Identification of processes in Cu ore heap leaching using Cu is 2024 Hydrome

Copper isotopic fractionation (in δ65Cu) and leachate characterization were studied in the context of heap leaching at the Tschudi copper mine in northern Namibia. The leached solution is of Mg-SO4 type with high Al and Fe concentrations. The source of Mg and Al in the leachate can be from the alteration of micas such as Mg-bearing muscovite confirmed by X-ray diffraction and scanning electron microscopy; however, the source of Mg cannot be determined with certainty. The principal secondary minerals identified in the leached ore are gypsum and jarosite. The value of pH in leachate is ~1.21 and the concentration of dissolved Cu, occurring mostly as CuSO40 and Cu2+, is about 2 g/L. In comparison with unleached ore (avg. δ65Cu ~ 1.47 ‰), leached ore exhibits lighter isotopic values (avg. δ65Cu ~ 6.01 ‰) with apparent isotopic fractionation Δ65Cu leached ore-unleached ore of about ~ 4.54 ‰. In contrast, there is isotopic enrichment of leachate in heavier 65Cu isotope (leachate δ65Cu 0.34 ‰) with apparent isotopic fractionation Δ65Cu leachate-unleached ore value of + 1.81 ‰. These results are in good agreement with Cu isotopic fractionation and depletion in heavier 65Cu isotope.