EFFECT OF TOPOGRAPHIC AND GEOLOGIC HETEROGENEITIES ON THE DISTRIBUTION PATTERN OF AQUIFERS IN AKWA IBOM STATE, SOUTHEASTERN NIGERIA

Geologic heterogeneities and topographic variations in relation to aquifer distribution ad occurrence in Akwa Ibom State have been assessed based on geologic and geophysical studies sixty-six sounding points together with electric log responses of representative wells together with surface geologic data have been integrated and used in deciphering subsurface variations in hydrologic unit in the state. The results show that three aquiferous units, made up of medium to coarse grained whitish sands exist within a depth range of 72 to 98 meters and having resistivities less than 1500 ohm metres. These aquifers are clearly defined in those locations close to the coast and in the hinterlands whereas towards the northern parts of the state they appear to pinch-out or dip downward to much greater depths. Measurements of elevation across the study area show a drastic decrease in altitude tending toward the mean sea level within the hinterland and coastal regions, whereas towards the northern part, relatively higher elevations-exist. The increase in altitude in addition to the occurrence of thick columns of compacted shales greatly account for the scarcity of aquiferous zones in this northern part of the study area contrary to the localities within and surrounding the coastal and central regions. KEY WORDS: Heterogeneities, aquifer, topography, pinch-out, hydrologic. Global Jnl Geological Sciences. Vol.2(1) 2004: 125-13

Groundwater potentials of parts of Ibiono Ibom local government Area of Akwa Ibom State Southern Nigeria by vertical electrical sounding technique

Geophysical investigation into groundwater potential in Ibiono Ibom Local Government Area of Akwa Ibom State has been done by interpretation of modeled resistivity curves generated for the area. The vertical electrical sounding (VES) technique using the Schlumberger's electrode array with a maximum half electrode spacing (AB/2, M) of 450m was used. Eight communities were selected for the study and further classified into three main districts comprising Afaha Utuat, Oko-Ita and Ikot Obio-Okon respectively for a generalized presentation. Interpretations of the modeled resistivity curves show that in the Oko-Ita district the anomalous high resistivity of 2000 ohm-m is probably attributable to the presence of compacted clay (clay stone of not less that 30m thick. Well cuttings obtained from two (2) isolated/abortive boreholes in the area, coupled with the lithofacies characteristics observed from thick sections along orad cut further lend credence to this fact. Contrary to this, in the Afaha Utuat district, low resistivity values (200-300 ohm-m) is probably due to the presence of highly fossilized clay units dominating the area. Within these districts the probable aquifer suspected to be layer 3, occurs at a depth of 110m from the interpreted curves. Groundwater development scheme in these areas could therefore best be based on the drilling of deep boreholes not shallower than 100meters. In the alternative, surface water development schemes by tapping from available river in the area or rainwater harvesting may equally be adopted. On lthe contrary, better prospects exist in the Ikot Obio okon district where layers 2 and 3 with resistivities of 30 – 350 ohm-m constitute the main aquifers between 45 and 50m depths. Nigerian Journal of Physics Vol. 16(2) 2004: 116-12

The appraisal of a proposed barite quarry in Akpet Area, Cross River State, from resistivity investigation

Electrical resistivity survey was done at a site at Akpet area, Cross River State to evaluate the subsurface for barite mineralization. Both vertical electrical sounding (VES) and horizontal resistivity profiling (HRP) were performed in conjunction with surface geological mapping in the area. In both VES and HRP, the Schlumberger electrode array was adopted and measured resistivity data interpreted using conventional curve matching techniques and iterative computer modelling. Results show that three (3) zones designated A, B and C with barite mineralization occur within a depth of 5m in the subsurface at the project site. The combined high specific gravity of 4.4 g/cc and high BaSO4 (>92%) show that the barite of the study area are of high quality. The practical recovery of over 8 tons of barite at the project site shortly after this report which revealed the occurrence of large deposit of barite in the area; show that the applicability of the resistivity method in the search of barite and other minerals alike is very reliable. KEY WORDS: Barite, resistivity, subsurface, recovery. Global Journal of Geological Sciences Vol.2(2) 2004: 171-17

Regional tectonic effects on the composition and mode of distribution of barite mineralization in Akpet Area, SE Nigeria

Reconnaissance geologic mapping for barite mineralization within Akpet Central and environs had been successfully done. The results of the study show that the mineralization of barite is largely structurally controlled although minor sedimentary processes have also contributed. Barite mineralization in the area therefore probably displays both metamorphic/igneous and/or sedimentary origins. Those that are derived from igneous processes occur mainly as veins and exhibit thicknesses which depend on the width of the fractures found in the rocks. On the other hand, barite mineralisation in the northeastern flank of the study area occurs as alluvial deposits and in few cases as domes. Chemical compositions for samples obtained from the northwestern and southwestern parts of the area show greater concentration of BaSO4 than in those samples from northeastern axis which exist in alluvial forms. Hence, both regional tectonic activities and the mode of occurrence of barites constitute important factors in the evaluation of barite mineralization. All the barite samples of the study areas analyzed are of high quality to stand the test of time in the world market. KEY WORDS: Mineralization; Barite; Fractures; quality; alluvial. Global Journal of Geological Sciences Vol.2(2) 2004: 177-18