The Kushaka schist belt in the Kwona Mutua and Kushaka areas is one of the 12 well recognized N-S trending belts composed of igneous, metamorphic and metasedimentary rocks in varying proportion. The major rocks of the belt comprise the Migmatite-Gneiss-Quartzite Complex, schists and Pan-African granitoids. Banded and granite gneisses constitute the bulk of the Migmatite-Gneiss-Quartzite Complex. Banded gneiss consists of paleosome and leucosome of dioritic, tonalitic, granodioritic and granitic composition while granite gneiss is composed of biotite, staurolite–biotite and staurolite-muscovite gneiss. Major mineral constituents of these rocks are quartz, orthoclase, plagioclase, pyroxene, biotite, muscovite, orthoclase, microcline and staurolite while the accessory minerals are titanite, apatite and iron oxides. Metamorphism may have reached grannulite facies locally with pyroxenes crystallizing in the dioritic and granodioritic rock. Analysis of geochemical data reveals marked variation in the abundance of SiO 2 (60.77-77.53 wt %), Al 2 O 3 (12.9-15.99 wt %), Fe 2 O 3 (0.78-7.04 wt%), Na 2 O (1.67-5.15 wt%) and K 2 O (1.64-6.13 wt %), typical of rocks of hybrid sedimentary–igneous protoliths. Igneous protolith reveals decreasing P 2 O 5 content with increasing silica content, low K 2 O/ Na 2 O ratio (0.24 – 0.87), low K 2 O values (< 2.5 wt %) displaying mixed tholeiitic and calc-alkaline, metaluminous and peraluminous, ferroan and magnesian character, and high-K calc-alkaline to shoshonitic affinities. By contrast, the rocks of sedimentary protolith shows high K 2 O/ Na 2 O ratio (1.19 – 2.5), high Na 2 O values (> 3 wt %) and staurolite mineral. Their pelitic and mafic attributes were derived essentially from a quartz-diorite, granodiorite and granite-quartz monzonite source. Fractional crystallization and partial melting of older dioritic-granodioritic-tonalitic source rock derived from upper mantle materials contaminated by continental crust played important roles during their genesis. They are enriched in Large Ion Lithophile Elements (LILE) but depleted in Nb, P and Ti typical of volcanic arc and syn-collisional settings. Keywords : Banded gneiss, Pan-African, sedimentary, igneous, granodiorite, protolith, Kushaka, Nigeria DOI: 10.7176/JEES/11-4-05 Publication date: April 30 th 2021

The granitoids and the associated volcanic rocks of the northern part of Kushaka and Birnin Gwari schist belts were emplaced in the ca. 3.5 – 1. 0 Ga remobilized basement complex terrain composed of metasedimentary and metaigneous rocks that later underwent medium- to high-grade metamorphism during the Pan-African thermo-tectonic event. They comprise dominantly of diorite, granodiorite, granite, granite gneiss and basalt, and are product of metasomatism and injections. The diorite and granodiorite occur as paleosome and the granite as leucosome with the development of high temperature minerals, locally attaining granulite facie metamorphism. Plagioclase, biotite, hornblende, pyroxene and olivine fractionation played an important role during their genesis through fractional crystallization of basaltic magma and partial melting of older dioritic-granodioritic source rock in the deep crust which were themselves ultimately derived through fusion of mantle materials contaminated by continental crust and enriched by fluids derived from oceanic crust in an arc setting. Geochemical characteristics have revealed different chemical trends in granitoids and basalts. The granitoids are calc-alkaline, ferroan and magnesian, metaluminous and peraluminous in character. They also exhibit I- and S-type signatures with enrichment in LILE, radioelements (Th and U), depletion in Nb, Sr, P and Ti, high LREE fractionation factors (La/Yb) (1.05 to 77.20), and pronounced negative Eu anomalies (Eu/Eu* = 0.34 to 1.10). Similar patterns of spidergrams show that the rocks are genetically related and were emplaced in a volcanic arc and syn-collisional setting. The basalt is tholeiitic, metaluminous and high in Fe and Mg with relative enrichment in LILE, HFSE, low and near flat LREE and HREE, low fractionation [(La/Yb)N = 1.4] with Eu/Eu* value of 1.10. It is evidently a back arc cum mid-ocean ridge (MORB) basalt. The consistent decrease in the content of MgO, Fe2O3 MnO, CaO, Sc, Cr and V of the basalt, diorites, granodiorites, and granites indicates continuous igneous crystallization process. It seems that extrusion of basaltic magmas from the sub-circular Kushaka Complex derived from subduction of oceanic crust resulted in complete change in the genesis of the magmas at the time, in this region. The granitoids and the basalt may have formed behind subducted Pan-African plate due to effects of compressional and tensional forces caused by oceanic plate roll-back which resulted to a zone of extension, parallel to the island arc. The granitoids present similar chemical characteristics to those in the other areas underlain by the basement complex and schist belts in the north and eastern parts of the Pan-African mobile belt, while basalts are similar to ophiolites and amphibolites in other schist belts of Nigeria forming a lateral continuation of the same mobile belt.Â

