Petrophysical Characterization and Lithological Mapping of the Ikole–Itapaji Basement Complex, Southwestern Nigeria

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The Ikole–Itapaji area forms part of the Precambrian Basement Complex of southwestern Nigeria and comprises diverse crystalline rocks whose lithological and structural characteristics influence their inferred petrophysical behaviour. This study focuses on the petrophysical characterization and lithological mapping of the Ikole–Itapaji Basement Complex using detailed field geological investigations, structural measurements, rock sampling and lithological interpretation. Geological mapping was conducted across accessible exposures, while lithological characteristics, weathering conditions and structural features were systematically documented. Thirty-five representative rock samples were collected from the major lithological units to support lithological characterization. The mapped basement comprises gneiss, migmatite, granite, pegmatite and charnockite, distinguished based on their mineralogical, textural and field characteristics. Structural features, including foliation, joints, fractures, folds, quartz veins, and shear zones, were also identified and measured. The petrophysical characterization was qualitative and geologically constrained because direct measurements of porosity, permeability, density and electrical resistivity were not undertaken. The results indicate that the inferred petrophysical behaviour of the basement is primarily controlled by lithology, weathering and structural discontinuities. Fresh, massive crystalline rocks are expected to have very low primary porosity, whereas weathered, fractured, and jointed zones may develop enhanced secondary porosity and permeability. Gneiss and migmatite exhibit relatively greater potential for secondary fluid movement where structural discontinuities and weathering are well developed, while granite, pegmatite and charnockite are comparatively massive and have limited primary pore space. The study demonstrates that lithological mapping integrated with structural and weathering characteristics provides a useful basis for qualitative assessment of the petrophysical behaviour of crystalline basement rocks in the Ikole–Itapaji area.

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