<p>The South Setifian region in northeast Algeria has strong hydrogeothermal potential due to its tectonic structure (horsts and grabens), which allows deep fluid circulation through fractured and karstified Jurassic–Cretaceous carbonate reservoirs. Seven sampling points were selected along an E–W transect from Zana El Baidha to Hammam Guergour, covering the main lithological and structural ensembles (Lias–Cretaceous carbonate horsts, Triassic evaporitic formations, Mio-Plio-Quaternary grabens) to ensure the representativeness of the hydrogeological compartments. The analysis shows a strong signature of calcium and magnesium sulfate-chloride facies with a secondary sodium tendency. This signature is attributed to long-term water-rock interactions with carbonate and Triassic evaporitic formations, as confirmed by stoichiometric diagrams and the International Institute of Geothermal Research classification. The absence of tritium and the very low carbon-14 (¹⁴C) activities (0,006− 0,016&#xa0;Bq), determined here for the first time using low-background liquid scintillation spectrometry, indicate that these waters are ancient, deep-seated, and characterized by long residence times. This supports their short-term non-renewable nature and underscores the need for controlled exploitation and protection of deep reservoirs. The concentrations of trace elements reflect three distinct geological contexts: the eastern zone shows low concentrations, governed by circulation in the Lias-Berriasian/Lower Cretaceous-Turonian carbonate formations; the central zone shows a progressive enrichment related to the dissolution of Triassic evaporites; finally, the northwestern zone records the highest concentrations attributed to a deeper circuit. The localized anomalies in cadmium and lead require rigorous analytical monitoring before any exploitation, and constitute an initial evaluation of potential health risks.</p>