Abstract
To further develop high-enthalpy geothermal energy in Lesser Antilles arc, it is necessary to identify possible new key targets, and to better understand the modes of fluids and heat transfers in geothermal reservoirs. The objective of this work is thus to characterize the spatio-temporal evolution of hydrothermalism at the upper plate of the arc in Guadeloupe with a multidisciplinary approach (combined structural, geochemical, mineralogical, petrological and geochronological analyses) focussed on the oldest volcanic complexes of the archipelago. In the north of Basse-Terre Island reveals an arc metamorphism developed under sub-Greenschist facies. The standard thermal state of the arc crust in Guadeloupe thus established shows a brittle-ductile transition located at depths of 3 to 4 km. An exhumed geothermal paleo-reservoir, identified at the south of Basse-Terre Island, indicates a hydrothermal metamorphism developed under Greenschist facies synchronous with the development of schistose corridors and attests for both vertical and lateral hydrothermal fluid transfers at depths between 2 and 3 km. Comparison of the age of the volcanic activity and Ar-Ar dating of the high-temperature hydrothermal phases allows us to estimate a maximum operating time of the paleo-reservoir at 650 ka. Finally, the discovery, the analysis and the K-Ar dating of a new hydrothermal breccia, within the active geothermal system, reveals a link between current geothermal activity and volcanic activity of the Soufrière, interpreted as a distal epithermal system. Our results lead to a conceptual model for the operation of a high-energy geothermal reservoir in the context of an active arc.