Kogi west geophysical mineralisation appraisal using Analytical Hierarchy Process (AHP)

Abstract

In a recent report by the Nigerian Geological Survey Agency, new minerals, including gold, lepidolite, and tantalite, were discovered in the western part of Kogi State. If found in sufficient quantities, these commercially valuable minerals have the potential to drive technological advancement, create jobs, and promote economic growth, which are crucial for the sustainable development of Nigeria. This study aims to delineate these occurrences, extensions, and other potential mineralisation zones using integrated high-resolution airborne magnetic and gamma-ray spectrometry geophysical datasets aided by the Analytical Hierarchy Process (AHP) and weighted overlay analysis (WOA). The AHP and WOA algorithms were employed based on expert opinions and the accuracy of each signal enhancement technique to delineate the mineralisation potential of the study area (using the IMOs as control). Centre for Exploration Targeting (CET) grid analysis, analytic signal (Asig), and Euler deconvolution were used to enhance the magnetic datasets, while radiometric ratios and ternary images were utilised for the radiometric datasets. The Asig categorises the magnetic amplitude into low (<0.023 nT/m), intermediate (0.023–0.105 nT/m), and high (>0.105 nT/m). It reveals magneto-structures and intrusive zones, which are potential targets for mineralisation. WNW-ESE and NE-SW are the dominant fault trends, with the IMOs being more consistent with NE-SW faults. The estimated depth of potential mineralisation zones ranges from 20.87 to 87.34 m. The ternary image and radiometric ratio maps (K/Th and Th/K) indicate that the mineralisation zones have undergone advanced weathering, resulting in potassium leaching and thorium enrichment. Asig, lineament density, and the Th/K ratio map were integrated to assess the mineralisation potential. Employing the ArcGIS weighted overlay tool and AHP evaluation, the mineralisation potential of Kogi West was classified as high, intermediate, or low. 90% of the IMOs fall within the high class, while 10% are in the intermediate category. The high-potential zones should be prioritised for further exploration and exploitation. The high correspondence indicates the effectiveness of the integrated geophysical approach in identifying regions with favourable geological conditions for mineralisation. However, while the study provides a promising framework for targeting potential mineral deposits, future exploration activities should consider the following implications to improve the reliability and applicability of the results: validation with ground-truthing, incorporating other geophysical methods (such as electrical, gravity, and electromagnetic surveys), and acknowledgement of eventualities that high potential mineralisation zones not been economically viable, may be due to poor mineral grade or volume. These endeavours and acknowledgements will refine the current understanding of the high-potential mineralisation zones and expand the scope of mineral exploration in Kogi West.