Geochemical Characterization and Rare-Metals (Ta-Nb) Mineralization Potentials of Pegmatites Around Lokoja, Central Nigeria

Authors : Daniel Imariabe OMORUYI, Ebo Gabriel IMEOKPARIA

Pages : 61-69

View : 60 | Download : 11

Publication Date : 2020-12-15

Article Type : Research Paper

Abstract :Five pegmatite dykes in suburbs of Lokoja area, central Nigeria are studied using field, petrographical and geochemical data to characterize and determine the rare-metals insert ignore into journalissuearticles values(Ta-Nb); mineralization attributes. The pegmatites which occur as near-vertical, large veins and dykes are hosted by migmatitic biotite gneiss. The pegmatites consist of quartz, feldspar, muscovite with rare biotite, occasional beryl and some minor/accessory apatite and zircon. Composite whole-rock samples were analysed for major, trace and rare earth elements using X-Ray Fluorescence Spectrometer insert ignore into journalissuearticles values(XRF); and Inductively Coupled Plasma Mass Spectrometer insert ignore into journalissuearticles values(ICP-MS);. The results reveal the pegmatites are considerably siliceous with SiO2 values of 69.00% to 74.60%. Al2O3 values are relatively moderate insert ignore into journalissuearticles values(14.80% to 19.60%);. Na2O and K2O abundances are low with ranges of 2.32% – 5.93%, 1.22% – 11.00% respectively. MgO abundances are generally low insert ignore into journalissuearticles values(0.03 – 0.07%);. Fe203 values are also low; ranging from 0.31% to 1.16%. Alumina Saturation Index insert ignore into journalissuearticles values(A/CNK); computation with values ranging from 1.40 to 3.06 indicates the pegmatites are peraluminous. Trace and rare-earth elements results show Bakunba location pegmatite is mineralised insert ignore into journalissuearticles values(Nb: 571.86ppm, Ta: 180ppm); and compare favourably with other mineralised pegmatites in Nigeria; while Ganaja-2 location insert ignore into journalissuearticles values(Nb: 100.37ppm, Ta: 26.6ppm); are moderately mineralised. Nb-Ta values of Shagari location insert ignore into journalissuearticles values(33.14ppm; 2.7ppm);, Ganaja-1 location insert ignore into journalissuearticles values(12.6ppm; 3.6ppm); and Crusher location insert ignore into journalissuearticles values(0.91ppm; 0.2ppm); show they are barren. Various variation plot diagrams, such as Kb/Rb vs Cs, K/Rb vs Rb, also show mineralization status of these pegmatite bodies as compared with some local and foreign pegmatites. Plots of Zr vs SiO2, Rb vs Y+Nb and Rb vs Sr indicate the pegmatites are magmatic, from within plate granites and in crustal thickness of more than 30 km during the time of emplacement.
Keywords : Pegmatite, Rare metals mineralization, Trace elements, Niobium, Tantalum

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