Department of Geology and Mineral Science

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    Geochemical Fingerprints; Implication for Provenance, Tectonic and Depositional Settings of Lower Benue Trough Sequence, Southeastern Nigeria
    (The International Institute for Science, Technology and Education (IISTE), 2013) Olubunmi C. Adeigbe, Yusuf A. Jimoh
    The study areas, Asu River Group (ARG) and Cross River Groups (CRG) belong to Lower Benue Trough. The Trough is thought to have been deposited by marine transgression and regression. ARG covers Awi, Abakaliki and Mfamosing Formations while Ekenkpon, Eze-Aku, New Netim, Awgu and Agbani Formations fall within CRG. Sampling was done to cover both the Abakaliki Anticlinorium and Calabar Flank. The study aimed at using geochemical approach to deduce weathering, provenance, tectonic setting as well as depositional environment in a holistic manner which hitherto has not been used by any worker. A total of 56 fresh outcrop samples were obtained from the study area. The samples were subjected to detailed lithologic description by visual examination. Geochemical analysis was done using Inductively Coupled Plasma Mass Spectroscopy and Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-MS/AES) to determine major, trace and rare-earth elements using lithium metaborate/tetraborate fusion method. Weathering Indices of Chemical Index of Alteration (CIA), Plagioclase Index of Alteration (PIA), Chemical Index of Weathering (CIW) and Ruxton Ratio (RR) of ARG has a range of (0.18-86.1, 0.13-99.3, 0.18-99.5 and 1.80-25.2) with median of (76.7, 92.6, 93.5 and 5.76) respectively while CRG has a range of (2.93-97.7, 2.78- 99.7, 2.94-99.7 and 1.83-46.4) and median of (76.1, 85.5, 87.7 and 10.9) respectively, indicating moderate to high weathering at the source. The Al2O3-(K2O+CaO+MgO)-(Fe2O3+MgO), (AKF) ternary plots reveals sediments of ARG and CRG deposited in Continental, Transition and Marine zone and dominated by argillaceous, carbonaceous argillite, carbonaceous and a ferruginous argillites confirming a chemically altered sediments deposited in oxidizing and shallow marine environment. The plots of Log (Fe2O3/K2O) vs Log (SiO2/Al2O3) reveals sediments deposited in the Fe Shale, Shale, Wacke, Subarkose and Quartz arenite field. The discriminant function plots of Herron characterized the sediments as been derived from Quartzose sedimentary provenance, Intermediate igneous and Felsic provenance. Trace elements ternary plots of La-Th-Sc, Th-Sc-Zr/10 and Th-Co-Zr/10 reveal deposition within Continental Island Arc, Passive Margin and Oceanic Island Arc settings. This confirmed the tectonic discriminant plots of K2O/Na2O vs SiO2. This discriminant function diagram proposed by Roser and Korsch (1986) distinguish the sources of the sediments into four provenance zones, mafic, intermediate, felsic, igneous and quartzose sedimentary using ratio plots and raw oxides. Most of the sediments of ARG and CRG fall in, quartzose sedimentary provenance using raw oxide plots, and exceptions are the limestones that fall in intermediate igneous provenance this also corroborates with the ratio plots. Conclusively, the study shows that the Cretaceous clastic sediments of ARG and CRG have multiple provenances subjected to moderate to high weathering conditions and were deposited within an oxidizing and shallow marine setting and derived from Upper Continental Crust (UCC).
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    Rock-Eval pyrolysis and organic petrographic analysis of the Maastrichtian coals and shales at Gombe, Gongola Basin, Northeastern Nigeria
    (Arabian Journal of Geosciences: Springer, 2016-05-19) Ayoola Y. Jimoh & Olusola J. Ojo
    The Gongola Basin forms one of the inland Cretaceous to tertiary sedimentary basins in Nigeria with relatively unknown petroleum system. In this study, the investigated source rock intervals of the Maastrichtian Gombe Formation are located at the Maiganga coal mine, near Gombe, Gongola Basin, Nigeria. The exposed part of the mine consists of about 35-m thick coarsening upward section with the basal part made up of coal and shale interbeds while the upper part consists of siltstone and sandstone and probably deposited in fluvio-deltaic environment. The coal and interbedded shale appear most prospective source rock facies in the formation and were evaluated with respect to their hydrocarbon source rock potential. The organic geochemical results showed high TOC for the coals (37.71–65.29 wt%) and moderate organic carbon concentration (1.19–4.81 wt%) for the shales. S2 values ranges from 57.96 to 103.21 mgHC/g rock and 0.51–6.22 mgHC/g rock for the coal and shales, respectively. The HI is less than 200 mgHC/gTOC in all the coal and shale samples suggesting Type III kerogen and predominant plant contributions from terrestrial sources. Consequently, gaseous hydrocarbon potential is exhibited in the source beds. The organic petrography shows vitrinite as dominant maceral followed by inertinites and liptinites with inorganic minerals like pyrite and kaolinite. The Tmax is less than 435 °C in all the samples indicating pre-oil window stage; this is corroborated by the Romax value ranging from 0.45 to 0.55 %. Plot of PI against Tmax indicates low level organic matter conversion while the vitrinite reflectance values suggest a sub-bituminous coal. The study suggests that the investigated coal and shale samples constitute good source rock and have potential for gas. The generally low HI in the coals and the associated shales indicate more allochthonous and hydrogen poor organic matters in the source beds. Maceral composition of the coals suggests wet swamp environment and predominance of arborescent vegetation type. At present level, the organic matters are immature to marginally mature deeper level equivalents might have generated gas.
