Aeromagnetic Data Interpretation for Basement Structure Mapping in Zamfara State

This study interprets aeromagnetic data to map basement structures and identify mineralisation targets in Zamfara State, North West Nigeria. Zamfara State hosts significant gold mineralisation in its Precambrian basement complex, and illegal artisanal gold mining activities across the state have caused severe environmental and public health impacts. Systematic geophysical mapping of structural controls on gold mineralisation is needed to support formal exploration and mineralisation target delineation. This study processes a 1:50,000-scale aeromagnetic dataset for the Anka sheet from the Nigerian Geological Survey Agency archive. Processing steps include IGRF removal, microlevelling, reduction to the pole, upward continuation for regional analysis, and computation of total horizontal derivative and first vertical derivative for structural enhancement. Lineament extraction is performed using automated edge detection on the first vertical derivative image, supplemented by manual interpretation. Euler deconvolution estimates source depths for magnetic bodies. Findings reveal a northeast-trending structural fabric of basement lineaments that correlates with the orientation of shear zones known to host gold quartz veins in the geological literature. Seventeen magnetic anomaly closures are identified, with depths to magnetic source ranging from 50 to 450 metres. Three anomalies showing steep depth gradients and coincidence with mapped shear zones are identified as priority targets for ground follow-up. The study demonstrates the potential of existing NGSA aeromagnetic archives for systematic mineral prospectivity mapping in northern Nigeria, recommending resurveying at higher resolution for target areas.

Keywords: aeromagnetic interpretation, basement structure, gold mineralisation, Zamfara State, structural lineaments.