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Hydrothermal alteration and multi-phase 3D structure of the summit of La Soufrière de Guadeloupe

Aida Mendieta1, Marina Rosas-Carbajal1, David Jessop2,Raphaël Bajou1,3, Patrick Baud4, Sébastien Deroussi1, Tomaso Esposti Ongaro5, Jean-Christophe Komorowski1, Alexandra R. L. Kushnir6, Marlène Villeneuve7, and Michael J. Heap4,7

  • Affiliations:  1Université de Paris, Institut de Physique du Globe de Paris, CNRS, Paris, France; 2CNRS, IRD, OPGC Laboratoire Magmas et Volcans, Université Clermont Ferrand Auvergne, F-63000, Clermont-Ferrand, France; 3IRFU, CEA, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France;4Université de Strasbourg, CNRS, Institut Terre et Environnement de Strasbourg, Strasbourg, France; 5Instituto Nazionale di Geofisica e Vulcanologia, Sezione di Pisa, Pisa, Italy; 6Rock Physics and Geofluids Laboratory, EPFL, Lausanne, Switzerland; 7Subsurface Engineering, Montanuniversität Leoben, Leoben, Austria; 8Institut Universitaire de France (IUF), Paris, France. 

  • Presentation type: Poster

  • Presentation time: Thursday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 25

  • Programme No: 3.8.9

  • Theme 3 > Session 8

Abstract

Hydrothermal alteration plays a major role in volcanic instability. Thus, improving techniques that allow us to better understand the processes and timescales of alteration in active volcanoes is paramount. Since the reactivation of the fumarolic field at the top of the dome of La Soufrière de Guadeloupe (Guadeloupe, France) in 1992, and its expansion in recent years, the top of the dome has been subjected to prolonged and variable alteration. Such alteration has promoted past flank collapses and can also influence permeability and thus subsurface overpressurization. During a field campaign in May 2022, we performed 25 electrical resistivity tomography (ERT) profiles on the summit of La Soufrière, next to active fumaroles and acid boiling ponds. These ERT profiles were inverted together using the open-source code E4D. From field studies, we have identified clays, sulfates and pyrites which are all byproducts of alteration. Thus, we infer that high electrical conductivity zones (>1 Sm-1) correspond to alteration and areas fully saturated with acid brines, and that low electrical conductivity zones (<0.001 Sm-1) correspond to unaltered rock or gas filled pockets. We account for ground temperature and spatial variability to interpret the electrical conductivity anomalies, and we use this first high-resolution 3D conductivity map as the first step in a time-lapse inversion of the surveyed area.