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    Variability in the Highway Geotechnical Properties of Two Residual Lateritic Soils from Central Nigeria
    (2017)
    Sixty-four bulk samples of two residual lateritic soils forming the subgrade of the failed sections flexible highway pavement linking Ilorin to Mokwa in central Nigeria were investigated. This was with a view to determining the level of variation in the geotechnical properties of soil samples taken systematically within restricted area in two locations underlain by different bed rocks. One set was developed over sandstone formation of the Southern Bida Basin while the other set was developed over migmatite-gneiss. Consistency limits, grain size distribution, specific gravity, compaction, California Bearing Ratio (CBR), permeability and compressibility characteristics of these soils were determined using the British standard procedures 1377. Coefficient of variation was used to measure the degree of variation in the determined properties. The coefficients of variations for the sandstone derived soil (1.68% and 56.86%) are higher than that of the migmatite-gneiss derived soil (1.28%-54.40%). Permeability, linear shrinkage, and coefficient of volume compressibility possess the highest variability. Atterberg limits and derived indices, amount of fines, soaked and unsoaked CBR possess moderate variability, while moisture density parameters (MDD and OMC), natural moisture content and specific gravity exhibits the least variability. In order to prevent design errors, field sampling should be very thorough involving collection of several samples. This approach will eliminate wrong inferences often associated with results of testing of few samples
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    An Appraisal of the Barite Resources of Cross River State, Southeastern Nigeria: Origin, Distribution and Economic Potentials
    (International Journal of Current Research, 2017-06) Ajadi Jimoh and Ajenipa Rasaq Adeleke
    The occurrence of barite mineralization in both the sedimentary and basement rocks in Cross River State shows a genetic linkage in relations to source of the metal for fluids that drain the basements. This agrees with current opinion based on isotopic and fluid inclusion data obtained by previous workers who on the basis of observed strontium data, Pb isotope composition of galena and rare earth element patterns in fluorite suggested that the basement rocks in the Benue trough or their weathered equivalents are likely sources of metal for mineralizing fluids in the Benue trough. The gentle dip of the basement rocks are believed to have generated slow migration of the fluids, a condition that is necessary to prevent quick flushing thereby allowing adequate time for enough leaching of barium from the basement rocks to form the barite deposits. The NE-SW trend of the barite veins, the identified sinistral faults as well as the fact that the barites that are associated with wall rock alteration usually display well developed crystal habits are suggestive that the barite mineralization is structurally controlled. Ore fluid formation from juvenile and circulating connate brines have been proposed for the formation of the barite deposits in Cross River State and indeed in Nigeria.
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    Characterisation of soils derived from different parent rocks from north central Nigeria
    (2018)
    Mineralogy and geotechnical properties of residual lateritic soils derived from sandstone and migmatite–gneiss (MG) were compared. The aim was to determine the influence of the parent rock geology of sandstone and MG on their engineering properties. This was done using the statistical method of Student’s t-test. Thin sections show that the MG samples are rich in feldspars and micas with up to 45 and 23% modal estimates, respectively. The dominant clay mineral in the two soils was kaolinite, while the dominant oxides were silicon dioxide, aluminium oxide and ferric oxide. The silica/sesquioxide ratio of the MG-derived soils (MGS) ranged from 1·7 to 3·2 while those of sandstonederived soils (SS) were 2·9–6·6. SS samples which contained essentially quartz grains exhibited better compaction characteristics, higher California bearing ratio and lower plasticity than MGS. Better engineering properties exhibited by SS can be attributed to the high quartz content present in the parent rock. Feldspars and micas present in MG are weathered into plastic and hydrophilic clay minerals. These are likely to have a negative impact on the engineering properties of the derived soils. Statistical treatment of all determined engineering parameters showed significant differences in all cases except in relation to specific gravity, permeability and compressibility.
