Carbon Flux Dynamics in Subduction Zones

Subduction zones form the principal conduit by which carbon is transferred from Earth’s surface reservoirs into its deep interior and back to the atmosphere via arc volcanism. As oceanic crust and its sedimentary cover descend, pressure–temperature conditions induce a series of metamorphic reactions that liberate CO₂ and reduced carbon species into aqueous and carbonate-rich fluids. These fluids migrate through the mantle wedge, triggering decarbonation of slab lithologies, the formation of hydrous carbonatitic melts and the crystallisation of diamond, methane and magnesite under high-pressure conditions. The balance between fluid-mediated carbon release at forearc depths and retention of refractory carbon phases at greater depths governs the efficiency of carbon recycling to the deep mantle. Fluid pathways are controlled by tectonic discontinuities, lithological heterogeneity and hydration reactions, with profound implications for seismicity, volcanic CO₂ fluxes, long-term climate regulation and the sustenance of deep subsurface microbial ecosystems.

Research from Nature Portfolio

Recent studies have elucidated the pivotal role of reduced fluids in mobilising carbon and triggering mechanical failure in forearc rocks. One investigation reveals that CH₄-H₂-rich fluids, generated by carbonate reduction during high-pressure serpentinisation, accumulate along shear zones, drive pore-fluid overpressure and may induce seismic slip at depths of 30–40 km. Another study demonstrates that hydrous carbonatitic liquids dominate carbon transfer at subarc depths (150–200 km) under moderate thermal regimes, with water depressing the stability of Ca-rich carbonates and facilitating pervasive carbonatite generation at temperatures as low as 850 °C. These findings converge on a model in which fluid composition and overpressure govern both deep carbon transport and mechanical behaviour of subducting slabs.

Carbon Flux Dynamics in Subduction Zones publication trend

The graph below shows the total number of articles in carbon flux dynamics in subduction zones across all publications each year (not limited to Nature Index journals).

Technical terms

Subduction zone: A convergent plate boundary where an oceanic plate descends beneath another plate into the mantle.

Slab: The subducting tectonic plate, comprising oceanic crust and overlying sediments, that sinks into the mantle.

Mantle wedge: The region of mantle material above the subducting slab and below the overriding lithosphere, where fluids and melts accumulate.

Decarbonation: Metamorphic reactions that break down carbonate minerals, releasing CO₂ into fluids.

Carbonatitic liquid: A carbonate-rich melt or fluid phase that transports carbon at high pressures and moderate temperatures.

Serpentinisation: Hydration of ultramafic mantle rocks, producing serpentine minerals, H₂ and promoting abiotic hydrocarbon formation.

References

1. Methane-hydrogen-rich fluid migration may trigger seismic failure in subduction zones at forearc depths. Nature Communications (2024).
2. Pervasive hydrous carbonatitic liquids mediate transfer of carbon from the slab to the subarc mantle. Communications Earth & Environment (2023).
3. Tracking carbon from subduction to outgassing along the Aleutian-Alaska Volcanic Arc. Science Advances (2023).
4. Deep carbon cycling during subduction revealed by coexisting diamond-methane-magnesite in peridotite. National Science Review (2023).
5. Formation of abiotic hydrocarbon from reduction of carbonate in subduction zones: Constraints from petrological observation and experimental simulation. Geochimica et Cosmochimica Acta (2018).
6. Subduction hides high-pressure sources of energy that may feed the deep subsurface biosphere. Nature Communications (2020).