Browsing by Author "Adedoyin, Adeonipekun Dele"

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    Axis Rotation of a Major F1 Fold during a Retrograde F2 Deformation in Southwestern Nigeria
    (2017) Adedoyin, Adeonipekun Dele; Ojo, Olusola Johnson; Alebiosu, Mercy Titilayo; Adekeye, J.I.D.; Bamigboye, O.S
    North east of Ilorin, South-western Nigeria, a NE-SW trending (F₁) fold which was later refolded, was identified in part of the Basement Complex of the country. The area falls within the West African domain of the Pan African (600±150Ma) remobilized metamorphic terrain. Polyphase deformations, which involved at least three tectono-thermal episodes, were also identified. The area falls within the N-S trending Schist Belts where a large-scale sheeted S1 penetrative metamorphic imprint was successively deformed into an overturned antiformal (F₁) fold and, later, to a broad synformal (F2) fold whose axial traces are generally NE-SW and E-W, respectively. The first deformation episode was essentially metamorphic while the subsequent ones were tectonic. Petrological associations indicate that the rocks are mainly gneisses, psamites and psamitic to semi-pelitic schists, cut by Pan African granitoids. These rocks were deformed under high-temperature, low-pressure amphibolite facies conditions, but downgraded from high to medium grade metamorphic interface during a later tectonic event, under a high geothermal gradient within the upper crust. An occurrence of an overturned fold in the northern end of the axial trace of F1 is attributed to irregular strain distribution that culminated in the open F₂ antiform during the third deformation episode. Of interest, within the context of the structural geology of Nigeria, is the E-W trend of the axis of the F2 fold, which is apparently discordant to the observed general N-S structural trends in the Basement Complex of Nigeria. The origin of this latter structure is attributed to localized tangential deformation, culminating in fold axis rotation in the direction of the X axis, and subsequently overturning and tightening of the original F1 fold during the late- to post- tectonic phases of the Pan African tectonism.
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    Evaluation of the Spatial Distribution of Grain Size Characteristics and its Role in Determining the Environment of Deposition of Sediments in Orlu and Environs, Imo State South Eastern Nigeria
    (2021) Iheme, Kenneth Obinna; Okolo, C.J.; Adedoyin, Adeonipekun Dele; Ibrahim, Oluwatoyin Khadijat; Alebiosu, Mercy Titilayo
    The depositional environments of sediments around Orlu and environs, Imo state, was studied using various statistical parameters including Mean size, Standard deviation, Skewness, and Kurtosis. These parameters were obtained from sieve analysis of fifteen (15) sediment samples obtained within the area of the study at different depth. The grain size distribution curves for the study area showed that about 80% by weight of the sediments are medium to coarse-grained sand and fine gravels, while the remaining 18% and 2% are fine-grained sand and coarse silt. The sorting indicates that the samples are very poorly sorted around Afor-nta and Isiekenesi areas, and are moderately sorted at Ihioma, and others area within the study. Other textural analysis also shows that the samples ranges from strongly fine skewed, very platykurtic to extreme leptokurtic and are uniformly graded, except in Afor-nta and Isiekenesi with wellgraded sediments. Analysis of the environment of deposition for the study area showed that the samples were deposited in beach/shallow agitated and fluvial agitated environments. Marine influence on the sediments seem to be dominant in the southern parts of the study area while fluvial influence is evident in the northern part of the area.
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    Geochemical Assessments of Owa-Kajola Marble, Southwestern Nigeria.
    (2020) Adedoyin, Adeonipekun Dele; Ojo, Olusola Johnson; Adekeye, Jacob Ishola Dele; Alebiosu, Mercy Titilayo
    Extensive deposit of dominantly calcitic marble occurs around Owa-Kajola, Sheet 224 (Osi) NW, south-western Nigeria. Geological field mapping on scale 1:10,000 showed that the marble is intercalated with variably migmatized gneisses, pelitic to semi-pelitic schists, amphibolite, and quartzite, all of which are intruded by late- to post- Pan African granite and pegmatites. Geochemical investigations of the marble were done with a view to ascertaining its industrial applications for national development. Results show that the marble, for which there is no published work, is white, with well-interlocked sub-hedral to euhedral crystals, and medium- to coarse-grained. The physical properties also indicate that it can be used in the production of scouring soap, glass, tooth paste, rubber, polished stones, and lime. The relatively low MgO content against CaO, Slica-Alumina Ratio, Silica Modulus, and the Total Alkali content make the deposit adequate for cement production. The combined high CaO and the low P (<0.1%) and S (<0.5%) make the deposit applicable in the steel industry but the low dolomite content may disqualify it for being used as refractory lining in metallurgical engineering. The amounts of the components of marble such as CaO, MgO, SiO2, P2O5, Fe2O3, Na2O and K2O are within the tolerable limits for the production of Portland Cement while the low levels of P(0-0.1), Pb (<5ppm), U (<0.4ppm) and other deleterious elements make such an industrial venture environmentalfriendly.
