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The geologic investigations of rocks around Angwan Madaki and its evirons, North Central Nigeria

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The geologic investigations of rocks around Angwan Madaki and its environs, North Central Nigeria 1Ekeleme I.A., 2Uzoegbu M.U., 3Olorunyomi A.E. and 4Abalaka I.E. 1,3,4 Department of Geology, University of Jos, Plateau State. 2 Department of Geology, Michael Okpara University of Agriculture, Umudike.

The studied area lies within Latitude 8⁰41'40''N and 8⁰52'40''N and Longitude 8⁰41'10''E and 8⁰45'10''E within the North Central Nigerian Precambrian Basement Complex. It is bordered by Angwan Mission in the North, Konva in the West, River Arikiya in the South and Farin Ruwa in the south East. The rock types include the Precambrian gneisses; granite and porphyroblastic gneiss, banded gneiss and migmatites with characteristic pegmatites and vein intrusions. These rocks experienced various tectonic episodes which resulted to their different structural styles such as mineral lineation, foliation, jointing, veins, faults, dykes and minor folds. The geological mapping of the area reveals five (5) dominant lithologic units namely; migmatites, banded gneiss, granite and porphyroblastic gneiss, older granites and dolerite respectively. Systematic structural mapping of the area also confirmed the preponderance of different folds such as crenulation fold and ptygmatitic fold. Other structures such as dykes, joints, quartz-veins, fractures and micro-faults were detected on the rocks. The overall result showed that the studied area is a manifestation of Pan African deformation as revealed by the magnitude and style of the folding and other structural features of rocks in the area. Petrographic studies also reveal the mineral assemblages and structural features that were key in identifying these rock types.

Key words: Basement Complex, lithologic units, Petrography, Precambrian, Older granite, Structural styles. INTRODUCTION Nigeria lies to the rest of the West African Craton in the region of Late Precambrian to Early Paleozoic orogenesis. The Basement Complex is made up of Precambrian rocks and these rocks consist of the schist belt infolded (Rahaman, 1988). The Precambrian rocks in the study area are part of the Precambrian Basement Complex of Nigeria which is made up of the Migmatite-Gneiss Complex, the Schist Belts and the Granitoids. The study area is around Angwan Madaki and environs which lies within Latitude 8⁰52'40'' to 8⁰51'20'' and longitude 8⁰41'10'' to 8⁰45'10'' (Fig. 1). The main lithologic units in the study area include; migmatite, gneiss, granite and porphyroblastic gneiss, older granites and dolerite with well delineated geologic boundaries. These rocks have undergone polycyclic deformation thereby causing the deformation observed as both micro and macro structures displayed on the rocks exposed in the study

area. Geologic structures in rocks that can be used as clues in determining the geologic history of the area includes–fractures (i.e, faults and fold), foliation, dyke etc. Some of them are not deformational but are secondary structures developed during metamorphism or after the emplacement of the rocks (Rahaman, 1988). Representative rock types were sampled and analysed for petrographic studies.

*Corresponding Author: Dr. Uzoegbu M. Uche, Department of Geology, Michael Okpara University of Agriculture, Umudike, PMB. 7267, Umuahia, Abia State. E-mail: [email protected], Tel.: +234088030715958. Co-authors: +2348061398330; E-mail: [email protected], [email protected]

International Journal Geology and Mining Vol. 3(1), pp. 090-102, June, 2017. © www.premierpublishers.org. ISSN: 0907-3409x

Research Article

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Uzoegbu et al. 091

Studied location

Figure 1. Geologic map of Nigeria showing location of the study area (After Obaje, 2009).

