Geochemistry of the Ironstones in Abiati Area, Southeastern Nigeria: Implications for Ore Genesis and Economic Potential

Abstract

Iron is, from an economic perspective, the most significant metal. The ironstone resource at Abiati has been examined by integrating geochemical discrimination plots and statistical techniques to decipher its provenance, and economic potential. Twenty-five (25) representative ironstone samples were collected and subjected to laboratory analysis using XRF (X-Ray Flourescence) techniques to determine their chemical compositions. XRF results revealed SiO₂ (8.201), Al₂O₃ (5.102), Fe₂O_3(t) (71.436), CaO (0.252), MgO (0.796), SO₃ (0.004), K₂O (0.052), Na₂O (0.043), and LOI (12.298) on average; all in units of weight percent (wt.%). However, P₂O₅ and TiO₂ were either not found in the samples or they were below detection limits. The absence of P₂O₅ and low concentration of MgO and SO₃ suggest a warm-temperature, wide-range non-marine, lacustrine or shallow marine environment for the ironstones; thus, ruling out the possibility of full marine origin and/ or reworking. Low levels of CaO and the absence of CO₃ indicate that the environment is oxidizing. Hence, the analyzed samples suggest deep weathering, strong lateritisation, metasedimentary origin, and a post-depositional secondary diagenetic modification (i.e., supergene enrichment) under oxidizing and shallow marine conditions within the post-Precambrian/ Phanerozoic age range. Compared with the generalized world market standards/ benchmarks, the computed ore grade results indicated a low-grade (Fe_(t) - av. 49.962 wt.%) with an appreciable amount of impurities. Although it can be used for cement production, beneficiation is required to upgrade its quality to attain acceptable levels for usable iron ores, utilisation for cast iron and steel production, and valorisation in other industrial applications.