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Spatio-Temporal Relationships between Fumarolic Activity, Hydrothermal Fluid Circulation and Geophysical Signals at an Arc Volcano in Degassing Unrest: La Soufrière of Guadeloupe (French West Indies)

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Istituto Nazionale di Geofisica e Vulcanologia, sezione di Bologna, 40128 Bologna, Italy
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Institut de Physique du Globe de Paris, Université de Paris, UMR7154 CNRS, 75005 Paris, France
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Laboratoire Magmas Volcans-OPGC, Université Clermont Auvergne, 63170 Clermont Ferrand, France
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Observatoire Volcanologique et Sismologique de Guadeloupe, Institut de Physique du Globe de Paris, 97113 Gourbeyre, France
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Istituto Nazionale di Geofisica e Vulcanologia, sezione di Catania, 95125 Catania, Italy
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Department of Earth Sciences, Simon Fraser University, 8888 University Drive, Vancouver, BC V5A 1S6, Canada
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Institut des Sciences de la Terre—Institut de Recherche pour le Développement—BPPTKG—PVMBG Badan Geologi, Yogyakarta 55166, Indonesia
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Author to whom correspondence should be addressed.
Geosciences 2019, 9(11), 480; https://doi.org/10.3390/geosciences9110480
Received: 1 October 2019 / Revised: 6 November 2019 / Accepted: 9 November 2019 / Published: 15 November 2019
(This article belongs to the Special Issue Exploring and Modeling the Magma-Hydrothermal Regime)
Over the past two decades, La Soufrière volcano in Guadeloupe has displayed a growing degassing unrest whose actual source mechanism still remains unclear. Based on new measurements of the chemistry and mass flux of fumarolic gas emissions from the volcano, here we reveal spatio-temporal variations in the degassing features that closely relate to the 3D underground circulation of fumarolic fluids, as imaged by electrical resistivity tomography, and to geodetic-seismic signals recorded over the past two decades. Discrete monthly surveys of gas plumes from the various vents on La Soufrière lava dome, performed with portable MultiGAS analyzers, reveal important differences in the chemical proportions and fluxes of H2O, CO2, H2S, SO2 and H2, which depend on the vent location with respect to the underground circulation of fluids. In particular, the main central vents, though directly connected to the volcano conduit and preferentially surveyed in past decades, display much higher CO2/SO2 and H2S/SO2 ratios than peripheral gas emissions, reflecting greater SO2 scrubbing in the boiling hydrothermal water at 80–100 m depth. Gas fluxes demonstrate an increased bulk degassing of the volcano over the past 10 years, but also a recent spatial shift in fumarolic degassing intensity from the center of the lava dome towards its SE–NE sector and the Breislack fracture. Such a spatial shift is in agreement with both extensometric and seismic evidence of fault widening in this sector due to slow gravitational sliding of the southern dome sector. Our study thus provides an improved framework to monitor and interpret the evolution of gas emissions from La Soufrière in the future and to better forecast hazards from this dangerous andesitic volcano. View Full-Text
Keywords: la soufrière; guadeloupe; volcanic gas; volcanic unrest; hydrothermal gas; multigas; extensometry la soufrière; guadeloupe; volcanic gas; volcanic unrest; hydrothermal gas; multigas; extensometry
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Tamburello, G.; Moune, S.; Allard, P.; Venugopal, S.; Robert, V.; Rosas-Carbajal, M.; Deroussi, S.; Kitou, G.-T.; Didier, T.; Komorowski, J.-C.; Beauducel, F.; De Chabalier, J.-B.; Le Marchand, A.; Le Friant, A.; Bonifacie, M.; Dessert, C.; Moretti, R. Spatio-Temporal Relationships between Fumarolic Activity, Hydrothermal Fluid Circulation and Geophysical Signals at an Arc Volcano in Degassing Unrest: La Soufrière of Guadeloupe (French West Indies). Geosciences 2019, 9, 480.

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  • Externally hosted supplementary file 1
    Doi: 10.1594/IEDA/111184
    Link: https://doi.org/10.1594/IEDA/111184
    Description: Fumarolic gas compositions at La Soufrière were directly measured in the field by using MultiGAS. Walking traverses have been carried out downwind around the craters. The transects have been used to fit a plume profile and calculate gas fluxes.
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