Timing of geothermal activity in an active island-arc volcanic setting: First ⁴⁰ Ar/ ³⁹ Ar dating from Bouillante geothermal field (Guadeloupe, French West Indies)

Abstract

Mineral separates of adularia have been extracted from three samples of highly silicified hydrothermal breccias, newly discovered in the active Bouillante geothermal field (Guadeloupe archipelago), and investigated by 40 Ar/ 39 Ar geochronology in order to constrain the timing of geothermal activity in this part of the active Lesser Antilles island arc. The inverse isochron diagram indicates an age of 248 + 50 ka (2s) for all adularia from one breccia sample (n ¼ 8), with an initial 40 Ar/ 36 Ar ratio of atmospheric composition (309 + 12 (2s)) attesting that this age is valid. This age is concordant with the weighted mean age of 290 + 40 ka for the same sample. Adularia from other samples yields concordant ages. The obtained 40 Ar/ 39 Ar ages can be related either to the magmatic activity of the Bouillante Volcanic Chain (c. 850-250 ka ago) or to the initiation of the volcanic activity of the active Grande Découverte-Soufrière system (200 ka ago-present day). Our results demonstrate that the Bouillante hydrothermal event is coeval with change in the volcanic pulses previously recognized in the magmatic history of the studied area. The possible duration calculated for this hydrothermal activity requires at least two superposed volcanic pulses to be developed.

Tectonic evolution of Les Saintes archipelago (Guadeloupe, French West Indies): relation with the Lesser Antilles arc system

“…The duration of hydrothermal activity (i.e. timescales for efficient fluids and heat transfers) in high-enthalpy geothermal systems is still a poorly constrained factor, mainly because geochronological studies on active geothermal fields are rare [see review in Verati et al, 2014]. Our results offer an interesting opportunity to address this question.…”

“…2). The intersection of these two fault families is responsible for the collapse of the central part of the Terre-de-Haut island contemporaneous with the development of a geothermal system similar, if we consider its structural and epithermal settings, to the present-day active Bouillante geothermal system [Bouchot et al, 2010;Calcagno et al, 2012;Patrier et al, 2013;Verati et al, 2014]. Therefore, the exhumed Terrede-Haut geothermal paleo-system offers a unique opportunity to observe an analogue of the deep parts of active high-temperature geothermal systems.…”

“…Some of these faults are seismically active, and all the faults likely control (1) the volcanic activity from Montserrat to Martinique island, and (2) the superficial earthquakes encountered in the overriding plate of the subduction system. Moreover, it has been proved in the Basse-Terre that this fault network enables the hydrothermal fluid circulation and thus is responsible for the geothermal resources exploited in the Bouillante bay [Bouchot et al, 2010;Calcagno et al, 2012;Verati et al, 2014]. The archipelago of Les Saintes, located southeast of Basse-Terre of Guadeloupe ( fig.…”

Tectono-metamorphic evolution of shallow crustal levels within active volcanic arcs. Insights from the exhumed Basal Complex of Basse-Terre (Guadeloupe, French West Indies)

“…This rheological interface is then potentially a preferential pathway for regional heat and fluid transfers, and in connection to the already known fault network and/or to volcanic structures (interfaces between lava flows, volcanic fabrics,...), offering a system of connected physical vertical and more horizontal discontinuities able to drive the hydrothermal fluids circulation at the whole scale of Basse-Terre arc crust. This result opens new exciting perspectives first for the exploration of geothermal resources, only known and already exploited in the Bouillante bay (Bouchot et al, 2010;Calcagno et al, 2012;Verati et al, 2014), and second in a more general way for the understanding of genesis of metallic ore deposits in volcanic arcs, following the idea that epithermal systems are comparable to geothermal systems (White & Hedenquist, 1995).…”

“…Several authors have focused their petrographic and geochemical studies on fresh volcanic rocks of the southern active volcanic part of the archipelago, and most of the studies have concentrated further south or near La Soufrière volcano or Bouillante geothermal field providing a revision of the ages of the volcanic formations and the lithological contours Dagain, 1981;Blanc, 1983;Boudon et al, 1989;Samper et al, 2007Samper et al, , 2009Patrier et al, 2013;Verati et al, 2014;Ricci et al, 2017). A recent study has shown the evolution of petrophysical properties from fresh to hydrothermalized volcanic rocks in the volcanic island of Guadeloupe archipelago (Navelot et al, 2018).…”