A geochemical approach for the evaluation of the geothermal potential of Yemen

Thermal springs, fumaroles and boiling water pools from continental Yemen have been investigated for chemical and isotopic compositions. Whatever the emergence, all the water discharges have an isotopic signature of meteoric origin. Springs seeping out from high altitudes in the central volcanic plateau show a prevalent Na-HCO3-composition, clearly affected by an anomalous flux of CO2 deriving from the active hydrothermal systems located in the Jurassic Amran Group limestone sequence, likely underlying the 2000-3000 m thick volcanic suite and/or the Cretaceous Tawilah Group sandstone. All the CO2-rich gas samples have a ?13C-CO2 signature that falls in the range of mantle CO2 (-3<?13C<-7 ? V-PDB). The relatively high 3He/4He (1<R/Ra<3.2) ratios measured in all the CO2-rich springs and also some mixed N2-CO2 gas vents in the far east Hadramaut region support the presence of mantle magmas and related hydrothermal systems residing at the crust level in several areas of Yemen. This well agrees with the presence of Quaternary magmatic activity along the Gulf of Aden as well as the inland Quaternary volcanic fields. Liquid- and gas-geothermometry and geological considerations suggest that three areas (Al Lisi, Al Makhaya and Damt) inside the Yemen volcanic plateau may have promising perspectives for the future development of geothermal energy in Yemen.