Oceanic intraplate explosive eruptions fed directly from the mantle

Abstract

Constraining the volatile content of magmas is critical to our understanding of eruptive processes and their deep Earth cycling essential to planetary habitability [R. Dasgupta, M. M. Hirschmann, Earth Planet. Sci. Lett. 298 , 1 (2010)]. Yet, much of the work thus far on magmatic volatiles has been dedicated to understanding their cycling through subduction zones. Further, studies of intraplate mafic volcanism have disproportionately focused on Hawaii [P. E. Wieser et al., Geochem. Geophys. Geosyst. 22 , e2020GC009364 (2021)], making assessments of the overall role of intraplate volcanoes in the global volatile cycles a challenge. Additionally, while mafic volcanoes are the most common landform on Earth and the Solar System [C. A. Wood, J. Volcanol. Geotherm. Res. 7 , 387–413 (1980)], they tend to be overlooked in favor of silicic volcanoes when it comes to their potential for explosivity. Here, we report primitive (olivine-hosted, with host Magnesium number – Mg# 78 to 88%) melt inclusion (MI) data from Fogo volcano, Cabo Verde, that suggest that oceanic intraplate silica-undersaturated explosive eruptions sample volatile-rich sources. Primitive MI (melt Mg# 70 to 71%) data suggest that these melts are oxidized (NiNiO to NiNiO+1) and very high in volatiles (up to 2 wt% CO 2 , 2.8 wt% H 2 O, 6,000 ppm S, 1,900 ppm F, and 1,100 ppm Cl) making Fogo a global endmember. Storage depths calculated from these high volatile contents also imply that magma storage at Fogo occurs at mantle depths (~20 to 30 km) and that these eruptions are fed from the mantle. Our results suggest that oceanic intraplate mafic eruptions are sustained from the mantle by high volatile concentrations inherited from their source and that deep CO 2 exsolution (here up to ~800 MPa) drives their ascent and explosivity.

Geomorphology and Age Constraints of Seamounts in the Cabo Verde Archipelago, and Their Relationship to Island Ages and Geodynamic Evolution

“…Future studies on the samples collected from these sites, as well as the analysis of the sequences observed, will shed light on the origin of these eruptions, but a mechanism involving the eruption of magmas extremely rich in volatiles (particularly CO 2 ) is tentatively suggested as the most probable reason to explain the high volcanic fragmentation at these depths. This hypothesis is supported by the occurrence of unusually high CO 2 contents in primitive magmas from Fogo volcano, interpreted to drive their ascent and explosivity (DeVitre et al., 2023).…”

Disequilibrium in Historic Volcanic Rocks from Fogo, Cape Verde Traces Carbonatite Metasomatism of Recycled Ocean Crust

“…On the neighbouring island of Brava, there is a temporal distinction with similar characteristics to the northern islands until 0.5 Ma, when the EM1-like component appears (Mourão et al, 2012). Carbonatites are present in the Cape Verde Archipelago, including on the island of Fogo and recent studies have shown high volatile contents and associated deep exsolution of CO 2 beneath Fogo (DeVitre et al, 2023;Hoernle et al, 2002).…”

Reliability of Raman analyses of CO2-dominated fluid inclusions as a rapid barometer at Kīlauea

“…Olivines from tephra of the 1951 eruption of Fogo Volcano in Cabo Verde (DeVitre et al, 2023), were also picked under binocular microscope and individually mounted in CrystalBond™. FI were revealed by grinding using 600-2000 grit wet paper and polish refined using 1 and 0.3 um wet paper and alumina paste.…”

“…Even after such meticulous work, calculated pressures are typically associated with considerable analytical and systematic uncertainties (e.g., melt and bubble volume measurements, solubility models, post-entrapment crystallization corrections). Such uncertainties can range from 20% to 50% when fully propagated (Tucker et al, 2019;Wieser et al, 2021;DeVitre et al, 2023).…”