Science Publishing Group, US.

 Journal

 The Relationship Between Morpho-structural Features And Borehole Yield In Ilesha Schist Belt, Southwestern Nigeria.

 Akeredolu, B.E., Adiat, K.A.N., Akinlalu. A.A., And Olayanju, G.M.

 2022

Aeromagnetic data and Landsat image, were assessed to establish a relationship between morphostructural feature and borehole yield of a sub-basin of Osun basin in the Northern part of Ilesha, southwestern Nigeria. Four morphostructural factors (Geomorphological unit, Slope, regional structure, and lineament) were considered. Geomorphological units were classified based on digital elevation model (DEM), Lineaments were identified and extracted using edge detection technique, slope were generated from the digital data derived from Landsat imagery, and the regional structure were extracted using magnetic data filtering and enhancement techniques processes. The results of morphostructural features shows five (5) various geomorphic units; (Denudation hill, linear ridge, pediment inselberg complex, pediment and moderately weathered Pediplain) and four (4) main structural trends (NE-SW, NW-SE, ENE-WSW and E-W directions). The relationship between the morphostructural factors and borehole yield were assessed using spatial global autocorrelation and spearman rank correlation. Moran’s I global tests for dependence shows that geomorphological units, and regional structures were clustered given the zscores of 2.46 and 1.99, p-values of 0.01 and 0.04, Moran’s I index value of 0.08 and 0.06 respectively. Likewise, borehole yield, lineament and slope were dispersed given the z-scores of 0.89, -0.43 and -1.15, p-values of 0.38, 0.66 and 0.25, Moran’s I index value of -0.06, -0.04 and -0.07 respectively. The Spearman’s rank correlation for the four independent variables (Geomorphological unit, Slope, Fracture, and Lineament) are statistically significant to the observed borehole yield, with correlation coefficients of -0.332, 0.137, -0.031, 0.200 respectively. The study concluded that slope and lineament are capable of favoring high borehole yield indicative of active surface recharge mechanism that is prominent in Schist belts and regional structures have little or no contribution to borehole yield in schist belts due to the influence of developed clayey filling resulting from the deep weathering processes. 

 Jenrs.com, US.

 Journal

 Geophysical And Geotechnical Investigations For Subsoil Competence At A Proposed Hostel Site At Oba-Nla, Akure, Southwestern Nigeria.

 Eebo, F.O., Abidakun, B.S., And Olayanju, G.M.

 2022

A foundation study was carried out at a proposed Hostel site for the student of Federal University of Technology Akure, Nigeria with the aim of evaluating the competence of the overburden as foundation materials. Geophysical survey involving Electromagnetic method and magnetic method were conducted in conjunction with geotechnical tests in the study area. Electromagnetics and Magnetics data were acquired along the five traverses established across the study area with 20 m inter-traverse spacing and 5 m inter-station spacing. The geophysical results were interpreted qualitatively and quantitatively, and the results were presented as profiles and geomagnetic sections. From the results of the Very Low Electromagnetic survey conducted, several conductive zones possibly characterized by clayey materials were found to make up the overburden materials in the area. Characteristic magnetic anomalies in the area also revealed series of features at shallow depths identified to be fractures / fault at shallow depths with depth to bedrock varying between 2 m and 7 m. The presence of geologic features such as fracture and conductive clayey materials are likely going to pose a serious threat to engineering structure in the area. Geotechnical tests were carried out on soil samples from the study area and different geotechnical parameters analyzed include the natural moisture content, Atterberg Limits, unconfined compressive strength and shear strength. The specific gravity of the soils is within the range of 2.722 – 2.73 g/cm3, revealing materials of low water absorption capacity. However, the soils are highly plastic with the plastic limit ranging from 20.4 – 24.4% and a plasticity index range of 23.75 – 35.90%. In addition, the soils have shear strength within the range of 75 to 102 kPa and unconfined strength ranging from 150 to 203 kPa revealing stiff soils that are not suitable for shallow foundations. It was observed that the form of foundation suitable for infrastructural development in the study area is a properly designed deep foundation that can transfer load at grater depths. 

