Abstract
Carbon in the asthenosphere is unevenly distributed, reflecting interactions between the depleted mantle and materials added by plumes or subducting slabs. Nevertheless, mid-ocean ridge basalts (MORB) from the Arctic Gakkel Ridge, far from any existent hotspots and subduction zones, are unusually carbon-rich. Here we show that the MORB along the Gakkel Ridge display systematically elevated Zn isotopes (δ66Zn = 0.27‰–0.41‰) relative to typical global MORB (0.26 ± 0.03‰). Their heavy δ66Zn ratios correlate with indicators for mantle source carbon enrichment. We attribute this signature to result from recycled surficial carbonates stored in deep upper mantle under the Arctic Ocean. These carbonate components were likely delivered by ancient oceanic subduction and subsequently entrained into the mantle upwelling feeding the Gakkel Ridge. Our results demonstrate that vestiges of past subduction can dominate carbon budgets beneath plume‑unaffected ridges, and act as a principal driver of large‑scale carbon heterogeneity in the upper mantle.
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Data availability
Supplementary Note 1–4, Supplementary Figs. 1–12, and Supplementary Data 1–6 are available through figshare at https://doi.org/10.6084/m9.figshare.30189946. Source data for each figure are provided as a Source Data file with the paper. Source data are provided with this paper.
Code availability
The estimations of primary magma CO2 contents in this study make use of previously published machine learning models2. The original implementation and trained models are publicly available at Github repository (https://github.com /ZJUEarthScienceJIA /MORB_primary_CO2_TiantingLei). No new machine learning code was developed for this study.
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Acknowledgements
We thank Shitou Wu, Yanhong Liu, Huan Li, Yunxiu Li, and Jihao Zhu for their help during the geochemical measurements. This study was financially supported by the National Natural Science Foundation of China (42025201 to C.Z.L., 42025601 to W.W.D., 42576067 to W.Q.Z.), Zhejiang Provincial Natural Science Foundation of China (LZYQ25D060002 to W.Q.Z.), Scientific Research Fund of the Second Institute of Oceanography, MNR (grand no. SZ2542 to W.Q.Z.), and the National Natural Science Foundation of China (42203050 to W.Q.Z., 42573019 to Z.Q.Z.).
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W.Q.Z., W.W.D., and C.Z.L. designed this research and acquired fundings; C.J.L., T.Z., Y.J.W., P.C.T., Y.X.F., and J.B.L. acquired the samples; W.Q.Z. performed the geochemical and isotopic measurements; W.Q.Z., W.W.D., and C.Z.L. wrote the manuscript; W.Q.Z., W.W.D., C.Z.L., C.J.L., T.Z., J.G.L., P.C.T., Z.Q.Z., Y.X., Y.X.F. and J.B.L. interpreted the data, review and edited the manuscript.
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Zhang, WQ., Ding, WW., Liu, CZ. et al. Zinc isotope evidence for extensive carbonate recycling in the Arctic asthenosphere. Nat Commun (2026). https://doi.org/10.1038/s41467-026-71022-w
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DOI: https://doi.org/10.1038/s41467-026-71022-w
