A Prefeasibility Economic Evaluation and Geochemical Characteristics of Abuja Leather Mining District Pegmatites, Southwestern Nigeria

Abstract

The Abuja leather mining district located in southwestern Nigeria is one of the productive pegmatite field in Nigeria and is known to bear valuable economic minerals and associated with granite gneiss were studied with a view to evaluate their petrogenetic characteristics and economic evaluation of the rare metal Ta-Nb mineralization in the area. A systematic geological survey, pitting, geochemical analysis and economic evaluation were carried out. Petrological studies were carried out on some selected representative rock samples were prepared and studied for petrographic analysis. Mineralization is limited to the pegmatites which are moderately weathered in the prospect zones and these streams of pegmatitic veins are semi discordant and they contain mainly quartz, muscovite, mica-plagioclase (albite), and microcline as the main minerals while tourmaline and beryl occur in subordinate amounts.Geochemical analysis revealed that the pegmatites are siliceous and of rare – metal type. The host rocks are peraluminous and of S – type. Albite, lepidolite and muscovites (extracted from the pegmatites) are significantly enriched in Li, Rb Cs, Nb and Ta compared to the granite gneiss. The whole rock samples showed strong affinity to the syn-collisional and volcanic arc granites with an enrichment LREE and a depletion in HREE with a strong negative Eu anomaly. the rare-metal pegmatites exhibit pronounced negative Eu and slightly positive Ce anomalies. The low K/Rb ratio of the pegmatites indicates fraction accompanied by Rb enrichment and Ba depletion. Probable reserves of Ta₂O₅, Nb₂O₅ and SnO₂ for prospect 1 up to 20m assuming grade constancy is 131.00tons, 396.11tons and 306.96tons respectively, for prospect 2 is 279.05 tons, 858.913 tons and 783.08 tons respectively, for prospect 3 is 60.58 tons, 822.16 tons and 697.96tons respectively, for prospect 4 is 3.59 tons, 8.72 tons and 32.55 tons and for prospect 5 is 255.52 tons, 616.98 tons and 441.41 tons respectively. Proper process method to maximize recovery is suggested to make the venture profitable as enumerated in this research. The present system of recovery using simple planning method can only guarantee 11% recovery, which will not be economical considering the size of the deposit.

Keywords: pegmatite, economic evaluation, geochemistry, recovery, Nigeria.