Basement Complex Of Nigeria Research Articles

Distribution and Economic Potential of Manganese Deposits in Nigeria: A Review

The Northern basement complex of Nigeria contains a large number of manganese deposits. So far, ten deposits of manganese have been reported by previous workers. These deposits occur within Precambrian metasediments (schist belt), mafic and ultramafic rocks which are Proterozoic in age and folded into synclinorial belts within the crystalline basement complex. Considering their widespread distribution in space, time and tectonic setting, some are considered to be of ensilalic mode of evolution while others are ensimatic. However, the mineralizations are mostly of poor grade, and thus require beneficiation processing. The local steel industries within the country have continued to depend on manganese ore. No satisfactory substitute for manganese in steel production has been identified as at present. The applications of manganese deposits by geologists, chemical and environmental engineers, ceramicists, soil scientists and microbiologists shows a bright future for manganese ore in Nigeria. The ever increasing demand for steel products has continued to put pressure on Federal Government of Nigeria to complete the construction work at the nation’s steel producing plant which, will result in the need for a manganese concentrates for economic growth and development.

Geochemical characterization of Granitoids in Katchuan Irruan area: further evidence for peraluminous and shoshonitic compositions and post-collisional setting of granitic rocks in the Precambrian Basement Complex of Nigeria

Petrographic studies on Granitoids from Katchuan Irruan and adjoining areas, southeastern Nigeria, has shown that they are garnetiferous biotite granite, aplitic granite, porphyritic hornblende biotite granite, porphyritic muscovite biotite granite, weakly foliated leucogranodiorite and simple pegmatite. They are closely associated with the Precambrian Basement Complex rocks which they intruded. Modal analysis shows that the rocks consist of quartz (10%–25%), oligoclase (10%–30%), K-feldspar (15%–35%), biotite (3%–25%), with occasional garnet, hornblende, muscovite, and accessory chlorite, haematite and magnetite. Geochemical data indicates that the rocks are generally shoshonitic, alkali-calcic to calcic, ferroan and peraluminous. They are enriched in large ion lithophile elements as well as high field strength elements (Hf, Ta, Yb, Sm, Zr and Y). Their trace elements and REE patterns are similar, indicating that they are co-genetic. They are characterized by high fractionation factor (La/Yb)N (3.04–228.44) and pronounced negative Eu anomalies (Eu/Eu*) (0.23–0.71). Their overall geochemical features indicate that they were most likely derived from partial melting of crustal materials in an orogenic (post-collisional) tectonic setting. They are therefore related to the Pan-African granites, otherwise known as the Older Granites which were emplaced during the Pan African orogenic event.

Tectonic and structural analysis of the Migmatite–Gneiss–Quartzite complex of Ilorin area from aeromagnetic data

ABSTRACTIn an effort to have better understanding of the geologic settings and structural disposition of the Nigerian basement rocks, Ilorin area, a notably complex region within the South-western Basement Complex of Nigeria was studied using aeromagnetic data so that existing knowledge on the geology of the area can be appraised and updated. The aeromagnetic data was enhanced using various techniques which include the Total Horizontal Derivative (THD), Standard Euler Deconvolution, Tilt Derivative and Spectral Analysis. Striking features observed over the Residual Magnetic Field map were NE-SW trending anomalies aligned diagonally and running from the SW to the NE, forming a band having a width of between 16,000 and 20,000 m that coincided with the Banded Gneiss region on the geologic map; conspicuous E-W trending magnetic low whose location lies very close to the boundary between Migmatite and Banded Gneiss; and a ring-like magnetic low occurring in the south-eastern part of the residual map with no surface expression on the geologic map. Residual Magnetic Field values ranged from +157 to −202 nT. The THD map showed that the Banded Gneiss was the most deformed unit within the Migmatite–Gneiss–Quartzite complex. Major fractures coincident with Banded Gneiss boundaries appeared to be possible channels from which heat was leached in the regional system during metamorphism such that the Banded Gneiss region attained a relatively lower grade metamorphism than the Migmatite sharing boundary with it. Result from the spectral analysis showed that the magnetic basement in the eastern region was downthrown abruptly relative to that in the western portion. The abruptness was interpreted to mean that such subsidence was fault controlled. The study concluded that the presence of major fractures interfering with metamorphic processes in a regional settings may influence the grades of metamorphism that may result; that the schist region in the study area could be overlying a region of downthrown bedrock; and that the stress pattern that defined the crustal deformation pattern at the near crust in the past had changed compared to the currently dominant pattern.

