Ilesha Schist Belt Research Articles

Evaluation of gold mineralisation potential using AHP systems and weighted overlay analysis

The demand for sustainable development goals and the absence of systematic development and organised exploration for gold has prompted this study to integrate magnetic and radiometric datasets with lithology to evaluate the gold mineralisation potential in the Ilesha schist belt. This study considers 3168.72 km2 of the Ilesha schist belt in southwestern Nigeria, a frontier belt for gold deposits. The high-resolution airborne magnetic and radiometric datasets were processed using enhancement techniques, including the analytical signal, lineament density, and K/Th ratio. CET grid analysis, Euler deconvolution, and analytical signal depth estimation methods were used to aid the interpretation. The spatial integration and interpolation were performed using the Analytical Hierarchy Process (AHP) and weighted overlay analytical tools within the ArcGIS environment. The dominant structural controls for potential mineralisation are ENE–WSW and ESE–WNW trends. The depth of the magnetic sources revealed by the analytical signal ranged from 63.17 to 629.47 m, while depths ranging from 47.32 to 457.22 m were obtained from Euler deconvolution. The delineated highly magnetic edge sources, dense lineaments, radiometrically highlighted alteration zones, and lithological hosts for gold mineralisation were integrated to establish the gold mineralisation potential map. The AHP deductions reveal that 10.52% of the study site is within the high mineralisation potential class, a remarkable 60.39% falls within the moderate class, a significant portion (28.86%) falls within the poor class, and 0.23% is considered unfavourable. The result was optimised by validation using known mines, with 94% (i.e., 15 out of 16 mining sites) plotting within the high mineralisation potential class. This assessment provides invaluable insight for stakeholders and policymakers to embark on gold exploration and exploitation and promote sustainable mineral development.

Evaluation of Three Geosites Within Ilesha Schist Belt Southwest Nigeria as a Potential Geoheritage Site for Sustainable Regional Development

Evaluation of Three Geosites Within Ilesha Schist Belt Southwest Nigeria as a Potential Geoheritage Site for Sustainable Regional Development

English

The Osogbo central solid waste dumpsite in Osun State, Nigeria falls within the Ilesha Schist Belt, southwestern basement complex of Nigeria. Thirty-three (33) Vertical Electric Sounding (VES), and 2-D Electric Resistivity Tomography (ERT) data were acquired across various locations in the study area using ABEM Terrameter SAS 300, respectively. Schlumberger configuration with a maximum spread length of 100 m, for the VES was used, while four traverses of ERT were conducted, using Dipole-Dipole Array with average traverse length of 112.50 m. A smoothness-constrained least-squares inversion was then applied to the ERT data using a 2-D inversion algorithm [that is, DIPRO for Windows, version 4.01. Generally, the results defined the contaminated leachate plumes as electrically conductive, with anomalous resistivity values. Both the VES and the 2-D tomography identified zones of low resistivity values, between 24 and 67 ?m, from 10 to 20 m deep, as leachate contaminant plumes. Some of the weathered and fractured basement rocks indicated that the subsurface soil and groundwater have been contaminated by the leachates, which appears to have migrated outside landfill site. Zones within the sub-surface, with resistivity values relatively high (> 300 Ωm) and depth above 30 m might be pollutant free. Solid wastes management calls for the adoption of the best practicable environmental management approach through the governments’ enforcement of circular economic policies, using extended producer responsibility (EPR) model and construction of engineered landfills to replace unsanitary landfills. The conduct of environmental impact assessment (EIA), prior to commencement of operations and phytoremediation of closed sites is also crucial. Key words: Tomography, leachate, pollution, contaminant plume.

Hydrochemical Assessment of Groundwater Around Osogbo Central Dumpsite, Onibu-Eja, Osun State

