- 1Dipartimento di Scienze della Terra e Geoambientali, Università degli Studi di Bari Aldo Moro, via E. Orabona, 4, 70125 Bari, Italy
- 2Dipartimento delle Scienze Chimiche, Fisiche, Matematiche e Naturali, Università degli Studi di Sassari, Via Piandanna, 4, 07100 Sassari, Italy
- 3Dipartimento di Architettura, Design e Urbanistica, Università degli Studi di Sassari, Via Piandanna, 4, 07100 Sassari, Italy
- 4Dipartimento di Scienze di Base e Applicate, Università degli Studi della Basilicata, Via dell’Ateneo Lucano, 10, 85100, Potenza, Italy
Around 30 million tonnes of bauxite residues (red muds), resulting from aluminium extraction via Bayer process, are stored at the Porto Vesme disposal site in southern Sardinia, Italy. The primary crystalline components of these residues include iron oxides, aluminium hydroxides, titanium oxides, silicates, carbonates, and halides, along with several minor phases. Lanthanide-rich phosphate minerals are occasionally detected. The Na-aluminosilicates are results of desilication, while the aluminium hydroxides and oxyhydroxides are residual alumina minerals, and the iron oxides, most titanium minerals, and REE-rich phosphate minerals originate from the parent bauxite. LREE ferro-titanates have also been identified.
The residues are predominantly composed of Fe2O3, Al2O3, SiO2, Na2O, TiO2, and calcium, with the REEs being significantly enriched compared to the parent bauxite. LREEs are the most abundant, followed by HREE+Y and Sc. Cerium is the dominant lanthanide, and the chondrite-normalized patterns reveal substantial positive Ce anomalies. Vanadium (V) is the most abundant critical metal, followed by niobium (Nb), gallium (Ga), and hafnium (Hf).
Factor analysis of the major elements (SiO2, Al2O3, Fe2O3, CaO, Na2O, TiO2, P2O5), REEs, and critical metals (V, Co, Cu, Ga, Nb, Hf, Ta, W) indicates that the first factor (52.1% variance) reflects the competition between desilicated minerals and secondary phases that host the LREEs and critical metals such as V, Cu, and Nb. The second factor (15.2% variance) is associated with zircon’s role in distributing HREE+Y.
The HREE+Y and metals like Hf, TiO2, and W are enriched relative to the Upper Continental Crust, suggesting a high supply risk and economic importance. Several profitability indices, including the outlook coefficient, critical REEs to total REEs ratio, and the (Nd+Dy+Ce+Pr+La)/Σ(REE+Y) ratio, indicate that the bauxite residues at Porto Vesme have significant economic potential.
Keywords
Red muds, geochemistry, LREE, HREE+Y, profitability, Sardinia
How to cite: ouladmansour, A., Mameli, P., Schingaro, E., Mesto, E., Lacalamita, M., Cerri, G., Idini, A., Cisullo, C., and Mongelli, G.: Rare Earth Elements (La-Lu, Sc, Y) and Other Critical Metals deportment in Bauxite Residues: Assessing the Economic Viability of Red Mud Deposits at the Porto Vesme Disposal Site, Sardinia, Italy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12788, https://doi.org/10.5194/egusphere-egu25-12788, 2025.