Petrographic and structural analysis of exposed rocks of Musawa Sheet 56, Northwestern Nigeria

This work is among the few studies conducted in Musawa sheet 56 NE, which is part of the basement complex rocks of TudunWulli - Kankia area. The study area lies between Latitude 12º 19ʹ 00ʹʹ to 12º 23ʹ 00ʹʹN and longitude 7º 42ʹ 00ʹʹ to 7º 46ʹ 00ʹʹN. Due to the continuous play of geologic processes on the earth, there is the need to continuously update the geology of the Nigeria basement complex as this has a very important economic implication especially in areas like mineral and groundwater exploration. Equally, less attention has been given to this sheet unlike other sheets within the zone. The study done in this area has revealed the various rock types and their geological characteristics: field relation, macroscopic and microscopic features as well as structural elements. Results from the study shows that the area consists of granite, migmatite- gneiss and quartzite which all display a variety of colors, textures and mineralogy. Careful analysis of the distinctive mineralogy, textures, optical and structural characteristics led to the nomenclature of the rocks. The migmatite-gneiss display two petrographic varieties base on their foliation: one with linear foliation of alternating light and dark color minerals, and the other with wave like foliation. While granite is generally fine to medium grained in texture. The dominant structural trend of joints and faults in the study area are NNE-SSW and NW-SE. All these trends are consistent with the general trends of the Nigeria basement rocks. A study of thin sections of the rocks under a petrological microscope reveals optical properties peculiar to each rock type. The type and nature of structural elements associated with the rocks together with their geometry reveal that the rocks have undergone more than one deformational event. The occurrence of numerous brittle and ductile structures shows that the area has a great potential for groundwater and mineralization. But the area still experience shortage of water for domestic purposes.Keywords: basement complex, brittle structures, foliation, petrographic varieties, thin sections

Regional Structural Architecture of Part of Northern Nigeria Basement Complex inferred from Upward Continuation of Magnetic Field Intensity Data

2–D upward continuation of total magnetic field intensity data at Katsina area Northern Nigeria Basement Complex, aimed at identifying major regional features, has been carried out and interpreted in this study. The significance is to update the existing geology map of Nigeria and to guide further exploration studies in the area. Data for six aeromagnetic field maps were merged to form the composite data. 2–D upward continuation at various planes of observation was applied to the gridded magnetic field intensity data after coordinates were first converted (from degrees to meters) to understate anomalies due to shallow features. The plane was 15 km above the ground level. The continuation results revealed a high magnetic region at center surrounded by low magnetic parts, especially at the southern part. Corroboration with geology suggested that the high magnetic region could be a central structural uplift of the bedrock, highly rich in magnetic minerals. The low magnetic area at southern part is interpreted as sedimentary deposit, extended from the prominent Bornu Basin. The south – eastern part of the study area is moderately magnetic in nature, and corresponds to the metamorphic rocks of the Kazaure schist belt.

Forward and Inverse Modeling of Hand Digitized Aeromagnetic Data from Ilesha South West, Nigeria

Results of aeromagnetic data interpretation of Ilesha SW, Nigeria are presented here. The geology of Ilesha which is Precambrian falls under the basement complex of Nigeria. Depths to source rocks in this area are expected to be shallow. The results obtained revealed the presence of rocks such as amphibolites, quartz and schist which are the common rock types present in the study area. An aeromagnetic map of scale 1:50,000 was hand digitized, while forward and inverse modeling was achieved via the use of Potent, version 4.10.02. The field data were qualitatively and quantitatively interpreted and results showed NE-SW trending of the fault zone in the study area and anomalous bodies whose total magnetic intensity ranges from a minimum negative peak value of -625.5 nT to a maximum positive peak value of 179.43 nT. The maximum depth to top of the magnetic source body obtained is 34.2 m and minimum depth is 0.5 m. The results obtained indicate shallow depths to magnetic anomalies, as expected in most areas of the basement complex of Nigeria.

