GEOLOGIC STRUCTURES AND GEOCHEMICAL WEATHERING INDICES: IMPLICATIONS ON GROUNDWATER POTENTIALS IN PART OF MINNA, NIGER STATE, NIGERIA

Abstract

The major structural features that favour ground water potential in basement rocks are fractures, folds and inter-connected and penetrative joints. Joints often impart a well-develop fracture induced permeability to bedrocks, as a result, joints strongly influence, even control the natural circulation of fluids, groundwater and pollutants within aquifers. The structural elements that accompany the tectonic event play different role in ground water quantity and quality within the basement complex of Nigeria. The study area falls within the north-western basement complex of Nigeria and extension of Kushaka Formation that comprises of migmatite, schist and granitiod of varying textural and mineralogical composition. Field mapping unrevealed the lithology and structural elements of the area while XRF was used to determine trace and major elements concentration in the sampled rocks. This study therefore unravels the lithology, geological structures and geochemical weathering intensity, and its control on groundwater potentials in Minna area. Correlation of all observed, measured structural elements and obtained bole-holes log with water yield potential in the study area varies with lithology. The average Ruxton Ratio Weathering Index value suggested of rocks in the area revealed weak weathering and intermediate weathering respectively. It is therefore worthy to note that Maitumbi, part of Tunga, Tunga Gade, Chanchaga and the Nigeria Army Barrack areas that constitutes the central part of the study area favored high yield ground water potential throughout the years. Its therefore recommended that the areas with low yield ground water potential and intermediate weathering index should be properly investigated before sinking borehole and a minimum depth of one hundred and eighty meters will increase water yield.