Daouda Keita

The West African Craton hosts some of the world’s largest BIF-hosted iron ore deposits and represents a globally important iron province. Compilation of data from Guinea, Liberia, Sierra Leone, Mauritania, and Nigeria reveals marked regional variability, from high-grade hematite-rich direct-shipping ores to lower-grade magnetite-rich itabirites. At the province scale, Guinea is dominated by high-grade hematite ores, Liberia contains both hematite and magnetite-bearing ores, Sierra Leone hosts large magnetite-rich and hematite-rich resources, Mauritania combines Archean magnetite-rich and Paleoproterozoic high-grade hematite systems, whereas Nigerian deposits are generally smaller and lower-grade. Their mineralogical and geochemical characteristics record multistage evolution, involving primary sedimentation, metamorphic and structural reworking, hypogene alteration, and supergene enrichment. Geochemical discrimination diagrams indicate broad Algoma- and Superior-type affinities but are not uniquely diagnostic of ore genesis. Airborne geophysics, remote sensing, and geochemistry emerge as complementary exploration tools, particularly for delineating concealed BIFs and alteration zones regionally. Ore variability results in contrasting beneficiation requirements, and four generalized flowsheets link the principal ore types to appropriate processing routes. Major research gaps concern correlations between BIF belts, primary depositional signatures, fluid sources, enrichment timing, prioritized isotopic geochemistry, rare earth element systematics and the limited integration of mineralogical variability with beneficiation performance.

Mining waste is an obvious source of environmental pollution due to the presence of heavy metals, which can contaminate soils, water resources, sediments, air, and people living nearby. The F-(Ba-Pb-Zn) deposit of Hammam Zriba located in northeast Tunisia, 8 km southeast of Zaghouan was intensively exploited from 1970 to 1992. More than 250,000 m³ of flotation tailings were produced and stored in the open air in three dumps without any measure of environmental protection. Thus, in this paper, mineralogical and chemical characterization, especially the sulfide and carbonate phases, were carried out to evaluate the potential for acid mining drainage (AMD) and metal leaching (ML). Conventional analytical methods (XRD, XRF, SEM) have revealed that this mining waste contains on average 34.8% barite–celestine series, 26.6% calcite, 23% quartz, 6.3% anglesite, 4.8% fluorite, 2.1% pyrite, and 0.4% sphalerite. The content of sulfides is less important. The tailing leaching tests (AFNOR NFX 31-210 standard) did not generate acidic leachate (pH: 8.3). The acidity produced by sulfide oxidation was neutralized by calcite present in abundance. Furthermore, the leaching tests yielded leachates with high concentrations of heavy metals, above the authorized thresholds. This high mobilization rate in potential toxic elements (PTE) represents a contamination risk for the environment.