The Kushaka and Birnin Gwari metasediments and associated banded iron formations constitute important lithological units within the Precambrian Basement Complex. They were studied to evaluate their compositional characteristics and petrogenesis in order to contribute further to the understanding of the geodynamic evolution of Nigeria’s Schist belts. The Kushaka metasediments comprise quartzite, graphite and sulphur bearing staurolite-muscovite quartz schist interbedded with Banded Iron Formations (BIFs) while the Birnin Gwari schist comprise staurolite-biotite quartz schists with lithic (angular to rounded clastic quartz, schistose, volcanic and quartzo-feldspathic) sandstones. These schists are associated with fissile and ferruginous quartzite, banded and granitic gneisses, basalts and amphibolites. Petrographic work revealed varying proportions of quartz, staurolite, biotite and muscovite with subordinate iron-oxide minerals. Geochemically the metasediments in the Kushaka are enriched in SiO 2 (61.23 to 65.99 wt %) with elevated values of Al 2 O 3 (16.53 – 20.93 wt %), Ba, V, W, La, Nb, Nd, Rb, Th and Zr; while the Birnin Gwari schists, even though enriched in SiO 2 (63.03 to 65.13 wt %), has moderately elevated Al 2 O 3 (15.4 – 15.16 wt %) values but is depleted these trace elements. Field and geochemical characterization of the Kushaka metasediments suggests peraluminous, tholeiite and calc-alkaline character; arkosic and shale-greywacke sedimentary protoliths derived from quartzose sedimentary and granite-quartz monzonite provenance. Calculated ICV values of 0.52 - 0.99 and occurrences of graphite and sulphur in the Kushaka metasediment suggests shallow stable shelf-type sediment of carbonate and iron formations in a reducing environment with matured sedimentary protolith. The Birnin Gwari metasediments on the other hand have a peraluminous and calc-alkaline character, inherited from shale-greywacke and quartzose sedimentary protoliths derived from granodioritic and granite-quartz monzonite provenance. ICV values of 1.12 – 1.18 and angular and volcanic clasts suggest rapid subsidence of basin during genesis and / or tectonic instability in the surrounding environment with immature sedimentary protolith. This is an indication of two contrasting environment in an arc setting with contribution from basaltic and andesitic detritus. Available geochronological data on granite and granitic gneisses have ascribed the Kushaka schist belt to Kibaran and the Birnin Gwari schist belt a Pan-African age. Keywords : Metasediments, protolith, Kushaka, Birnin Gwari, quartzite, provenance, shale, greywacke. DOI: 10.7176/JEES/11-16-05 Publication date: June 30 th 2021

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 biotite-staurolite 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. Keywords: Basement Complex, Pan-African, metamorphism, deformation, Kushaka, Birnin Gwari, Nigeria DOI: 10.7176/JNSR/12-12-02 Publication date: June 30 th 2021

