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<p>Subduction of carbon rich sediments and crust at convergent plate boundaries exerts a crucial control on Earth’s mantle chemistry and surface habitability. Recent attention has focused on exposures of fully-carbonated mantle rocks as these may attest to an overlooked sink for subducted carbon not sampled by arc volcanism. However, even in the best-studied example, the Semail Ophiolite, Oman, the setting for carbonation remains highly contentious, with conflicting inferences from geochemistry and geochronology. We approach this problem by combining microanalysis of halogens and detailed petrography to fingerprint the origins of carbonating fluids. Fluids were derived from both sedimentary pore fluid expulsion and deep slab decarbonation reactions in a subduction zone setting. Through mass balance modelling we show that CO<sub>2</sub> fluxes into the forearc from deep decarbonation (1.7–3.4 ×&#xa0;10<sup>13</sup> gyr<sup>−1</sup> C) could represent up to 90% of the global flux entering subduction zones, indicating that carbonated mantle peridotites likely represent a major sink for subducted CO<sub>2</sub> which may have varied through geological time.</p>

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Carbonated mantle peridotites represent a hidden sink for subducted CO2

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年2月27日

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  • Elliot J. Carter,
  • Brian O’Driscoll,
  • Ray Burgess,
  • Patricia L. Clay,
  • Hélène Balcone-Boissard,
  • Pierre Bürckel

摘要

Subduction of carbon rich sediments and crust at convergent plate boundaries exerts a crucial control on Earth’s mantle chemistry and surface habitability. Recent attention has focused on exposures of fully-carbonated mantle rocks as these may attest to an overlooked sink for subducted carbon not sampled by arc volcanism. However, even in the best-studied example, the Semail Ophiolite, Oman, the setting for carbonation remains highly contentious, with conflicting inferences from geochemistry and geochronology. We approach this problem by combining microanalysis of halogens and detailed petrography to fingerprint the origins of carbonating fluids. Fluids were derived from both sedimentary pore fluid expulsion and deep slab decarbonation reactions in a subduction zone setting. Through mass balance modelling we show that CO2 fluxes into the forearc from deep decarbonation (1.7–3.4 × 1013 gyr−1 C) could represent up to 90% of the global flux entering subduction zones, indicating that carbonated mantle peridotites likely represent a major sink for subducted CO2 which may have varied through geological time.