The ancient rocks of the Nigerian Province are split up by thrust and shear zones. The Migmatite-Gneiss Complex covers half of Nigeria's surface area and encompasses Archean gray gneisses, with tonalite and granodiorite consistencies. Within this complex are occurrences of schist, migmatite, garnet, sillimanite, kyanite and staurolite, which together indicate high-grade metamorphism up to the level of amphibolite on the sequence of metamorphic facies.