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    Characterisation of soils derived from different parent rocks from north central Nigeria
    (2018)
    Mineralogy and geotechnical properties of residual lateritic soils derived from sandstone and migmatite–gneiss (MG) were compared. The aim was to determine the influence of the parent rock geology of sandstone and MG on their engineering properties. This was done using the statistical method of Student’s t-test. Thin sections show that the MG samples are rich in feldspars and micas with up to 45 and 23% modal estimates, respectively. The dominant clay mineral in the two soils was kaolinite, while the dominant oxides were silicon dioxide, aluminium oxide and ferric oxide. The silica/sesquioxide ratio of the MG-derived soils (MGS) ranged from 1·7 to 3·2 while those of sandstone￾derived soils (SS) were 2·9–6·6. SS samples which contained essentially quartz grains exhibited better compaction characteristics, higher California bearing ratio and lower plasticity than MGS. Better engineering properties exhibited by SS can be attributed to the high quartz content present in the parent rock. Feldspars and micas present in MG are weathered into plastic and hydrophilic clay minerals. These are likely to have a negative impact on the engineering properties of the derived soils. Statistical treatment of all determined engineering parameters showed significant differences in all cases except in relation to specific gravity, permeability and compressibility
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    An Appraisal of the Geologic Setting in the Basement Complex Terrain Around Malete, Southwestern Nigeria: Implications on Groundwater Occurrence
    (FUOYE Journal of Pure and Applied Sciences, 2018-12-03) Ajadi Jimoh, Adeyemi Sultan Faruq, Olasunkanmi K. Nurudeen, Babalola Olufemi
    In an attempt to update the geologic setting and investigate groundwater resources of Malete in Moro Local Government area of Kwara State, reconnaissance geological mapping and electrical resistivity geophysical field mapping were carried out. The lateral lithologic geometry and geologic features were established on the outcrops while the vertical extents were interpreted from resistivity sounding that involved Schlumberger electrode configuration. The lithologic units formally reported by Nigeria Geological Survey Agency as comprising migmatitic gneiss and porphyritic granite, were updated as including massive and foliated quartzites, porphyroblastic gneiss, biotite granite and other minor intrusives viz; pegmatites, aplites, and vein quartz. The granitic rocks discordantly intrude the migmatites and quartzites and mostly appear to have been caught up by tectonism at the waning stage of the Pan African orogeny as evident from the observed tectonic imprints not Nigerian older granite suites. Occurrences of intermittent pelitic bands observed to be alternating with large blocks of massive quartzitic layers suggest a sedimentary precursor for the quartzite bodies in the area. The resistivity variation ranged between 13.6 and 7740.4 Ωm and four-layer earth model which comprised sand lateritic topsoil, clayey sand, weathered basement and fresh/fractured basement were identified. The models revealed KH, HK, HA and AK types apparent resistivity curves with overburden thickness range between 0.2 and 9.6 m. The HK-type with geoelectric sequence of resistive–conductive–resistive–conductive, within quartzitic layer and thick overburden exhibit good aquifer characteristic and depict probable point for groundwater in the area.
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    Geochemical and Palynological Studies of Some Maastrichtian Source Rock Intervals (Patti and Gombe Formations) in Nigeria: Implications for Hydrocarbon Prospectivity
    (American Association of Petroleum Geologist (AAPG), 2019-01-14) Olusola J. Ojo, Ayoola Y. Jimoh, and Juliet C. Umelo
    The Maastrichtian Patti and Gombe Formations are located in Bida and Gongola Basins respectively. These two inland basins form part of the targets currently being tested for hydrocarbon prospectivity in Nigeria. Road cuttings and core samples of coal, coaly shale, and shale from the formations were analyzed using standard organic geochemical and palynological techniques to unravel their organic matter quantity, quality, palynofacies, expulsion efficiency, and thermal history. The age of the sediments were also constrained from the palynological data. Palynological data suggest a Maastrichtian age and influence of freshwater swamps for the sediments based on the microfloral assemblage like Retidiporites magdalenensis, Echitriporites trianguliformis, Buttinia andreevi, and Botrycoccus braunii. The organic geochemical results show relatively high TOC for the Patti shales (0.79-12.9 wt.%) and Gombe coals (38.8-61.2 wt.%) implying moderate to high concentrations of organic matter. Hydrocarbon source potential range from 0.19-0.70 mgHC/g rock except for a certain interval with high yield (30.23 mgHC/g rock) in the Patti shales. The Gombe coals have source potential ranging from 32.77-69.38 mgHC/g rock. Generally, the samples show low HI except one of the Patti shale samples with HI of 230 mgHC/g TOC (thought to be formed under reducing condition) and one of the Gombe coal samples with HI of 170 mgHC/g TOC. In spite of the favorable organic parameters, the thermal maturity is low with vitrinite reflectance and Tmax ranging between 0.41-0.52 % and 413-431 °C respectively. Biomarker analysis of the hydrocarbon extracts show abundance of odd number alkanes C27-C33, low sterane/hopane ratio (0.06-0.25). Pr/Ph in the samples are greater than 2. We conclude from the study that the Maastrichtian source rocks were sourced terrestrially under a prevailing oxic condition and dominated by Type III organic matter. Type II organic matter with oil and gas potential may be possible in the Patti Formation in the Agbaja area of Bida Basin. Thermal maturity and conversion ratio were low and not much hydrocarbon could have been generated from the source rocks.