This research was therefore necessitated for the detailed mapping and identification of the different rock units of the Basement Complex in the area being part of the Wamba sheet 210s as well as the need for detailed petrographic and structural analyses as a possible aid in the construction of the petrogenesis of the area. REGIONAL GEOLOGIC SETTING Many workers on a regional scale have carried out researches on the Basement Complex. Among these researchers is Falconer (1911), who first studied the Nigerian Basement Complex and distinguished the Younger Granite from the Older Granites. In one of the early records of the mineral survey, the occurrence of pegmatite cassiterite and columbite-tantalite was mentioned though not much attention was given to the pegmatite from which they were derived (Jacobson and Webb, 1946). Falconer (1911), gave brief accounts on the pegmatite fields of Wamba-Jema’a region of the Plateau Province and Kabba Province. Oyawoye (1964) classified the Basement rocks as Older Meta-sediments, which includes Gneiss, Migmatites and Older Granites and Younger Meta-sediments. In reviewing the Basement geology of the Precambrian to Lower Paleozoic rock of Northern Nigeria, Mc Curry (1976), recognized four major groups; i. An underlying high amphibolite facies complex of quartzo-felspathic biotite and hornblend gneiss,

migmatites and high grade metasedimentary relics comprising of older, metasediments. ii. A supracrustal cover of low to medium grade meta-sediments. iii. A suit of post syntectonic to late syntectonic granitoids, the older Granite intrudes the crystalline complex and the belts unto the younger metasediments. iv. Volcanic rocks belonging to the Post Pan-African (Older Granite) episode of high level magmatic activity. Oyawoye (1964), succeeded in subdividing the Basement Complex rocks into three major groups which he described as (a) the older meta-sediments, consisting of calc-silicate rocks. He considered this group as the oldest rocks of the Basement Complex. (b) The Gneisses, Migmatites and the Older Granites. In this group, two major types of gneisses were identified: the biotite gneiss and the banded gneiss. He also grouped the migmatites into two types, namely; the lit-par-lit gneiss and the migmatitic gneiss. On the basis of petrography, Oyawoye (1964) suggested that the gneisses and migmatites originated through silica-potash metasomatism. The Basement Complex rocks in the study area have received very little attention from researchers as evidenced in literature. Much of the information on the area is contained in Geological Maps of Nigeria produced by the Geological Survey of Nigeria (Okezie, 1974, Okezie, 1984, Ojo, 1994). The recent work done in parts of the studied area was by Anudu et al. (2012). These authors’ studies covered areas like Otagu, Angwan


Int. J. Geol. Min. 092 Mission, Okuso, Zamatak, Lange, Kangara, Mugu and Arikiya which bound the area of study. Their works were on a larger scale as against the present study whose focus is on a smaller scale. The Geological Map of Nigeria by Okezie (1974) shows that the Precambrian Basement Complex can be divided into two distinct zones, namely: a western zone in which the N-S trending elongate Schist belts are separated from one another by Migmatite Gneisses and Granites, and an eastern zone, comprising mainly Migmatite Gneisses and granites, in which the Schist belts are scarcely present. Cooray (1974) in further review added another family of rocks (the intrusive) to the works of Oyawoye (1964). He further effected some changes in the conclusions of Oyawoye (1964) such as (a) that the Older granites and related charnockitic rocks are of intrusive rather than metasomatic origin; (b) the Older granites and granodiorites based on the relative time of emplacements and deformation are subdivided into; syn-tectonic microcline-megacrystic, partly foliated granites and late- tectonic, less richly megacrystic, weakly foliated xenolithic granites and granodiorites with cross-cutting contacts and occasional thermal aureoles (McCurry and Wright, 1977; Jones and Hockey, 1964); (c) the north-south to northeast-southwest structural pattern in the Basement Complex has been pointed to have resulted from polyphase metamorphism which has affected the Basement Complex leaving an imprints of at least three plutonic events during the Eburnean, Kibaran and the Pan-African orogenic episodes (Grant, 1978). Rahaman (1976, 1988) and Rahaman and Ocan (1978) presented a more classical description of the rocks. Rahaman (1988) had described the rocks of the Schist belt as composed of predominantly metamorphosed pelitic to semi-pelitic rocks, granites, sandstones, polymeta- conglomerates, calcareous rocks, mafic to ultramafic rocks with minor amounts of greywacke and acid to intermediate volcanic rocks. Umeji and Caen-Vachette (1991) reported that the Basement Complex in the vicinity of Nassarawa-Eggon which is several kilometers North East of the study area contains granitic gneisses, gneissic granites and occasional lenses of amphibolites. They reported that the Pan-African tectonics imposed NE-SW to ENE-WSW trends on all the rocks and that the Basement Complex is locally sheared with a mylonitic shear zone (340m). The schist belts occupy N-S trending synformal troughs and such troughs have been identified and described (Ekwueme, 2003). According to Obiora (2005), the schistose components of the migmatitic terrain were designated, “the older meta-sediments” while the distinct N-S trending schist belts, which are clearly younger than the gneisses and migmatites were mapped as “the younger meta-sediments”. It is good to note that the Older Granites occur intricately in association with the Migmatite-Gneiss Complex and the Schist Belts into which they generally intruded. This means that the rocks

