Field Occurrence, Petrography and Structural Characteristics of the Basement Rocks in the Northern Part of Kushaka and Birnin Gwari Schist Belts, Northwestern Nigeria

Field, studies and geological mapping on a scale of 1:50000 were carried out to determine the lithologic framework and structural features of the Basement Complex rocks in northern parts of the Kushaka and Birnin Gwari schist belts (Kushaka Sheet 122). The area is underlain predominantly by five main rock types mainly (i) Migmatite-Gneiss-Quartzite suite comprising dioritic, granodioritic and granitic gneisses with fissile and ferruginous quartzites and banded iron formations (BIF); (ii) Kushaka graphite and sulphur bearing biotite and muscovite quartz schist inter-banded in places with iron formations; (iii) Birnin Gwari quartz schist; iv) the Kushaka Gneiss Complex composed of basalts (which is being reported for the first time), staurolite and muscovite gneisses and banded iron formations (BIF), and (v) syn-tectonic and late-orogenic biotite-hornblende syenite (BHS) and biotite-hornblende granite (BHG) in the Kushaka schist belt and biotite muscovite granite (BMG) in the Birnin Gwari schist belt area. Petrographic studies have revealed that essential minerals are quartz, K-feldspars (orthoclase, microcline), plagioclase, pyroxene, epidote, hornblende, biotite and muscovite while the accessory minerals are titanite, zircon, apatite, iron oxide (magnetite and hematite). With pyroxenes occurring in the dioritic and granodioritic rocks, metamorphism may have locally reached grannulite facies. Imprints of Pan-African thermo-tectonic events have shown observable migmatization as the first thermo-tectonic event resulting in plastic deformation D 1 and regional S 1 foliation, demostrated by presence of tight isoclinals fold, compositional banding and N – S preferred orientation of mafic minerals. The D 2 deformation is co-axial with D 1 and resulted in the formation of decimeter sized F 2 isoclinal folds, B 2 boudins and eye ball structures that are parallel to S 1 plane schistocity. Strike-slip faults with dextral sense of movements were mapped in a number of places. D 3 deformation is concentrated in the Kushaka Gneiss Complex with near circular deep fractures south of the Kalangai fault. Here granitization and fragmentation of proto-mylonitic staurolite resulted in brittle deformation and F 3 open fold that refolded or transposed the earlier tight isoclinal F 2 folds. The D 4 deformation resulted in N-S and NW-SE quartz veins and pegmatite dykes which serve as channels for epigenetic gold-sulphide and rare metal bearing ore fluids. and banded iron formations (BIF) and (v) syn- tectonic and late- orogenic biotite-hornblende syenite (BHS) and biotite-hornblende granite (BHG) in the Kushaka schist belt and biotite muscovite granite (BMG) in the Birnin Gwari schist belt area. The Kushaka and Birnin Gwari granites are assumed to be the youngest rock which intruded the Migmatite-Gneiss-Quartzite Basement Complex and Kushaka and Birnin Gwari schist belts.


