Isotopically heavy carbon in the core

Constraining the origin of Earth’s carbon requires knowing the isotopic composition of the core—a geochemical signature long presumed to be beyond observation for the planet’s largest carbon reservoir. Here, we report high-precision δ 13 C measurements from Hawaiian plume melt inclusions entrapped before significant degassing and sampling distinct mantle sources. Melt inclusions from shield-stage lavas, interpreted to sample the plume’s central axis, inferred to be rooted in the core–mantle boundary thermal boundary layer, converge toward a primary δ 13 C signature of –1 ± 2‰. In contrast, melt inclusions from rejuvenated-stage lavas, derived from entrained mantle at the plume’s periphery, record a normal mantle source signature of –7 ± 2‰. We interpret the uniquely 13 C-rich shield-stage signature as the isotopic fingerprint of carbon exchanged from the core into the mantle. Our results point to 13 C-rich carbonaceous chondrites as the primary source of Earth’s carbon.

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Publication Details

Journal
Proceedings of the National Academy of Sciences
Published
2026-11-09
DOI
https://doi.org/10.1073/pnas.2610912123
Primary Topic
Geological and Geochemical Analysis
Type
article
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article

Isotopically heavy carbon in the core

Estelle F. Rose Koga, Yves Moussallam, Guillaume Georgeais, Matthew Gerard Jackson et al.
Proceedings of the National Academy of Sciences
Geological and Geochemical Analysis
article

Isotopically heavy carbon in the core

Estelle F. Rose Koga, Yves Moussallam, Guillaume Georgeais, Matthew Gerard Jackson, Allan H. Lerner, Damanveer S. Grewal, Olivia E. Anderson, Paul Wallace, Hyunjoo Lee, Natália Gauer Pasqualon, Bridgett Holman
article en

Abstract

Constraining the origin of Earth’s carbon requires knowing the isotopic composition of the core—a geochemical signature long presumed to be beyond observation for the planet’s largest carbon reservoir. Here, we report high-precision δ 13 C measurements from Hawaiian plume melt inclusions entrapped before significant degassing and sampling distinct mantle sources. Melt inclusions from shield-stage lavas, interpreted to sample the plume’s central axis, inferred to be rooted in the core–mantle boundary thermal boundary layer, converge toward a primary δ 13 C signature of –1 ± 2‰. In contrast, melt inclusions from rejuvenated-stage lavas, derived from entrained mantle at the plume’s periphery, record a normal mantle source signature of –7 ± 2‰. We interpret the uniquely 13 C-rich shield-stage signature as the isotopic fingerprint of carbon exchanged from the core into the mantle. Our results point to 13 C-rich carbonaceous chondrites as the primary source of Earth’s carbon.

Proceedings of the National Academy of SciencesVol. 123(46)
University of Hawaiʻi at Mānoa (US), United States Geological Survey (US), Centre National de la Recherche Scientifique (FR), American Museum of Natural History (US), Lamont-Doherty Earth Observatory (US), University of California, Santa Barbara (US), University of Oregon (US), Brown University (US), Cascades Volcano Observatory (US), Yale University (US), Institut des Sciences de la Terre d'Orléans (FR), Columbia University (US)
Geological and Geochemical Analysis
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