Groundwater sources around Oshogbo central dumpsite in Osun state, Nigeria, have been evaluated with the aim of detecting possible influence of dumpsites on nearby aquifers and suitability for domestic use. The site covers an area of 79 200m 2 with an undulating surface. Being part of Ilesha Schist Belt, the major rock types in the area include amphibolites, pegmatites and quartzites. Preliminary tests were conducted on the water samples to determine some parameters, such as PH, Oxidation-reduction potential, Conductivity, Total Dissolve Solids, (TDS), E. Coli , etc, as investigative markers. To detect the presence of Heavy Metals and other parameters, there was random collection of a total of thirty (30) samples of leachates/water, using sterilized bottles. At dried areas, soil samples were collected and distilled water was introduced to extract leachates. The samples were then tested for the following heavy metal pollutants: Cadmium, Iron, Lead, Mercury, Zinc, Chromium, Nickel, Arsenic, Copper, and Cobalt. An appraisal of the results using World Health Organization (WHO’s) and National Standards for Drinking water Quality proved among others, the presence of Mercury, Cadmium, Iron, Arsenic, and high level of Lead contamination. There were also exceeding values of Cadmium in most samples, except in a few others where it was totally absent. Mercury had exceeding values in few samples and absent in the rest of the samples. Heavy metals pollution has harmful effects on the Biological system, via bio-accumulation, and cannot undergo biodegradation. Therefore appropriate remedial treatment is required for the groundwater in the study area since most of the heavy metals in the samples are above the WHO’s and National standards. Keywords: Heavy Metals, Biodegradation, Pollutants, WHO DOI: 10.7176/JEES/12-12-04 Publication date: December 31 st 2022

Aeromagnetic Mapping and Radioelement Influence on Mineralogical Composition of Mesothermal Gold Deposit in Part of Ilesha Schist Belt, Southwestern Nigeria

ABSTRACT 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.

Geochemical Exploration for Metallic Minerals in the Meta-Sedimentary Rocks of Ogotun, Ikeji-Ile and Ipetu, Southwestern Nigeria

The south-eastern part of Ilesha Schist belt which comprises of (Ogotun,Ikeji-Ile and Ipetu-the study area has been totally neglected by previous researchers without any literatures that could serve as clues to mineral exploration in the study area which necessitate this research. Geological mapping was undertaken to determine the underlying rocks followed by systematic sampling at one rock per 3.25km2, petrographic and geochemical analysis of the rocks. The results of field examination confirmed the existence of migmatite-gneisses, quartzites, quartz-schists, meta-conglomerates and porphyritic granites as the dominant rocks while petrographic studies revealed quartz, biotite, feldspar (microcline and plagioclase) and opaque minerals. However, five rocks samples whose thin sections showed opaque minerals were viewed under the reflecting light microscope and a brassy yellow mineral called chalcopyrite was confirmed. Geochemical analytical results revealed that SiO2 (67.37%-62.46%) and Al2O3 (17.35%-11.62%) have higher concentrations, indicating the aluminosilicate nature of the rocks. The trace elemental analysis revealed very high concentrations of Ba (2533-10) ppm and Fe (55000-4100) ppm, followed by moderate to low and very low concentrations of Cu (38.40-12.50) ppm, Pb (.90-39.40) ppm, Zn (156.00-7.00) ppm, Co (65.20-1.40) ppm, Mn (148.00-981.00) ppm,, As (1.00-3.00) ppm, Th (0.50-10.00) ppm, Rb (311.60-50) ppm ,Cr (1310.-5.00) ppm and U (>0.1-6.3) ppm. Similarly, the principal component analysis (PCA) of the rocks revealed Cu-Pb-Zn-Mn-Fe mineral associations with 35.24% also confirmed massive sulphide mineralization. Therefore, the overall results indicated the potentials of the study area to be possibly enriched with other hidden ore deposits and radioactive minerals.

The Relationship Between Morpho-structural Features and Borehole Yield in Ilesha Schist Belt, Southwestern Nigeria: Results from Geophysical Studies

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 z-scores 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.

CONTROLLED METHOD OF DETERMINE GOLD MINERALIZATION POTENTIALS IN AN UNEXPLOITED AREA; A CASE STUDY OF ITAGUNMODI AND OSU, SOUTHWESTERN, NIGERIA

