Feasibility of Geothermal Energy in Mozambique: Geological and Geochemical Characterization of the Tete Area

Mozambique is located in the southwestern branch of the East African Rift, which is known for its considerable geothermal potential. Geothermal energy is an important autochthon resource to address the improvement of the electrical system of the Country and its economic growth, especially in the northwestern provinces, where several thermal springs are present. Moreover, unlike most of the other renewable energy resources, geothermal power generation does not depend on weather conditions and can therefore help to provide the country with a reliable baseload renewable energy resource. The aim of this work is to evaluate the geothermal potential in the Tete area through geological and geochemical surveys. The Tete area is located in the northwestern part of Mozambique and is characterized by the presence of some thermal springs with temperatures up to 80°C. The studied area is approximately 800 km2 , with Tete town and Zambesi River in its center. The study was structured in four phases. First, a collection and review of the existing data was carried out to evaluate missing data and to plan further analyses and activities. Remote sensing analysis turned out to be essential to identify tectonic structures and plan the geological and geochemical field surveys. Secondly, field activities were carried out: a congruous number of rock samples were collected, and water samples were obtained from three hot springs. Rock samples were used to verify the reliability of available lithological maps and the results of previous petrographic studies. As for the water samples, deuterium and oxygen-18 indicate that the sampled hot springs discharge meteoric waters. The temperature of the reservoir fluids was estimated by different geothermometers with ranges from 90 to 120 °C. Thirdly, a preliminary conceptual geothermal model was refined, obtaining that local geothermal circuits are recharged by meteoric waters descending at depths of some kilometers, where the main geothermal reservoirs are hosted in the Proterozoic basement. The circulation of fluids occurs along fractures-faults with discrete permeability, as testified by the position of the hot springs. Finally, a preliminary assessment of the geothermal potential in terms of extractable energy, was conducted using the Montecarlo simulation of the Volume Method. The result of the simulation confirms the possibility to exploit the geothermal resources of the Tete area for several uses, both direct and indirect.