Magnetic Survey for Iron Ore Prospect Evaluation in Kogi State

This study conducts a ground magnetic survey to evaluate iron ore prospecting targets in the Itakpe-Agbaja iron ore belt of Kogi State, North Central Nigeria. Iron ore production is strategically important for Nigeria's steel industry, and Kogi State hosts the country's primary iron ore deposits at Itakpe, which supplies the Ajaokuta Steel Company. Defining the lateral extent and structural geometry of iron ore bodies requires geophysical mapping to complement geological outcrop mapping. This study acquires total magnetic intensity data along 25 east-west trending profiles at 50-metre line spacing and 20-metre station intervals using a proton precession magnetometer. Diurnal drift corrections are applied using a base station recording. Data processing includes instrument correction, regional trend removal, and reduction to the pole transformation using the International Geomagnetic Reference Field 2020. Total horizontal derivative and analytical signal amplitude maps are computed to enhance structural boundaries. Interpretation involves forward modelling using Potent software to estimate body geometry and susceptibility. Findings reveal two principal magnetic anomaly clusters with positive amplitudes of 850 to 2,400 nanoteslas, interpreted as iron ore-bearing banded iron formation units. Modelling suggests ore body widths of 60 to 120 metres dipping steeply to the southeast at depths ranging from surface outcrop to 80 metres. The northern anomaly cluster shows better continuity and is recommended as a priority target for follow-up diamond drilling. The study demonstrates the utility of ground magnetic surveys for iron ore target ranking in Nigeria's itabirite terrain.

Keywords: magnetic survey, iron ore, Kogi State, banded iron formation, total magnetic intensity.