Integrating aeromagnetic and Landsat™ 8 data into subsurface structural mapping of Precambrian basement complex

The integration of Aeromagnetic data and remotely sensed imagery with the intents of mapping the subsurface geological structures in part of the South-western basement complex of Nigeria was developed using the PCI Geomatica Software. 2013. The data obtained from the Nigerian Geological Survey Agency; was corrected using Regional Residual Separation of the Total Magnetic field anomalies enhanced, and International Geomagnetic Reference Field removed. The principal objective of this study is, therefore, to introduce a rapid and efficient method of subsurface structural depth estimate and structural index evaluation through the incorporation of the Euler Deconvolution technique into PCI Geomatica 2013 to prospect for subsurface geological structures. The shape and depth of burial helped to define these structures from the regional aeromagnetic map. The method enabled various structural indices to be automatically delineated for an index of between 0.5 SI and 3.0 SI at a maximum depth of 1.1 km that clearly showed the best depths estimate for all the structural indices. The results delineate two major magnetic belts in the area; the first belt shows an elongated ridge-like structure trending mostly along the NorthNortheast-SouthSouthwest and the other anomalies trends primarily in the Northeast, Northwest, Northeast-Southwest parts of the study area that could be attributed to basement complex granitic intrusions from the tectonic history of the area. The majority of the second structures showed various linear structures different from the first structure. Basically, a significant offset was delineated at the core segment of the study area, suggesting a major subsurface geological feature that controls mineralisation in this area.

Sedimentological Study and Heavy Mineral Analysis of Sediment Samples from Well-S, Niger Delta, Nigeria

Sedimentological study and petrographic analyses were carried out on thirty ditch cutting samples from well-S, Niger Delta, Nigeria, with the aim of determining the provenance and depositional environment of the sediments. The samples were subjected to soxhlet extraction for the removal of soluble organic matter from them and particle size analyses using Pipette and Emery sedimentation techniques in order to determine the grain size distribution of the sediments. Separation of heavy of mineral from the samples was done with the aid of bromoform to enable petrographic analyses of the heavy mineral suite, under the polarising microscope. The data obtained from the grain size analysis were used in preparing histograms, from which some simple statistical parameters were derived. Graphic mean values obtained range between 0.74 and 2.64 O, which implies that the sediments are predominantly fine-medium grained. The inclusive standard deviation values ranges from 0.53 to 1.24 O, indicating that the sediments are moderately well sorted to moderately sorted. Inclusive graphic skewness values of 0.29 to 0.70 indicate that the sediments ranges from finely skewed to strongly finely skewed and the graphic kurtosis values of 0.61 to 1.54 shows that the sediments are predominately very platykurtic which implies a low energy environment of deposition. The polymodal nature displayed by the histograms indicates that the sediments have been derived from various sources. The study concluded that the sediments were deposited in a fluvial environment. It also established that the sediments originate from metamorphic and acid igneous rocks of the Nigeria Basement Complex and mineralogically mature to sub-mature.

Crustal structure of Nigeria and Southern Ghana, West Africa from P-wave receiver functions

We report new estimates of crustal thickness (Moho depth), Poisson's ratio and shear-wave velocities for eleven broadband seismological stations in Nigeria and Ghana. Data used for this study came from teleseismic earthquakes recorded at epicentral distances between 30° and 95° and with moment magnitudes greater than or equal to 5.5. P-wave receiver functions were modeled using the Moho Ps arrival times, H–k stacking, and joint inversion of receiver functions and Rayleigh wave group velocities. The average crustal thickness of the stations in the Neoproterozoic basement complex of Nigeria is 36km, and 23km for the stations in the Cretaceous Benue Trough. The crustal structure of the Paleoproterozoic Birimian Terrain, and Neoproterozoic Dahomeyan Terrain and Togo Structural Unit in southern Ghana is similar, with an average Moho depth of 44km. Poisson's ratios for all the stations range from 0.24 to 0.26, indicating a bulk felsic to intermediate crustal composition. The crustal structure of the basement complex in Nigeria is similar to the average crustal structure of Neoproterozoic terrains in other parts of Africa, but the two Neoproterozoic terrains in southern Ghana have a thicker crust with a thick mafic lower crust, ranging in thickness from 12 to 17km. Both the thicker crust and thick mafic lower crustal section are consistent with many Precambrian suture zones, and thus we suggest that both features are relict from the collisional event during the formation of Gondwana.