The high-K calc-alkaline granitoids in the northern part of the Mandara Hills are part of the well-exposed post-collisional plutons in northeastern Nigeria. The calc-alkaline rock association consists of quartz monzodiorite, hornblende biotite granite, biotite granites and aplite which intruded the older basement consisting mainly of low-lying migmatitic gneisses and amphibolites during the Neoproterozoic Pan-African Orogeny. Petrological and geochemical studies have revealed the presence of hornblende, iron oxide, and metaluminous to slightly peraluminous characteristics in the granitoids which is typical of I-type granite. The granitoids are also depleted in some high field strength elements (e.g. Nb and Ta) as well as Ti. Plots of Mg# versus SiO2 indicate that the granite was derived from partial melting of crustal sources. Lithospheric delamination at the waning stage of the Pan-African Orogeny possibly triggered upwelling of hot mafic magma from the mantle which underplated the lower crust. This, in turn, caused partial melting and magma generation at the lower to middle-crustal level. However, the peculiar geochemical characteristics of the quartz monzodiorite especially the enrichment in compatible elements such as MgO, Cr, and Ni, as well as LILE element (e.g. K, Ce, Cs, Ba, and Sr), signify that the rock formed from an enriched upper mantle source. The emplacement of high-K granites in the Madara Hill, therefore, marked an important episode of crustal reworking during the Neoproterozoic. However, further isotopic work is needed to confirm this model.

The Lessel and Ihugh areas are underlain by Precambrian rocks comprising of banded gneiss, medium-grained muscovite granite, coarse-grained biotite muscovite granite, and Turonian arenaceous Lessel Sandstone in the Lower Benue Trough, southeastern Nigeria. Baryte mineralization occurs at Lessel-Mbagwa, Ihugh and Bunde commonly as vein and cavity type deposits within NE-SW and NW-SE trending fracture zones. Major oxides and trace element analysis of baryte and the host rocks was undertaken using Inductively Coupled Plasma Mass Spectrometry (ICP-MS), in order to establish the geochemical characteristics and to constrain the origin of the baryte mineralization. The data revealed enrichment in Ba and Sr and depletion in SiO2, TiO2, Al2O3, Fe2O3, MgO, CaO, Na2O, K2O, LILEs, HFSEs relative to background values obtained from sandstones and granitic rocks in the area. Baryte mineralization from Lessel-Mbagwa, Bunde and Ihugh is marked by positive Gd (17.1–21.4) and negative Eu (0.02–0.05) anomalies. Negative Ce anomaly (0.06) is evident in barytes from Lessel-Mbagwa and Bunde whereas baryte from Ihugh is characterized by positive Ce anomaly (1.3). The structurally controlled nature of the mineralization, depleted major and trace elements concentration in the barytes in addition to REE anomalies indicate that mixing of a strongly differentiated residual Ba-bearing fluid and sulphur-rich seawater occurred under low temperature and oxidizing-reducing conditions. The tectonic event which occurred during the Santonian to Early Campanian reactivated the NE-SW, NW-SE structural pathways in the basement gneiss and also created similar structures in the Turonian Lessel Sandstone.

Natural radioactivity levels and radiation risks from mud buildings in Miango, North Central Nigeria have been assessed. The town is located within Naraguta Sheet 168 NW. The area is underlain mainly by porphyritic Pan-African granites, Mesozoic anarogenic Younger Granite consisting of biotite granite and granite porphyry, and newer basalt. Weathering and decomposition of these rocks have produced thick layers of clayey soils (mud) which are used for building residential houses. Concentrations of 238 U, 232 Th and 40 K in the mud houses were determined using RS-230 Gamma Spectrometer integrated with a BGO (Bismuth Germanate Oxide) detector for improved accuracy. The content of 238 U, 232 Th and 40 K in the mud houses varies from 3.77-10.77ppm, 27.08-73.77ppm, and 1.47–6.27% respectively. Activity concentrations of these radioelements vary from 46.52-132.97 Bq/Kg for 238 U, 109.76-299.49 Bq/Kg for 232 Th, and 459.07-1961.47 Bq/Kg for 40 K. On the basis of these activity concentrations, radiation exposure parameters such as absorbed dose rate in air, annual effective dose equivalent, radium equivalent activity, excess lifetime cancer risk, and internal hazard index were calculated for the buildings. Results obtained vary from 146.79-291.69 nGy/h, 0.68-1.34 mSv/yr, 322.49-642.26 Bk/kg, 2.36 x10 -3 - 4.70 x10 -3 , and 1.00-2.08 respectively. These values are generally high for safety, thus suggesting that there is a good chance that using the clayey soils from this area for building houses may have negative health implications on the inhabitants in the long term. Keywords: Uranium. Thorium. Potassium.  Activity concentration.  Absorbed dose rate in air. Annual effective dose equivalent. Radium equivalent activity. Excess lifetime cancer risk. Internal hazard index. Miango.

