Geochemical Characterization of Mineralized Pegmatites around Wowyen Areas, Akwanga, Northcentral Nigeria

This study aims to account for the petrogenesis and mineralization of pegmatites around the Wowyen area, northcentral basement complex,Nigeria. Field studies, petrography and whole rock geochemistry (Major oxides were estimated by X-Ray Fluorescence while the trace elements were estimated by Inductively Coupled Plasma Mass Spectrometry) where the methods adopted. The pegmatites around Wowyen area are emplaced in the remobilized belt of the Nigerian Basement complex. They are predominantly complex pegmatites (rare-metal pegmatites) which are intruded in the biotite-muscovite gneiss while the simple pegmatites intruded more in the migmatitic banded gneiss. The major components of the complex pegmatites are quartz, albite and muscovite and tourmaline.The accessory constituents are garnet; ilmenites; cassiterite-columbitetantalite oxides in contrast to quartz, microcline and biotite of the simple pegmatites. The complex pegmatites show higher peraluminous than the simple pegmatites, however, higher fractionation is observed in the complex pegmatites than the simple pegmatites. The complex pegmatites are rather enriched in rare elements such as Li, Rb, B, Cs, Sn, Nb, Be and Ta and show low ratios in Al/Ga and K/Rb than the simple pegmatites. The pegmatites are likely product of sedimentary origin and originated from post-collisional tectonic event.

Groundwater Potentiality Prediction Using AHP-MCDA and GBT Model in a Typical Basement Complex, Nigeria: Insights From Remote Sensing and Geophysical Datasets

Delineation of geologic features that are capable of hosting water in economic quantity in the Basement Complex has been a major concern because they are usually localized due to restricted fractured and weathered rock. To effectively evaluate the groundwater potentiality prediction index (GPPI) accuracy of an area, solely depends on the groundwater potentiality predictors (GPPs) considered and the statistical model used in analyzing the data. Therefore, the acquired remotely sensed and geophysical depth sounding database processed using autopartial curve matching software and computer aided iteration to determine was analyzed using the conventional Analytical Hierarchy Process (AHP) model and the machine learning Gradient Boosting Tree (GBT) data driven model. Such a data driven model (GBT) is efficient in solving complex and cognitive problems in high uncertainty and complex environments. Twelve (12) groundwater potentiality predictors (GPPs) namely: Digital Elevation Model (DEM), Slope (S), Drainage Density (Dd), Land Use (Lu), Aquifer Resistivity (ρa), Aquifer Thickness (h), Overburden Thickness (b), Aquifer Hydraulic Conductivity (k), Aquifer Transmissivity (Tr), Aquifer Storativity (St), Aquifer Diffusivity (D), Aquifer Reflection Coefficient (Rc). The efficacy of GBT model was applied using the Salford Predictive Modeler 8.0 software. The data were partitioned into training and test dataset in ratio 90:10 using k-10 cross validation techniques. Their prediction importance was determined and the groundwater potentiality prediction index calculated and processed in the ArcGIS environment to produce the groundwater potential prediction index (GPPI) map of the investigated area. The investigated area was classed into three (3) zonations of low, moderate and high groundwater potential with about 56% classed within the low groundwater potential zone. Fifteen (15) water column measurement from wells was used to validate the developed model by calculating the predictive correlation accuracy (PCA) using the spearman's correlation analysis. The AHP-GPPI and GBT-GPPI model gave a correlation of (rs = 0.66; p = .007) and (rs = 0.74; p = .002) respectively. In conclusion, the model has proven that the drop in aquifer resistivity doesn't necessitate the presence of groundwater but rather several parameter should be integrated together to better understand the true nature of the aquifer.

