Fluid circulation pattern inside La Soufrière volcano (Guadeloupe) inferred from combined electrical resistivity tomography, self-potential, soil temperature and diffuse degassing measurements

Abstract

International audienceAfter a drastic decline in 1983, hydrothermal activity at La Soufrière lava dome (Guadeloupe, Lesser Antilles) has been progressively increasing in the summit area since 1992, raising the threat of a renewed eruptive activity. To better constrain the geometry of the hydrothermal system, an extensive high-resolution self-potential survey was performed on the dome and three multi-method profiles combining electrical resistivity tomography, self-potential, ground thermometry and soil CO 2 diffuse degassing measurements were carried out to cover its southern periphery in January 2011. Results indicate that hydrothermal ascending flows are currently restricted to a proximal area including the dome and its very vicinity. The extension of hydrothermal alteration inferred from electrical resistivity tomography reflects the presence of a heat source just below the dome. A first-order correction of topography-related self-potential variations allows the identification of major hydrothermal fluid circulations pathways, as well as significant meteoric infiltration zones. Local shifting of hydrothermal fluids towards the dome periphery is favored by the presence of major axes. The regional La Ty fault appears as the major axis draining large volumes of hydrothermal and magmatic fluids. However hydrothermal activity remains confined inside a collapse structure surrounding the dome, that formed in the last 9000 years as a result of recurrent edifice collapses, the latest occurring at the onset of the 1530 AD eruption. The combination of these qualitative results with structural analysis leads to a synthetic model of magmatic and hydrothermal fluids circulation inside the dome, which may be useful for the assessment of potential hazards associated with a renewal of fluid pres-surization, and a possibly associated partial flank-failure

Zeta potential of porous rocks in contact with mixtures of monovalent and divalent electrolytes

“…; Mauri, Williams‐Jones and Saracco ; Brothelande et al . ) and detection of contaminant plumes (e.g. Martinez‐Pagan et al .…”

3D assessment of an underground mine pillar by combination of photogrammetric and geoelectric methods

“…Results in this paper imply that for the common practice of performing a DTM, one has to take particular care during a geophysical survey. For the example of volcano surveys (Finizola et al, 2002;Brothelande et al, 2014Brothelande et al, , 2015, or engineering applications (hydraulic structures [Fargier et al, 2014]), the desired ERI resolution is often weaker than the DTM variations between two adjacent electrodes. In this case, our experience shows that the use of a very accurate surface description must become of major importance when the variation between interelectrode spacing and surface electrode spacing (at the same scale) is greater than 30%.…”

The hydrothermal alteration of cooling lava domes

“…hydrothermal system of specific lava domes at given points in time (Bedrosian et al 2007;Finn et al 2007;Finn and Deszcz-Pan 2011;Brothelande et al 2014). Such studies are logistically challenging and cannot provide information about temporal variations of a system unless they are repeated.…”

“…At the Mount St. Helens lava dome (Bedrosian et al 2007), electrical resistivity surveys revealed that meteoric water circulated in the young dome due to heat input from a nearsurface magmatic source, but did not capture longer-term changes occurring in the hydrothermal system as the dome subsequently cooled. Aeromagnetic and electromagnetic surveys of Cascade volcanoes (Finn et al 2007;Finn and Deszcz-Pan 2011) and the La Soufriere volcano (Brothelande et al 2014) have indicated the presence of water and altered material in specific locations in the edifices at the times of the surveys, but provide limited information about flow pathways within the hydrothermal systems and how they might be expected to have evolved or evolve in the future..…”