occur in most places where rocks of the Migmatite-Gneiss Complex or of the Schist Belt occur (Obaje, 2009). The Precambrian Basement Complex of Nigeria (Fig. 2) is exposed in five major locations, namely: Northeastern zone, Southwestern zone, Southeastern zone (extension of the Bamenda Massif into Nigeria), Northeastern zone (the Hawal massif) and South-southeastern (the Oban Massif) (Obiora, 2005). MATERIALS AND METHODOLOGY Field Description The rocks encountered on the field were systematically lumped into five different units as shown on the geologic map (Fig. 1). The rock types encountered within the area and its environs include; Migmatite-Gneiss, Porphyroblastic and banded Gneisses, Granite-Gneiss, Older Granites and Dolerites (Figs. 2-3). Representative samples of each of these were taken for petrographic analyses.

Figure 2. Banded Gneiss (x2)

Figure 3. Boulders of Older Granite (x2) Thin Sectioning Based on the field observations and megascopic studies of hand specimen of the different rock types in the area, each representative samples were selected and thin


Uzoegbu et al. 093 sections on gneiss, granitic-gneiss, granite, dolerite were prepared on rocks from different locations in the studied area at the University of Ibadan Laboratory (Figs 4-5).

Figure 4. Cross Polarized Light image of migmatite (x4).

Figure 5. Quartz at extinction (x4) RESULTS OF PETROGRAPHIC STUDIES Microscopic assessment of rocks in the area in both plane polarized and crossed polarized light revealed the presence of varying compositions of constituent minerals such plagioclase, quartz, muscovite, biotite, hornblende and opaque minerals. The petrographic descriptions are given below for the different rock types in the study area. Migmatite: The plagioclase in fig. 4 shows its polysynthetic twin property with low relief and interwoven into the other minerals. Colourless quartz with anhedral form which sometimes looks tabular were seen in the section. At extinction the quartz shows a bluish colouration which changes at the rotation of stages at different angles (i.e 20˚, 45˚, etc). Several biotites were seen with their distinctive brown colour and perfect cleavage on one side. Alteration of the biotites to a greenish mineral (i.e, chlorite) is a common feature on

most samples. It has a high relief and shows pleochroism and goes extinct at 48˚.Pinkish-green muscovite were observed which cleave together with the biotite (Table 1). Gneiss: Geneiss shows euhedral and anhedral crystals of mafic and felsic minerals. The dark coloured minerals are hornblende, biotite and some opaque minerals. The orientation of dark and light minerals defines the foliations and lineation in the rock. The rock shows a coarse grained texture due to development of mineral grains into well defined crystals though some have been deformed. Hornblende occurs as xenoblastic crystals, green in colour and shows pleochroism from yellowish green to dark green. It shows high relief and two directional cleavages which are lacking in some crystals. Plagioclase occurs as large crystals, colourless in PPl and anhedral in shape. The crystals are well developed with characteristic polysynthetic twinning. It shows moderate relief; poor cleavage traces and is non pleochroic. Microcline shows cross hatching. Biotite occurs as brownish coloured crystals poikiloblastic within the hornblende. It is anhedral in shape, exhibit pleochroic haloes, a very high relief, no cleavage and lacks twinning. It is tabular and anhedral in shape and does not exhibit pleochroism, exhibits high interference colour of yellow to brown. The quartz occurs as a colourless crystal with inclusions of unidentified minerals with low relief. Some other properties of the rocks as seen under the microscope are displayed in Table. 2 for the four photomicrograph. Structural Systems The study area is comprised of rocks of the Basement Complex which includes; pegmatites, quart-veins, older granite, granite-gneisses, migmatites and banded gneisses. Major rocks in this area had undergone various deformational episode evident from the nature and style of the structural elements such as mineral lineation, foliation, jointing, veins, faults, dykes and minor folds (Macledo et al., 1971; Leblanc, 1981; Fitches et al., 1985; Ajibade et al., 1987; Rahaman, 1988). Generally, the nature and extent of the structures depend on the duration and intensity of the deformation. The general trends of the structures are NNE-SSW, NW-SE, NE-SW and a few E-W. Examination of the various geological structures found in the study area was carried out using basic geological techniques of field mapping to determine the attitude of the structures. Rose plots were plotted using the data obtained in order to determine the trends of deformation on the rocks. Joints Joints are planes of parting in rocks which involves neither displacement nor infillings. Joints can form in both competent and incompetent rocks (Fitches et al., 1985;