 Taylor & Francis Group, UK.

 Journal

 Aeromagnetic Mapping And Radioelement Influence On Mineralogical Composition Of Mesothermal Gold Deposit In Part Of Ilesha Schist Belt, Southwestern Nigeria.

 Olomo, K.O., Bayode, S., Alagbe, O.A., Olayanju, G.M., And Olaleye, O. K.

 2022

Airborne magnetic and radiometry data sets over potential gold mineralisation associated with mesothermal alteration zones in the western Ilesha schist belt, Southwestern Nigeria, were interpreted. This was done to provide information on possible extent of geologic transformations that accompanied gold mineralisation in the area. Interpreted gamma spectrometric data were successfully used in delineating zones of hydrothermal alteration associated with potassium K enrichment as the target for gold deposits. The geological structural features that host the ore deposits were identified as lineament represented by lithological contacts and faults/ fractures that were successfully exacted from the airborne magnetic data. The potassium deviation (KD) map was computed to enhance the potassium signature of rocks in the area of study. Thus, the KD map represents real potassium distribution across the study area emanated from hydrothermal alteration where hydrothermalised zones were displayed by high KD values. First vertical derivative (FVD) and total horizontal gradient (THG) maps were used to delineate lineaments. These lineaments were connected using the frequency rose diagram with two main lineament set,; major and minor lineaments observed. The 3D Euler deconvolution (EUD) method was also applied on the THG map to locate and evaluate depths to subsurface structures. The best 3D EUD solution for dykes and contacts modelled using the Structural Index of zero (S.I = 0) was used to estimate the depth to these anomaly sources at 300 to 700 m in the study area. The EUD results also revealed several subsurface structures which were hidden in the existing geological map of the study area. A prospective mineralisation map was produced from the synthesis of both magnetic lineaments and alteration zones maps derived for the study area, showing the areas of probable high mineral resources. Strong relationships were observed between the mapped hydrothermal altered zoneseologic structures and superimpose known gold mining pits. 

 Elsivier UK.

 Journal

 Mapping The Possible Origin Of Anomalous Saline Water Occurrence In Agbabu, Eastern Dahomey Basin, Nigeria: Insights From Geophysical And Hydrochemical Methods.

 Adeyemo, I.A., Oladimeji, E.O., Sanusi, S.O., And Olayanju, G.M.

 2022

Many researchers have suspected saltwater occurrence in Agbabu in the eastern Dahomey Basin. However, there is a need to get an insight to the possible origin of saltwater in the area. The aim of this study is to determine the source of saltwater in the inland aquifers of Agbabu, southwestern Nigeria for proper management of scarcely available freshwater resource in the area. 23 vertical electrical sounding, 2D electrical resistivity tomography (ERT), aeromagnetic and hydrochemical data (11 subsurface water samples) analyses were utilized in this study. The results from the magnetic analysis revealed the inland extension of the Chain Fracture Zone (CFZ). This NESW trending fracture zone cuts across the entire eastern Dahomey Basin, including Agbabu and its environs. Four (4) geoelectric layers were delineated across Agbabu namely, the topsoil (4 - 2806 ?m), clayey sand (3 - 1280 ?m), clayey (3 - 161 ?m) and bituminous sand (1 - 10390 ?m) layers. Anomalously low resistivity (1 - 20 ?m) zones suspected within the bituminous sand correspond to the saltwater intrusion zones. The bituminous sand unit harbouring freshwater exhibits characteristic resistivity values of 33 – 160 ?m. The interface between the freshwater and saltwater intruded zones in the area was suspected at 10 m depth with resistivity values ranging between 21 ?m and 33 ?m. The results from the hydrochemical water analysis also confirmed the presence of saltwater intrusion in the area. The salinity extent chart which was generated from the VES results indicated the mobility of the saltwater into the groundwater system. The fracture connectivity between the complex aquifers of Agbabu and the Atlantic Ocean (CFZ), that was mapped from the aeromagnetic and electrical resistivity results, is suspected to be primarily controlling the localization of saltwater in the study area. 

