A comprehensive hydrogeochemical survey of the geothermal waters from the Nappe Zone (Maghrebides fold-and-thrust belt) was undertaken to determine the origins of geothermal waters and to assess the health risks associated with their potentially toxic elements. A total of 11 geothermal water and 3 stream water samples were collected and analysed for major and trace elements (As, B, Ba, Fe, Mn, Pb, Sr, Zn). Two main geothermal water groups were highlighted by hydrogeochemical diagrams and multivariate analyses (PCA, HCA): the first group is the Na−Cl type, TDS > 10 g/L, controlled by deep circulation, while the second group is the Na-Cl−HCO₃ type, TDS < 2 g/L, and controlled by shallow circulation. A curved hydrogeochemical evolution path, observed from mixed bicarbonate shallow groundwater to chloride geothermal water, indicates that the interaction with evaporites drives the chemistry of the geothermal samples. On these, the As enrichments come from sulphide oxidation polymetallic mineralisation during the upwelling to the surface from E–W major lineaments. Therefore, E–W lineaments are potential areas for mineral prospecting. The health risk assessment reveals that the concentration of potentially toxic elements in geothermal waters are lower than the guideline values for the protection of freshwater aquatic life and dermal exposure (bathing or balneology).

Since 2004, the processing of the iron oxide–copper–gold (IOCG) ore of Guelb Moghrein, Akjoujt, Mauritania, has resulted in the generation of approximately 40 million tons of mine tailings. The storage of these tailings poses significant environmental challenges particularly to surface and underground water resources. To address this issue, we propose an approach involving both mineralurgical and environmental characterization. Our mineralogical analysis reveals that the TSF tailings consist of sulfides and iron oxides associated with a silico-carbonated matrix. This mineralogical analysis also shows that the TSF tailings consist of secondary minerals, resulting from sulfides oxidation. Furthermore, our findings indicate that the chemical analysis of the TSF tailings contains potential toxic elements (PTEs) such as Cu, As, Co, Ni, Sb, and Se. Regarding the environmental characterization of the tailings, conducted through acid-based accounting (ABA) static tests, we demonstrate that leaching from the tailings generates a contaminated neutral drainage (CND).