The research was conducted to open up further unexploited areas for gold mineral exploitation in part of Ilesha schist belt using geological and geophysical approach. Itagunmodi was used as a control in order to determine the mineralization potentials of Osu as a case study. Both towns lie within Ilesha schist Belt, Southwestern Nigeria. The residual magnetic anomaly map of the study area revealed magnetic low in the two towns indicating the presence of geological structure serving as a conduit for mineralizing fluid. Airborne radiometry interpretation showed that both Itagunmodi and Osu are affected by hydrothermal alteration which is an indication of gold mineralization. Overall interpretation of aeromagnetic and airborne radiometry datasets show that hydrothermal alteration generally is associated with fault and shear zones in the study area. The isolated altered zones were subjected to further investigation by using six samples of stream sediment collected along Imo (Itagunmodi) and Olomumu (Osu) stream channels for the grain size and geochemical analyses. The results from the grain size analysis revealed that sediments in both areas are fine to medium grained, poorly sorted, fine to moderately fine skewed, which implied fluvial depositional settings, and revealed that the occurrences of gold mineralization in both areas are of secondary deposits (alluvial). The concentration of identified trace elements as related to their threshold values revealed similar contents of low to high concentrations in both areas. The results of the analyses observed in Itagunmodi are similar to that of Osu, which implies that Osu is also mineralized will gold deposit.

MULTIFACETED INVESTIGATION OF PORPHYRY CU-AU-MO DEPOSIT IN HYDROTHERMAL ALTERATION ZONES WITHIN THE GOLD FIELD OF ILESHA SCHIST BELT

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.

Mineralization Characterization of Psammitic Rocks in Efon-Alaaye and Environs using Remote Sensing and Field Studies

This paper analyses remotely sensed data over a part of the Psammitic Rocks in Efon-Alaaye and Environs to elucidate its geology and structural framework as well as delineate the potential zones of mineralization. The study area belongs to the Precambrian Basement Complex terrain of Southwestern Nigeria and lies within the eastern unit of the Ilesha schist belt. The lithologic units comprise schistose quartzites, quartz schists, quartz-mica-schists, and granitic gneisses. Landsat 8 satellite imagery and Shuttle Radar Topography Mission imagery (SRTM), both of path 190 and row 055, were used for the purpose of this study. A total of 138 lineaments of total length of 147.948 Km, were automatically extracted from both data. Rose diagram showed that the lineaments are bi-directional, with major lineaments trending NE-SW, E-W and the subsidiary ones in the NW-SE direction. These lineaments are mostly mapped on the schistose quartzites. Also, N-S trending faults were mapped from the Digital Elevation Model map generated from the SRTM data which was confirmed to be reverse fault based on field studies. The mineral alteration map generated revealed signatures of gold, iron oxides and silica minerals, while the mineralization potential map was done with reference to established geological settings of the area in conjunction with the structural elements such as folds, faults, joints and fractures mapped and measured on the field. These structures are typical of gold mineralization and associated metallic minerals in the Ilesha schist belt. This study also confirmed that mineralization in the study area is structurally controlled and type of mineralization is epigenetic in nature as a result of favorable ground preparation.

Airborne and ground geophysical evaluation of potential mineralized zone in parts of Ilesha schist belt, southwestern Nigeria

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.

Aeromagnetic and electrical resistivity mapping for groundwater development around Ilesha schist belt, southwestern Nigeria

Aeromagnetic and vertical electrical sounding around Ijano, southwestern Nigeria, was investigated for groundwater potential. Aeromagnetic dataset and vertical electrical sounding were acquired and used to investigate the study area. Oasis Montaj, Microsoft Excel and Arc GIS were used to present the results in maps, images and profiles. In order to map out the geological structures of the study area, magnetic image enhancing filters applied to the total magnetic intensity using Geosoft (Oasis Montaj) are reduction to equator, vertical derivative, total horizontal derivative and upward continuation. These filters helped define the lithological boundaries, geological structures, faults, folds and contacts. The lineament of aeromagnetic map was generated from derived field intensity gradients and solutions of Euler deconvolution carried out on the aeromagnetic data using structural index of 0.5 and 1. The processed image shows the lineaments trends majorly towards NE–SW directions. From these combined results of the study area, consistent aeromagnetic lineament map was generated showing the probable positions and trends of the suspected fractured/faulted zone as well as other basement structures. Hydro-lineament density maps based on lineament were produced from the generalized structure trends in the area. The result from the depth sounding data interpretation indicates three curve types which are H, HA and KH, where curve type H has the highest occurrence. The results from the vertical electrical sounding data revealed that the areas with the highest hydro-lineament density are good for groundwater prospect and development. The study has led to the delineation of areas where groundwater occurrences are most promising for sustainable supply, suggesting that an area with high concentrations of lineament density has a high tendency for groundwater prospecting. The results from the study show that the aeromagnetic technique is capable of extracting lineament trends in an inaccessible tropical forest.

