Malaysian Journal of Geosciences (MJG)

Charnockites could be of magmatic, metamorphic, or metasomatic origin and formed in varying tectonic settings. Lack of detailed geological mapping of plutonic charnockites around Ikare necessitated this work. Hence, this study was designed to investigate the petrography of plutonic charnockites, in order to infer post-cystallization event that prevailed in the area. Ten (10) chip rock samples purposively collected were prepared into thin and polished sections for petrographic studies using petrological microscope. The mineral assemblages observed are quartz, plagioclase feldspar, alkali feldspar, horhblende, biotite, orthopyroxene ± clinopyroxene. The accessory minerals are apatite, magnetite, ilmenite and zircon. Anti-perthite and myrmekite intergrowth are common. BSE images show close association between alkali feldspar and barium suggesting that barium is replacing potassium in the feldspar. Also,hornblende are found enclosing orthopyroxene suggesting a retrograde event. Relicts of quartz and alkali feldspars are found in biotite grain suggesting partial melting of the rock under high temperature conditions. Based on petrographic evidence, the charnockite magma that produced these charnockites must have been emplaced at deep crustal level under granulite facies conditions and followed by strong ductile deformation.

The study area is underlain by migmatite-gneiss quartzite rock suits with infolding mica schist which is intruded by batholitic Pan-African granitoids. Petrographic studies revealed quartz, orthoclase, hornblende and biotite as major minerals which are common to all members of rock units. The geochemical result of gneissic rock shows SiO2 content that range between 77.04%.wt to 80%.wt while mica schist depicts SiO2 content of 74.42 to 77.42%.wt. this implies silicious protolith for the both rock units. On the discrimination diagram gneiss and mica schist plot mainly in High-K calc-alkaline to calc-alkaline fields. Whereas, bivariate diagram of TiO2 versus SiO2 revealed that both gneissic rock and mica schist have sedimentary progenitors. High Rb, La and Th and low Nb, Sr, and Ti values shown by both gneiss and mica schist are compatible with typical crustal melts and suggest evolution from partial melting of crustal materials. The Pan-African granitoids has similar geochemical relationships. Geochemical studies shows that the rock units have limited variation in their major element compositions and give a decrease in CaO wt. %, and increasing Ba/Sr, Zr/Y ratios, K2O wt. % with increasing silica. The rocks are distinctly peraluminous, calc-alkaline as they plot in the High-K calc-alkaline and calc-alkaline, syn-collision fields on various discrimination diagrams. The characteristics suggest that the Basement rocks of the study area were formed from the fractional crystallization of a calc-alkaline magma in a syn- collision tectonic terrain.

The qualities of road construction materials are essential in their choice for various civil works. Therefore, engineering geological properties of the sub-soil that constitute sub-grade materials along Supare- Emure road were investigated in order to determine the causes of the failure of the pavement along the unstable sections. A total of twelve (12) sub- grade soil samples were collected from unstable and stable sections of the road and were subjected to various geotechnical tests. These tests include natural moisture content, atterberg limits, linear shrinkage, plasticity index and grain size. Results showed that the natural moisture content of the stable sections range from 5% to 11%, while those of unstable sections range from 23.8% to 37.2%. The range of the unstable sections fell short of required specification. For the plasticity index, both sections have values less than required 30%, while the unstable sections had linear shrinkage above 8%. On the grain size results, unstable sections have values greater than the specified 35% passing. Bedrock chemistry and clayey nature of sub-grade soils have been found to be responsible for the failed sections of the road investigated..

