Application of mineralogical, geochemical, and statistical analyses to investigate waste rock heaps at the abandoned Zeïda mine (Northeastern Morocco)
摘要
The Zeïda mine, an abandoned site in northeastern Morocco, was one of the largest lead reserves for thirteen years. Large volumes of mining waste were stored as tailings and exposed to meteoric agents, creating geochemical hazards. This study investigated the potentially toxic elements (PTEs) in mine wastes, specifically identifying Pb and As as the most prevalent and hazardous elements. The samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), particle size distribution analysis, and multivariate statistical techniques. The mineralogical composition of the waste rock heaps was dominated by quartz, feldspars, illite, kaolinite, muscovite, and biotite, with associated minerals including dolomite, halite, fluorite, barite, and iron oxides. In contrast, the mine tailings were rich in quartz, low in clay minerals, and lacked carbonates. In terms of chemical composition, Pb and As were detected at higher concentrations in the studied mine wastes (Pbmax = 15,000 mg/kg, Asmax = 114 mg/kg) making them the most prevalent PTEs. SEM analysis revealed that the lead ore in the host rock primarily occurred as galena and cerussite. Bivariate correlation analysis suggested that Pb was poorly correlated with Fe, Al, and K, implying a limited association with clay minerals or Fe-oxy-hydroxides. Cluster analysis and Pearson correlation indicated that Pb, Cu, and As are grouped together, suggesting a common source in the mine wastes. Under alkaline conditions, Pb in solution precipitated whereas As showed high mobility leading to environmental contamination of surface water, groundwater, cultivated soils and posing a risk to human health. These findings highlight the environmental risk posed by lead and arsenic in the region, with implications for remediation strategies and future policy-making in mining waste management.