Subject
geophysics, Hydrothermal system, Caldera, Yenkahe, Yasur, Resurgent dome, [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology

Domains
Volcanologie, Sciences de la Terre, Géophysique

Description

International audience In this contribution, we focus on one of the most active resurgences on Earth, that of the Yenkahe dome in the Siwi caldera (Tanna Island, Vanuatu), which is associated with the persistently active Yasur volcano. Gravity and magnetic surveys have been carried out over the past few years in the area, as well as electrical methods including electrical resistivity tomography (ERT), time domain electro-magnetics (TDEM) and self-potential (SP). These investigations were completed by thermometry, CO2 soil gas measurements, field observations and sampling. This multi-method approach allows geological structures within the caldera to be identified, as well as associated hydrothermal features. The global structure of the caldera is deduced from gravity data, which shows the caldera rim as a high density structure. Large lava fields, emplaced before and after the onset of resurgence, are evidenced by combined gravity, magnetic and resistivity signals. In the middle of the caldera, the Yenkahe dome apparently results from a combination of volcanic and tectonic events, showing that lava extrusion and resurgence have been operating simultaneously or alternately during the Siwi caldera post-collapse history. There is a clear distinction between the western and eastern parts of the dome. The western part is older and records the growth of an initial volcanic cone and the formation of a small caldera. This small caldera (paleo-Yasur caldera), partially filled with lava flows, is the present-day focus of volcanic activity and associated fluid circulation and alteration. The eastern part of the dome is presumably younger, and is characterized by intense, extensive hydrothermal alteration and activity. Its northern part is covered by lava flow piles and exhibits a shallow hydrothermal zone in ERT. The southern part has hydrothermal alteration and activity extending at least down to the base of the resurgent dome. This part of the dome is built up of low cohesion rock and is thus potentially prone to gravitational landslides. Lastly, while self-potential and temperature data suggest that widespread hydrothermal circulation occurs throughout almost all of the caldera, and possibly beyond, the most active parts of this hydrothermal system are associated with the dome. The presence of this active hydrothermal system is the clearest indicator that these methods can provide of a potential shallow magmatic body underneath the dome.

Keywords

Language
English (en-GB)

Creators
Brothelande, Élodie, Lénat, Jean-François, Chaput, Marie, Gailler, Lydie-Sarah, Finizola, Anthony, Dumont, S., Peltier, Aline, Bachèlery, Patrick, Barde-Cabusson, Stéphanie, Byrdina, S., Menny, P., Colonge, J., Douillet, G. A., Letort, J., Letourneur, L., Merle, O., Di Gangi, F., Nakedau, D., Garaebiti, E.

Contributors
Laboratoire Magmas et Volcans (LMV) ; Observatoire de Physique du Globe de Clermont-Ferrand (OPGC) ; Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG) ; Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST) ; Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire GéoSciences Réunion (LGSR) ; Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris), Bureau d’études Stratagem974, Observatoire Volcanologique du Piton de la Fournaise (OVPF) ; Institut de Physique du Globe de Paris (IPG Paris), Institute of Earth Sciences Jaume Almera ; Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Institut des Sciences de la Terre (ISTerre) ; Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Ecole et Observatoire des Sciences de la Terre (EOST) ; Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Ludwig-Maximilians-Universität München (LMU), Bartington Instruments Ltd, Instituto Nazionale di Geofisica e Vulcanologie Sezione di Palermo, Vanuatu Meteorology and Geohazards Department, ANR-10-LABX-0006,CLERVOLC,Clermont-Ferrand centre for research on volcanism(2010)

Sources
ISSN: 0377-0273, Journal of Volcanology and Geothermal Research, https://hal.univ-reunion.fr/hal-01448830, Journal of Volcanology and Geothermal Research, 2016, 322, pp.241-262. ⟨10.1016/j.jvolgeores.2015.08.021⟩, https://www.sciencedirect.com/science/article/pii/S0377027315002772

Relation
info:eu-repo/semantics/altIdentifier/doi/10.1016/j.jvolgeores.2015.08.021

Coverage
Vanuatu

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