Chemical and Isotopic Studies of Geothermal Prospects, in the Southern Afar Region, Ethiopia

Abstract

Isotopic and chemical studies have been carried out in Wonji, Fantale, Dofan and Meteka geothermal prospects in the Southern Afar region, Ethiopian Rift Valley. Deuterium, tritium and oxygen-18 are most important in separating ground water systems into different types. Based on the isotopic data, three groundwater systems are identified: 1) Wonji area, 2) Fantale and Meteka areas, and 3) Dofan area. Tritium results show that the geothermal waters are not contaminated with tritium waters from the hydrogen-bomb tests performed during the 1950s, except for the Wonji thermal springs and the Metehara cold spring. The thermal waters in Fantale, Dofan and Meteka have very low tritium values, suggesting that the waters are pre-1950. Solute geothermometery indicated that the reservoir temperature is in the range of 110-142?C (average). Future studies should give priority to Dofan and Fantale geothermal prospects, followed by Meteka and Wonji.