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Updated: Nov 27, 2025

Measuring Carbon-based Contaminant Mineralization Using Combined CO2 Flux and Radiocarbon Analyses
Published on: October 21, 2016
Pervasive subduction zone devolatilization recycles CO2 into the forearc.
E M Stewart1,2, Jay J Ague3
1Department of Earth and Planetary Sciences, Yale University, 210 Whitney Avenue, New Haven, CT, 06511, USA. estewart@caltech.edu.
Subducting carbon dioxide (CO2) is largely released through metamorphic decarbonation in the forearc, not lost to deep Earth. This field study shows significant CO2 release, impacting mantle carbon depletion over geologic time.
Area of Science:
- Geochemistry
- Petrology
- Tectonics
Background:
- The fate of subducted carbon dioxide (CO2) is debated, with models predicting either extensive loss or minimal release.
- Fluid history of subducted rocks is key, as water-bearing fluids enhance CO2 release during metamorphism.
Purpose of the Study:
- To investigate the efficiency of decarbonation in a subducting slab.
- To provide field-based evidence to constrain models of deep carbon cycling.
Main Methods:
- Comprehensive field study of decarbonation in the Cyclades, Greece.
- Analysis of metamorphic reactions in subducting crustal rocks.
Main Results:
- Approximately 40% to 65% of CO2 in the subducting crust is released via metamorphic decarbonation at forearc depths.
- This indicates significant CO2 release rather than deep subduction.
Conclusions:
- Extensive deep subduction of most CO2 is unlikely.
- The Earth's mantle has likely become progressively depleted in carbon over geologic time due to this release mechanism.
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