Contrasting slab decarbonation patterns control deep carbon cycling efficiency in hot vs. cold subduction zones
- Hengrui Zhang
- Yang Wang
- Zhong-Hai Li
- Taras V. Gerya
- Hong-Yan Li
- Shui-Jiong Wang
- Xin Zhou
- Yangfan Deng
- Yu Wang
- Jason P. Morgan
2026-07-29
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.