Geochemical and Petrographic Assessment of the Sedimentary Ironstone Exposures of Kaduna-Ife, in the Northern Anambra Basin, Nigeria

This study presents a comprehensive petrographic and geochemical analysis of ironstone deposits in the Northern Anambra Basin, Nigeria, employing thin-section microscopy and X-ray fluorescence (XRF) spectroscopy. The primary objective was to evaluate these mineralogical composition, textural features, and geochemical characteristics to infer their depositional environment and assess their potential for economic utilisation.Petrographic examination revealed that the ironstones are predominantly composed of iron oxides, notably hematite and goethite, with significant amounts of silica andalumina. Quartz grains exhibited undulose extinction and embayment against the groundmass, indicating minimal alteration and a stable depositional environment. Biotite minerals displayed pleochroism and were associated with alteration products, reflecting diagenetic processes that have contributed to the iron enrichment of the rock. The opaque minerals, likely iron oxides, indicate lateritic weathering under oxidising conditions.Geochemically, the ironstones exhibited high iron content, averaging approximately 49.265%, with low levels of deleterious elements such as sulfur and phosphorus. The silica content was within permissible limits, while the alumina content was relatively high, suggesting the presence of gangue materials. The low levels of calcium oxide and the absence of sulfur oxides point to an oxidising environment during deposition.These findings align with those observed in other ironstone deposits in Nigeria, such as the Agbaja ironstone, which also exhibits high iron content and low levels of sulfur and phosphorus. The integrated petrographic and geochemical analyses indicate that the ironstones of the Northern Anambra Basin formed under conditions conducive to iron enrichment, likely through processes such as lateritic weathering and diagenetic alteration. The high iron content and favourable geochemical characteristics suggest that these ironstones have the potential for economic exploitation, provided that the silica and alumina content are reduced in the beneficiation process. This research contributes to understandingthe mineralogical and geochemical characteristics of ironstone deposits in theMamu Formation of the Northern Anambra Basin by providing valuable insights for future exploration and exploitation endeavours.