Contrasting slab decarbonation patterns control deep carbon cycling efficiency in hot vs. cold subduction zones

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Abstract
Subducting slabs play a crucial role in deep Earth carbon cycling, yet the carbon-cycling efficiency of different subduction zones remains debated. Here, we systematically compare decarbonation characteristics in the extremely cold Tonga and hot Colombia subduction zones using observation-constrained thermo-petrological modeling, integrated with volcanic degassing and arc geochemistry. Two contrasting slab decarbonation patterns are identified: efficient “focused” decarbonation in hot subduction zones versus sluggish “diffuse” decarbonation in cold subduction zones. Hot Colombia exhibits a high decarbonation efficiency >15%, dominated by metamorphic carbon release within a narrow depth range of ∼75–115 km and supplemented by partial melting-induced decarbonation. In contrast, cold Tonga shows a much lower decarbonation efficiency of ∼1% by dissolution-dominated carbon removal over a broad depth range of ∼75–310 km. These findings suggest a contrasting efficiency of different subducting slabs for deep carbon cycling and volcanic degassing in present-day and ancient subduction systems.
Funding Information
  • National Natural Science Foundation of China (42225403)
  • National Natural Science Foundation of China (92579208)
  • National Natural Science Foundation of China (42574139)
  • National Key Research and Development Program of China (2022YFF0801001)
  • Fundamental Research Funds for the Central Universities
  • Deep Earth Probe and Mineral Resources Exploration-National Science and Technology Major Project (2025ZD1005604)

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