Introduction
The Nigerian Basement Complex is part of the Benin-Nigeria shield and lies within the Pan-African mobile belt to the east of West African craton and northwest of Congo craton. It is divided into two provinces (east and west) separated by latitude 8 0 E marked by a major lineament on the Landsat image (Ananaba and Ajakaiye, 1987). The eastern province comprises mainly a migmatite-gneiss complex intruded by larger volumes of Pan-African granites and the Mesozoic ring complexes of North-Central Nigeria. The western province of the Nigeria Basement Complex is characterized by narrow and sediment dominated, N-S trending, low-grade schist belts separated from each other by migmatite-gneiss complexes, intruded by Pan-African granitic plutons Woakes et al., 1987;Onyeagocha and Ekwueme 1990) (Fig 1). The ages of the protolith are still unclear in these provinces.
Structural trends as observed in the basement complex are the results of orientation and magmatic induced veins and pegmatite dykes (Ajibade et al., 1984;Rahaman, 1988). The two phases of deformation are both ductile and brittle; the former being responsible for formation of planar structures (foliation) and the latter resulting in white and fissile facie occurs in Nasarawa Kwona as poorly exposed on low lying ridges and are aligned in N-S foliation direction (Fig. 4). The ferruginous quartzite occurs as Iron-formation interbedded with quartzite stratiform with typically finely banded structure, and is well exposed in Maganda area (Fig. 4). In the adjourning Kusheriki schist belt, south west of the study area, they are interlayered with phyllites. Migmatite gneisses occur as highly jointed and foliated high and low level rocks in which plastic deformation, mainly meso and microscopic fold structures and N -S schistocity are well preserved. They are also characterized by alternating dark bands of biotite and other dark (2 -6 cm) and light quartzo-fedspathic minerals, referred to as Pan-African migmatite.
Migmatitic Gneiss occurs as thick bands of felsic and mafic minerals. It is easily distinguished from the migmatites with its less pervasive N -S foliation, thick bands of paleosome and leucosome with granitic injections. The leucosome is granitic, porphyritic and discordant rock in which feldspar porphyry and dark biotite minerals are aligned in E-W direction against the general N-S foliation trend. The migmattic gneiss also occurs as dykes in which minor dextral movement in the dioritic leucosome has been recorded (Fig. 4).
Granite gneiss is a high and low levels, weakly foliated fine grained, grayish to pink and reddish brown equigrannular rocks. Although the rock is similar to the migmatite gneiss with its weak N-S trending foliation, it differs from this rock as a result of thick bands of paleosome and leucosome injections. The granite gneiss is well-exposed in Kampani Doka area where it is being quarried for constructional purpose (Fig. 4). 3.1.1.2 Petrography Migmatite gneiss comprises thin and thick bands of paleosome composed of diorite, tonalite and granodiorite and leucosome made up of granite. i) Diorite: This rock outcrops as a hill approximately 569m high along the Birnin Gwari -Kaduna road. It is characterized by thick alternating dark (paleosome) and light (leucosome) bands, both of which vary from 0.5 to 15m, and are aligned in the N-S regional foliation direction. The leucosome occur as cross cutting dyke with dextral displacement (Fig. 5). Microscopically, the leucosome component consists of quartz (30%), K-feldspar (40%), plagioclase (10%) and mafic components as biotite (10%) and iron-oxide (5%), with accessory minerals as apatite and magnetite. K-feldspars are tabular perthite and microcline with zoned inclusions of dense clay minerals. Plagioclase is also tabular and zoned in places. Quartz occurs as hypidiomorphic four to six-sided crystals at 120 0 junction ( Fig. 5) (Table 1). Accessory minerals are apatite and magnetite. ii) Granodiorite: Granodioritic rocks consisting of thick bands of paleosome and leucosome occurs as a hill rising up to 538m in Ungwan Madaki, Gwaska and Kwona Mutua area. It is a fine to medium grained rock, composed of 3-30m thick bands of felsic and mafic minerals, aligned in the N-S regional foliation direction (Fig. 5). Under the microscope the rock is seen to be composed essentially of augite (45%), hornblende (15%) and biotite (5%) and iron-oxide (5%) set in groundmass of quartz (20%) and feldspars (10%). Elongate, needle-like crystals of augite are mainly aligned in sub-parallel fashion although a few crystals have different crystallographic orientation. Accessory minerals are apatite, magnetite and iron-oxides (Fig. 5). iii) Tonalite exposed along River Rafin Magami, and found as boulders and whale backs which are traceable westward for few kilometers from the bridge across the Birnin Gwari -Funtua road, north of Sabo-Layi village (Fig. 6). It is a fine to medium grained rock, grey in colour and weakly foliated tonalitic and granodioritic in composition. Under the microscope, it is observed to consist of orthoclase (5%), plagioclase (60%), quartz (20%), biotite (10%), pyroxene (5%) with accessory iron-oxide (hematite and magnetite) and apatite. The plagioclase (An15-20) exhibits simple polysynthetic twinning. iv) Granite (leucosome) is coarse grained to porphyritic rock which occurs as injection in the granodiorite and paleosome in areas around Ungwan Madaki and Gwaska. Under the microscope it is found to be composed of quartz (40%) and K-feldspar (40%), with biotite (15%) as ferromagnesian mineral. Quartz occurs as euhedral to subhedral medium sized crystals in between the feldspars and is characterized by mykeritic intergrowth with orthoclase. K-feldspar consists of orthoclase (perthitic and micro-perthitic) and microcline with cross hatch twinning (Fig. 6D). The feldspars also contain dense mass of clay and mica minerals as alteration products; additionally, there is also an overgrowth of K-feldspar at the edges of the plagioclase on perthite and microcline ( Fig. 5D and 6D). Anhedral crystals of biotite are scattered in the matrix and along cracks in the feldspars and as inclusions in orthoclase (Fig. 5F). Accessory minerals include zircon, apatite and magnetite. This may have been the earliest component of the Older Granites in this area as earlier reported by Ajibade et al. (2008) or gneiss and migmatite considered to be related to the Older Granite plutonism and subsequently referred to as Pan-African migmatites by Truswell and Cope (1963). v) Granite Gneiss: Occurs as prominent outcrops (about 520m high) which is being quarried for constructional material in Kampani Doka area and as low lying whale back exposures along river channels in Kugu area. It is fine grained, weakly foliated equigrannular pink to reddish and greyish brown rock, (Fig. 4). Under the microscope, the reddish brown rock is seen to be composed mainly of quartz (30%), orthoclase (25%) muscovite (25%), ironoxide (10%) and biotite (5%). Accessory minerals include zircon, apatite, titanite and magnetite.