Int. J. Geol. Min. 094

Table 1: Microscopic Description of Migmatite (IS-37). Quartz

(Qz) Biotite (Bi) Plagioclase (Pl) Muscovite

(Mu) Hornblende (H)

Colour Colourless Pale to deep greenish brown, or brown.

White to Grey Pink to Green Green

Relief Low Relief Med.-High Low- moderate Low Relief Moderate

Habit Anhedral Tabular, irregular

Tabular (anhedral and euhedral)

Anhedral Irregular

Cleavage None Perfect cleavage

perfect cleavage

1-perfect cleavage

2-perfect cleavage

Pleochroism None Pleochroic None None From green to brown

Alteration Not visible Alters to chlorite

Not visible None None

Birefringence 0.009 0.04-0.08 0.007-0.013 0.036-0.049 0.014-0.026

Interference Colour

1st order pale yellow

3rd to 4th order colour

1st order 2nd and 3rd order pinkish purple to green

2nd Order blue.

Extinction Undulose Parallel and shows birds eye texture.

Inclined Parallel to cleavage (birds eye texture)

Parallel to cleavage

Twinning None None Polysynthetic None Observed

Table 2: Microscopic Description of Gneiss (IS-20). Quartz

(Qz) Microcline (Mi)

Plagioclase (Pl) Muscovite (Mu)

Biotite (Bi) Hornblend(H)

Colour Colourles Colourless White to Grey Pink to Green Brown Green

Relief Low Relief Low Relief Low- moderate Low Relief Med.-High Moderate

Habit Anhedral Tabular(anhedral)

Tabular (anhedral and euhedral)

Anhedral Tabular, irregular

Irregular

Cleavage None 2-perfect cleavage

perfect cleavage 1-perfect cleavage

Perfect cleavage

2-perfect cleavage

Pleochroism None None None None Dark brown to pale brown

From green to brown

Alteration Not visible Alters to a brownish mineral

Not visible Alteration seen

Alters to chlorite

None

Birefringence 0.009 0.007 0.007-0.013 0.036-0.049 0.04-0.08 0.014-0.026

Interference Colour

1st order pale yellow

1st order white to pale yellow

1st order 2nd and 3rd order pinkish purple to green

3rd to 4th order colour

2nd Order blue.

Extinction Undulose Inclined Inclined Parallel to cleavage(birds eye texture)

Parallel and shows birds eye texture.

Parallel to cleavage

Twinning None Cross-hatch Polysynthetic None None Observed

Ajibade et al., 1987; Rahaman, 1988). Formation of joints can be traced to several origins such as contraction

during cooling of igneous body or as a result of stresses set up during tectonic process and expansion during


Uzoegbu et al. 095 overburden removal. This was the most common structure seen on almost all the rock units visited in the study area. They were extensive on the gneisses and to a less extent on the older granites. At some points the joints were penetrating while they are mostly non-penetrating. Orientation data for joints were collected and rose diagrams was plotted as shown in fig.6. The major joint trend on the rocks is NE-SW, NW-SE, NNE-SSW in agreement with the general structural trends on the Basement Complex (Rahaman, 1988, Ogezi,1977).