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    Petrography, Geochemistry and Petrogenesis of grey Gneisses of part of Oke-Ode Area, South-Western Nigeria
    (2022) Adedoyin, Adeonipekun Dele; Alebiosu, Mercy Titilayo; Bamigboye, Olufemi Sijuade; Olobaniyi S.B.; Omorinoye, Omolayo Ajoke; Iheme, Kenneth Obinna
    Oke-Ode area, northeast of Ilorin, is part of the Precambrian Basement Complex of southwestern Nigeria. There are no published data on the gneisses, which are well exposed, unlike the adjacent terrains. The area was mapped in order to determine the petrographic, geochemical and petrogenetic attributes of the grey gneisses. The acquired sets of field, mineralogical, and geochemical data indicated that the medium-to coarse-grained gneisses are of igneous origin, and have witnessed multiple tectono-thermal readjustments. Occurrence of xenoliths in the rocks points to magmatic origin. The range of anorthite molecular contents of the plagioclase (An26-34) suggests an andesine to oligoclase composition, indicating derivation from granodioritic to tonalitic progenitors. Petrographic studies showed that the rocks witnessed complex interplay between metamorphism, deformation, and migmatization, which culminated in grain-boundary migration under a relatively stable, low-strain, hightemperature conditions involving mechanical rotation, during grain-scale dynamic recrystallization. Geochemically, plots of Ni vs Zr/TiO₂ and K₂O/Al₂O₃ vs Na₂O₃/Al₂O₃ also constrained the the gneisses to the igneous field while the TiO2 - K2O - P₂O₅ ternary plot further indicated a continental tectonic setting prior to the widespread Pan African magmatism. The rocks are essentially peraluminous calc-alkaline rocks, which are moderately saturated with respect to silica. They are products of fractional crystallization of a basaltic magma in a continental setting but later reworked during the Pan African time. The grey gneises have similar geo-chemical characteristics with some gneisses from other parts of the Basement Complex of Nigeria, but at distinct variance with others.
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    Utilization of Marble as a Stabilizer of Lateritic Soil for Pavement Works in Southwestern Nigeria
    (Civil Engineering Department, University of Ilorin, 2017) Adedoyin, Adeonipekun Dele; Yusuf, I.T.; Alebiosu, Mercy Titilayo; David, O.O.; Agbaje, M.O.; Babalola, F.M
    The increasing cost of traditional stabilizing agents and the need for the economical utilization of alternative materials for beneficial engineering purposes requires an investigation into the stabilizing potential of marble for the stabilization poor lateritic soils, to improve their geotechnical properties for pavement works. A lateritic soil classified as A-2-6(0) according to AASHTO classification system was treated with 0 – 6% (2% increment) proportions of crushed marble by dry weight of soil. A total of ten samples of laterite, five samples each, were collected from burrow pits in Oyun and University of Ilorin campus, Ilorin, Kwara State, Central Nigeria. The samples were mixed with marble in various proportions, and subjected to Compaction and California Bearing Ratio (CBR) tests. It was observed that the Maximum Dry Density (MDD) at 0, 2, 4 and 6% marble content were 2.0, 2.1, 1.9 and 2.0 g/cm3, respectively and the Optimum Moisture Content (OMC) were 14.5, 10.5, 13.5 and 15% for the laterite sample at Oyun. The corresponding values of MDD and OMC for the sample at the University of Ilorin Campus were 1.65, 1.83, 1.69 and 1.87g/cm3 and 20, 17, 21 and 12%, respectively. Results show that, for all marble contents, the unsoaked and soaked CBR values increased with increase in marble content from 0-2%, and decreased for further increase in marble content up to 6%. Also, the CBR for both the unsoaked and soaked conditions reached maximum values at 2% marble content, indicating that the optimum content of marble required to stabilize an A-2-6(0) lateritic soil is 2%. The soaked CBR values of %0 and 47% obtained, respectively for unsoaked and soaked conditions for the sample at Oyun, which are greater than 30% imply that 2% marble content is suitable for stabilizing lateritic soil for the production of subbase course in pavement works.