Evaluation of Resistivity Anisotropy of Parts of Ijebu Igbo, Southwestern, Nigeria Using Azimuthal Resistivity Survey (ARS) Method

This study was carried out to determine the anisotropic properties of parts of the Southwestern Basement Complex of Nigeria in Ijebu Igbo, which is underlain by migmatite gneiss and older granites.The surface water level (SWL) of 107 hand-dug wells were measured to determine the groundwater flow direction of the area. Thirty Azimuthal Resistivity Survey (ARS) were investigated along four azimuths; 0°, 45°, 90°, and 135° to determine the electrical anisotropy, the trend of fractures and their behavioural pattern with depth. The quantitative interpretation of the Radial Vertical Electrical Sounding (RVES) curves involved the use of partial curve matching, and computer iteration using WINRESIST program ...

Preliminary Investigation of Stream Sediments Contaminations Caused by Mining Activities in Ibodi and Its Environs, S/W Nigeria Using Geological and Geochemical Assessment Approach

Mining and related activities are sources of heavy metal contamination in streams, such as copper, zinc, cadmium, arsenic and lead . The study is focused on Ibodi, southwestern Nigeria which is located in the basement complex of Nigeria and it is to assess the stream sediments of Ibodi in order to decipher the environmental impact assessment of mining activities on the environment. A total of ten stream sediment were collected from the study area and its environs along major tributaries, air dried at room temperature, sieved with 75 micron sized sieve and analyzed in the laboratory using ICP-MS (inductively couple plasma mass spectrometry technique). The analytical results of the major elements analyses show that Iron oxide [Fe2O3] has the highest major element composition, value ranging from 2.36% - 10.61% with an average value of 5.262%. This highest concentration of Iron oxide was found in location 1, with a value of 10.61% and this can be attributed to the underlying geology of amphibolites' in the Ibodi study area, which are known to be rich in Iron as well as magnesium i.e ferromagnesian minerals. Magnesium oxide [MgO] range in composition from 0.11% - 0.92% with an average value of 0.349%, the highest concentration was found in location 3. [Al2O3] ranges in composition from 0.83% - 4.158% with an average value of 2.109% the highest value was also found at location 3, it is the next in abundance to Iron oxide in the Ibodi study area. Potassium oxide [K2O] range in composition from 0.04% - 0.65% with an average value of 0.183%, other major oxides such as [P2O5], [TiO2], [Na2O] and [CaO] have average values of 0.109%, 0.096%,0.008% and 0.162% respectively; These values are generally low within the Ibodi study area, The analytical results for trace element geochemistry of Ibodi study area show that Vanadium [V] has a high concentrations and it range from 35.00 ppm - 202.00 ppm with an average mean value of 92.50 ppm, the highest concentration of this element was found in location 1 of the Ibodi study area. Arsenic [As] range from 0.10 ppm - 1.6 ppm with an average value of 0.644 ppm, there is a significant enrichment of Cobalt [Co] and Chromium [Cr] with concentrations ranging from 4.0 ppm - 53.50 ppm and 35.20 ppm -150.70 ppm respectively, with average mean values of 17.73 ppm and 88.78 ppm respectively; Manganese [Mn] has the highest concentration in the study area, with concentration value ranging from 86.00 ppm - 2165.00 ppm having an average value of 768.20 ppm; the highest concentration of this element was found in location 1 of the study area. [Ga], [Ni] and [Pb] show considerable enrichments within the study area with concentration values ranging from 3.10 ppm - 9.50 ppm, 5.30 ppm - 37.70 ppm and 6.75 ppm - 18.44 ppm, with average values of 6.08 ppm,19.80 ppm, 12.209 ppm respectively, Rubidium [Rb] range in concentration from 6.50 ppm - 30.90 ppm with an average value of 13.41 ppm, Strontium [Sr] has concentration values that range from 4.70 ppm - 37.20 ppm with an average value of 15.06 ppm. [Y], [Zr] and [Zn] has concentration values that range from 7.99 ppm - 21.10 ppm, 1.20 ppm - 4.00 ppm and 26.20 ppm-83.60 ppm respectively with average mean values of 15.065 ppm, 2.21 ppm and 46.58 ppm, the value of zinc [Zn] is considerably high in the study area with the highest value found at location 4 of the study area indicating some level of enrichment of this metals within the study area, also [Rb], [Y] and [Sr] show some considerable enrichments within the study area. from the study of the environmental parameter such as box plot and Geo-accumulation indexes the values of the selected trace elements are all less than 1, meaning that all the selected trace metals in Ibodi study area have values less than zero and are in the negative zone. In order to determine the pollution status of the study area, the values of the elements when compared to the Muller classes of geo-accumulation suggests that the study area is practically uncontaminated with the selected trace metals, the elements fall into the class 0 i.e. Practically unpolluted.

