Geology
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Item COMPOSITIONAL FEATURES AND Ta-Sn-Nb RARE METAL MINERALIZATION POTENTIAL OF OGODO-ODOBOLA PEGMATITE, CENTRAL NIGERIA(Nigerian Mining and Geosciences Society (NMGS), 59th Annual International Conference & Exhibition Book of Abstract, 2024-03) Omanayin, Y. A.; Waziri, N. M.; Onoduku, U. S.; Alabi, A. A.Large pegmatite bodies are abundant in Ogodo-Odobola area. They occur in tabular forms and concordant to discordantly intruding the host rocks of migmatitic gneiss, schist and granite. This research is aimed at assessing the geochemical characteristics of pegmatite in the Ogodo-Odobola area to evaluate their rare metal potential. Field investigation was undertaken to determine the occurrences and relationships of the pegmatites with the host rocks. Thirty-three (33) fresh pegmatite samples were analysed using X-Ray Fluorescence (XRF), Inductively Coupled Plasma Optical Emission Spectrometry (ICP OES) and Inductively Coupled Plasma Mass Spectrometry (ICPMS) techniques at the National Geoscience Research Laboratory, Kaduna and the Activation Laboratories Ltd. (Actlab), Ontario, Canada respectively. Major oxides in the whole rock pegmatite show that they are of siliceous (SiO2; 72.82 wt.% average) and peraluminous (Al2O3; 16.78 wt.% average) composition. The K2O, Na2O and Fe2O3 contents average 4.81 wt.%, 3.13 wt.% and 1.27 wt.% respectively while CaO, MnO, MgO, TiO2 and P2O3 are each less than 1.0 wt.%. Average values of trace elements in the pegmatite are Ta (12.40 ppm), Sn (18.36 ppm), Nb (94.51 ppm), Be (16.14 ppm), Rb (480.23 ppm), U (12.47 ppm), Cs (17.14 ppm), Ga (39.91 ppm), Ge (3.91 ppm), W (4.81 ppm), Li (40.98 ppm), Mn (890 ppm) and B (18.96 ppm). Ratios of diagnostic elements of K/Rb (75.21 ppm), K/Cs (3348.39 ppm), Rb/Sr (25.55 ppm), Rb/Cs (37.18 ppm), Ta/W (2.78 ppm), Nb/Ta (8.81 ppm), Ba/Rb (0.07 ppm) indicate a moderate index of fractionation. A/CNK >1 and Al2O3>CaO+Na2O+K2O with enrichment of SiO2, Al2O3, Na2O, K2O and depletion of Fe2O3, MnO and MgO suggests that Ogodo-Odobola pegmatite is of peraluminous bulk composition and plots of A/NK versus A/CNK and Rb versus (Y+Nb) discriminates the pegmatite in the peraluminous Lithium-Caesium-Tantalum (Li, Rb, Cs, Be, Ga, Nb Ta, Sn, B, Ge, U, W) of syn-collisional to within plate granitic family. The plots of Ta versus Cs, Ta versus Ga, Ta versus (Cs+Rb) and Be versus K/Nb, with over 70 % of the samples plotting below the Beus line and 100 % below the Gordiyenko line reveal that the pegmatites from the study area are barren to marginally mineralized in rare metals (Ta>Sn>Nb). Keywords: Pegmatite, Siliceous, Peraluminous, Rare metal, Syn-collisionalItem Environmental Impact of Artisanal Gold Mining on Soils in Saigbe and Environs, Part of Minna Sheet 164, North-Central Nigeria(Minna Journal of Geosciences (MJG), 2017) Omanayin, Y. A.; Abdurrahman, R.; Akande, W. G.; Mamodu, A.; Alkali, Y. B.; Alabi, A. A.The environmental geochemistry of soils from Saigbe and environs, Minna, North-central Nigeria was studied in an attempt to assess the impacts of artisanal gold mining activity in Saigbe and environ. Geological fieldwork carried out in the area revealed that the underlying lithologies include schist, granite and amphibolite. A geochemical soil survey was also carried out and a total number of twenty (20) soil samples were systematically collected from both mined and unmined sites within the study area, of which eight (8) representative samples were geochemically analyzed. Elemental concentrations (major and trace elements) in the soil samples were determined using X-Ray fluorescence (XRF) technique. The physical impacts observed during fieldwork in the area include loss of vegetation, land degradation, water pollution and abandoned pits. The average concentrations of the elements determined were compared with the published upper crustal abundance of the individual elements and subsequently their enrichment ratios were computed. Elements such as Ag, Au and Hg show high enrichment with 1.81 ppm, 0.03 ppm and 0.11 ppm concentrations respectively. The result from accumulation index (Igeo) also shows possible Hg contamination. This potentially toxic element can cause serious damage to the skin, nervous and digestive systems in man through direct or indirect consumption.