Kushaka Gneiss Complex
The Kushaka Gneiss Complex consists of low-lying sub-circular bodies of felsic and mafic rocks in south-west of Journal of Natural Sciences Research www.iiste.org ISSN 2224-3186 (Paper) ISSN 2225-0921 (Online) Vol.12, No.12, 2021 the Kalangai transcurrent fault where it truncated the Kushaka metasediments. The rocks include basalt, granitoids rocks of granodioritic composition and granite gneiss. At the edge of the Kalangai transcurrent fault, the subcircular bodies rises up to 500m above the surrounding area and generally dip at angle of 20 0 to 60 0 E and SE. The basalt outcrops in the central part around Marinai and Kabugu as a dark and dense, fine grained massive volcanic rock, granular in texture, highly fractured with brittle deformation and block jointing. Under the microscope, the basalt is seen to be composed essentially of pyroxene (60%), ranging from anhedral to subhedral glomerocryst to small prismatic crystals and showing preferred alignment of minerals. Olivine is about (10%) in the basaltic rock and occurs as subhedral phenocrysts. It is pale brown in colour under plain polars. Quartz (20%) and plagioclase (10%) form part of the groundmass. Accessory minerals are titanite, zircon, apatite and garnet ( Fig. 7) ( Table 1).
The high level granite gneiss is characterized by minor folding (F3) transposing the F2 folds with dextral displacement (Fig. 12). The western part of the granite-gneiss intrusion consists of light-coloured staurolite and muscovite gneiss with bands of dark coloured minerals in Gwagwaulu area. This phase of the rock is closely associated with banded iron formations (BIFs) and pegmatites (Fig. 3).

Kushaka Quartz Biotite-Muscovite Schist
The Kushaka metasediment comprises Fe-rich biotite, muscovite quartz schist interbedded with banded iron formations (BIFs). Two varieties are recognized in the field. (i) Fine-grained grey to silvery grey type recorded in the river channels in Kugu area; (ii) The yellowish to grayish type graphite and sulphur bearing, with iron-oxide minerals which occurs in Sabo-Layi (Fig. 8). Graphite is silvery grey to black in colour with greasy feel and smudges the hand when touched. Yhis mineral has been transformed or altered to magnetite and haematite as observed under the microscope. The Kushaka metasediments is interbedded with BIFs in Kugu and ferruginous quartzite in Maganda area, and it is characterized by microfolds, crenulation cleavages, nearly vertical dips and shows a well-defined schistocity.

Birnin Gwari Quartz Biotite-Staurolite Schist
The staurolite-biotite quartz schist of the Birnin Gwari schist belt is a whale back N-S trending Younger metasedimentary rock composed of clastic components of quartz, schist, volcanic and quartzo-feldspathic rocks. Three units of this rock can be observed in the field namely: i) The bluish to light grey, fine to medium-grained clastic rock with flow structure. The clast (mixture of quartz, schist, volcanic and quartzo-feldspathic components) range from less than 2mm to 5cm and make up to 25-40% of the constituent of the rock showing angular to rounded and flattened, and are poorly sorted with range of particle sizes from sand to cobbles; ii)Dark grey finegrained rock in which the precursory sedimentary structures ripple marks, cross bedding and cross lamination are preserved and (iii) Dark, fine-grained rock with granular texture. This rock is characterized by lack of clastic materials and precursory sedimentary structures. It is found close to the Mando granite pluton (Fig. 8).

Banded Iron formation
The banded iron formation occurs as series of N -S trending ridges and isolated hills (with elevation of ≥ 600 m) in Sabo-Layi and Galadimawa area. The banded iron-formation is also interbedded with quartzite which stands out along the ridges in Maganda towards Akachi area. Ferruginous quartzites interlayered with phyllites have been observed by previous workers in the Kusheriki, south west of the study area. BIF is also interbanded with quartz schist in Kugu area where the iron-formations preserved the metasediment, making it more resistant (Fig. 3).

