Aeromagnetic Characterization of Subsurface Structures and Their Hydrogeological Significance for Groundwater Exploration in Parts of Lokoja, North-Central Nigeria

Aeromagnetic methods offer an efficient reconnaissance approach for narrowing exploration targets by rapidly mapping subsurface structures over large areas. This study applies aeromagnetic data interpretation to characterize geological structures controlling groundwater occurrence in the crystalline basement environment of Lokoja, North-Central Nigeria. Total Magnetic Intensity (TMI) data were processed using Reduction to the Magnetic Equator (RTE), Upward Continuation, Derivatives filters (X, Y, THDR and TDR) to enhance structural boundaries and lithological variations and SPI, ED Euler Deconvolution and Spectral Analysis for depth estimations. Results revealed dominant NW-SE and NE-SW trending magnetic lineaments consistent with the Pan-African tectonic imprints. Total Magnetic Intensity (TMI) values ranging from − 78.9 nT to 128.3 nT and low magnetic intensity zones (-78.9 to -12.2 nT) in the southeastern and northwestern sectors, correlating with weathered or fractured basement favorable to groundwater accumulation. Analytical Signal Mapping (ASM) highlighted sharp magnetic contrasts. SPI depth (28.2m − 320m), 3D Euler Deconvolution (structural indices = 1–3) constrained source depths to 55.3–265.0 m. Spectral analysis further resolved magnetic source depths into shallow (33–49 m), intermediate (220–336 m), and deeper (246–617 m) domains, correlating with potential aquifer bearing zones. Lineament analysis confirmed dominant NW–SE and NE–SW structural trends, consistent with the regional basement fabric. The high density and connectivity of lineaments in the eastern and southeastern sectors, particularly within the Migmatite Gneiss, Granite Gneiss, and Sandstone units, strengthen the interpretation of structurally controlled hydrogeological corridors.. The study demonstrates that aeromagnetic characterization effectively isolates and delineates exploratory groundwater-targeting zones, which amplify the accuracy of exploration targets for borehole siting, and a reduction in drilling risk in basement terrains.