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    Organic petrography, Rock–Eval pyrolysis and biomarker geochemistry of Maastrichtian Gombe Formation, Gongola Basin, Nigeria
    (Journal of Petroleum Exploration and Production Technology (Springer), 2019-08-31) Ayoola Y. Jimoh, Olusola J. Ojo, Samuel O. Akande
    The Maastrichtian Gombe Formation is located within one of the inland basins of Nigeria (Gongola Basin). Surface and borehole samples of coal and interbedded shale of this formation were evaluated to determine the organic matter richness, quality, maturity, source and depositional environment through organic geochemical techniques such as total organic carbon (TOC) determination, Rock–Eval pyrolysis, chromatography and organic petrography. The genetic potential and average TOC value of the coals, shales and coaly shales are 38.03 wt%, 3.14 wt% and 12.1 wt%, respectively, indicating moderate-to-good source potential. HIs are less than 200 mgHC/gTOC for all the samples indicating Type III kerogen for most of the samples (gas prone) and plant contributions from terrestrial sources. The source rocks were characterized by high molecular weight n-alkanes which range from C10– C41 in the coals and C9– C41 in the shales. The n-alkanes distributions in the coals maximize at C29 indicating terrestrial sourced organic matter, while the shales maximize at C16 and C29 indicating mixed sources. Pr/ Ph of the coals and shales ranges from (2.15–3.51) to (0.95–2.37), respectively, suggesting fluvio-deltaic deltaic and coastal swamp depositional environments. The predominance of pristane over phytane suggests humic origin of the organic matter. The sterane/hopane values (< 0.6) indicate incorporation of bacterial inputs commonly associated with terrigenous organic matter in the coals. The CPI is greater than unity, Tmax is generally < 435 °C and vitrinite reflectance less than 0.55 Ro for most of the samples and suggest the samples are of low maturity status to expel liquid hydrocarbon.
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    Efect of cyclic heating on some engineering characteristics of some soils from Ilorin, Nigeria
    (2020)
    This work investigates probable changes during repeated heating and cooling cycles on some index and engineering properties of some lateritic soils. Bulk soil samples were taken within Ilorin metropolis. These samples were oven dried for 24 h at 110 oC and cooled naturally to room temperature. This procedure was repeated four times. The effect of cyclic heating and cooling on various soil properties including Atterberg limits, particle size distribution, moisture— density relationship and California bearing ratio (CBR) were investigated. The results show that maximum dry density (MDD) reduced consistently with repeated heating and cooling while optimum moisture content (OMC) increased. CBR increased with repeated heating and cooling up to 23.5%. A percentage decrease in liquid limit up to 25% was recorded while plastic limit and plasticity index reduced in all samples. Increase in CBR is an indication of increase in strength with repeated heating while the decrease in MDD is an indication of reduced density on account of increase in OMC of the soil samples with repeated heating.