 Zibeline International, Malaysia.

 Journal

 Multifaceted Investigation Of Porphyry Cu-Au-Mo Deposit In Hydrothermal Alteration Zones Within The Gold Field Of Ilesha Schist Belt.

 Olomo, K.O., Bayode, S., Alagbe, O.A., Olayanju, G.M., And Olaleye, O. K.

 2022

This study was carried out to map the distribution of porphyry systems within Ilesha Schist belt Southwestern Nigeria for easy accessibility of commercial gold as well as copper and molybdenum deposits to boost exploitation activities within the area. Airborne magnetic and radiometric data of the area were utilized. The acquired total magnetic intensity map of the field was enhanced with reduction to equator, vertical derivative, analytic signal and spectral analysis. Enhanced total magnetic intensity map of the study area revealed magnetic anomalies related to concealed intrusive rock associated with Cu-Au-Mo deposit at depth ranges from 306 - 421 m. Vertical derivative map revealed shallow magnetic bodies in the southern and western parts, which are probable zones for Cu-Au-Mo deposit. Analytical signal map, with magnetic zones of high intensity value between 0.1 nT/M and 1.7 nT/M highlighted faulted basement blocks impregnated with porphyry the Cu-Au-Mo deposit. Airborne radiometry image shows radioelement distributions for different lithologies. High concentration of potassium signatures observed over some parts of the area revealed hydrothermal alteration zones favourable to concentration of Cu-Au-Mo deposits. Computed Th/k ratio and composite potassium maps enhanced the signature of potassium enrichment associated with hydrothermal alteration zones. Validation of airborne results using geochemical analyses confirms the presence of copper-gold-molybdenum elements within the mapped hydrothermal alteration zones. This research has identified other valuable ore deposit, such as copper and molybdenum, to enhance exploitation activities within the area. 

 International, Malaysia,

 Journal

 Subsoil Evaluation In Geomorphologically Unstable Condition Using Geophysical And Geotechnical Methods At Oke-Igbo, Southwestern Nigeria.

 Afolabi, R.K, Olayanju, G.M., Ikubuwaje, C. O., And Tanimola, M. O.

 2022

The competency of the subsoil material for engineering site characterization in a Geomorphological unstable Oloruntele town a suburb of Oke Igbo was evaluated using geophysical and geotechnical methods in producing an integrity assessment of the subsurface geology. The deployed geophysical measurements involved running both electrical resistivity imaging with the aids of dipole– dipole array in conjunction with vertical electrical sounding along the established traverses, followed by geotechnical analyses. Specific geotechnical analyses conductedinclude the gravimetric, hydraulic conductivity and strength tests of the collected soil samples along road segment that traverse the study area. The results of the resistivity imaging revealed conductive zones and geologic features identified as fractures and cavities, which can affect the competency of the subsoil as sub-base or subgrade foundation materials. The zones were characterized by relatively low resistivity values; the cavities were observed to probably consist of materials moved into their present positions from materials from the landslide that occurred along the section of the study area, which aggravated creeping of the soil materials from the hilly terrain. From the electrical soundings conducted, four distinct geoelectric layers were delineatedthat comprise the topsoil, weathered layer, fractured bedrock and fresh bedrock.Furthermore, values in the range of 4-15%, 2.6-2.7 g/cm, 1.6-28.7%, 19-33%, 21-22%, 4-11%, 1-7, 1.2 × 10 - 1.9 × 10 cm/s, 1810-1880kg/m, 4-6%, 31-79%, 219-312KPa and 102-156KPa were obtained from geotechnical parameters; viz soil natural moisture content, specific gravity, percentage of finer, Liquid limits, plastic limits, plasticity index, Linear shrinkage, permeability, Maximum dry density, Optimum moisture content, California bearing ratio, Unconfined compression test and undrained shear strength respectively, resulting from the geotechnical analysis of the soil samples which indicates that the soil in the area are majorly sand and loose fragments of nearby quartzite ridge, which can easily move under gravity when heavy load are applied on them. 