Amphibolite
The amphibolites occur in low lying outcrop in Kungwi area. Some of the dykes are over 1 km in length and >6m in width and trending N160 0 direction. It is a mediun grained dark coloured rock with acicular quartz occurring as bands (1 -2 mm), trending in the regional N -S foliation direction.

Kushaka Granite
The granite plutons intruded the Kushaka metasediments and are found in Maganda, Nasarawa-Kwona, Koriga, Manini, Udawa, Sabon-Kushaka and Kugu. They comprise biotite and hornblende-bearing syenite, biotite bearing granite and granodiorite. These intrusions form N-S trending oval and elongated bodies or whaleback with moderate to high relief on either side of the transcurrent Kalangai fault. The granite plutons occupy the intervening area/region of the basement migmatite gneisses and metasediments of the Kushaka and Birnin Gwari schist belts (Fig. 3). Megascopically, the granites range from light to dark grey, grayish yellow, grayish brown to light (iron) red in colour. They also occur as porphyritic, coarse porphyritic and medium grained, and are generally devoid of pervasive foliation, but intense deformation responsible for S1 foliation has caused some varieties to develop slight banding, with the dark minerals forming mafic enclaves. Syenite: The syenite is a medium-to coarse-grained rock with hypidiomorphic texture and mafic enclaves. It is composed of potash feldspars (35%), quartz (20%), hornblende (20%), biotite (10%), plagioclase (5%) and ironoxide (5%). Parallel to sub-parallel alignment of the crystals of hornblende and biotite define the foliation direction ( Fig. 9) (Table 1). Zircon, magnetite, apatite and iron oxides are the main accessory minerals. Granite: This is a coarse-grained, grey-coloured rock with outcrop slightly elongated and 615m elevation. Megascopically, it consists of grey coloured feldspar and quartz, contrasted by dark colour biotite and shining and flaky muscovite. This is a coarse hypidiomorphic rock in which the proportion of felsic minerals constitutes more Journal of Natural Sciences Research www.iiste.org ISSN 2224-3186 (Paper) ISSN 2225-0921 (Online) Vol.12, No.12, 2021 than 60% with almost equal amounts of K-feldspar and plagioclase. The main consistuent minerals are quartz (30%), K-feldspar (30%), plagioclase (30%) and biotite (10%). Accessory minerals are muscovite, haematite and magnetite (Fig. 9).

Birnin Gwari Granite
Granite outcrops are found on the fringes of the Birnin Gwari metasediments. It is coarse porphyritic to medium grained granite which is composed of pinkish to milky feldspars, silvery muscovite flakes, and black to brownish biotite. The slightly weathered muscovite shows brownish green colour. Under the microscope, quartz (30%) occurs as subhedral phenocryst, orthoclase (25%) and microcline (25%) are euhedral crystals, closely interlocked with plagioclase (5%), and with each other (Fig. 9) (Table 1). K-feldspar occurs as subhedral phenocryst of orthoclase and micro-perthite and as subhedral to euhedral medium-grained crystals with microcline and biotite. Biotite and muscovite are fibrous and needle-like in shape, squeezed together and align in the regional foliation direction. Accessory minerals include magnetite and apatite. The ductile structures trend in the NNE-SSW and NE-SW direction while the brittle structures trend in the NNW-SSE; NW-SE and E-W direction, the E-W is predominant in the granitoids. The rose diagram plot shows that the data plot mostly in the NNE-SSW and NE-SW directions (Fig. 10). This agrees with the composite lineament aeromagnetic, Landsat and DEM maps of the study area (Fig. 5) and conforms to the strike of regional foliation trend. Abubakar (2012) combined lineaments deduced from 3D total magnetic intensity field raster image, Landsat ETM+ and digital elevation model (DEM) to produce composite lineament map of aeromagnetic, Landsat and DEM with newly interpreted lineament which shows NE-SW and NW-SE as the major structural trend in the study area. The rose plot when compared with the aeromagnetic, Landsat and DEM lineament map shows its alignment with majority of the linear structures and similarity of field data with aerial view (Fig. 11). Four deformational episodes (D1 -D4) have led to the generation of three major foliation trends namely: near vertical N-S, NNE-SSW and NE-SW earlier documented by Grant (1978) were recorded. The planar (foliation) surfaces were observed mainly in the migmatite-gneiss-quartzite Basement Complex, Kushaka and Birnin Gwari metasedimentary rocks while joints and fractures cut across all lithologies in the area.

