INVESTIGATING THE POTENTIAL OF PYRITE AS A REPOSITORY FOR CRITICAL ELEMENTS AND PRECIOUS METALS IN HISTORIC COPPER TAILINGS: INSIGHTS INTO REPROCESSING COPPER TAILINGS

Pyrite, the dominant sulfide phase in copper sulfide tailings, is an important host of various critical elements. However, the distribution of these elements within pyrite remains inadequately understood. This study aims to assess the potential role of pyrite as a major reservoir for critical elements and precious metals in historic copper tailings including Te, Au, and Ag. The representative samples were collected from various depths of the historic tailings dam, via core drilling. Trace element analysis and mineralogy of representative samples were conducted using various techniques, including Inductively Coupled Plasma Mass Spectrometry (ICP-MS), Tescan Integrated Mineralogical Analysis (TIMA), and Scanning Electron Microscope (SEM). ICP-MS analysis revealed relatively low concentrations of Te, Au, and Ag measuring at 0.4 ppm, 172 ppb, and 0.7 ppm, respectively. Tetradymite (Bi₂Te₂S) emerged as the predominant Te-bearing mineral (75% of total Te), while altaite (PbTe) and hessite (Ag₂Te) were identified as minor Te carriers. Tetradymite and other Te minerals were found coexisting with pyrite in fine-grained (<7.2 µm) inclusions. Gold was found occurring as electrum and as complex Ag tellurides that contained selenium, bismuth, and lead, as identified by EDS spot analysis. Reprocessing copper tailings, particularly through pyrite recovery, presents a viable strategy to enhance Te, Au, and Ag enrichment.