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Forearc carbon sink reduces long-term volatile recycling into the mantle

TitleForearc carbon sink reduces long-term volatile recycling into the mantle
Publication TypeJournal Article
Year of Publication2019
AuthorsBarry PH, de Moor JM, Giovannelli D., Schrenk M., Hummer D.R, Lopez T., Pratt C.A, Segura Y.A, Battaglia A., Beaudry P., Bini G., Cascante M., d'Errico G., di Carlo M., Fattorini D., Fullerton K., Gazel E., Gonzalez G., Halldórsson S.A, Iacovino K., Kulongoski JT, Manini E., Martinez M., Miller H., Nakagawa M., Ono S., Patwardhan S., Ramirez C.J, Regoli F., Smedile F., Turner S., Vetriani C., Yucel M., Ballentine C.J, Fischer TP, Hilton DR, Lloyd K.G
Date Published2019/04
Type of ArticleArticle
ISBN Number0028-0836
Accession NumberWOS:000465594200039
Keywordsconvergent margin; costa-rica; helium; isotope; noble-gases; plate; santa elena ophiolite; Science & Technology - Other Topics; southern central-america; subduction; systematics; volcanic arc

Carbon and other volatiles in the form of gases, fluids or mineral phases are transported from Earth's surface into the mantle at convergent margins, where the oceanic crust subducts beneath the continental crust. The efficiency of this transfer has profound implications for the nature and scale of geochemical heterogeneities in Earth's deep mantle and shallow crustal reservoirs, as well as Earth's oxidation state. However, the proportions of volatiles released from the forearc and backarc are not well constrained compared to fluxes from the volcanic arc front. Here we use helium and carbon isotope data from deeply sourced springs along two cross-arc transects to show that about 91 per cent of carbon released from the slab and mantle beneath the Costa Rican forearc is sequestered within the crust by calcite deposition. Around an additional three per cent is incorporated into the biomass through microbial chemolithoautotrophy, whereby microbes assimilate inorganic carbon into biomass. We estimate that between 1.2 x 10(8) and 1.3 x 10(10) moles of carbon dioxide per year are released from the slab beneath the forearc, and thus up to about 19 per cent less carbon is being transferred into Earth's deep mantle than previously estimated.

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