Figure 6: Joints on Migmatite (x2)

Foliation Foliations are parallel arrangement of platy minerals in rocks. Foliation results from the homogenous deformation in the rocks involving preferred orientation of platy minerals perpendicular to the direction of maximum stress. They can be formed through the action of mineral segregation during metamorphism. It is a penetrative structure and can act as a slip plane or plane of weakness. The migmatite-gneisses and gneisses are highly foliated. The NE-SW is foliation bands.

Figure 7. Foliations (x2) Veins These are formed as a result of recrystallization of silicate grains in the rock crevices or joints which are being filled up with hydrothermal fluid which is rich in quartz, feldspar and muscovites. Some of these veins may be discordant

to foliation planes. This structure is mapped on almost all the outcrop visited in the study area. The veins seen are pegmatitic, quartzo-feldsparthic and quartz veins. They generally show a common directional trend i.e, NW-SE as seen in the rose diagrams.

Figure 8: Quartzo-feldspathic vein (x2) Figure 9: Quartz vein (x2) Faults This is a discontinuity on surface across which there has been shearing or displacement. Micro faults were observed on the rock units which were majorly faulted sinistrally. These faults were more on the gneissic terrain and have displacements range of between 5cm to 30cm.

Figure 10: Intense Sinistral fault (x2) Dyke This is a sheet of rock that formed in a fracture in a pre-existing rock body. Magmatic dykes form when magma intrudes into a crack then crystallizes as a sheet intrusion, either cutting across layers of rock or through an unlayered mass of rock. Most of the dykes as seen in the study area are doleritic and to a less extent pegmatitic dykes. Xenoblast Xenoblast is a rock fragment within an intrusive igneous body that is unrelated to the igneous body itself (Obiora, 2005). Xenoblast represent pieces of older rock



Figure 11: A doleritic dyke (x2) incorporated into the magma while it was still fluid. Also, it could also be as a result of a partial digestion or incomplete digestion of a country rock. This structure was mapped on the migmatite outcrop; it has a fine texture compared to the surrounding bodies.

Figure 12: Xenoblast seen on migmatite (x2). Spheroidal Weathering In rocks that are at or near the surface, water seeps along the joints, attacking unstable minerals (Obiora, 2008). This causes rocks to decompose and disintegrate at their edges, opening the joints wider and allowing even more water to reach the surfaces. At corners where two or more joints meet, water attacks from more than one direction causing more decomposition by chemical weathering. This extra disintegration at joints intersections tends to change sharp corners into rounded surfaces.

Figure 13: Spheroidal weathering along River Arikiya (x2).

Ptygmatitic Fold This is a primary folding in migmatites (injection gneisses, etc.), caused by the high temperature and high-pressure processes to which the migmatites owe their origin and composite character. The conditions under which ptygmatic fold develop occur when the country rock as in a granitized area is locally less competent or more yielding than quartzo-felspathic magma which may intrude it. Veins therefore which are being driven forward by pressure from behind, will buckle plastically if they encounter a resistance during injection, and a succession of such buckles will produce a typical ptygmatic gently recumbent fold.

Figure 14: Ptymatitic fold on migmatite (x2)

Boudinages This is a lenticular structure developed when competent units embedded in a yielding matrix are pulled apart by deformation. Boudinage structures are often developed from small dikes or veins in rocks. Individual pillow-shaped unit is called a boudin about 5cm. Boudinage is a geological term for structures formed by extension, where a rigid tabular body such as hornfels, is stretched and deformed amidst less competent surroundings (Obiora, 2005). The competent bed begins to break up, forming sausage-shaped boudins. The study of boudinage can, also, help provide insight to the forces involved in tectonic deformation of rocks and their strength. Boudins are typical features of sheared veins and shear zones where, due to stretching along the shear

https://en.wikipedia.org/wiki/Hornfels

https://en.wikipedia.org/wiki/Competence_%28geology%29

https://en.wikipedia.org/wiki/Vein_%28geology%29

https://en.wikipedia.org/wiki/Shear_zone


Uzoegbu et al. 097 foliation and shortening perpendicular to this, rigid bodies break up. This causes the resulting boudin to be its characteristic sausage or barrel shape. They range in size from about 5cm thick to about 1m.