Spectral analysis of aeromagnetic data for geothermal energy investigation of Ikogosi Warm Spring - Ekiti State, southwestern Nigeria

Aeromagnetic data of the Ikogosi warm spring region was used to calculate the basal depth of the magnetic layer (Curie point depth) in the region. The warm spring issues from a crossing of fractures from a metasedimentary suite of Effon Psammite formation which form part of the Precambrian basement complex in Nigeria. The adopted computational method transforms the spatial data into the frequency domain and provides a relationship between radially average power spectrum of the magnetic anomalies and the depths to the respective sources. Heat flow density and equivalent depth extent of heat production from radioactive isotopes in the area were also evaluated. The average Curie point depth for the Ikogosi warm spring area is 15.1 ± 0.6 km and centres on the host quartzite rock unit. The computed equivalent depth extent of heat production provides a depth value (14.5 km) which falls within the Curie point depth margin and could indicate change in mineralogy. The low Curie point depth observed at the warm spring source is attributed to magmatic intrusions at depth. This is also evident from the visible older granite intrusion at Ikere - Ado-Ekiti area, with shallow Curie depths (12.37 ± 0.73 km). Results indicate that the area is promising for further geothermal explorations.

Geophysical Investigation of Shallow Subsurface Fracture Distribution in Parts of the Eastern Basement Complex of Nigeria

Very low frequency electromagnetic method was carried out at twenty three (23) locations within Parts of the Eastern Basement Complex of Nigeria. The field data were collected using ABEM Wadi VLF (very low frequency) electromagnetic instrument with other accessories. A transmitter located at Cutler, Maine USA, designated as NAA with 24.0 KHz frequency and 1000Kw transmission power was used throughout the data collection exercise. The profiles were of lengths between 120m and 650m. The station interval along each profile was 5m with profile lines oriented in N–S, and E–W directions. Data were analyzed using KHFFILT software. The results of the study showed that majority of the fractures were oriented in the NE – SW direction, followed by fractures oriented in the NW – SE direction indicating that the study area is well fractured and has good potentials for ground water. Key word: ABEM Wadi, Basement, fracture, groundwater, Very low frequency.

Integrated geoelectrical and structural studies for groundwater investigation in parts of Abuja, North Central Nigeria

ABSTRACTAbuja, the capital city of Nigeria, West Africa, is underlain by Precambrian basement rocks consisting mainly of porphyroblastic gneisses, granitic‐gneisses, migmatitic gneisses, amphibolites, Pan‐African granites and undifferentiated schists. The geology of Abuja, therefore, makes the groundwater conditions in the area very unpredictable. Geophysical surveys were carried out at 12 locations within and around the Gosa area and the results integrated with 88 lineament (fractures) extracted from hill‐shaded Shuttle Radar Topography Mission (SRTM) data. The dominant fracture trend for the area is NNE–SSW and N–S, which corresponds to the Pan‐African trends in the basement complex of Nigeria. It is observed that in the Gosa area, whereas fractures exist, they do not possess sufficient interconnectivity; this may have adversely affected the permeability of the fractured zone, resulting in the incidence of dry wells in the area. Moreover, evidence from interpreted two‐dimensional (2D) geoelectric sections reveals that in some parts of Abuja, the weathered overburden is not thick enough to support sufficient yield for a viable borehole. Interconnected fractures therefore become the desirable structural feature capable of improving the aquifer potential. This study demonstrates the usefulness of integrating conventional vertical electrical sounding (VES) surveys with structural data derived from enhanced SRTM imagery in a hydrologically complicated terrain.

