Byrdina Svetlana, Vandemeulebrouck J., Cardellini C., Legaz A., Camerlynck C., Chiodini G., Lebourg T., Gresse M., Bascou P., Motos G., Carrier A., Caliro S. (2014). Relations between electrical resistivity, carbon dioxide flux, and self-potential in the shallow hydrothermal system of Solfatara (Phlegrean Fields, Italy). Journal of Volcanology and Geothermal Research, 283, p. 172-182. ISSN 0377-0273.
Titre du document
Relations between electrical resistivity, carbon dioxide flux, and self-potential in the shallow hydrothermal system of Solfatara (Phlegrean Fields, Italy)
Année de publication
2014
Auteurs
Byrdina Svetlana, Vandemeulebrouck J., Cardellini C., Legaz A., Camerlynck C., Chiodini G., Lebourg T., Gresse M., Bascou P., Motos G., Carrier A., Caliro S.
Source
Journal of Volcanology and Geothermal Research, 2014,
283, p. 172-182 ISSN 0377-0273
We present the results of an electric resistivity tomography (ERT) survey, combined with mappings of diffuse carbon dioxide flux, ground temperature and self-potential (SP) at Solfatara, the most active crater of Phlegrean Fields. Solfatara is characterized by an intense carbon dioxide degassing, fumarole activity, and ground deformation. This ensemble of methods is applied to image the hydrothermal system of Solfatara, to understand the geometry of the fluid circulation, and to define the extension of the hydrothermal plume at a high enough resolution for a quantitative modeling. ERT inversion results show Solfatara as a globally conductive structure, with resistivity in the range 1-2000 Omega m. Broad negative anomaly of self-potential in the inner part of Solfatara with a minimum in the area of Bocca Grande suggests a significant downward flow of condensing liquid water. Comparison between spatial variations of resistivity and gas flux indicates that resistivity changes at depth are related to gas saturation and fluid temperature. These variations delineate two plume structures: a liquid-dominated conductive plume below Fangaia mud-pool and a gas-dominated plume below Bocca Grande fumarole. The geometry of the Fangaia liquid-saturated plume is also imaged by a high resolution 3-D resistivity model. In order to estimate the permeability, we propose a 2-D axis-symmetric numerical model coupling Richards equation for fluid flow in conditions of partial saturation with the resistivity calculation as function of saturation only. Alternatively, we apply the Dupuit equation to estimate the permeability of the shallow layer. Using these two approaches we obtain the permeability of the shallow layer below Fangaia which ranges between (2-4) x 10(-14) m(2).
Plan de classement
Hydrologie [062]
;
Géophysique interne [066]
Description Géographique
ITALIE
Localisation
Fonds IRD [F B010062538]
Identifiant IRD
fdi:010062538