Figure 15: Boudinage on migmatite (x2). Geologic Contacts A geologic contact is the surface along which one rock touches another. Several of these contacts were seen in the field which is mostly gradational. The sharp contacts mostly exist where there is an intrusion as in the case of a dolerite intrusion as seen in the field.

Figure 16: Sharp contact of dolerite and granitic gneiss (x2) Lineament Map The areas are underlain by the migmatities, gneisses, Older Granites, Younger Granites, Awgu Shale and Lafia Formation. ARCMAP imagery of the area has been analysed and interpreted in order to determine the lineament trends, lineament density and groundwater potential across the area. The drainage pattern is structurally controlled and mostly influences both the groundwater and surface water flow directions in the area. Rose (azimuth-frequency) diagram of the lineaments delineated on the imagery shows trends in the NE-SW, NNE-SSW, E-W, NNW-SSE and N-S directions with NE-SW and NNE-SSW as the major trends which agrees with the general structural trends on the Basement Complex (Ogezi,1977, Rahaman,1988). Field observations agreed with the results from the analysis of the ARCMAP imagery.

Field verification of these lineaments (structures) was carried out around the study area. The major structures observed and measured on the Basement rocks in the area are joints, foliations and veins. The Rose diagrams of the joints measured on the Migmatites, Gneisses and Older Granite in the area show dominant trends in the NNE-SSW and NE-SW direction. The three common types of veins found in the area are pegmatite veins, quartzo-feldspathic veins and quartz-vein. These veins were more on the migmatite and gneisses. The Rose diagram of strikes of the veins in the rocks show dominant trend in the NE-SW direction (Fig. 17) and may represent the oldest fractures.

Figure 17: Google Image of the studied area (ARCMAP). DISCUSSION The mineral assemblages and field observations of the rocks as described above were good factors for the classification of the rock. Incorporating this with the strikes and dips measured, we produced the geological map of the area as presented in fig. 3. Juxtaposing our classification with earlier workers (for example Jones and Hockey, 1964; Rahaman, 1989, Caby and Boesse, 2001) reveals the extension of migmatites to the central area mapped, though omitted in the published geologic map of Nigeria (2004). The Older Granite has high proportion of quartz mineral. The extent of the gneisses was also not reported in the earlier geologic map, probably due to the regional nature of the work. The structures on the outcrop aptly bear the imprint of evolution and or paleotectonic activities. For example, on sample IS-37 (Granite- gneiss in Figs. 6-16), microscopic mineral lineation of the background felsic and mafic minerals (biotite and felspar) in a preferred orientation suggests the re-adjustment of mineral compositions of the rock during metamorphism. Though folding and faulting are not prominently displayed on the rocks, the fact that the rocks were fractured (jointing) is an evidence of paleo-tectonic magmatic cycle associated with the Pan-African orogeny (Obaje, 2009). On the structural measurements, the resultant orientation of foliations and vein shows a NE-SW, NW-SE, NNE-SSW trending analogous to the direction of tectonic event



Table 4: Data for lineament extraction of the studied area.

S/N Beginning long.

Beginning Lat. Endpoint Long.

Endpoint Long.

Bearing in Deg.

Length of lineament (m)

1 465628.8168 979174.7855 467201.7611 980683.7145 46.19 2179.68 2 467659.0123 980189.8832 468811.2854 979019.32 135.45 1642.54 3 467823.6227 979266.2357 468445.4844 980509.9591 26.57 1390.52 4 469478.8722 980144.1581 469634.3376 979787.5021 156.45 389.07 5 469634.3376 979787.5021 469579.4675 979055.9001 184.29 733.66 6 468792.9953 980308.7685 469396.567 980445.9439 77.2 618.96 7 469396.567 980445.9439 470594.5652 980336.2036 95.23 1203.01 8 470064.1538 981378.7364 470878.061 980263.0434 143.89 1381.02 9 472597.3256 981058.6605 471637.098 979933.8225 220.49 1478.95

Figure 18: Lineament map derived from Landsat TM Band 5 Imagery over Angwan Madaki and Environs.

