Fonctionnement d'un système hydrothermal associé à un contact tectonique alpin (La Léchère, Savoie).
Apports de l'hydrogéologie, de la géochimie et de la modélisation hydrodynamique et thermique en vue de la gestion
de la ressource.

Abstract : The La Léchère hydrothermal system is studied with an interdisciplinary approach associating (1)
geology, (2) hydrodynamic, (3) hydrogeochemistry and (4) hydrodynamic and thermic modeling.
(1) The strike-slip thrust at the contact between the carbonated cover and micaschists of the crystalline basement, is underlined by discontinuous tectonic slices of Triassic evaporites. At the intersection between this contact and the Isère valley, thermal waters diffuse in a glacial basin through an old rock avalanche, identified by the re-interpretation of previous drilling descriptions.
(2) The system is characterized by a decompressed zone where shallow circulations are located; this zone is considered to be an overflow of the deep system. The global system is recharged by diffuse meteoric infiltration and by losses along the Eau Rousse torrent. In the discharge area, flows will be ascending as long as the level of the deep aquifer will stay higher than that of the shallow aquifer.
(3) During their flow path, thermal and triassic shallow waters interact with dolomite, cargneules and gypsum (Ca, SO4 and Mg). Thermal waters differ from triassic waters due to a deep flow path of several thousands years and interaction with halite (Cl), metamorphic (Si, K exchange Ca/Na) and Permocarboniferous rocks (organic matter, H2S) before mixing with shallow waters of the discharge area.
(4) Hydrodynamic and thermic modeling shows that hot waters are flushed towards the valley by flow re-activation at the beginning of the last deglaciation. Thermal resource exploitation accelerates the natural cooling of the thermal aquifer. However, this acceleration is not observed during the last 10 years of monitoring.
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Submitted on : Tuesday, March 18, 2008 - 6:19:15 PM
Last modification on : Thursday, January 11, 2018 - 6:20:37 AM
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Emilie Thiébaud. Fonctionnement d'un système hydrothermal associé à un contact tectonique alpin (La Léchère, Savoie).
Apports de l'hydrogéologie, de la géochimie et de la modélisation hydrodynamique et thermique en vue de la gestion
de la ressource.. Hydrologie. Université de Savoie, 2008. Français. ⟨tel-00265333⟩

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