Geochemical Study of Hanle Geothermal Field, Djibouti

Abstract

The Republic of Djibouti is located in East Africa, in the Great Rift Valley and Afar Triple Junction. From a geological point of view, the Hanle lava plateau is composed of basaltic lava layers called the Afar Stratoid Series. Faults or fractured systems were formed in the NW-SE direction in the plateau. Hydrothermal activities are found in fumaroles with temperatures higher than 98°C and a hot spring. Using the chemical compositions of the fumaroles and hot springs, reservoir temperature was estimated to be 180°C–260°C with gas geothermometers and 125°C with a solute geothermometer. The major solute components of the hot spring suggest that the spring water is created by mixing of groundwater and heated fossil seawater or dissolution of evaporating by heated groundwater. In that area, geothermal steam discharges most vigorously at Garabbayis and Goros. These zones can be a prospect for subsequent exploration including test drilling.