Geochemical and mineralogical evaluation of Libale iron- rich manganese deposit, North-central Nigeria

Abstract

The iron-rich manganese deposits of Libale area is located within the basement complex of North-central Nigeria. Mineralogically, the major mineral phases are: goethite (Fe₂O₃.H₂O), spessartine (Mn₃²⁺Al₂(SiO₄)₃), hematite (Fe₂O₃), and quartz (SiO₂), while minor mineral phases are orthoclase (Al₂O₃.K₂O.6 SiO₂), illite (KAl₂Si₃AlO₁₀(OH)₂), and manganite (Mn₂O₃.H₂O) suggesting a trend of mineral assemblage attributed to the differential mineralization of the iron-manganese deposit that may have been caused by the geochemical tectonic activity during its formation. Geochemically, on average, the Fe₂O₃, SiO₂, Al₂O₃, CaO, P₂O₅ content are 34.59 wt.%; 26.30 wt.%; 6.94 wt%, 2.60 wt%, 2.01 wt% correspondently while K₂O and TiO₂ are less than 1wt%. Suggesting oxide facies type for the deposit. The trace element composition of V (1040 ppm), Cr (100 ppm), Co (833.33 ppm), Cu (1740 ppm), Nb (1280 ppm), W (240 ppm), Ta (320 ppm) and Zr (302 ppm) were relatively high compared to Maro, Muro and Kakun BIFs in North-central Nigeria. Bivariate plot of Fe₂O₃ Vs. Al₂O₃, suggest enrichment of Fe₂O₃ but depleted in SiO₂ and Al₂O₃, which possibly indicates replacement of precursor silica and kaolinite with goethite which are subsequently dehydrated to hematite. Al₂O₃-SiO₂-Fe₂O₃ ternary diagram indicates Precambrian Banded Iron Formation (BIF) for the Libale iron- rich manganese deposits, this was confirmed by MnO Vs. FeO. Discriminative plots: FeO. SiO₂ - (FeO + MnO) - Fe₂O₃ and Al₂O₃+ K₂O + Na₂O Vs. MnO + FeO confirmed mixed facies as the analyzed data plots between silicate facies and magnetic-silicate facies, this is linked to chemical association between Al₂O₃ and SiO₂ for the iron-rich as it confirms a transitional grade of silicate facies to magnetite-silicate facies. SiO₂ Vs. Al₂O₃ plot revealed hydrothermal and diagenetic processes for its deposition. The iron-rich manganese deposit is of low grade iron (Av. Fe=24.19%) characterized by ferruginous manganese (Av. MnO₂=23.82%) based on the generalized percentages of element of major interest in assessing quality of iron and manganese ore, therefore, good for cast iron production.