Geochemical Study of Arta Geothermal Field, Djibouti

Abstract

Arta is located in the east of the Republic of Djibouti. Located at an altitude of 750 m, on a mountain overlooking the Gulf of Tadjourah, the atmospheric temperature can drop to 10 °C. The study of the Arta area involved sampling for six hot springs and seven water wells (dug wells) as well as three fumaroles. The region of Arta is considered as one of geothermal site the most estimated by the Republic of Djibouti. The flush volcanic trainings (formations) are: Rhyolites of Ribta, Rhyolites of Mabla, Basalt of Dalha, series stratoid of the Afar and Basalts of the gulf. The waters of Arta region springs and wells had neutral pH values. The temperature of the waters varied from 29.0°C to 39.0°C. The general nature of spring waters is chloride-sulfate type whereas waters from water wells vary in chloride and bicarbonate contents. Boudadh, Qiqle, Bolleh, and Qof are rich in sodium and potassium of cation. Two water wells Boudadh and Qiqle are possibly partially equilibrated with rock, or affected by mixing of seawater. The other samples are considered immature water. The fumaroles of Arta area are very weak that the gases were significantly mixed with soil air underground. Helium isotopic ratio of Fumarole 4 showed a slight magmatic gas contribution to the fumarolic gas, indicating presence of magmatic heat source beneath the zone of fumaroles.