The oxidation state of the Earth's sub-oceanic mantle from oxygen thermobarometry of abyssal spinel peridotites

L. Taras Bryndzia*, Bernard J. Wood, Henry J B Dick

*Corresponding author for this work

    Research output: Contribution to journalArticle

    27 Citations (Scopus)

    Abstract

    THE oxygen fugacity (fO2), or redox state, of the Earth's mantle is an important parameter in the evolution of mantle-derived magmatic rocks. Most estimates of the upper-mantle redox state have been based on samples of the sub-continental mantle and terrestrial lavas, and estimates of fO2 obtained by thermo-barometric methods tend to cluster within ±1.5 log units of the FMQ (fayalite-magnetite-quartz) reference oxygen fugacity buffer. Much less is known about the redox state of the sub-oceanic mantle, the ultimate source of mid-ocean-ridge basalts (MORBs). Here we use oxygen thermobarometry of abyssal spinel peridotites, representative of most of the Earth's mid-ocean-ridge systems, to show that the redox state of the sub-oceanic mantle lies at values of up to 4 log units (average of 1.35 log units) more reduced than FMQ. Our results are in excellent agreement with oxygen fugacities of MORBs obtained from Fe3+/Fe2+ ratios of quenched glass in pillow basalts. This agreement confirms the redox state of the MORB source region and suggests that MORB glasses (as opposed to the cores of pillow basalts) have not undergone significant oxidation (hydrogen degassing) during their ascent.

    Original languageEnglish
    Pages (from-to)526-527
    Number of pages2
    JournalNature
    Volume341
    Issue number6242
    Publication statusPublished - 1989

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    Bryndzia, L. T., Wood, B. J., & Dick, H. J. B. (1989). The oxidation state of the Earth's sub-oceanic mantle from oxygen thermobarometry of abyssal spinel peridotites. Nature, 341(6242), 526-527.