Mineralisation potential assessment using analytical hierarchy process (AHP) modeling technique: A case study of Ilesha schist belt, southwestern Nigeria

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.

Integrated geophysical investigation of the mode of occurrence of mineralisation in part of Ilesha Schist Belt, Southwestern Nigeria

Integrated geophysical investigation of the mode of occurrence of mineralisation in part of Ilesha Schist Belt, Southwestern Nigeria

Pan African Nappe system: evidence of thrust structures from Okemesi, southwestern Nigeria

The Okemesi area, southwestern Nigeria, is part of the Ilesha schist belt and play host to the Okemesi fold belt and the Ifewara Shear Zone. Nappe structures had been proposed for some parts of Southwestern Nigeria without very clear meso or micro structural evidence. This study provides a lot of new structural evidences to substantiate the inferred Nappe structures within the Okemesi fold belt. Mapping of the Okemesi fold has been hampered by thick vegetation in the past. However, a major deformation zone was exposed by the recent landslide activities in the area, structures and lithologies exposed by the landslide were studied and structural features that are typical of transtensional and transpressional settings were observed. This paper presents the result of the systematic filed mapping which revealed the complete, fold transposition, elements of internal strain such as cleavages and mineral lineation, intrafolial folds, flexure slip, sheath, recumbent and conjugate kink folds, winged porphyroblast, faults (low angle reverse faults, dextral faults, normal faults), ramp and flat structures, etc. The characteristics and the geometry of the observed thrust structures make it an important piece of evidence, not only to infer the tectonic events in the area, but also to constrain the timing and nature of movement associated with thrusting in the area.

Structural mapping and gold mineralisation potential evaluation from airborne time – domain electromagnetic (TDEM) data of Ilesha Schist Belt, southwestern Nigeria

The airborne Time-domain electromagnetic data acquired over the Ilesha Schist Belt in southwestern Nigeria were filtered, enhanced and analysed to generate ground conductivity responses at different time gates and employed to characterise the subsurface in terms of rock distribution, structural framework as well as evaluate the gold and base metal mineralisation potential of the region. The near-surface sensitive early time gate conductivity responses (EMZ1 – EMZ3) indicate relatively high subsurface conductivity distribution (60–120 mS/m) in amphibole schist and pegmatite terrain in the west while medium to low-conductivity (<5 mS/m) values were recorded in the east underlain by granitic rocks. Major and minor linear/sub-linear conductive features having conductivity in excess of 2 mS/m and trending NE-SW, NNE-SSW, NNW-SSE and ENE-WSW directions were delineated on the mid conductivity time gate responses (EMZ3 – EMZ5). One of which presents geometry and pattern consistent with the well-reported Ifewara – Iwaraja fault system that runs through the entire Ilesha Schist Belt. Very high anomalous conductivity (160–300 mS/m) responses at late conductivity time gates (EMZ10 – EMZ13) with characteristic long decay curves were obtained over isolated zones, especially along fractures and veins suggesting the occurrence of structurally controlled gold and base metal mineralisation.

Mineralogy and Geochemistry of Hydrothermally altered Talcose rocks from Ila Orangun-Oyan areas, part of Southwestern Nigeria

Background/Objectives: Talcose rocks within Precambrian Basement Complex serve as relics of Archean greenstones. alterations associated with polycyclic-orogenies that affected this complex is studied to understand mineralogical and geochemical alterations. Methods: Five fresh samples of talcose rocks were collected during field mapping. These samples were cut into thin sections to reveal modal mineralogy, altered minerals and degree of alteration of such minerals. Mineral phase identification of the talcose rocks was conducted using X-ray Broker D8 ADVANCE diffractometer while whole rock analysis was carried out using Inductively Coupled Plasma Mass Spectrometry. Findings: Lithological relationship revealed from field evidence showed that the talc bodies occurred in close association with micaceous schist. The mineral assemblage of talc, tremolite, actinolite, chlorite and calcite suggest low grade greenschist metamorphic facies from possible hydrothermal alteration. Geochemical results revealed the following range of concentrations; SiO2 42.19-59.03%; Al2O3 1.1 - 11.8%; Fe2O3 7.64-9.56%; MgO 24.47-26.639%; Ni 594-1207ppm; Co 43.2-113.9ppm; Sn 6-41ppm; V 32-75ppm and Zr 1.3-58.7ppm, and these are typical of talcose rocks. Petrogenetic studies suggest a komatiitic origin with a peridotitic komatiite precursor for the talc-chlorite-tremolite schist. Enrichment in LREE, depletion in HREE and a negative Eu anomaly suggest alteration of the parent magma for the talcose rock and plagioclase fractionation. The trends observed for the LILE, HFSE and REE suggest possible contamination or mixing of crustal and mantle materials during the formation of the protolith. Ni and Co concentrations are higher than average crustal values with implication for ultrabasic to basic magma composition for the komatiitic progenitor and also suggestive of possible mineralisation. Conclusion: Mineralogical examination has revealed a talc-chlorite-tremolite composition for the talcose rocks with peridotitic komatiite precursory while geochemical composition supported ultrabasic magmatism similar to those with the Ilesha schist belt.

