Geochemical interpretation of thermal water and gas samples from Lake Abbe, Djibouti

Abstract

The Lake Abbe geothermal area field is located in the south-western region of the Republic of Djibouti, on the border with Ethiopia. This area is dominated by stratoid basaltic rock and is marked by hydrothermal activities which are manifested by hot springs with surface temperatures of more than 90°C; fumaroles and travertines are also found in this area. Hot springs and fumaroles were sampled and analysed and geochemical data is interpreted in this report to estimate the reservoir temperatures and properties. The different geothermometers estimate the temperature of the reservoir to be in the range of 120-160°C. Hydrothermal data shows that the thermal waters have a high concentration of Cl which classifies them as volcanic waters and that these waters are equilibrated with the rock. The stable isotopic composition and Cl/B ratio were used to determine the origin of the water. The thermal waters are local meteoric waters from the same source and they are not mixed with Lake Abbe’s water. The presence of the travertines shows that calcite deposition has occurred in the reservoir during geothermal production. The estimated reservoir temperatures suggest that the Lake Abbe geothermal area is a low-temperature geothermal system.