Figure 19: Rose diagram for lineaments Orientation from ARCMAP of the area.

responsible for the metamorphism and/or fracturing of rock in the region (Rahaman, 1989; Obaje, 2009). Foliation is defined by the planar alignment of micas which defines a syn-metamorphic mineral lineation (Caby and Boesse, 2001). Strike of joint were also studied

which indicate NE-SW, NNE-SSW and few E-W trending. Joints are studied for engineering or hydrologic applications. Optical study of the thin sections prepared from rock samples collected revealed five distinct rock units which are migmatite, banded gneiss, Granite and


Uzoegbu et al. 099 Table 5: Strike readings for foliations, joints and veins.

S/N FOLIATIONS JOINTS VEINS 1 48 190 200 352 10 196 190 114 246 258 232 352 2 68 110 205 12 350 354 360 64 192 298 358 22

3 70 120 66 16 338 54 228 16 358 244 342 24

4 72 120 106 16 68 84 66 12 242 250 242 250 5 228 120 96 12 80 78 335 18 220 242 90 246 6 60 220 268 6 188 248 250 92 260 196 198 225 7 30 220 300 44 18 4 2 44 226 40 45 40 8 190 216 358 14 130 350 18 68 358 84 310 30 9 25 38 114 12 88 350 88 60 76 86 104 86 10 47 2 28 335 60 2 206 60 76 136 266 270 11 310 316 82 156 22 22 256 246 304 4 66 18 12 30 10 42 162 82 60 268 68 242 250 250 244 13 78 64 286 172 130 76 84 104 245 238 44 46 14 206 188 248 204 260 60 80 56 90 50 78 108 15 320 288 256 6 90 66 82 56 115 125 198 198 16 204 340 12 2 260 70 8 148 225 44 62 66 17 12 12 12 24 56 62 125 220 44 44 40 60 18 16 6 12 34 45 22 130 220 242 18 136 270 19 44 156 162 34 230 40 130 216 88 252 264 245 20 172 204 198 16 250 40 134 250 198 98 78 214 21 134 22 20 2 62 18 60 250 234 44 310 324 22 190 216 358 14 130 350 18 68 358 84 310 30 23 25 38 114 12 88 350 88 60 76 86 104 86 24 47 2 28 335 60 2 206 60 76 136 266 270 25 310 316 82 156 22 22 256 246 304 4 66 18 26 30 10 42 162 82 60 268 68 242 250 250 244 27 78 64 286 172 130 76 84 104 245 238 44 46 28 206 188 248 204 260 60 80 56 90 50 78 108 29 320 288 256 6 90 66 82 56 115 125 198 198 30 204 340 12 2 260 70 8 148 225 44 62 66 31 12 12 12 24 56 62 125 220 44 44 40 60

Figure 20: Rose diagram for foliation No. of data=118, Dominant Trend=NNE-SSW, NW-SE, NE-SW

porphyroblastic Gneiss, Older Granite and Dolerites which have not been reported in the area before as no work has been done there before. The rock types in this study area are members of the Basement Complex of Nigeria. The mineralogical assemblages of these rocks are generally quartz, micas (biotite and muscovite), hornblende, feldspars (plagioclase and microcline) and others (opaque minerals (iron oxide) and the accessories). Most mineral components of the rocks

show evidence of metamorphism. The imprint of deformational tectonic events that accompanied Pan African orogeny was observed in the area as possible pre cursors to the development of structural elements such as mineral lineation, foliation, jointing and veins. Statistical data of joints, foliation and veins were integrally processed. Rose diagram plotted from these data revealed a major NW-SE and minor NE-SW and E-W trends (for the foliations and veins).



