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Syneruptive and diffuse degassing of mercury at Piton de la Fournaise volcano (Reunion Island)

Bhavani Bénard1,2, Olivier Magand3, Jeroen Sonke4, Andrea Di Muro5, Nicolas Desfete2, Aurelien Dommergue6, Yann Bertrand6, Hélène Angot6

  • Affiliations: 1Université de La Réunion, Laboratoire Géosciences Réunion, 97744 Saint Denis, France 2Université Paris Cité, Institut de Physique du Globe de Paris, 75005 Paris, France 3Observatoire des Sciences de l'Univers de La Réunion, UR, CNRS, Meteo-France, IRD, Saint-Denis, La Réunion, France 4Géosciences Environnement Toulouse, CNRS/OMP/Université de Toulouse, 31400 Toulouse, France. 5Université Claude Bernard Lyon 1, Laboratoire de Géologie de Lyon: Terre, Planètes, Environnement (LGL-TPE),  69622 Villeurbanne, France 6Université Grenoble Alpes, CNRS, INRAE, IRD, Grenoble INP, IGE, Grenoble, France

  • Presentation type: Poster

  • Presentation time: Friday 16:30 - 18:00, Room Poster Hall

  • Poster Board Number: 271

  • Programme No: 3.17.38

  • Theme 3 > Session 17

Abstract

Volcanoes are the primary natural source of mercury in the atmosphere. However, these emissions remain poorly understood, particularly in intraplate settings. Available data from volcanic vents during eruptions indicate low mercury emissions compared to arc volcanoes. Intraplate volcanoes, however, tend to release most of their gases through continuous diffusion from magma stored at significant depths, as opposed to during eruptive events. This is well-documented for carbon dioxide, but whether the same holds true for mercury remains unknown. In this study, we use the Piton de la Fournaise volcano (Réunion Island) as a natural laboratory to investigate volcanic degassing of mercury, both diffuse and syneruptive. Previous research has detected magmatic CO₂ in soil gases, groundwaters, and surface waters along a rift zone, attributing this degassing to magma reservoirs located at different depths (10 km and 30 km) or to plume deposits. We measured the concentration and isotopic composition of mercury in these same gases and waters, as well as in soils and in the atmosphere. Our results show low mercury concentrations in all samples, with isotopic signatures in soil gases suggesting a magmatic contribution from diffuse degassing from the deepest magma reservoir.