Freundlich and Langmuir Isotherm Studies of Phosphorus Sorption unto Soils Derived from Basement Complex Rock, Alluvium, Coastal Plain Sand and Shale Parent Materials

To provide information on best model to predict Phosphorus (P) Sorption unto Soils derived from Basement Complex Rock, Alluvium, Coastal Plain Sand and Imo Shale Parent Materials in 3 states of Nigeria. Completely randomized design was used to collect surface soil samples in 3 replications from 4 locations in Nigeria. Samples were collected from Idanre, Koko, NIFOR and Uhonmora in Ondo, Delta and Edo states Nigeria, laboratory analysis was carried out in the Central analytical laboratory of Nigerian Institute for Oil-Palm Research (NIFOR) Benin City, Nigeria between march 2016 and September 2017. Soil samples were equilibrated in 25 ml of 0.01 M CaCl2 containing various concentration of P as KH2PO4 to give 0, 50, 100, 150, 200 and 250 mg/L P for 24 hours (h) at room temperature 25 ± 2oC. 3 drops of CHCl3 was added to inhibit P mineralization. The suspension was shaken for 24 h on a reciprocating mechanical shaker, centrifuged at 7000 rpm After equilibration, decanted and P determined using spectrophotometer. The sorption data were fitted to linear Freundlich and Langmuir sorption isotherm. Considering the Freundlich model, P adsorption capacity (a) and P sorption energy (n) was highest in soils B (1400 mg kg-1) and (2.806 L kg-1) respectively. The Freundlich model fitted better to the data obtained with average root mean square error (RMSE) and R2 value of 0.69 and 0.951 respectively, as against average RMSE and R2 value of 1.60 and 0.883 respectively obtained from Langmuir model. The sorption data fitted well to Freundlich and Langmuir isotherms of which Freundlich Adsorption model was found to be better based on lowest RMSE (0.69) and highest regression (R2 = 0.951) value. Freundlich model should be adopted to determine P sorption characteristics of the soils studied. These predictors, however, need further works to validate reliability.

Magnetic and Restivity Investigation of Geologic Structures in the Basement Complex of Aran-Orin, Kwara-State, Nigeria.

The study aims to integrate magnetic and vertical electrical sounding (VES) resistivity methods to determine groundwater prospective in part of Aran-orin Sheet 224. A total of three traverses were established in the study area for the vertical electrical sounding using the Schlumberger electrode configuration. A total of 17 VES points was established using the ABEM Terrameter SAS 1000C model with maximum half-current electrode spacing (AB/2) of 120m. A total of eight traverses were established for the magnetics survey with station intervals of 10 m and inter-profile spacing of 100 m. The magnetic and VES data were qualitatively and quantitatively interpreted using IPI2WIN and OASIS MONTAJ package respectively. The geo-electric sections reveal a maximum of 3-4 layers beneath the sub-surface an overburden thickness ranges from 8.2 m to 64.9 m and the corresponding lithology inferred are topsoil, weathered Rock, fractured basement and fresh basement. The depth to basement using half-width method showed that the depth ranges from 8.4-56.04 m, which corresponds with the electrical survey.

Magnetic and Restivity Investigation of Geologic Structures in the Basement Complex of Aran-Orin, Kwara-State, Nigeria.

The study aims to integrate magnetic and vertical electrical sounding (VES) resistivity methods to determine groundwater prospective in part of Aran-orin Sheet 224. A total of three traverses were established in the study area for the vertical electrical sounding using the Schlumberger electrode configuration. A total of 17 VES points was established using the ABEM Terrameter SAS 1000C model with maximum half-current electrode spacing (AB/2) of 120m. A total of eight traverses were established for the magnetics survey with station intervals of 10 m and inter-profile spacing of 100 m. The magnetic and VES data were qualitatively and quantitatively interpreted using IPI2WIN and OASIS MONTAJ package respectively. The geo-electric sections reveal a maximum of 3-4 layers beneath the sub-surface an overburden thickness ranges from 8.2 m to 64.9 m and the corresponding lithology inferred are topsoil, weathered Rock, fractured basement and fresh basement. The depth to basement using half-width method showed that the depth ranges from 8.4-56.04 m, which corresponds with the electrical survey.

