Browsing by Author "Adedoyin, A.D."
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Item Axis Rotation of a Major F1 Fold during a Retrograde F2 Deformation in Southwestern Nigeria(Centrepoint Journal (Science Edition), 2017) Adedoyin, A.D.; Ojo, O. j.; Alebiosu, M.T.; 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.Item Combined Petrographic and Geochemical Studies of Maastrichtian Patti Formation Sandstone, Bida Basin, Nigeria: Implications for Provenance and Compositional Maturity(Faculty of Physical Sciences, University of Ilorin, 2015) Ojo, O.J.; Adepoju, S.A.; Adedoyin, A.D.Geochemical data on sandstone facies of the Maastrichtian Patti Formation in Bida Basin, Nigeria, is presented and interpreted in this paper with respect to its provenance and compositional maturity. Petrographic data from thin sections and X-Ray Diffractometry were also integrated. Petrographic data from the sandstones classified them mainly as quartz-arenites and minor sub-arkose while geochemical indices such as high average values of SiO2/Al2O3, low Na2O+K2O and K2O/Na2O values also indicate the samples are sub-litharenite to quartz-arenite type. Relatively high average values of total REE (141.40 ppm), Th (7.59 ppm), Hf (6.82 ppm), and Zr (205.12 ppm) coupled with low concentrations of Ni (3.06 ppm), Co (1.66 ppm) and V (20.65 ppm) in the sandstones indicate felsic igneous provenance. The discrimination functions plot shows that the sandstones were sourced mainly from matured sedimentary provenance and a passive margin setting is deducted based on the plots of TiO2 versus Fe2O3+MgO and K2O/Na2O versus SiO2. The sandstones show high average value of SiO2 (86.8 %) and low values of Al2O3 (6.11 %), K2O (0.12) and Na2O (0.02 %), suggesting that the sediments are mature. Plot of SiO2 versus (Al2O3+K2O+Na2O) further lend credence to chemical maturity and reveals semi-humid to humid paleoclimate. The Chemical Index of Alteration (CIA) value of 96.49 and the Plagioclase Index of Alteration (PIA) of 99.05 respectively are supportive of high weathering of the source area. The sands were most probably recycled from older Lokoja Formation during the late Maastrichtian Tethys inundation in the basin. Keywords: Agbaja, humid, maturity, Patti, plagioclase, provenance 1. IntroductionItem Contamination and Risk Assessment of Heavy Metals from Sadong River, Malaysia(2021) Omorinoye, O.A.; Assim, Z.B.; Adedoyin, A.D.; Bamigboye, O.S.Item DUCTILE SHEARING AND REMOBILIZATION OF PORPHYRITIC GRANITE IN KORO-EGBE AREA, SOUTHWESTERN NIGERIA.(Faculty of Pure and Applied Sciences, LAUTECH, Printed in Nigeria, 2013) Adedoyin, A.D.; Bamigboye, O.S.; Adekeye, J.I.D.; Ojo, O.J.Penetrative metamorphic tectonite fabrics, folds, and shear zones constitute the main structural elements in Koro- Egbe area. Results of field mapping, which was used to constrain the shear zone, revealed the nature of the fabrics in the grey gneiss, schist, meta-basites and the Pan African granites in the area. The development of penetrative fabrics in the large-scale sheeted rocks defines the first deformation episode, D1. The second deformation episode D2, is revealed in the horizontal asymmetric folds (Koro-Egbe folds), while a major shear-zone developeded during a post-folding phase defines the D3 event. Within the shear-zone, bodies of porphyritic biotite granite of Pan African age (600±150Ma) were strongly tectonised with a north-easterly steeply-dipping foliation. Outside the shear zone, the porphyritic granite is relatively undeformed, preserving strong igneous textures. Smaller bodies of fine-medium grained biotite granite occur within the deformed porphyritic bodies in the shearzone. It is consideredthat the petrogenesis of these smaller bodies is strongly linked with the shearing under a high geothermal condition.Item Geochemical Composition and Petrogenesis of Schists and Amphibolites of Parts of Sheets 203 (Lafiagi) SW and 224 (Osi) NW, Southwestern Nigeria(Faculty of Physical