Physical–Chemical Characterization of the Neves Corvo Extractive Mine Residues: A Perspective Towards Future Mining and Reprocessing of Sulfidic Tailings

Neves Corvo is an underground high-grade Cu–(Sn)–Zn mine, located in the Portuguese part of the world-class Iberian Pyrite Belt (IPB), which is currently producing copper, zinc, and lead concentrates. The operation is owned by SOMINCOR, a subsidiary of Lundin Mining, with a maximum capacity of 2.6 Mtpy for the copper processing plant and 1.0 Mtpy for the zinc processing plant. From 2010 till end of 2019, the mine has accumulated 7.3 Mt of waste rock and 17 Mt of thickened tailings. These mining residues are stored in Cerro do Lobo Tailings Management Facility (Cerro do Lobo TMF), which completes a volume of 47 Mt since the beginning of the operation in 1989 (30 Mt are slurry tailings). The deposition method changed in 2010 from slurry subaquatic deposition to sub-aerial thickened tailings stack (vertical expansion) in co-deposition with potentially acid-generating (PAG) waste rock. X-ray fluorescence analysis have shown copper and zinc grades variation in the waste rock between 0.12 and 0.4%, and 0.1% and 0.3%, respectively, and concentrations up to 0.6% and 1.3% of copper and zinc, respectively, in the tailings. Mineralogically, the tailings consist mainly in pyrite, sphalerite, chalcopyrite, ± arsenopyrite, ± tetrahedrite-tennantite, and gangue minerals such as quartz, phyllosilicates, carbonates, and some oxides, and have a non-uniform particle size distribution ranging between 1 and 100 µm. The waste rock fraction is millimetric to centimetric in size and is formed by the local host rocks, mineralogically consisting in quartz, chlorite (clinochlore and chamosite), calcite, and variably abundant disseminated sulfides, largely dominated by pyrite. Both mining residues might be envisaged as materials with valorization potential both for base metal recovery (tailings) and/or as non-metallic raw materials for construction or other applications (waste rock). Graphical Abstract