 Geoscienceworld.org, UK.

 Journal

 Airborne And Ground Geophysical Evaluation Of Potential Mineralization Zone In Parts Of Ilesha Schist-belt, Southwestern Nigeria.

 Ogungbemi, O.S., Amigun, J. O., Olayanju, G.M., And Badmus, G.O.

 2021

Integrated airborne and ground geophysical studies were conducted in parts of Ilesha schist belt, southwestern Nigeria. The goal was to provide a useful guide for mineral prospecting, with the hope of considerably narrowing down the future search for mineral deposits within the study area. Aeromagnetic and aeroradiometric data were analyzed for the reconnaissance study. In addition, the reduction-to-equator transform, analytic signal, tilt derivative, and Euler deconvolution filters were applied to the aeromagnetic data to enhance shallow and deep geologic features. The aeroradiometric data were used to determine spatial variations in the concentrations of uranium (U), thorium (Th), and potassium (K) in near-surface rocks and to map spatial lithologic changes. The 2D-magnetic sections, radiometric profiles, inverted resistivity, and induced polarization (IP) sections were generated from the integrated geophysical data. The electrical resistivity tomography (ERT) results reveal the subsurface heterogeneity (to a depth of approximately 197 m) and varied geoelectric layers (topsoil, lateritic-clay, weathered rock, and basement rock). The IP sections show varying degrees of chargeability and features that suggest the presence of disseminated mineralized bodies concealed in some areas. The overburden thickness varies between 4 and 85 m as determined from the 2D-magnetic and electric resistivity sections. Anomalous peaks on profiles of elemental ratios (eTh/K, eTh/eU, and K/eU) correlate with the results of IP and ERT. Data sets are well correlated and highlight areas with relevant structural and lithologic signatures favorable for mineral deposition. The methodology adopted in our research is well adapted, and the interpretation techniques provided insight into regional and local lithostructural settings. These anomalous areas are suggested as targets for future exploration works. 

 Elsevier, UK.

 Journal

 Mineralisation Potential Assessment Using Analytical Hierarchy Process (AHP) Modelling Technique: A Case Study Of Ilesha Schist Belt, Southwestern Nigeria.

 Akinlalu. A.A., Olayanju, G.M., Adiat, K.A.N., And Omosuyi, G.O.

 2021

A mineralisation potential assessment in part of Ilesha Schist belt of southwestern Nigeria was carried out using multi criteria decision analysis (MCDA) in the context of analytical hierarchy process (AHP). Three parameters sourced from aeromagnetic, electrical resistivity and geological data were identified to favour gold mineralisation in the study area. These parameters include lineament density (Ld), lithology (Lt), and electrically derived coefficient of anisotropy (An). The application of data enhancement techniques such as total horizontal derivative, 3-D Euler deconvolution and source edge detection were employed in the production of lineament map of the study area. Two hundred and sixty-five (265) vertical electrical sounding (VES) points were investigated using Schlumberger configuration. Coefficient of anisotropy derived from the Dar-Zarouk parameters was obtained from the synthesized VES data. The lithologic information was obtained from the existing geological map of the area. The orientations of lineaments displayed on the aeromagnetic results suggest predominantly NE-SW trending structures, which are characteristic of the Pan African orogenic events in the area. However, few of the E-W trending lineaments are imprints of secondary structural alteration. Furthermore, the Euler deconvolution solutions revealed that the area is characterised by geological contacts with estimated depth of 94–600 m. The coefficient of anisotropy results obtained from the geo-electric parameters vary from 1.00–2.87. AHP weighting and ranking technique was used to develop a reliable mineralisation potential model (MPM). In line with the recommended lower limit of 10 %, the consistency ratio of the developed model is 9.61 %. The produced MPM was classified into low, moderate and high mineralisation potential zones. Preliminary validation of the MPM using the existing pits in the area showed 79 % success rate. The validation of the model using the existing geochemical information from the previous studies indicated 85 % agreement with the conceptual model; thus, confirming the reliability of the produced MPM. The developed model is therefore believed to serve as a future reference in the resource management of the study area. 