D1 Phase of Deformation and Structures
The E -W compressional stress / deformation has resulted in the regional N -S foliation trend manifesting as synform and antiform as revealed by structural trend lines. The D1 deformation is observed in migmatite and gneisses, rocks of Birnin Gwari and Kushaka schist belts, and is associated with S1 foliation. In migmatites and gneisses, the S1 foliation is outlined by compositional banding and by preferred orientation of the dark minerals and quartzo-feldsphatic layers (Fig. 12). The D1 deformation in the Kushaka schist within the migmatites and gneissic envelope shows N -S foliation trend and is also responsible for the observed regional N -S alignment of the Banded Iron Formation (BIF) and its associated ferruginous quartzite earlier described by Grant, (1978) as continuous interbanded Banded Iron and Kushaka quartz schist outcrop extending for about 25 km, observed in Maganda outcrop in the north. D1 deformation in Birnin Gwari staurolite and quartz schist is characterized by wellpreserved ripple marks, cross bedding, phenocrysts of vesicles and flow structure in N -S regional foliation trend (Fig. 8). A planar orientation is also observed in the granites where the porphyritic varieties show aligned feldspar porphyries parallel to regional foliation direction. The F1 fold even though occurs at megascopic scale was not observed in the field, but photo geological trend did show the major antiform and synform in the gneisses and migmatites and Kushaka metasediment respectively; with axes oriented in N -S direction. The F1 megascopic folds have S1 as axial plane schistocity. All axial trends are parallel and vary between 160 0 and 180 0 (Fig. 10).

D2 Phase of Deformation and Structures
The D2 deformation has been recorded both in the metasediments and metamorphic rock units. It is characterized by heterogeneous deformation affecting the N -S regional orientation of the D1 fabric. The D2 deformation led to development of minor structures in the metasediments, migmatites and gneissic rocks. The most widely developed are the F2 and F3 folds. Clearly visible in the migmatites and gneissic rocks are the F2 isoclinal folds, B2 boudins and eye ball structure. The F2 fold occurs only as decimeter sized isoclinal fold with S1 parallel to the axial plane schistocity and in places with crestal thickening (Fig. 12). These structures are not observed in the granite gneisses, implying that the gneisses may post-date the D2 phase. F2 folds over-printed the D1 structures and S1 schistocity is folded by the F2 folds. The D2 folds represent the main folding phase and are clearly visible at megascopic scale. These F2 folds also have various morphological aspects: (i) upright folds; (ii) disharmonic folds (iii) simple fold. The wavelength of many F2 folds varies from 15 -30 cm with the amplitude of 10 -20 cm. Some of the F2 small scale folds have either asymmetric S or Z shape and symmetric M or W shape depending on their location and relation to F3 folds. The D2 deformation is also marked by sub-vertical fractures resulting in leucosome injection and strike slip fault all which are oriented in the regional foliation direction (Fig. 4). This could be the late phase of D2 deformation, as observed from porphyritic granite injection in the migmatite gneiss rock in Gwaska area.

D3 Phase of Deformation and Structures
The D3 deformation is preserved in the Kushaka Gneiss Complex, south of Kalangai transcurrent fault and the Kushaka ferruginous quartzite as microfolds and crenulation cleavages. It is a phase of superimposed folding, where the structures associated with this phase of deformation are the result of the transposition and re-orientation of the D2 structures. The F3 folds typically form interference patterns that are associated with the development of later minor folds across the earlier structures. The fold axes of F3 folds are parallel to F2 fold axes, thus F3 open fold orientation is probably coaxial with the earlier tight and isoclinals F2 folds (Fig. 12). In the Kushaka Complex, the D3 phase of deformation and structures are marked by F3 open folds and the fold axes are perpendicular to the foliation direction. The S3 schistocity overprinted the pre-existing S1 schistocity in form of stretching lineation parallel to the N -S axial plane but with moderate dip 35 0 -40 0 E. The L3 lineation associated with S3 is subparallel to F3 fold axes. The shearing movement associated with the D3 phase of deformation is dextral and trend 180 0 on the average. This is clearly visible in Kabugu and Marinai where F3 fold limbs are dissected by C3 shear plane (Fig. 12).

