Isotopically heavy carbon in the core.

Shield-stage Hawaiian plume melt inclusions show a primary δ13C of -1 ± 2‰, distinct from rejuvenated-stage inclusions’ -7 ± 2‰ mantle signature.

• Why it matters: Pinning down Earth’s carbon origin depends on measuring the core’s isotopic composition, a geochemical signal long thought unobservable.
• What they did: High-precision δ13C was measured in Hawaiian plume melt inclusions trapped before significant degassing, sampling central-axis shield-stage lavas and peripheral rejuvenated-stage lavas.
• The result: The 13C-rich shield-stage δ13C is interpreted as a core-to-mantle exchange fingerprint, implying 13C-rich carbonaceous chondrites as Earth’s primary carbon source.

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