Petrology of the explosive deposits from the April 2021 eruption of La Soufrière volcano, St Vincent:A time-series analysis of microlites

Frey, H. M., Manon, M. R., Barclay, J. ORCID: https://orcid.org/0000-0002-6122-197X, Davies, B. V. ORCID: https://orcid.org/0000-0001-5771-2488, Walters, S. A., Cole, P. D., Christopher, T. E. and Joseph, E. P. (2024) Petrology of the explosive deposits from the April 2021 eruption of La Soufrière volcano, St Vincent:A time-series analysis of microlites. In: The 2020-2021 Eruption of La Soufriere Volcano, St Vincent. Geological Society Special Publications, 539 . Geological Society of London, pp. 201-230.

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Abstract

After more than three months of lava dome extrusion, La Soufrière (St Vincent) transitioned to a series of explosive eruptions in April 2021. Here we present a time-series petrologic analysis of the phenocryst and microlite populations during the first c. 48 h of explosivity to constrain ascent conditions and processes that drove changes in behaviour. Primary eruptive products were crystal-rich (45–50 vol%) basaltic andesites with similar phenocryst phase assemblages and compositions. The change in eruptive style is consistent with over-pressurization as a consequence of second boiling from anhydrous microlite crystallization. The microlites display variation between the explosive phases, with two populations: (1) ‘inherited’ − normally zoned high-An plagioclase (>An 70) + olivine (Fo 62–79) + clinopyroxene + titanomagnetite, inferred to have crystallized at depths >15 km and high water pressures; (2) ‘juvenile’ − unzoned plagioclase (An 45–65) + clinopyroxene + orthopyroxene + intermediate pyroxene (Wo 12–38) + titanomagnetite, inferred to have crystallized upon ascent due to decompression and degassing. Scoria from the first explosions featured extensive groundmass crystallization and a significant ‘inherited’ microlite population. Later explosions had a more abundant ‘juvenile’ microlite population and lower crystallinity, consistent with more rapid ascent from depth, initiated by decompression following initial blasts and destruction of the lava dome.

Item Type: Book Section
Additional Information: Funding Information: This study was supported by the United States National Science Foundation (NSF) through Grants for Rapid Response Research (Award # 2132566) to H.F. and M.M. J.B., B.V.D. and P.C. were supported by the UK Natural Environment Research Council (NERC) through an Urgency Grant (NE/W000725/1).
Faculty \ School: Faculty of Science > School of Environmental Sciences
UEA Research Groups: Faculty of Science > Research Groups > Geosciences
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Depositing User: LivePure Connector
Date Deposited: 10 May 2023 15:30
Last Modified: 24 Sep 2024 08:24
URI: https://ueaeprints.uea.ac.uk/id/eprint/92018
DOI: 10.1144/SP539-2022-291

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