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Description
Ugep Southwest is an extension of the Nigerian Basement Complex. It consists of Precambrian crustal rocks that include a succession of deformed metamorphic rocks and non-deformed sedimentary rocks that overlie the basement rocks. The metamorphic rocks are intruded by granodiorites and pegmatites. Gneisses display a sharp contact relationship with the schists, occurring in association with quartzite as observed in Ikot Ekperem. Granodiorites contain enclaves of schistose xenoliths, indicating that magmatic stoping was the mode of emplacement during the Pan-African Orogeny (600 ± 50 Ma). Ugep Southwest has undergone various stages of deformation, as evidenced by complex structures such as folding, faulting, fracturing, lineation, and foliation. The grade of metamorphism was progressive from lower greenschist facies (phyllites and schists) in the west to middle amphibolite facies (gneisses) in the east. Petrological observation using Scanning Electron Microscope (SEM) reveals that the metamorphosed rocks are dominantly composed of plagioclase, biotite, chlorite, and muscovite. Pegmatites have a higher concentration of quartz relative to their magma source. Geochemical analysis using X-ray Fluorescence Spectrometer (XRF) reveals high contents of silica and alumina, implying a crustal origin for the rocks. Barium concentration was higher, suggesting contamination by crustal materials. The geochemistry of these rocks reveals that phyllite and schist are metasediments of pelitic and greywacke composition, while the gneiss is orthogneiss. Granodiorite is calc-alkaline, and the dolerite is tholeiitic. The plots in variation diagrams confirm these geochemical signatures.
