Carbon fluxes from subducted carbonates revealed by uranium excess at Mount Vesuvius, Italy

Riccardo Avanzinelli, Martina Casalini, Tim Elliott, Sandro Conticelli

Research output: Contribution to journalArticle (Academic Journal)peer-review

6 Citations (Scopus)
240 Downloads (Pure)

Abstract

The fate of carbonate-rich sediments recycled at destructive plate margins is a key issue for constraining the budget of deep CO2 supplied to the atmosphere by volcanism. Experimental studies have demonstrated that metasomatic melts can be generated by partial melting of subducted carbonate-pelitic sediments, but signatures of the involvement of such components in erupted magmas are more elusive. We have made new U-Th disequilibria, Sr-Nd-Pb isotope, and high-precision δ238U analyses on lavas from Mount Vesuvius (Italy) and show that their measured 238U excesses require a mantle source affected by the addition of U-rich carbonated melts, generated by partial melting of subducted calcareous sediments in the presence of residual epidote. Accordingly, we argue that the occurrence of 238U excesses in “sediment-dominated” arc magmas represents diagnostic evidence of addition of carbonate sediments via subduction, hence providing constraints on deep carbon cycling within Earth. Our quantitative enrichment model, combined with published experimental results, allows us to estimate a resulting flux of 0.15–0.8 Mt/yr CO2 from the subducted carbonates to the mantle source of Mount Vesuvius.
Original languageEnglish
Pages (from-to)259-262
JournalGeology
Volume46
Issue number3
Early online date17 Jan 2018
DOIs
Publication statusPublished - 1 Mar 2018

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