Application of selected geothermometers to Continental Intercalaire thermal water in southern Tunisia

The aquifer system in the Tunisian Chotts region is composed mainly of two aquifers: the upper confined/unconfined Complexe Terminal and the deeper confined Continental Intercalaire aquifer. The deep Continental Intercalaire thermal water represents approximately 20% of agricultural water supply in southern Tunisia. Its temperature varies between 46 and 73 °C, and it is mainly used for heating greenhouses and irrigation of oases. The non-thermal water (20–35 °C) is pumped from the Complexe Terminal aquifer with an average depth of 300 m. The Continental Intercalaire geothermal field is generally considered a thermal energy resource and should be evaluated for adequate purposes in the study area. Different chemical geothermometers were used in this work to assess the highest temperature that can be found in the Continental Intercalaire aquifer. Temperature values varying between 95 and 133 °C were obtained by using a Na–Li geothermometer. The multiple mineral equilibrium approach yielded a temperature of 87 to 112 °C.