Structural geological mapping and mineralization potential indicators in the psammitic rocks of efon-alaaye and environs, Southwestern Nigeria

Abstract

Asubiojo Folaseye Emmanuel and Ayodele Olusiji Samuel*

The geological and structural studies of the Basement Complex rocks in Efon-Alaaye and Environ area revealed that the basement rocks has undergone polyphase deformation episodes leading to its structural realignment. The dominant rock types are the metasedimentary assemblages referred to as the “Efon Psammite Formation” and the older quartzo- feldspathic gneisses. Two phases of deformation have affected the entire study area. The first phase was characterized by intense deformation and folding accompanied by regional metamorphism. It is mostly a fabric forming deformation that also resulted in low angle plunge and mineral lineation development generally in the N-S direction, synformal, antiformal and overturned folds are typical of this deformational stage. Also, the development of associated fault to the Iwaraja (ductile) shear zone occurred during the second deformation episode, as well as the N-S trending pegmatite vein that crystallized along the lineation of the granitic gneiss. Extensional fractures (joints) in the various outcrops have bi-modal orientations in the NE-SW, E-W and ESE-WNW directions. These structures are believed to be imprinted on the basement rocks during the end of the Pan African orogeny, and are believed to be themineralization potential indicators in the study area.