Application of electrical resistivity tomography for mapping gold mineralization potential in Iperindo, Ilesha schist belt, southwestern Nigeria

This study applied Electrical Resistivity Tomography geophysical investigation technique to evaluate the gold mineralization potential of Iperindo in Ilesha Schist Belt, southwestern Nigeria, where commercial exploitation capable of generating revenue and employment for the inhabitants has been challenged by lack / inadequate subsurface geological/geophysical information. The filtered and inverted electrical resistivity data acquired through five (5) 336 m long E – W trending profiles, established 10 m apart from each other, delineate isolated near surface but thick (&gt; 30 m) low resistivity zones, especially at the eastern and western ends of the study area. Some of the delineated low resistivity zones (3 – 200 𝛀m) present vertical sharp edges, likely created by vertical faults that flank the zones on both sides. The low resistivity of these zones could be attributed to the occurrence of conductive material such as gold and associated base metals which probably exist in pegmatitic veins within the zones.  Â

Understanding Precambrian Komatiite Petrochemistry from talc bodies within the Ilesha Schist belt, Southwestern Nigeria

The nature of parentage of talc bodies from the northern part of Ilesha schist belt was investigated and compared with altered ultramafic – Komatiite. Observations from thin sections revealed altered serpentine with included nodular olivines. Talc, chlorite and tremolite were other minerals present. Geochemical analysis of five (5) rock samples taken from talc bodies outcropped from both sides of the Ifewara Shear Zone (ISZ) revealed magnesia (MgO) > 18% and Al2 O3 /TiO2 values ~ 40. MgO values ranged from 23.01 – 32.79 wt. %. Al2 O3 and TiO2 values averaged 2.34 and 0.04wt. % respectively. Mg# values (87.93 – 90.71) supported ultramafic precursor. Major oxide variation plots against magnesia revealed negative correlation in Al2 O3 TiO2 vs MgO. Co, V, Ni and Cu concentrations were significantly higher than the incompatible elements. Maximum Ni and Co values were 1765.10 ppm and 108.60 ppm respectively. The rare earth element (REE) concentrations showed relative enrichment in light rare earth element (LREE). The values of Gd/Yb(N) ranges from 0.94 – 1.86. The Gd/Yb(N) and Al2 O3 /TiO2 suggested that the precursor to the talc bodies were possible Gorgona group IIItype komatiite. Plot of V vs Ti indicated an Island arc environment for the emplacement of these talc bodies.Keywords: Gorgona-type-Komatiite, Talc-bodies, ISZ, Serpentine, Magnesia

Geochemical characterization of soil samples from gold mining areas using PIXE spectroscopy.

Particle-induced x-ray emission (PIXE) spectroscopy has been used to characterize soil samples from two relatively old gold mine sites (Iperindo and Itagunmodi) in the Ilesha schist belt of Southwestern Nigeria. This is with a view to identifying the indicator or pathfinder elements of gold for fingerprinting and toxicity potential assessment purposes. Average elemental concentrations of 19 major, minor, and trace elements were determined, and the geochemical data of Mn, Ni, Cu, Zn, Ag, As, Pb, and Au together with multivariate factor and cluster statistical analyses allowed to identify As and Ag as the pathfinder elements of gold. The high concentration of the determined pathfinder elements (As and Ag) as well as other toxic metals (Pb and Cu) implies a relatively high metal contamination risk to the miners and the ecosystem. The major hazard is represented by the abandoned mining wastes, pits, and ponds, already serving as fish ponds.