Interpretation of Aeromagnetic and Aeroradiometric Data for Potential Mineralization in Kuje Sheet 207SE, North Central Nigeria

Abstract

The thesis presents an interpretation of the aeromagnetic and aeroradiometric data of Kuje Sheet 207SE in the Federal Capital Territory of North Central Nigeria. The aim was to outline geological features and radiometric signals that might be indicative of possible mineralization zones within the Nigerian Basement Complex in this area.  The aeromagnetic data were processed through a number of enhancement filters including reduction to the equator, first and second vertical derivatives, analytic signal, tilt derivative and upward and downward continuation. These filters were utilized to recognize lineaments, lithological contacts and fault systems that may have acted as channels for mineralizing fluids. The aeroradiometric data of potassium, thorium and uranium concentrations were processed to generate the concentration maps, ternary map of radioelements and map of the potassium-thorium ratio for the purpose of identification of hydrothermal alteration zones. Euler deconvolution for depth estimation indicated that most of the magnetic sources are at depths shallower than 500 meters, a depth range compatible with typical mineral exploration targets in basement terrains. The structural analysis indicates that the study area is dominated by NE-SW trending lineaments, subordinate NW-SE and E-W orientations.  These structural patterns are consistent with the larger Pan-African tectonic setting of the Nigerian Basement Complex. The hydrothermal alteration is structurally controlled as indicated by the K/Th ratio map which shows several high ratio zones spatially correlated with the NE-SW trending lineaments. The integration of the magnetic and the radiometric data sets in a GIS environment enabled the classification of the research region into high, moderate and low mineral potential zones. The high potential zones are the places where high analytic signal values, high lineament density, tilt derivative zero contours and higher K/Th ratios coincide.  Three key target areas were identified; the middle part of the sheet from north of Kuje town to the eastern boundary, the NE-SW and NW-SE crossing structures at the NE corner and the Tagwai and south of Kwali to the south. These areas are entrants for additional geological mapping, geochemical sampling and possibly drilling. The study demonstrates the use of combined geophysical methods for mineral exploration in the Nigerian Basement Complex and provides a basis for future studies in the Kuje area.