Sciences, University of Ilorin, 2014) Adedoyin, A.D.; Adekeye, J.I.D.; Ojo, O.J.Precambrian meta-sedimentary rocks are widely exposed and are interbanded with amphibolitic rocks in Sheets 203 (Lafiagi) SW and 224 (Osi) NW, southwestern Nigeria. They are underlain by migmatitic and granitic gneisses and intruded by Late- to Post- Pan African granitoids. Petrographic and geochemical studies show that the metasediments are para-schists of arkosic to greywacke parentage which were sourced from a moderately weathered feldspathic igneous rock(s) while the amphibolitic rocks are sub alkaline Island Arc tholeiites whose original chemistry have been significantly altered during and after the emplacement. Derivation of the schists from K feldspar-rich protoliths is indicated by the enhancement of Ba over Rb while the presence of significant amount of mafic constituents is signified by relatively high amount of Cr and, sometimes, Ni. Low level of weathering of the protolith is suggested, based on the calculated CIA values. The geochemical characteristics of the amphibolites indicate a possible origin from a basaltic magma under an oxidizing condition. The study area shows similar petrological, structural and geochemical characteristics with the Ilesha Schist Belt to the south and to which it is considered to be the northern extension.Item Geochemistry and Origin of Fe-Mn Oxide Mineralization in Kaoje-Derena and Their Environs, Northwestern Nigeria(Arabian Journal of Geosciences, 2018) Bamigboye, O.S.; Adekeye, J.I.D.; Kadioglu, Y.K.; Adedoyin, A.D.; Omorinoye, O.A.The mineralogy and origin of the schist hosted manganite and sandstone hosted goethite mineralizations west of Zuru schist belt Nigeria was investigated. A total of five goethite and ten manganite samples were selected. Half of each samples were pulverized and subjected to geochemical analysis for the major oxides, trace and rare earth elemental compositions using X-ray fluorescence while the other halves were polished for their mineralogical analyses through Raman spectroscopy. The result of the Raman spectroscopy showed that the manganites were made up essentially of psilomelane, todorokite and brookite, while the goethites were dominantly goethite, rutile and ilmenite. The result of the elemental analysis was subjected to Principal Component Analysis (PCA) using SPSS 22 software and discriminating plots using TriPlot software. The results of the discriminating plots showed that the goethites were related to hydrothermal processes whereas the manganite ores related to detrital-diagenetic processes. The conclusion drawn from the integration of field evidences, geochemical results, mineralogy, cluster analysis and discriminating plots was that the manganite ores were products of supergene enrichment, while in contrast, the goethites were formed primarily from hydrothermal processes but have been remobilized to its present position as a result of changing Eh-pH conditions in Kaoje and its environs.Item GEOLOGICAL AND GEOCHEMICAL ASSESSMENTS OF STREAM SEDIMENTS OF EJUKU AREA(NSUK Journal of Science & Technology, Nasarawa State University, 2016) Alebiosu, M.T.; Adekeye, J.I.D.; Adedoyin, A.D.Geological and Geochemical assessments of Ejuku area, North-Central, Nigeria, was carried out with the aim of identifying the mineralization potential as well as delineating mineralized zones in the area. The geological investigation revealed that the area is underlain by porphyritic granite, medium-coarse granite, granitic and banded gneisses, amphibolite, quartzite and mica schist. Twenty five representative stream sediment samples were digested in aqua regia solution and analyzed by ICP-MS method for trace and rare earth elemental concentrations. The analysis of the stream sediment samples, revealed the following range of concentration for each element: Fe (0.59-4.97%), Mn (60-1273 ppm), Ce (19.3-608 ppm), La (2.5-307.5 ppm), Ba (8.5-149.8 ppm), Cr (9.0-125.2 ppm), V (3-121 ppm), Cu (6.78-40.10 ppm), Pb (2.18-30.19 ppm), Zn (3.7-44.0), Ag (2-24ppb), Ni (2.9-13.6 ppm), Co (0.9-18.6 ppm), U(0.57-11.18 ppm), Th (3.0-76.5 ppm), Rb (5.7-46.9 ppm), Au (0.2-0.9 ppb), Y (0.81-27.79 ppm) and Li (1.2-17.2 ppm). The correlation coefficient for the selected elements show very strong correlation between Pb, Co, Fe, Ba and Mn as well as between Th, La, Rb, Ce, Zn and Y. The isograde plots show that most elements have their peaks in the western and northeastern part of the study area. The study therefore revealed that the area is rich in manganese, iron, K-feldspar and mica which are hosted, possibly, by schist and amphibolites.Item Multivariate Analysis of Stream Sediments Geochemical Data from part of Egbe-Isanlu Schist Belt(Adamawa State University Journal of Scientific Research; Adamawa State University, 2015) Alebiosu, M.T.; Adekeye, J.I.D.; Adedoyin, A.D.; Bamigboye, O.S.; Omorinoye, O.A.Item PETROGRAPHY, GEOCHEMISTRY AND PETROGENESIS OF GREY GNEISSES OF PART OF OKE-ODE AREA, SOUTH-WESTERN NIGERIA(Published by Faculty of Physical Sciences, Chukwuemeka Odumegwu Ojukwu University, Anambra State, Nigeria., 2022) Adedoyin, A.D.; Alebiosu, M.T.; Bamigboye, O.S.; Olobaniyi, S.B.; Omorinoye, O.A.; Iheme, K.O.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, high temperature 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.Item Petrography, Geochemistry and Petrogenesis of Grey Gneisses of Part of Oke-Ode Area, South-western Nigeria(COOU Journal of Physical Sciences; Faculty of Physical Sciences, Chukwuemeka Odumegwu Ojukwu University, 2022) Adedoyin, A.D.; Alebiosu, M.T.; Bamigboye, O.S.; Olobaniyi, S.B.; Omorinoye, O.A.; Iheme, K.O.Item Shear Sense Analyses of Basement Complex Rocks in Parts of SW Nigeria(International Journal of Earth Sciences Knowledge and Applications, 2022) Bamigboye, O.S.; Bamidele, T.E.; Adedoyin, A.D.; Issa, T.A.; Omorinoye, O.A.The study area, Oko/Olla is part of Osi sheet 224 southwest and falls within the Basement Complex of South-Western Nigeria. Field and petrological studies revealed that the area is underlain by metamorphic complexes and late intrusives which include: migmatite, granite gneiss, porphyroblastic gneiss, banded gneiss, fine grain granite, diorite with aplite and pegmatite occurring as intrusions. Migmatite is the dominant rock within the study area. The petrogenetic affiliation of the rocks as indicated by the rocks and mineral assemblage represented by plagioclase +alkali feldspar +biotite ±muscovite ±hornblende in the quartzo-feldpartic rocks of the area, are suggestive of amphibolites facies of metamorphism. Kinematic markers which include folds, boudins, σ– and δ–type porphyroclasts, and strike-slip and dip-slip faults were used as shear sense indicators. Detailed analysis of folds revealed asymmetric fold shapes with preponderance of Z– shape folds. The dominant Z–shape drag folds are consistent with the ductile and brittle dextral shear sense indicated by asymmetric boudins and porphyroclasts geometry. Structural analysis from this study indicates that the ductile fabric was overprinted by brittle deformations resulting from the uplift of the area to a low temperature-pressure conditions which is more favorable for brittle deformations. This over printing relationship is suggestive of continued movement of Olla and Oko areas after uplift of the areas during Pan African thermo-tectogenesis. It is therefore concluded on the basis of petrological evidences as well as clear overprinting relationships as revealed by decisive kinematic markers that although there are some sinistral and conflicting shear sense indicators in the area, dominant network of dextral ductile and brittle shear sense in the study area is consistent with the N-S regional structure in the Basement Complex of Nigeria.Item Soil Geochemical Survey of Kaoje and its Environs(Science Focus; Ladoke Akintola University of Technology, Ogbomosho, 2015) Bamigboye, O.S.; Adekeye, J.I.D.; Omorinoye, O.A.; Adedoyin, A.D.; Adefila, I.