Magnetic and Restivity Investigation of Geologic Structures in the Basement Complex of Aran-orin, Kwara-state, Nigeria.

This study aims at integration of magnetic and vertical electrical sounding (VES) resistivity methods to determine groundwater prospective in part of Aran-orin Sheet 224. A total of three traverses were established in the study area for the vertical electrical sounding using the Schlumberger electrode configuration. A total of 17 VES points was established using the ABEM Terrameter SAS 1000C model with maximum half-current electrode spacing (AB/2) of 120m. A total of eight traverses were established for the magnetics survey with station intervals of 10 m and inter-profile spacing of 100 m. The magnetic and VES data were qualitatively and quantitatively interpreted using IPI2WIN and OASIS MONTAJ package respectively. The geo-electric sections reveal a maximum of 3–4 layers beneath the sub-surface an overburden thickness ranges from 8.2 m to 64.9 m and the corresponding lithology inferred are topsoil, weathered Rock, fractured basement and fresh basement. The depth to basement using half-width method showed that the depth ranges from 8.4-56.04 m, which corresponds with the electrical survey.

Geochemical trends in weathering profiles and their underlying Precambrian basement rocks in Akure, Southwestern Nigeria

Akure area in southwestern Nigeria falls within the basement complex underlain by migmatite, quartzite granite and charnockite. Geochemical features of these crystalline rocks and their overlying in-situ weathering profiles are investigated and reported. Analytical result from ICP-MS facility at the University of Malaya reveals average SiO2 content in quartzite (91.1%), granite (73.8%), migmatite (67.4%) and charnockite (58.6%) categorize the rocks as siliceous. SiO2 contents in the weathering profiles above these rocks are 61.9%, 60.2%, 52.2% and 54.6% respectively. Alumina contents in the weathering profiles overlying quartzite (23.8%), granite (19.9%), migmatite (26.3%) and charnockite (24.3%) are substantially higher than the precursor rocks. In the same order, average alkali (Na2O+K2O) contents in the profiles are 3.38%, 3.42%, 3.48% and 2.68%. Chemical features of the profiles reflect that there exists some correlation between the chemistry of crystalline basement and their in-situ weathering profiles. The residual soils contain low plastic clays with kaolinitic characteristics and compare well with other clays reported from other parts of Nigeria basement complex.

Geophysical and Geotechnical Investigation of Building Failure in A Typical Basement Complex Environment – A Case Study in Ile-Ife, Nigeria

A building located within the Basement Complex of the ancient town of Ile – Ife, Osun State, Southwestern Nigeria was observed to have failed due to excessive total and differential settlement. The failure was investigated using the electrical resistivity and geotechnical methods The electrical resistivity method involved the 2-D electrical resistivity imaging (ERI) technique using the dipole-dipole array along four traverses of 30 – 60 m in lengths. The geotechnical method involved the cone penetration test (CPT) using the 2.5-ton static penetrometer machine. Quantitative and qualitative analysis of the ERI data were made using the DIPROfWIN software for the pseudo-inversion while the CPT data were interpreted for lithology using standard chart. The results show that the topsoil, about 1.0 m thick, is composed of sandy clay/clay that is characterized by cone resistance (qc) of 0.2 – 2.0 MPa and resistivity of 75 - 200 Ωmm. The underlying clayey weathered layer, which constitute the shallow foundation soil is characterized by thickness of 4 - >10 m, qc of 0.2 – 1.0 MPa, resistivity of 25 - 75 Ωmm and estimated consolidation settlement of 200 – 500 mm. The basal layer is the saprock/fresh bedrock characterized by qc of > 8.0 MPa and resistivity of 100 - 1000 Ωmm. The subsoil is thus characterized by variably thick incompetent clayey weathered layer within which the shallow foundation was placed; hence the excessive total and differential settlements.