The complex dynamic processes such as the magma movements in the crust and uppermost mantle result in the anisotropic wave propagation. In case of the Rayleigh and Love surface waves, this anisotropy is known as the Rayleigh-Love wave discrepancy. The surface wave propagation beneath the Central Anatolia shows this discrepancy for which we utilize the vertical transverse isotropy in the form of forward solutions. We use single-station and two-station methods to attain the observed surface wave dispersion curves in the period range 7-40 s and then apply the two-dimensional (2-D) tomography to convert these curves into the velocity maps defined through a 0.05o x 0.05o – sized grid. The damped least-squares technique is used to invert the individual group and phase velocity curves for the one-dimensional (1-D) structure. The latter 1-D inversion provides the depth profiles for the Voigt isotropic average shear-wave velocity (𝑉𝑆) and the radial anisotropy (𝜉). The 𝑉𝑆 and 𝜉 depth profiles are employed to construct the vertical transverse isotropic (VTI) velocity structure beneath a grid point. Through the forward modeling, the VTI velocity structure is revised to jointly fit the observed Rayleigh and Love group and phase velocities. In the forward modeling, the fifth VTI parameter (𝜂𝐾) measuring the departure from the elliptic condition (𝜂𝐾=1.0) and the anisotropic velocity perturbations (𝑎𝑃2⁄ and 𝑎𝑆2⁄) are primarily adjusted to achieve the fit between the observed and theoretical dispersion curves. In the depth range ~20-30 km, the 𝜂𝐾 is generally found to be 𝜂𝐾<1.0 changing in the range 0.94≤𝜂𝐾≤0.95, which is consistent with the PREM and the expression 𝑎𝑃2⁄=0.5𝑎𝑆2⁄ appears to be valid for the mid-to-lower crust beneath the studied region. In particular, the Rayleigh group velocities require the setting 𝜂𝐾<1.0 in the mid-to-lower crustal depth range.

This work was undertaken to unravel the hydro geophysical characteristics of Keana metropolis Nasarawa State, northcentral Nigeria. This study aims to assess and determine the sustainability of groundwater resources in Keana Town by using geoelectric techniques to collect data and analyze subsurface characteristics that can assist identify suitable sites for groundwater extraction. Once accomplished, it will give useful information for groundwater resource management and contribute to Keana’s long-term growth. Fifteen (15) Vertical Electrical Sounding (VES) data with a maximum electrode spacing of (AB/2) of 200 meters were acquired using the Schlumberger electrode configuration. The VES data were interpreted using the conventional partial curve matching technique to obtain initial model parameters, which were used as input for computer iterative modelling using the IPI2WINTM software. The study revealed three (3) to six (6) geo-electric layers with underlying indurated sandstone and shale beds in some areas. In the study area, the apparent resistivity of the aquifer ranges from 32.4 to 407 m, with a depth ranging from 30 to 120m. Information extracted from iso-resistivity models and geoelectric cross sections revealed sandy strata with an exception around the northern portion i.e., around Federal Government Girls College Keana (FGGC) where a thick layer of shale is envisaged, extending to over 150 m depth with an average apparent resistivity value of 35Ω m. Thus, making the section fair to poor groundwater potential. However, this research has aided in delineating the groundwater potential of the area into three distinct zones.

The Magnetic Hinge deposits from Chirano Gold Mine lie within the Paleoproterozoic Birimian rocks of southwestern Ghana on the West Africa Craton. The Analytical Spectral Device (ASD) Terraspec Spectrometer is used to measure the composition and abundance of a variety of alteration minerals. The results obtained through the ASD on rock cores are plotted as strip logs plots, box plots and the creation of geological models using Leap Frog Geo. The different alterations identified using the ASD were sericite, chlorite, carbonate, amphibole, chlorite-amphibole, kaolinite and epidote. Cutoff grades lesser than 0.2 ppm were considered insignificant mineralization and hence were of no interest. The Magnetic Hinge boasts of carbonate, sericite, and sericite-chlorite alterations hosting good gold grades in rocks and this was observed from the results obtained. Moreover, Magnetic Hinge is a new project and reverse circulation was done to obtain information on the subsurface alterations, open pit mining may be done and as progress is made, diamond drilling can be done to obtain subsurface information for much deeper depth.

