Geology, Geothermometry, Isotopes and Gas Chemistry of the Northern Algerian Geothermal System

Abstract

Algeria belongs to the north-western part of Africa, with a quite large area, providing its complex geology and vigorous tectonic activity, which generates an important geothermal potential. In fact, the northern part of Algeria is considered as a part of the Alpine-Magrebides belts. A chemical study counting 35 hot springs data-base reveals the presence of four major types of a near neutral pH water in the northern part of Algeria; Na-Cl, Na-Ca–SO4, Ca-Mg-CO3 and Ca-Na-CO3. The isotopic results (δ O18, δD) indicate a meteoric origin of the thermal water in the western part of Algeria, while the use of gas chemistry in the eastern part of the country has enhanced the meteoric origin of the thermal water at the most of hot springs except 2 hot springs which are enriched in He. The major numbers of the studied hot springs are of immature water rather close to the Mg corner using the Na/1000-K/100-Mg1/2 diagram, and the estimated temperature ranges between 100 to 160°C, while the cationic geothermometers were estimated between 100-500°C. The northern Algerian geothermal system is a non-volcanogenetic system. The water has gained depth until 3 to 7 km, through the NE-SW and E-W faults and finally mixed with high Mg shallower cold carbonated ground water.