Exceptional eruptive CO2 emissions from intra-plate alkaline magmatism in the Canary volcanic archipelago

Alkaline mafic magmas forming intra-plate oceanic islands are believed to be strongly enriched in CO 2 due to low-degree partial melting of enriched mantle sources. However, until now, such CO 2 enhancement has not been verified by measuring CO 2 degassing during a subaerial eruption. Here, we provide evidence of highly CO 2 -rich gas emissions during the 86-day 2021 Tajogaite eruption of Cumbre Vieja volcano on La Palma Island, in the Canary archipelago. Our results reveal sustained high plume CO 2 /SO 2 ratios, which, when combined with SO 2 fluxes, melt inclusion volatile contents and magma production rates at explosive and effusive vents, imply a magmatic CO 2 content of 4.5 ± 1.5 wt%. The amount of CO 2 released during the 2021 eruptive activity was 28 ± 14 Mt CO 2 . Extrapolating to the volume of alkaline mafic magmas forming La Palma alone (estimated as 4000 km 3 erupted over 11 Ma), we infer a maximum CO 2 emission into the ocean and atmosphere of 10 16 moles of CO 2 , equivalent to 20% of the eruptive CO 2 emissions from a large igneous province eruption, suggesting that the formation of the Canary volcanic archipelago produced a CO 2 emission of similar magnitude as a large igneous province.