Reevaluating carbon fluxes in subduction zones, what goes down, mostly comes up

Area of Science:

• Geochemistry
• Geology
• Earth Science

Background:

• Subduction zones play a critical role in Earth's carbon cycle.
• Previous estimates suggested significant carbon recycling into the mantle.
• Accurate carbon flux data is crucial for understanding global carbon budgets.

Purpose of the Study:

• To re-evaluate carbon fluxes in subduction zones.
• To incorporate new data on carbon concentration in mantle peridotites.
• To assess the fate of carbon during subduction.

Main Methods:

• Estimating carbon concentration in subducting mantle peridotites.
• Modeling carbonate solubility in aqueous fluids along subduction geotherms.
• Considering the role of diapirism in carbon-bearing metasediments.

Main Results:

• Subducting carbon may be significantly less than previously estimated.
• Little carbon appears to be recycled back into the convecting mantle.
• Carbon input into the overlying plate exceeds output from arc volcanism and diffuse venting.

Conclusions:

• Substantial carbon is stored in the mantle lithosphere and crust.
• The subduction zone carbon cycle may be nearly closed on 5-10 Ma timescales.
• Increasing carbon content in the mantle lithosphere + crust + ocean + atmosphere is consistent with noble gas data.
• Carbon in diamonds represents a minor fraction of the global carbon inventory.