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Caractérisation du système hydrothermal du Piton des Neiges par des méthodes géochimiques et isotopiques

Abstract : Piton des Neiges volcano (Reunion Island) shows evidence of a hydrothermal activity that could potentially be used for geothermal energy generation. However, so far, the characteristics of this hydrothermal system (fluid temperature, heat source, recharge, etc.) remain too uncertain to consider exploiting it. To evaluate its geothermal potential, we carried out a vast prospecting campaign for markers of hydrothermal activity, performed geochemical analysis (major, trace elements, δ18O, δD, δ13C, 87Sr/86Sr, δ7Li, δ37Cl) on 38 thermal springs (including 21 new ones) and monitored the resource over time. Our results show that the hydrothermal activity is concentrated in the cirques of Cilaos and Salazie, along the N30 rift zone and inside a supposed caldera. Recharge is meteoric, local, plurennial and mainly comes from cyclones. There is no hydraulic connection between the two cirques, and barely with the ocean. Thermal waters interact with mantellic CO2, other more superficial magmatic gases (inside the edifice or at its base) and differentiated rocks. Geochemical geothermometers indicate a water-rock interaction temperature of above 210°C. The hydrothermal system of Piton des Neiges thus reaches computed temperatures compatible with high temperature geothermal use. Our work steers the next exploratory steps toward the geologic structures associated with the supposed caldera and the rift zone. Their geometry, their hydrodynamic property and their relation with the heat source will be decisive in the choice of a drilling site.
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Submitted on : Thursday, September 17, 2020 - 2:42:08 PM
Last modification on : Wednesday, October 14, 2020 - 3:46:35 AM
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  • HAL Id : tel-02941966, version 1


Bhavani Bénard. Caractérisation du système hydrothermal du Piton des Neiges par des méthodes géochimiques et isotopiques. Géochimie. Université de la Réunion, 2020. Français. ⟨NNT : 2020LARE0010⟩. ⟨tel-02941966⟩



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