Structural evolution of precambrian basement rocks of Jebba area, s.w. Nigeria

Abstract

Geological studies show that the Jebba area, S.W. Nigeria is underlain by metasedimentary and metaigneous rocks including gneisses which have been intruded by Neo-Proterozoic (Pan-African) granitic rocks. The metamorphic rocks including migmatitic gneiss, quartzofeldspathic gneiss, metagreywacke, quartzite, quartz-mica schist and granitic gneiss have been subjected to polyphase deformation. Early, D1, deformation gave rise to recumbent folds associated with axial planar foliation. Later, D2 event produced asymmetrical folds and axial planar crenulation cleavages. The D3 episode was associated with ductile thrusting at deeper crustal levels and D4 with brittle thrusting at upper crustal levels, as well as tight to open folds with subhorizontal axial planes. D5 involved strain localisation along steep, strike-slip faults.

Keywords: keJebba area, polyphase deformation, foliations, folds, ductile thrusts, stretching lineations, brittle thrust faults, strike-slip faults

Global Journal of Geological Sciences Vol. 6 (2) 2008: pp. 149-152