<p>We used hydrogeochemical and isotopic analyses to determine the source of groundwater in the Gohar-Zamin iron mine in south-central Iran. Through three phases of groundwater sample collection from seeps and boreholes, a total of 75 samples were gathered for analysis, including 12 samples containing metals and semi-metals and stable isotopic data (D and ¹⁸O), five samples containing ¹⁴C and ¹³C, and another five samples containing ³H data. Statistical analysis, as well as a time series of groundwater levels recorded in boreholes and multi-level vibrating wire piezometers, confirmed the multi-layered nature of the aquifer system, which includes at least three to four distinct aquifers. All the samples were saline and brackish water (EC &gt; 4 mS cm⁻¹), with a predominant sequence of Cl⁻–SO₄²⁻–HCO₃⁻–NO₃⁻, and Na⁺–Ca²⁺–Mg²⁺–K⁺ for anions and cations, respectively. Conservative tracers (Cl, Br, and B) and stable isotopes demonstrated that the Kheirabad Salt Lake (≈ 13&#xa0;km north of the mine) is not likely the groundwater source. Radiocarbon and tritium age dating suggest that most of the groundwater in the mining area infiltrated during the Holocene and late Pleistocene epochs (paleowater) rather than being replenished by recent rainfall. However, hydrochemical variations observed in samples collected during the wet season are generally attributed to the mixing of groundwater with surface water infiltrating through fractures around the mine pit.</p>