From iron ore to environmental risk: Geochemical, mineralogical, and acid generation behavior of mining wastes from the abandoned ouixane site, Northeastern Morocco

Abstract

The abandoned Ouixane iron ore mine in northeastern Morocco has generated a significant volume of mine wastes, which can generate contaminated water in the form of acid mine drainage (AMD) when sulfide minerals are present. This study evaluates the geochemical, mineralogical, and environmental characteristics of eleven representative samples (S1 to S11) collected from various zones of the site using X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), and static tests including acid-base accounting (ABA), net acid generation (NAG), and paste pH measurements. The results reveal high average concentrations of Fe 2 O 3 (mean 39.46 wt%) and SO 3 (mean 17.71 wt%), along with mean elevated levels of As (1.09 g/kg), Pb (0.73 g/kg), Zn (0.96 g/kg), and Cu (1.02 g/kg). Mineralogical analysis confirmed the presence of reactive sulfide and sulfate phases. Most samples exhibit highly acidic pH values (<2) and negative net neutralization potentials (NNP) ranging from −1025.73 to +34.96 kg CaCO 3 / t , with a mean of −263.54 kg CaCO 3 / t , indicating a strong acid-generating potential. These findings highlight critical risks of acid generation and metal contamination at the Ouixane site, providing essential data for effective remediation strategies in Morocco. • Integrated geochemical and mineralogical characterization of Ouixane mine wastes, northeastern Morocco. • Acid mine drainage (AMD) potential confirmed at the abandoned Ouixane site. • Static ABA–NAG–paste pH tests reveal strong acid-generating behavior in most samples. • Semi-arid climate enhances sulfide oxidation and promotes persistent sulfate formation. • Co-enrichment of Pb, As, Zn, and Cd indicates severe contamination and metal mobility risks.