Water samples collected from 60 wells located within Naraguta Sheet 168 in North Central Nigeria were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) for uranium concentrations and other selected trace elements. This is aimed at assessing the radiation dose arising from intake of uranium through drinking water pathway for different age groups in the area. Results obtained show that uranium concentration in groundwater within the study area is generally within the acceptable reference level of 0.1mSv/y except in some places around Bukuru, Rayfield and Bishichi areas underlain mainly by the Jos-Bukuru Younger Granite Complex. The uranium values in groundwater within Naraguta Sheet 168 vary from 0.02-168.7 ppb, representing an activity concentration of 0.516-4.353 mBq/l. Radiation dose due to intake of uranium through drinking water pathway from the area is calculated to be 0.045-378.098 (µSv/y) among infants of 0-6 months, 0.051-432.112 (µSv/y) among infants of 7-12 months, 0.029-247.829 (µSv/y) among children between 1-3 years of age, and 0.026-216.056 (µSv/y) for children between 4-8 years. For 9-13 years old male children, it is 0.031-259.267 (µSv/y), while for the female children of the same age range, it is 0.031-259.267 (µSv/y). Male teenagers of between 14-18 years receives 0.042-351.250 (µSv/y) and female in the same age category receives 0.042-244.811 (µSv/y). Among the adult males older than 18 years, the radiation dose is 0.031-264.710 (µSv/y) and among females of 18 years and above, it is 0.023-193.021 (µSv/y). With effective dose due to uranium in water exceeding the reference level of 0.1mSv/y in some localities, it is therefore necessary to always carryout radiological investigations alongside analysis of major anions and cations present in the groundwater for safety reasons. Keywords: Uranium. Activity Concentration. Dose Rates. Ingestion Dose Co-efficient. Naraguta Sheet 168. Jos-Bukuru Younger Granite Complex.

The Zaria granite batholith in northern Nigeria is an example of syn-tectonic batholith emplaced about 600 ± 150 Ma, ago during the Pan African orogeny. Its strain history and strain marker behavior have been studied in order to further elucidate the tectonics of the PanAfrican orogeny. Field observations, measurements and different methods of strain estimation were applied on 623 data to determine the strain intensity, direction of maximum elongation (σ3) and compression direction (σ1). The different methods produced strain values between 2.66 and 2.07, maximum elongation took place in the N S direction while the σ1 (maximum compression) trajectory was oriented E – W, making the direction the least favourable for strain marker (phenocryst and xenolith) growth. Strain partitioning revealed that the N S direction experienced the highest strain while the NE SW orientation showed a lower strain value than the NW SE direction regardless of the number of markers preferring the directions. Xenoliths, faults and joints lend credence to the measured strain results. It would seem that the E W compression during the Pan African orogeny was widespread and fairly constant throughout most of the period tracked by the granites.