Geophysical Evaluation of Magnetic Data of Okenugbo Area, Ago-Iwoye, Southwestern Nigeria

The results of a magnetic study of the Okenugbo Area of Ago-Iwoye, Southwestern Nigeria are presented for the evaluation of the geostructural settings in the area to determine the competency of the basement for building constructions. The study area lies within Longitude N 06°55.389’ - N 06°55.384’ and Latitude E 03°55.001’ and E 03°55.959’ in the basement complex of Nigeria. Three magnetic profiles were established for the evaluation and the magnetic anomaly map, the regional geology and its analytic signal amplitude helped in identifying the nature and depth of the magnetic sources in the study region. The magnetic residual values range from -2400 nT to +1800 nT. The area shows magnetic closures of various sizes at the Western part of the study area trending West with prominence at the center and distributed East-West which has been interpreted as fractured or faulted zones. The depth estimate revealed the apparent depth to the causative body from the surface and the basement depth range from 4.3 to 21.3 m which agrees with other literatures. The study has revealed that the area is generally competent for high rise structures and industrial site while the faulted/fractured zones are prospective better locations for hydrogeological purposes.

Geophysical Evaluation of Magnetic Data of Okenugbo Area, Ago-Iwoye, Southwestern Nigeria

The results of a magnetic study of the Okenugbo Area of Ago-Iwoye, Southwestern Nigeria are presented for the evaluation of the geostructural settings in the area to determine the competency of the basement for building constructions. The study area lies within Longitude N 06°55.389’ - N 06°55.384’ and Latitude E 03°55.001’ and E 03°55.959’ in the basement complex of Nigeria. Three magnetic profiles were established for the evaluation and the magnetic anomaly map, the regional geology and its analytic signal amplitude helped in identifying the nature and depth of the magnetic sources in the study region. The magnetic residual values range from -2400 nT to +1800 nT. The area shows magnetic closures of various sizes at the Western part of the study area trending West with prominence at the center and distributed East-West which has been interpreted as fractured or faulted zones. The depth estimate revealed the apparent depth to the causative body from the surface and the basement depth range from 4.3 to 21.3 m which agrees with other literatures. The study has revealed that the area is generally competent for high rise structures and industrial site while the faulted/fractured zones are prospective better locations for hydrogeological purposes.

Geophysical Evaluation of Magnetic Data of Okenugbo Area, Ago - Iwoye, Southwestern, Nigeria

The results of a magnetic study of the Okenugbo Area of Ago-Iwoye, Southwestern Nigeria are presented for the evaluation of the geostructural settings in the area to determine the competency of the basement for building constructions. The study area lies within Longitude N06°55.389̕-N06°55.384̕ and Latitude E003°55.001̕ and E003°54.959̕ in the basement complex of Nigeria. Three magnetic profiles were established for the evaluation and the magnetic anomaly map, the regional geology and its analytic signal amplitude helped in identifying the nature and depth of the magnetic sources in the study region. The magnetic residual values range from -2400 nT to +1800 nT. The area shows magnetic closures of various sizes at the Western part of the study area trending West with prominence at the center and distributed East-West which has been interpreted as fractured or faulted zones. The depth estimate revealed the apparent depth to the causative body from the surface and the basement depth range from 4.3 to 21.3 m which agrees with other literatures. The study has revealed that the area is generally competent for high rise structures and industrial site while the faulted/fractured zones are prospective better locations for hydrogeological purposes. DOI: 10.5901/ajis.2013.v2n10p179

Natural radioactivity in some rocks employed as dimension and decorative stones in the Nigerian building industry

