Geochemistry Overview of Hot Springs from the Lake Abhe Area: Republic of Djibouti

Abstract

The Abhé Lake site is located in the south-Western region of the Republic of Djibouti near the Ethiopian border. Geologically, the area is mainly composed of stratoïd basalts with a high plateaus and sedimentary plains. Several fumerolles and hot springs are identified in Abhe lake area. The temperature of the hot springs can exceed 100°C. Chemical analyses from 20 water sample, hot spring, shallow water well, lake and borehole from the Abhé Lake area were evaluated in order to investigate spring water origin, water–rock interaction mechanisms, and estimate the thermal potential of the geothermal areas. This study presents a preliminary geochemical data interpretation of the abhé area geothermal systems. Based on their hydrochemical facies, the water bodies are categorized into four main groups. The first group is Na-Cl type of water and represents all the boreholes catching the regional volcanic aquifer. Several springs located in Hanlé plain ( Agna, Oudgini…) belong also to this group. The hot springs in abhe lake area are characterised by Na-Ca-Cl type of water and form the group 2. At last the waters from sedimentary aquifers are on the one hand characterized by Na-HCO3- Cl type of the shallow water well and on the other hand are characterized by Na-SO4-Cl type of water for deep well. The Lake Abhé waters belong to the Na-HCO3 type with high salinity (155 g/l) and high pH values (>9). The use of geothermometers suggested that the investigated geothermal areas have high enthalpy fluids at depth with temperature estimated by Chemical geothermometers are mostly 160°C.