Geochemical Signatures and Mineralogical Composition of Basement Complex Lithologies in Afokpella, Southern Nigeria
Keywords:
Afokpella, Basement Complex Rock, Geochemistry, Petrography, Charnockite, Pan-African OrogenyAbstract
The Afokpella Area, located within the eastern extension of the Igarra Schist Belt in southwestern Nigeria, is underlain by a complex assemblage of Precambrian Basement complex rocks dominated by granites, charnockites, pegmatites, and marbles. This study investigates the geochemical and mineralogical characteristics of these rocks in order to constrain their petrogenesis, tectonic setting, and mineralization potential. Ten representative rock samples were collected and analyzed using X-ray fluorescence (XRF) for major oxide composition, complemented by petrographic thin-section analysis under a polarizing microscope. Results show that SiO₂ (55.82 wt.%), CaO (12.13 wt.%), Al₂O₃ (11.92 wt.%), and K₂O (5.21 wt.%) dominate the geochemical composition. Strong positive correlations were observed between Al₂O₃–SiO₂, Fe₂O₃–TiO₂, and LOI–CaO, while CaO shows strong negative correlation with SiO₂ and Al₂O₃, reflecting contrasting lithologic controls between silicate and carbonate rocks. Petrographic analysis reveals quartz, feldspars (microcline and plagioclase), biotite, hornblende, hypersthene, muscovite, and garnet as the dominant minerals. Geochemical discrimination diagrams classify the granitoids as high-K calc-alkaline to shoshonitic, peraluminous to slightly peralkaline, and emplaced within a passive continental margin setting. The marbles are characterized by very high CaO and LOI contents, indicating carbonate protoliths deposited in a shallow marine environment. Overall, the basement rocks of Afokpilla reflect crustal melting processes associated with Pan-African tectonism and possess significant industrial and economic mineral potential.
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