Geometric and Kinematic Characterization of Fractures within the Basement Complex Rocks of Ago-Iwoye, Southwestern Nigeria

Fractures within metamorphosed rocks in the Basement Complex of Ago-Iwoye in southwestern Nigeria were investigated based on their geometric and kinematic interactions. The main fracture attitudes described in this work include fracture types, geometric intersections, topological relationships, chronology, and displacement fields. The rocks found in the study area are migmatite gneiss, banded gneiss, granite gneiss, and pegmatites. The chronological and field relationships between the gneisses and the surrounding granite gneiss provide valuable insights into the Proterozoic rocks preserved within the reworked Pan-African granite rocks. In parallel, the fractures include three common types: unfilled opening-mode fractures, mineral-filled fractures, and mildly sheared extension veins, all showing both geometrically and kinematically coupled characteristics, as well as decoupled features. Geometrically coupled fractures share a common intersection line, while kinematically coupled fractures display overlapping displacement, stress, and strain fields. Importantly, the complex interactions among these fractures highlight the complex and polycyclic nature of the Nigerian Basement Complex rocks in the study area.