Some of the most CO2-rich magmas on Earth are erupted by intraplate ocean island volcanoes. Here, we characterise olivine-hosted melt inclusions from recent (<10 ky) basanitic tephra erupted by Fogo, the only active volcano of the Cape Verde Archipelago in the eastern Atlantic Ocean. We determine H2O, S, Cl, F in glassy melt inclusions and recalculate the total (glass + shrinkage bubbles) CO2 budget by three independent methodologies. We find that the Fogo parental basanite, entrapped as melt inclusion in forsterite-rich (Fo80-85) olivines, contains up to ~2.1 wt% CO2, 3–47 % of which is partitioned in the shrinkage bubbles. This CO2 content is among the highest ever measured in melt inclusions in OIBs. In combination with ~2 wt% H2O content, our data constrain an entrapment pressure range for the most CO2-rich melt inclusion of 648–1430 MPa, with a most conservative estimate at 773–1020 MPa. Our results therefore suggest the parental Fogo melt is stored in the lithospheric mantle at minimum depths of ~27 to ~36 km, and then injected into a vertically stacked magma ponding system. Overall, our results corroborate previous indications for a CO2-rich nature of alkaline ocean island volcanism. We propose that the Fogo basanitic melt forms by low degrees of melting (F = 0.06–0.07) of a carbon enriched mantle source, containing up to 355–414 ppm C. If global OIB melts are dominantly as carbon-rich as our Fogo results suggest, then OIB volcanism may cumulatively outgas as high as ~16–21 Tg of carbon yearly, hence substantially contributing to the global deep carbon cycle.

Lo Forte, F.M., Schiavi, F., Rose-Koga, E.F., Rotolo, S.G., Verdier-Paoletti, M., Aiuppa, A., et al. (2024). High CO2 in the mantle source of ocean island basanites. GEOCHIMICA ET COSMOCHIMICA ACTA, 368, 93-111 [10.1016/j.gca.2024.01.016].

High CO2 in the mantle source of ocean island basanites

Lo Forte, Francesco Maria
;
Rotolo, Silvio G.;Aiuppa, Alessandro;
2024-03-01

Abstract

Some of the most CO2-rich magmas on Earth are erupted by intraplate ocean island volcanoes. Here, we characterise olivine-hosted melt inclusions from recent (<10 ky) basanitic tephra erupted by Fogo, the only active volcano of the Cape Verde Archipelago in the eastern Atlantic Ocean. We determine H2O, S, Cl, F in glassy melt inclusions and recalculate the total (glass + shrinkage bubbles) CO2 budget by three independent methodologies. We find that the Fogo parental basanite, entrapped as melt inclusion in forsterite-rich (Fo80-85) olivines, contains up to ~2.1 wt% CO2, 3–47 % of which is partitioned in the shrinkage bubbles. This CO2 content is among the highest ever measured in melt inclusions in OIBs. In combination with ~2 wt% H2O content, our data constrain an entrapment pressure range for the most CO2-rich melt inclusion of 648–1430 MPa, with a most conservative estimate at 773–1020 MPa. Our results therefore suggest the parental Fogo melt is stored in the lithospheric mantle at minimum depths of ~27 to ~36 km, and then injected into a vertically stacked magma ponding system. Overall, our results corroborate previous indications for a CO2-rich nature of alkaline ocean island volcanism. We propose that the Fogo basanitic melt forms by low degrees of melting (F = 0.06–0.07) of a carbon enriched mantle source, containing up to 355–414 ppm C. If global OIB melts are dominantly as carbon-rich as our Fogo results suggest, then OIB volcanism may cumulatively outgas as high as ~16–21 Tg of carbon yearly, hence substantially contributing to the global deep carbon cycle.
mar-2024
Lo Forte, F.M., Schiavi, F., Rose-Koga, E.F., Rotolo, S.G., Verdier-Paoletti, M., Aiuppa, A., et al. (2024). High CO2 in the mantle source of ocean island basanites. GEOCHIMICA ET COSMOCHIMICA ACTA, 368, 93-111 [10.1016/j.gca.2024.01.016].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10447/624657
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