Hydrothermal activity of the Lake Abhe geothermal field (Djibouti): Structural controls and paths for further exploration

Abstract

Abstract. Lake Abhe is sitting on the Gob Aad graben within the tectonic Afar triangle in the Republic of Djibouti. It is known for its exposures of massive hydrothermal chimneys on the lake’s eastern shore. The many hydrothermal surface manifestations on this side of the lake, including steam vents, hot springs and carbonate chimney structures, reflect the geothermal field of this area. This study describes the structural settings of the Lake Abhe Geothermal Field (LAGF), using multiscale structural lineament distribution mapping. It also investigates the hydrothermal surface manifestations distribution in order to specify structural controls on local fluid flow and discuss its evolution. Structural features of the LAGF area are dominated by ESE-trending extensional faults that form a series of narrow elongated horst, graben and half-graben structures. Fault interaction and accommodation zones, as well as fault intersections, relay ramps and possible breaching faults are also recognized and may represent interesting structural features in terms of fluid flow pathways. Hydrothermal chimneys and hot springs distribution over the LAGF area is controlled by the main structural trends, and show signs of higher hydrothermal activity located at intersecting structural traces. Field observations, in conjunction with satellite images analysis, suggest a progressive lateral evolution of the LAGF hydrothermal fluid outflows over time. Therefore, this study provides new insights on the local tectonically driven fluid flow of the LAGF, that may support further exploration of this remarkable site and may promote its geothermal development.