Polynuclear aromatic hydrocarbons (PAHs), are known as persistent organic pollutants (POP) which exist in different media as contaminants in parts of the environment’s atmosphere, seawater, sediments, soils, and vegetation. PAHs have been known for their mutagenic, carcinogenic, and toxic properties to humans through the food chain. This study is aimed to characterize and investigate the distribution of PAHs in wet precipitations, surface waters, and soils from Ikot Abasi, Ibeno, and Eastern Obolo Local Government Areas of Akwa Ibom State, Nigeria. PAHs were determined in the environmental components by gas chromatography-mass spectrometry technique. Two soil and two surface water samples were taken from selected locations and wet precipitation samples were harvested on event basis from the study areas .The results reveal the presence of the following priority PAHs at different concentrations: naphthalene, (0.02-0.09 mg/L);benzo[k]fluoranthrene (0.001 -0.09 mg/L); benzo[e]pyrene (0.001-0.08 mg/L); benzo[a]pyrene (0.001 -0.09 mg/L) ; 3-methylcholanthrene (1.27-7.21 mg/L) during the rainy and dry seasons in Ikot Abasi. The concentrations of naphthalene ranges (0.02-0.06 mg/L), 3-methylcholanthrene ranges (2.40-3.65 mg/L), while other PAHs levels were below detection limits in rainwater from Ibeno in both seasons. The concentrations of naphthalene ranges (0.02-0.05 mg/L); 3-methylcholanthrene (2.30 – 5.65 mg/L), while other PAHs levels were below detection limits in rainwater from Eastern Obolo in both seasons The PAHs levels indicated were higher than the World Health Organization (WHO) acceptable limit of PAHs (0.0007 mg/L) in drinking water. The PAHs detected in the surface waters were in the order: Ikot Abasi (11.09 ±0.02 mg/L) > Eastern Obolo (3.87± 0.002 mg/L) > Ibeno (1.94 ± 0.004 mg/L), during the rainy season, while the PAHs detected in the surface waters were in the order: Ikot Abasi (13.79 ± 0.03 mg/L) > Eastern Obolo (3.95± 0.008 mg/L) > Ibeno (2.45±0.011 mg/L), during the dry season. The PAHs obtained for the soils in the three study areas during the rainy season were in the order: Eastern Obolo (776 ± 5.92 ug/kg) > Ibeno (732 ± 8.33 ug/kg) > Ikot Abasi (8 ± 0.07 ug/kg), while, during the dry season, the results were in the order: Ibeno (872±11.05 ug/kg) > Eastern Obolo (105±9.03 ug/kg) > Ikot Abasi (20 ± 1.95 ug/kg). Soils from Eastern Obolo and Ibeno have PAHs levels greater than 700 ug/kg, which is categorized as slightly polluted, with toxic equivalent concentrations (TEQ) higher than permissible limit (33 ug/kg).This may cause ecological risk and raises public health concern that should attract more attention. Molecular diagnostic ratio analyses show that the sources of PAHs in the three study area are mainly pyrogenic.

Multicriteria decision analysis for groundwater potential mapping utilizing analytical hierarchical process of six hydrogeologic parameters including aquifer layer thickness, aquifer layer resistivity, overburden thickness, transverse resistance, transmissivity, and coefficient of anisotropy; in relation to groundwater yield was carried out in Ile Oluji, Southwestern Nigeria. The aim was to develop groundwater potential map using calculated groundwater potential index values (GWPIV). The obtained GWPIV which ranged from 1.53 (granite) – 3.50 (migmatite) with an average of 2.18 suggestive of moderate groundwater potential (90 % of the study area). The low potential zone (10 %) are observed sporadically in the central and northwestern parts. All the geological units recorded overlapping hydrogeologic properties. The longitudinal unit conductance recorded regional average of 0.219876 mhos. Therefore the protective capacity of groundwater system in the study area is weak, and relatively less-weaker in granite environment; and in northwestern and central parts. Nevertheless, the water table aquifer (accounts for 80%) and the fracture basement (constitutes 20%, frequently occurring in gneissic environment) are the water bearing units, with average overburden thickness in migmatite, granite, and gneiss 24.3 m, 24.5 m, and 27.9 m respectively. The average coefficient of anisotropy (1.12); hydraulic conductivity (0.37 m/d), transmissivity 6.86 m2/d (migmatite: 7.17 m2/d, granite: 7.14 m2/d, and gneiss: 6.02 m2/d). Hence gneissic offered both thick weathered layer and fractured aquifer. Empirical model for plot of formation factor and hydraulic conductivity in migmatite, granite, and gneiss, showed positive correlations in descending order as: granite (0.3778), migmatite (0.1057), and gneiss (0.0641).