 Saudi Society For Geosciences, Springer, Switzerland.

 Journal

 Integrated Geophysical Investigation Of The Mode Of Occurrence Of Mineralisation In Part Of Ilesha Schist Belt, Southwestern Nigeria.

 Olomo, K.O., Olayanju, G.M., And Akinlalu, A.A.

 2021

This research has investigated the mode of occurrence of mineral deposit in Iperindo and its environs with integrated geophysical techniques. Total magnetic intensity map was enhanced by reduction to equator filter, magnetic susceptibility filter and analytic signal to suppress background noise and accentuate magnetic bodies within the field. 3-D Euler deconvolution and radial spectral analysis were both applied to locate and estimate the depth to magnetic anomalous bodies, suspected to host the mineral deposits. The magnetic deposits have a varying depth from 20 to 300 m. Two hundred and twenty-one (221) vertical electrical sounding (VES) stations were occupied to delineate geologic structure which could host mineral deposits within the study area. Quantitative interpretations of the VES curve revealed maximum of five (5) subsurface layers such as top soil, weathered layer, fresh basement and fractured basement. Combined vertical electric sounding and horizontal profiling (VES&HP) was acquired concurrently with induced polarization (IP) using dipole–dipole array to highlight areas with disseminated mineral deposits. The results revealed varying high and low resistivity anomalies across the study area. The observed high resistivity indicates the presence of quartz veins suspected to be hosting sulphide within schist. Areas with relatively low resistivity are suspected to be fault/fracture zones with a depth of 150 m of varying length, which are in agreement with high chargeability zones, indicating disseminated mineral deposits within the faulted/fractured zones. Delineated magnetic anomalies trend northeast–southwest direction implying geologic structures as a result of Pan-African orogeny, which were impregnated with mineralised bodies. 

 Springer, Switzerland.

 Journal

 Electrical Tomographic And Geotechnical Investigation Of Landslide Occurrence At Agbona Hill In Okemesi, Southwestern Nigeria.

 Olayanju, G.M., Ayodele, S.A., And Oni, A.V.

 2021

An integrated investigation of possible factors responsible for reoccurring landslide at Agbona Hill of Okemesi, in a typical Basement Complex terrain of southwestern Nigeria is presented in this paper. The landslide which rises to about 18.62 m at the point of failure, strikes N-S direction, and measured about 8.54 m in width and extends down the slope in length of about 265 m. The landslide which occurred immediately to the north of residential area resulted into damages of buildings and the road along the path of the mass movement. The investigation which involved resistivity imaging along four traverses with length varying between 180 and 210 m in the N-S direction was complemented with eight vertical electrical soundings and geotechnical analysis of soils samples at ten selected points. The inferred lithological depth sections from electrical properties revealed the nature of both the upper and lower sections of the landslide with thin topsoil, having resistivity and thickness values ranging from 104 to 871 ?-m and 0.8–1.5 m, respectively, observed to be characterized by loose sand to clayey sand and quartzite rubbles. The internal structures also revealed underlying layer classified into fairly to poorly weathered bedrock or indurated quartzite rocks. The resistivity ranges from 297 to 4381 ?-m and the thicknesses varying from 1.3 to 9.9 m. Both sections exhibited intermediate to steep internal slope with a series of fracturing observed over the outcropped quartzite ridge that extends deeply into these layers. The fractures serve as conduit for the groundwater to flow to the surface, thereby accelerating the weathering of the rock. The results of geotechnical study showed that the upper segment of the landslide comprise of highly weathered materials characterised by sandy clay or silt materials with plasticity index of the fines indicating slight medium plasticity, thereby serving as a trigger to the landslide under prolonged and torrential rainfall arising from the movement in the soils by the flow of groundwater which seeps to the surface through the fractures in the rock mass.