Petrographic and geochemical characterization of the Parawi bauxitic deposit, Republic of Guinea

Global population growth leads to a high demand for quality minerals, particularly for industrial production. Guinea, rich in mineral resources, has more than 23 billion tonnes of bauxite in the Boké region, of which the sub-prefecture of Sangarédi, operated by the Compagnie des Bauxites de Guinée (CBG), is a major site. In this context, a geological characterization study of the Parawi bauxitic deposit was carried out to better understand its petrographic, mineralogical and geochemical composition. The methodology adopted is based on a geological prospecting campaign, with samples collected in the field using an Estwing-type hammer, as well as in boreholes thanks to an ATLAS COPCO drilling rig. Petrographic analysis reveals that the deposit developed on Devonian aleurolites and argillites, intruded by Mesozoic dolerites, then topped with Cenozoic bauxites. The semi-quantitative mineralogical study indicates a predominance of gibbsite (43–84%), followed by boehmite (1–20%). The contents of hematite and goethite-alumogoethite vary between 1 and 21%, while kaolinite and quartz remain marginal (0–1%). On the classification diagrams, the samples are divided between bauxite, ferritic bauxite and kaolinitic bauxite. The high Al2O3 contents reflect a strong lateritization, while the SiO2 contents reflect a weak weathering. Observed bauxitisation processes include kaolinite preservation or destruction, deferruginisation and dehydration. This geological characterization is an essential step to ensure the profitability, safety and sustainability of the exploitation of the Parawi deposit, and guides decision-making at each phase of the mining project.