ALBERT

Description: Background and Objective: Petrostructural evaluation of Igarra and Otuo basement rocks is vital to understand the geology of the area. Petrostructural features of metaconglomerate in Igarra and Otuo areas, Southwestern Nigeria were investigated for mineralogical composition, characterization of structural features and complement existing research on the Basement Complex rocks of Igarra area. Materials and Methods: Six samples each from Igarra and Otuo were selected and prepared into thin section for optical examination while fresh whole rock samples of the metaconglomerate were pulverized for X-ray diffraction analysis following standard method. Results: Petrographical examination indicated that the rock matrix samples from both areas were dominated by quartz, chlorite, epidote and calcite while hornblende, magnetite and pyroxene constituted minor occurrence. X-Ray diffraction analyses indicated that Igarra metaconglomerate contained quartz (56%), epidote (9.7%), calcite (8.2%), chlorite (9.4%), hornblende (4.3%), feldspar (2.1%) and biotite (2.1%) while Otuo metaconglomerate had quartz (44.3%), epidote (13.2%), calcite (11.9%), chlorite (19.3%), hornblende (3.9%), magnetite (1.7%) and pyroxene (1.9%). Structural evaluation indicated that the rocks in both areas were strongly foliated with intense deformation. Conclusion: Petrographical and structural evaluation of metaconglomerate sequence in Igarra/Otuo area revealed mineralogical differences in the two areas but structurally, rocks in both areas were intensely deformed with dominant structural trend in the N-S direction. Prevalent brittle failures accompanied by viscous flow were responsible for the formation of the pinch and swell structures in the study area.