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Papers by Gabriel Obiefuna Phd

The aim of this study is to determine the geochemical and mineralogical composition of granitic r... more The aim of this study is to determine the geochemical and mineralogical composition of granitic rock deposit of Michika area of northeastern Nigeria. Detailed geological mapping of an area of 188.5 Km2 around Michika area has been mapped on a scale of 1: 50,000. The mapping revealed that the area is underlain by granitic rocks of Pan African Age. These are grouped into three types: coarse grained biotite granites, coarse porphyritic granites and medium grained granites which are intruded by the new basaltic rocks of Tertiary Age. A plot of Rose Diagrams indicate they trend in the NE-SW and NW-SE directions and occurs as irregular or massive bodies, veins and sometimes as a cross-cutting discordant dykes. The fracture ranges from about 5 cm to about 2 meters. Seven samples were collected at different locations representing the three types for petrographic analyses. Petrographic studies show that the samples are essentially composed of quartz, feldspar, mica and iron oxide. Twenty samples were analyzed geochemically using XRF method to determine some major oxides which include SiO2, Al2O3, K2O, Fe2O3 and CaO. The SiO2 content are mainly (70.58%), Al2O3 (14.30%), K2O (5.44%), Fe2O3 (2.73%) and CaO (2.62%) were obtained for the samples. The results indicate that granitic bodies of the Older Granites that underlie the study area are strongly peraluminous calcalkaline igneous series that are of both lithospheric origin or are associated with subduction related areas.

Geochemical studies of Yola area of Northeast Nigeria were studied during a dry season period (No... more Geochemical studies of Yola area of Northeast Nigeria were studied during a dry season period (November 2008). This was to determine the process controlling the water chemistry and to assess the quality of water. The results show that, based on ionic ratios, precipitation and water-rock interaction (silicate weathering) are the main controlling factors contributing to solute concentration in these areas. The main water types in the area include Mg 2+-HCO 3-and Na +-Cl-are the dominant ion types for the shallow groundwater, Mg 2+-Cl-, Mg 2+-HCO 3-and Na +-HCO 3-for the deep groundwater and Na +-Cl-for the surface water bodies. Equilibrium specification calculations revealed that the water samples are largely undersaturated with respect to calcite and dolomite in the water samples. Groundwater samples from the shallow groundwater indicate pH values (6.10 to 7.08) and Eh values (mean 0.72 volt) whereas those of the deep groundwater revealed pH range (6.60 to 7.80) and Eh values (mean 0.75 volt). They are slightly acidic to neutral, largely soft, clean waters with fairly low to moderate concentration of dissolved solids that fall within the international acceptable limits for drinking, domestic and irrigation purposes. However some samples indicate iron and nitrate values that are above the recommended limits and should be treated before use. Employing Electrical Conductivity (EC), Total Dissolved Solids (TDS), Sodium Adsorption Ratio (SAR), Magnesium Adsorption Ratio (MAR), Permeability Index (PI), Kellys Ratio (KR), and Residual Sodium Bicarbonate (RSBC) as criteria, the waters appear suitable for irrigation purposes.

Then Bima Sandstone aquifer is the main water resource in the semi-arid Yola area of Northeastern... more Then Bima Sandstone aquifer is the main water resource in the semi-arid Yola area of Northeastern, Nigeria. The rapid increase in water demand in this area has prompted the need to estimate available groundwater recharge for sustainable utilization. Groundwater recharge estimation methods and results are compared: chloride mass balance method (5.81 to 9.65 mm/year); water budget method (52.45 to 86.20 mm/year); Darcian method (16.38 to 104.04 mm/year) and hydrograph separation method (133.6 to 645.81 mm/year). The Chloride mass balance and the Darcian methods are well suited to identify the existence of recharge and enable one to determine good estimates of aerial and point values. A major limitation of the chloride mass balance is that there may be other sources of chloride in the soil (eg halites) other than the chloride contained in the rainwater. On the other hand in the Darcian method the hydraulic conductivity of the soil is poorly known due to heterogeneities and its variation with saturation. The water budget method is bedeviled by a number of limitations which include lack of lysimeter for measuring evapotranspiration but is simple and can be estimated as a residual in a continuity equation. A major drawback of the hydrograph separation method is that it estimates baseflow at lower elevations in a watershed which is assumed to be equal to recharge that occurred at higher elevation. It is however one of the few integrative measurement of recharge. The merits and demerits of each recharge method in terms of accuracy and applicability were also highlighted in this study. This study has shown that recharge occurs to some extent in even the most arid regions, though increasing aridity are characterized by a decreasing net downward flux and greater time variability. Thus as aridity increases, direct recharge is likely to become less important and indirect recharge more important in terms of total recharge to an aquifer. It is therefore concluded that estimates of direct recharge are likely to be more reliable than those of indirect recharge.

Growing gully sites in the Federal University of Technology Yola Nigeria were observed. The gulli... more Growing gully sites in the Federal University of Technology Yola Nigeria were observed. The gullies formed by erosion have caused extensive damage to the environment and are threat to the newly constructed/reconstructed infrastructures. The study shows that the gullies are caused partly by human activities and geomorphologic processes, but mainly by geological and geotechnical characteristics of the soils. Available geological and geotechnical data soils that are highly weathered and loose. Fractive force due to run-off and seepage flux are mainly resisted by the angle of internal friction since the value of cohesion is low. On the basis of the geological and geotechnical data, it is suggested that soil stabilization techniques such as grouting, dewatering and concrete lip-rap be applied to the affected areas to check the growth of the gullies.

Sixteen samples from the Bima Formation in Yola Area of Northeastern Nigeria have been analyzed f... more Sixteen samples from the Bima Formation in Yola Area of Northeastern Nigeria have been analyzed for major elements and the results used for sand-class classification scheme. In the scheme, Log ratios of SiO2/Al2O3 and Fe2O3/K2O which express and relate geochemical fractions of sands to the existing sandstone classification scheme, have been used to reclassify the Bima Sandstone member (Bima-1) from Yola area. Results of this method indicate that about 43.75% of the samples from the area plot in the iron-rich class, 31.25% in the sub-arkose to arkose class and 25% in the sub-lithic arenite class. These results indicate that the Bima-1 member of the Bima Sandstone Formation of the area is made up of three units. The lower units composed of sub-arkose to arkose unit and the sub lithic to lithic arenite whereas the upper unit is iron-rich.