Figure 21: Rose diagram for joints Number of data=198, Trend=NE-SW

Figure 22: Rose diagram for veins Number of data=97, Dominant Trend=NE-SW

The studied area has two main sources of water, surface water and underground water. The surface water includes all run-offs which may include seasonal streams or rivers and ponds. The major river within the studied area is River Arikiya which is a tributary of the River Benue. During the dry season, the minor streams are partially or completely dried up. The pattern of flow here is dentritic. All the rivers are structurally controlled as they are seen trending either NW-SE or NE-SW while River Arikiya was trending E-W. Subsurface water in this area is mostly by hand dug wells and the major river (River Arikiya) flows closely to various settlement. Most of their wells dry up during the dry season hence River Arikiya always serves as their alternative water source. The water in these wells does not form lather with soap, so we termed them as hard water. The pegmatites on studied area contains economic minerals such as quartz, feldspar, muscovite, tourmaline, garnet, topaz and beryl. The gemstones in these communities are mined illegally as some open pits were seen in the field. Some of the pegmatites mapped could serve as pointers to possible mineralized veins.

Tourmaline is used for the study of polarised light, and also for crystals in radio transmitters to give a definite frequency of sending waves. The varieties in the study area are black, green and pink. The locals were also seen mining cassiterite along the River Arikiya channels. The cassiterite is considered to be alluvial deposits probably demobilized and moved along the river channels from the pegmatites. Sharp sand was also seen along the river channels mostly along River Arikiya which can serves as raw material in the production of abrasives, refractories, and in the manufacture of glass. This large volume of sand can be extracted and used for engineering construction also. The feldspars are more in the porphyroblastic gneiss, Older granite and minor pegmatite veins in Angwan Madaki. Feldspars are used in ceramics and in making of glass. It also serves as a source of alumina and as a partial replacement of soda ash. It is an indispensable raw material used for the production of porcelain enamels, flux and filter in latex paints. It is in the manufacture of abrasive, cleaners, and polishes. Ground feldspars are extensively used in scouring and cleaning,


Uzoegbu et al. 101 and as non-skid dusting agent for oil and slippery floors. Micas occur in the pegmatitic rocks of the studied area, the major being muscovite. Muscovites are used as raw material in the manufacture of insulators in the electrical industries. They can also be used in cosmetic industries. Rocks are used as bulk materials in construction of structures such as bridges, roads and buildings. The construction materials found in the study area include granite gneiss, migmatite gneiss, older granite, laterite sands and clays. The laterite is a residual deposit of iron aluminium hydroxide formed by the weathering of the Basement rocks. The laterite is used by inhabitants for the production of mud blocks. The sand derived from the weathering and erosion of the basement is found along river channels and streams. CONCLUSION The geologic mapping of Angwan Madaki and environs was carried out in a prototype geological mapping and reporting model. Optical study of the thin sections prepared from five (5) rock samples collected reveals five distinct rock units which are migmatite, banded gneiss, granite and porphyroblastic gneiss, older granite and some intrusions of dolerites which have not been reported in the area. The rock types are the members of the Basement Complex of Nigeria. The major mineralogical assemblages of these rocks are quartz, biotite, plagioclase, hornblende, muscovite, microclines and other opaque and accessory minerals. Most mineral component of the rock shows evidence of metamorphism. The imprints of the deformational tectonic events that affected the rocks was mapped in the form of structural elements such as mineral lineation, joints, faults, folds, foliation and veins. Structural data were obtained and processed from the various rock types seen on the field. Rose diagrams plotted for these data revealed a NW-SE, NNE-SSW and NE-SW as dominant and subordinate trend for foliation, joints and veins respectively. The same trending was observed for most of the streams in the area as an indication that most of the streams are structurally controlled. The economic geology potential of the area was assessed and reported for a proper geological mapping in the future. REFERENCES Anudu GK, Obrike SE, Iyakwari S and Ikpokonte AE (

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Accepted 12 March, 2017. Citation: Ekeleme IA, Uzoegbu MU, Olorunyomi AE, Abalaka IE AI (2017). The geologic investigations of rocks around Angwan Madaki and its evirons, North Central Nigeria. International Journal Geology and Mining 3(1): 090-102.

Copyright: © 2017 Uzoegbu et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.

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