D4 Phase of Deformation and Structures
The D4 deformation is marked by locally developed strain-slip cleavage observed in the migmatites and gneisses. It cross-cut the Kushaka and Birnin Gwari schists, the banded iron formations and part of the granite gneiss of the Kushaka Complex, and probably reactivated the Kalangai fault. This deformation is also responsible for the squeezing of residual granitic magma into late sub-vertical fractures and joints, felsic pegmatite intrusion and strike slip faults (Fig. 12). Grant (1978) recognized 4 generation of minor folds (F1 -F3) followed by locally developed strain -slip cleavage cutting across associated F3 folds south of Kalangai fault.

Other Structures:
These are minor sedimentary structures like well-preserved ripple marks, cross bedding, lineation, phenocrysts, vesicles and flow structure in the Birnin Gwari meta-volcano-sedimentary rock. It is difficult to ascribe these minor structures to a particular deformation episode but probably D1 and D2.

Conclusion
Field mapping and analysis of petrographic and structural data on the rocks of the study area show that the main rock types are (i) a Migmatite-Gneiss-Quartzite suite comprising dioritic, granodioritic and granitic gneisses with fissile and ferruginous quartzites and banded iron formations (BIF); (ii) the Kushaka graphite and sulphur bearing biotite and muscovite quartz schists inter-banded in places with iron formations; (iii) the Birnin Gwari biotitestaurolite quartz schist; iv) the Kushaka Gneiss Complex composed of basalts (which is being reported for the first time), staurolite and muscovite gneiss and banded iron formations (BIF) and (v) syn-tectonic and late-orogenic biotite-hornblende syenite (BHS) and biotite-hornblende granite (BHG) in the Kushaka schist belt and biotite muscovite granite (BMG) in the Birnin Gwari schist belt area. The Kushaka and Birnin Gwari granites are assumed to be the youngest rock which intruded the Migmatite-Gneiss-Quartzite Basement Complex and Kushaka and Birnin Gwari schist belts.
Petrographic studies have revealed that the essential minerals are quartz, K-feldspars (orthoclase, microcline), plagioclase, pyroxene, hornblende, biotite, muscovite while the accessory minerals are titanite, zircon and iron oxide (magnetite and hematite). Migmatite-Gneiss-Quartzite Basement Complex rock contains pyroxene especially the dioritic and granodioritic rocks, which lend credence to its formation by anatexis; where metamorphism may have locally attained grannulite facie. Ajibade et al., (2008) have reported agmatitic and stromalitic migmatite, formed by anatexis in medium to high grade terrain in the adjacent Kusheriki sheet which hosts parts of Kushaka and Birnin Gwari schists. Graphic texture in orthoclase (perthitic and micro-perthitic) and microcline with cross hatch twinning in the granite leucosome is typical of magmatic intergrowths, however, overgrowth of secondary K-feldspar (light gray) on end and sides of albite-twinned plagioclase crystal (dark gray), this may have resulted from metasomatic processes. This is an indication that granite injections that had undergone matasomatism.
The rocks of the area recorded majorly N-S NNE-SSW and NE-SW planar structures and minor NW and E-W structural trend. The N-S, NNE-SSW and NE-SW represent ductile metamorphic structures that are probably pre-or contemporaneous Pan African deformation event that led to the widespread emplacement of granodioritic and granitic injections in rocks of the basement while the NNW-SSE, NNE-SSW and E-W brittle structures in-filled by pegmatite dykes and quartz veins are probably close or end of Pan-African.
Migmatization is believed to be the first thermo-tectonic event and resulted in plastic deformation D1 and regional S1 foliation, defined by tight isoclinal fold, compositional banding and N -S preferred orientation of mafic minerals. The D2 deformation which is co-axial with D1 resulted in the formation of decimeter size F2 isoclinal folds, B2 boudins and eye ball structures that are parallel to S1 plane schistocity. Granitic leucosome injection into the dioritic and granodioritic migmatite gneiss revealed strike-slip faults with dextral sense of movements. D3 deformation, commonly found in the Kushaka Gneiss Complex, south of Kalangai transcurrent fault is a phase of superimposed folding, where F3 structures transpose and re-orientate the F2 structures. Extrusion of tholeiitic basalt and granitization in the Kushaka Complex with near circular deep fractures south of the Kalangai fault and characterized by fragmented proto-mylonitic staurolite, resulted in brittle deformation and open fold (F3). The D4 deformation resulted in N-S, NE-SW and E-W fractures and joints which serve as channels for epigenetic gold-sulphide and rare metal mineralization reported in the study area.