The natural radioactivity in some selected granites and allied rocks from the Basement Complex of Nigeria for use as dimension/decorative stones was measured by gamma-ray spectrometry. The average activity concentrations observed for the selected rock samples range from 9 to 124 Bq kg⁻¹; 13 to 60 Bq kg⁻¹ and 1360 to 2326 Bq kg⁻¹ for ²²⁶Ra, ²³²Th and ⁴⁰K, respectively. The mean radiological hazard indices were 121.62 nGy h⁻¹; 239.73 Bq kg⁻¹; 0.65 Bq kg⁻¹ and 0.77 Bq kg⁻¹ for the absorbed dose rate, radium equivalent, external hazard and internal hazard, respectively. The results obtained were examined on the basis of existing International recommended limits and compared with data on similar rocks from other parts of the world. The values obtained for the rocks, except one, were found to be lower than the values recommended for building materials, and the rocks are considered safe for use as decorative stones as defined by OECD criteria (NEA-OCED Nuclear Energy Agency Dose Constraints in Optimisation of Occupational Radiological Protection Report by NEA Group Experts, OCED, France (2011)). Results highlight the fact that, despite meeting certain suitability criteria such as colour, texture, etc., the radioactivity content of the rocks is another factor of importance for their continued application in the human environment/building industry.

Petrographic and Structural Analysis of Exposed Rocks of Bishini Sheet (Block 2), North Central Nigeria

This study is the second of a series of work to be done on Bishini Sheet 165 SW, which is part of the basement complex of the Kushiriki-Minna area. The area lies between latitudes 9°34? N and 9°40? N and longitudes 7°00? E and 7°08? E. Due to the continuous play of geologic processes on the earth, there is the need to continuously update the geology of the Nigeria basement complex as this has a very important economic implication in areas like mineral and water exploration. Equally, less attention has been given to this sheet unlike other sheets within the zone. The study of the block has revealed the various rock types and their geological characteristics: field relation, macroscopic and microscopic features and structural elements. Results from the field shows that the block consists of migmatites, gneisses, schists and granites which all show a variety of colours, textures and mineralogy. The displacement of distinctive mineralogy, textures, optical and structural characteristics led to the nomenclature of the rocks. The granitic rocks displayed two petrographic varieties based on their textures. These are the fine-medium grained and coarse porphyritic varieties. The granitic rocks have greatly intruded other rocks and this is thought to be responsible for gold mineralization in the area, The NNE-SSW and the NNW-SSE are the major structural trends determined for the joints and faults while the minor ones are the NE-SW and NW-SE. All these trends are consistent with the general trends of the Nigeria basement rocks. A study of thin sections of the rocks under a petrological microscope reveals characteristic optical properties peculiar to each rock type. The type and nature of the minerals the rocks contain together with their geometry reveal that the rocks have undergone more than one deformational event since the time of their formation. The occurrence of numerous fractures (joints and faults) shows that the area has a great potential for water and mineral exploration.

Geology and Economic Evaluation of Odobola, Ogodo Feldspar Mineral Deposit, Ajaokuta Local Government Area, Kogi State, Nigeria

The Odobola, Ogodo area is part of the basement complex of Nigeria and is underlain mainly by schists and intrusive granitic and pegmatitic rocks along with sediments weathered from these rocks. The granitic and pegmatitic intrusives are source of feldspar with a significant K2O component (k-feldspar). A study of the area reveals the occurrence of feldspar deposit hosted by granitic and pegmatitic intrusives. Geochemical data for the feldspar samples show average Si2O, Al2O, K2O, Na2O, CaO, Fe2O3, MgO and TiO2 contents of 65.81wt%, 16.67wt%, 10.67wt%, 5.83wt%, 0.02wt%, 0.26wt%, 0.5wt% and < 0.001wt% respectively while mineralogical results reveals average anorthite, orthoclase and albite contents of 0.42%, 85.40% and 14.06% respectively. The results of the analyses compared with those of the British international Standard (BIS) shows that the feldspar deposit can be used in industries such as glass, ceramic tiles, sanitary wares and insulators. Field and petrographic evidence show that the area is a potential source of gemstones such as tourmaline and tantalite. Mineral Resource and Reserve Estimation classify the feldspar resource as an estimated proven feldspar-bearing Reserve of about 119Million tons. Apart from feldspar, inferred Minerals Resource of quartz, tantalite and tourmaline can also be obtained from this area.