possibly by photochemical dissociation of C-rich precursors.
    Original languageEnglish
    JournalProceedings of the National Academy of Sciences of the United States of America
    Early online date6 Aug 2018
    DOIs
    Publication statusPublished - 2018

    Keywords

    • carbonaceous chondrites
    • organic matter
    • oxygen isotopes
    • protosolar nebula
    • secondary ion mass
    • spectrometry

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