The pegmatites in Angwan Doka, north central Nigeria are genetically related to the basement granites formed during the Pan-African orogeny, 550-530 Ma ago. They occur as sharply discordant dykes in the granitic and metasedimentary basement rocks. The pegmatite population comprises of mineralogically simple and complexly zoned types that are characterized by LCT (Li, Cs and Ta) geochemical signature. The host granitoids range in composition from hornblende, titanite-bearing to biotite-muscovite granodiorites. Analysis of geochemical data of whole rock and muscovite from the different zones reveals compositional variations and evolution across the pegmatite body from border zone to the lepidolite-quartz core zone. Fractionation of Rb, Cs, Sr, Li, F, B, Be Sn, Zn, Ta, Nb and Mn which increases from host granitoids, through the border zone to the central core, with decrease in Fe, Mg, Ti, Ba content, is typical and marks the magmatic crystallization trend of the pegmatites. Other distinctive attribute of the pegmatites is occurrence of cassiterite believed to have formed as a consequence of greisenization, albitization and late-stage metasomatism, which led to enrichment in Sn (up to 886 ppm) in the intermediate zone. Chemical composition of muscovite from the different zones of the pegmatite reveals high concentration of primary magmatic columbite-Fe (ferrocolumbite and ferrotantalite) in the border zone and tantalite-Mn (manganocolumbite and manganotantalite) in the core zone. Ta predominates (352 ppm) in the most evolved lepidolite (Li- and F-rich) zone while Nb was enriched (up to 714 ppm) in the border zone. These geochemical features are ascribed to undercooling of the melt and crystallization in boundary layers accompanied with increased accumulation of incompatible and fluxing components. With increasing fractionation, Nb/Ta and Fe/Mn ratio decreased and is accompanied with increase in Rb, Cs, Li, F and Be typical of crystallization from magmatic process. The sequence of zonation, origin and formation of the different pegmatite zones can be explained by a single path of fractional crystallization. (C) 2015 Elsevier Ltd. All rights reserved.

The pegmatite group in the Angwan Doka area, Kokoona district is a part of the rare-metal pegmatites occurring in a SW–NE trending broad belt extending for about 400km from Ago-Iwoye in SW to Wamba, north-central Nigeria. The pegmatite group consists of discrete dikes of unzoned, simple and mineralized types, which are genetically linked to the late-orogenic Pan-African (600±150Ma) granodioritic host rock and are of the Li–Cs–Ta type. The zoned pegmatite dikes range from simple mineralogy, commonly at the outskirt of the internally zoned to highly mineralized facies in the inner-most zone where extreme fractionation and accumulation of rare lithophile element enrichment have been recorded. Analysis of geochemical composition of representative granitoids and muscovite from the different zones of selected pegmatite dikes reveals that Rb, Cs, Be, Li, F, B, Sn, Zn, Ta and Nb contents in the muscovite increase from the barren, simple pegmatite composed mainly of quartz and mica to the feldspar-rich border–wall zone consisting of muscovite with graphic intergrowth of quartz and schorl to more evolved intermediate spodumene-bearing zone and finally to the Li-mica, spodumene and elbaite-rich lepidolite unit. In general, the Rb, Cs, Be, Li and F contents of the pegmatite increase with decreasing K/Rb and K/Cs ratios. The corresponding increase in Li, F and MnO contents from the border to the core zone is concomitant with the decrease in Fe2O3, MgO, Al2O3 and TiO2 from the border zone toward the core of the pegmatite. These variations are consistent with rare-element enrichment via fractionation processes in which the melt evolved based on the degree of compatibility combined with partitioning of rare elements from the pegmatite melt into minerals and late stage volatiles. Enrichment of Mg and Fe in muscovite from the border and wall zones of the pegmatites reflects an interaction between the host rock and the pegmatite-forming fluids and consequently crystallization of tourmaline of the dravite–schorl solid-solution series. The high activities of F, Li and B coincide with the abundance and quality of tourmaline encountered in the core zone of the pegmatite. Variation in color and intensity of tourmaline ranges from dark blue–black in the border and wall zones to near colorless, pink, green to greenish-yellow, reddish to purplish-pink and dark green varieties in the spodumene to lepidolite (core) zone. The observable sharp contact and lack of metasomatic aureole between the pegmatite and host suggest that the pegmatite dikes crystallized inwards from the wall–rock contact in a closed system with limited alteration along the border to the host granodiorite. Differences in the geochemical evolution trend of muscovite among the pegmatite bodies investigated suggest that they reached variable degrees of fractionation. Transfer of chemical components is probably one way, from the host rock to the pegmatite magma, while infiltration of fluid from the pegmatite to the host is very minimal and almost negligible. The systematic increase and replacement of biotite by muscovite in the fractionated granodiorite of the Angwan Doka area, coupled with the increase in B, Li and F contents of the muscovite toward the lepidolite unit could serve as potential indicators of gem tourmaline mineralization in the pegmatite provinces of Nigeria.