Three-dimensional (3D) seismic data and well logs were conjointly used to characterize reservoirs in the Onshore field Niger Delta Field of South-eastern Nigeria. The goal was to model and improve on the limitations of seismic resolution in conventional inversion techniques. This is necessitated by the quest to better off understanding of the distribution of lithology and pore fluid. Both geo-statistical and deterministic inversion techniques were applied in this study to appreciate the impact of each process on reservoir recognition and demarcation. The methodology began with well log conditioning and well-to-seismic tie. Rock-Physics feasibility analysis prior to the seismic inversion was done to estimate the elastic attributes appropriate for distinguishing between different fluid types and lithologies. The rock Physics results revealed the separation of the Velocity ratio (Vp/Vs) versus Acoustic impedance (Ip) cross plot into three regions, which are hydrocarbon, brine and shale zones. This suggests that the inversion results would be capable of distinguishing hydrocarbon sands from shale. Cross-plots of Mu-Rho (μρ) versus Lambda-Rho (λρ) showed that clusters of data, which are separated into three different zones inferred to be potential hydrocarbon, oil, brine and shale zones. The geo-statistical stochastic inversion was done by integrating variogram models and probability density functions (PDFs) to identify high frequencies or low periods in the output inversion outcome. The deterministic inversion results show that hydrocarbon saturated-sands are identified from the following attributes: low values of acoustic impedance (2.11 – 2.24 ×104 ft/s*g/cc), low velocity ratio (1.70–1.82), low Lambda-Rho (14.4 –19.7 Gpa*g/cc). In all cases, the results of geo-statistical inversion provided more detailed and increased resolution than deterministic inversion, allowing for detailed reservoir characterization. In the geo-statistical inversion, some regions in deterministic inverted sections with low acoustic impedance, velocity ratio, and Lambda-Rho attribute values inferred to be hydrocarbon sands appeared as either shale or brine. The inversion shows that the lambda-Rho quality is more useful in determining fluid classification whereas the acoustic impedance attribute is a good lithology discriminator. The overall results demonstrate the workflow’s ability to accurately map the rock properties with higher resolution and the delineation of new forecast as an effective, cost-effective and decision-making instrument.

The palynofacies and sedimentological analyses of the sedimentary succession of the HB-001 well were carried out to establish biozones and the palaeodepositional environment. Ninety-six samples of ditch cutting within intervals of depth of 1250 -4011 m were analyzed. Most of the previous researchers established biozones with alpha-numeric method. The use of palynomorphs and palynofacies analyses to delineate paleoenvironment of deposition has been applied to a limited extent in the Niger Delta Basin in Nigeria. The analysis produced fairly diverse and moderately abundant pollen and spores with high recoveries of palynomaceral 1 and 2 and minimal retrievals of palynomaceral 3 and 4. The textural, lithologic, as well as wireline log data point out that the whole studied interval in the HB-001 well fit in to the Agbada Formation. Late Miocene age was assigned on the bases of the analysis of stratigraphic age range of indicative palynological markers for example Zonocostites ramonae, Verrucatosporites sp., Laevigatosporites sp., Monoporites annulatus, Pachydermites diederixi and Psila,tricolporites crassus. Two assemblage zones were established in the well with the use of the International Stratigraphic Guide for the biozones establishment. The two recognized palynostratigraphic zones are Cyperaceaepollis sp. – Nympheaepollis clarus, and Stereisporites sp Zones. Lower delta plain, pro-delta and delta front depositional environments have been deciphered for well with the use of the palynofacies association, palyno-ecological groupings, and sedimentological features. Bodies of sand that signify sub-environments inside these settings are deposited in sequences. Every sequence begins with a transgressive stage, after that considerable regression. The palyno-ecological groupings of the retrieved palynomorph taxa revealed that the well intervals studied were deposited under alternating wet and dry paleoclimatic settings. The zones of dry climate presented high account of montane and savannah taxa and low incidence of rainforest, mangrove and freshwater taxa. The zones of wet climate signified increased account of rainforest, freshwater and mangrove taxa and lower incidences of montane and savannah taxa.