EMES Colloquium Speaker: Esteban Gazel

Oceanic intraplate explosive eruptions fed directly from the mantle

One of the most important challenges in modern volcanology studies is constraining the depth of magmatic reservoirs that supply and sustain eruptions. The 2021 La Palma eruption provided an unprecedented opportunity to test the relationship between earthquakes and potential magma reservoirs. We performed density measurements from CO2-rich fluid inclusions (FI) hosted in olivine crystals highly sensitive to pressure via calibrated Raman spectroscopy. This technique can revolutionize our knowledge of magma storage and transport during an ongoing eruption in near real-time, given how fast (a few days) it can produce precise magma storage depth constraints from minimal sample preparation. Our FI record CO2 densities from 0.73-0.98 g/cm3, translating into depths of 15-27 km, which falls within the reported deep seismic zone recording the main melt storage reservoir. The depths were also confirmed by recent melt inclusion (MI) measurements from our lab. Another study from our lab focusing on storage depths recorded by MI volatile contents from Cape Verde also record mantle (~20-30 km, CO2 up to ~2 wt.%) storage. These new data in the context of the volatile record of intraplate volcanoes suggest that mafic explosive eruptions are sustained from the mantle by high CO2 concentrations inherited from their source, and that deep CO2 exsolution drives their ascent and explosivity.