A carbon-rich lithospheric mantle as a source for the large CO2 emissions of Etna volcano (Italy)

Etna volcano in Italy releases an exceptional amount of CO2 (9083 t/day) and contributes to 10% of global volcanic emission. The reasons for its extreme CO2 degassing are not yet understood. Using high-precision high field strength element (HFSE) concentrations in magmas from volcanoes in southern Italy, we show that the high Nb/Ta of Etna (up to 26) reveals a mantle source affected by carbonatite metasomatism, which is likely responsible for the large CO2 fluxes. As observed at Etna, carbon-rich mantle domains influence CO2 degassing also outside of continental rifts and therefore play a fundamental role in explaining volcanic CO2 fluxes in different geodynamic settings. Collectively, our study demonstrates that HFSE ratios in magmatic rocks are viable tracers for volcanic carbon degassing that can be used to study present-day settings and, possibly, past emissions.