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    Synthesis of a Geopolymer with the Blend of Clay from Share Deposit and Cullet of Cathode Ray Tube
    (2020)
    The potentiality of Share clay as an ingredient for synthesis of metakaolin based geopolymer and the effect of partially substituting the clay with the cullet of cathode ray tube (CRT) was investigated. Calcined clay in partial substitution with powdered CRT in the mix proportion of 0%, 25%, 50% and 75% by weight was reacted with sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). The resulting geopolymer samples were used to produce test specimens and the effect of different percentage addition of CRT on the physicomechanical properties were evaluated. The starting materials and the products were characterized using Scanning Electron Microscopy (SEM) to evaluate morphology, X-Ray Fluorescence (XRF) for oxides composition, X-Ray Diffractometer (XRD) for compositional phases, Atomic Absorption Spectroscopy (AAS) for elemental components and Fourier Transform Infra-Red microscopy (FTIR) for characteristic bonding. Results shows that the alumina and silica content of Share clay are 30% and 92% respectively while that of the CRT were 3% alumina and 29% silica. The water absorption of the geopolymer increases with increasing CRT addition. The Compressive strength in 24 hours ranged from 13 to 17 N/mm2. The drying shrinkage ranged from 0.5mm to 1.25 mm. CRT is as usable as other pozzolanic material to be used with kaolinite in the synthesis of geopolymer. This offers the opportunity for resource recovery from and beneficial use of CRT, which is considered a toxic e-waste.
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    Organic geochemical and palynological studies of the Maastrichtian source rock intervals in Bida Basin, Nigeria: implications for hydrocarbon prospectivity
    (Journal of Petroleum Exploration and Production Technology (Springer), 2020-09-02) Olusola J. Ojo, Ayoola Y. Jimoh, Juliet C. Umelo, Samuel O. Akande
    The Patti Formation which consists of sandstone and shale offers the best potential source beds in the Bida Basin. This inland basin is one of the basins currently being tested for hydrocarbon prospectivity in Nigeria. Fresh samples of shale from Agbaja borehole, Ahoko quarry and Geheku road cut were analysed using organic geochemical and palynological techniques to unravel their age, paleoecology, palynofacies and source bed hydrocarbon potential. Palynological data suggest Maastrichtian age for the sediments based on the abundance of microfloral assemblage; Retidiporites magdalenensis, Echitriporites trianguliformis and Buttinia andreevi. Dinocysts belonging to the Spiniferites, Deflandrea and Dinogymnium genera from some of the analysed intervals are indicative of freshwater swamp and normal sea conditions. Palynological evidence further suggests mangrove paleovegetation and humid climate. Relatively high total organic carbon TOC (0.77–8.95 wt%) was obtained for the shales which implies substantial concentration of organic matter in the source beds. Hydrocarbon source rock potential ranges from 0.19 to 0.70 mgHC/g.rock except for a certain source rock interval in the Agbaja borehole with high yield of 25.18 mgHC/g.rock. This interval also presents exceptionally high HI of 274 mgHC/g.TOC and moderate amount of amorphous organic matter. The data suggests that in spite of the favourable organic matter quantity, the thermal maturity is low as indicated by vitrinite reflectance and Tmax (0.46 to 0.48 Ro% and 413 to 475 °C, respectively). The hydrocarbon extracts show abundance of odd number alkanes C27–C33, low sterane/hopane ratio and Pr/Ph > 2. We conclude that the source rocks were terrestrially derived under oxic condition and dominated by type III kerogen. Type II organic matter with oil and gas potential is a possibility in Agbaja area of Bida Basin. Thermal maturity is low and little, or no hydrocarbon has been generated from the source rocks.
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    The use of Polidori's plasticity and activity charts in classifying some residual lateritic soils from Nigeria
    (2021)
    Over the years, Casagrande plasticity chart is mainly used to classify fine grain soils. However, the use of the plasticity chart has been questioned recently and this has led to the development of a new plasticity chart. Polidori in 2007 and 2009, respectively, developed the new plasticity and activity charts using the Atterberg's limits of pure clays (montmorillonite and kaolinite clay minerals) and their mixture with fine silica sand in different proportions. The applicability of Polidori's charts was evaluated using some residual lateritic soils from Nigeria. On the Casagrande's plasticity chart, the lateritic soils mostly plot above the A-line in the zone designated as clay and classified as either CL or CH. However, on the Polidori's plasticity chart, the lateritic soils classified as CL or CH, whereas on Casagrande's plasticity chart they are classified as ML or MH and vice versa. The classifications obtained from Polidori's plasticity chart are predominantly in agreement with the main soil fractions or component of the soils. This is different from the classification obtained from Casagrande's plasticity chart where lateritic soils with lower clay fractions than their silt/sand fractions are classified as clayey soils. Polidori's activity chart shows that lateritic soils that lie in the same plastic zone may show different behavior due to the different properties of the clay minerals in the soils. In cases where the lateritic soils lie in the zone that is not corresponding to their clay contents on the Polidori's plasticity chart, we presume that other factors apart from those stated by Polidori might also be responsible. Although the use of Polidori's plasticity chart gives a fair classification of the lateritic soils, nevertheless the peculiarity of residual soils such as the in situ structure that influenced the properties of the soils and properties developed due to weathering effects must be taken into consideration as well.
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