Pervasive subduction zone devolatilization recycles CO<sub>2</sub> into the forearc.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 33277477.
- Also identified by DOI 10.1038/s41467-020-19993-2 and PMC identifier 7718257.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The fate of subducted CO<sub>2</sub> remains the subject of widespread disagreement, with different models predicting either wholesale (up to 99%) decarbonation of the subducting slab or extremely limited carbon loss and, consequently, massive deep subduction of CO<sub>2</sub>. The fluid history of subducted rocks lies at the heart of this debate: rocks that experience significant infiltration by a water-bearing fluid may release orders of magnitude more CO<sub>2</sub> than rocks that are metamorphosed in a closed chemical system. Numerical models make a wide range of predictions regarding water mobility, and further progress has been limited by a lack of direct observations. Here we present a comprehensive field-based study of decarbonation efficiency in a subducting slab (Cyclades, Greece), and show that ~40% to ~65% of the CO<sub>2</sub> in subducting crust is released via metamorphic decarbonation reactions at forearc depths. This result precludes extensive deep subduction of most CO<sub>2</sub> and suggests that the mantle has become more depleted in carbon over geologic time.