Structural characteristics of basement rocks in Kanyang Area, Boki LGA, Cross River State

Abstract

Kanyang is part of Mukuru sheet 305NW, Boki Local Government Area of Cross River State. The area is part of the foot of the Bamenda massif of Cameroon extension into the Cross River Plain, which have undergone polyphase deformation. Field mapping and measurements of planar and linear features shows dominant trends in the N-S and NE-SW directions while minor E-W and NW-SE trends are also present. Three phases of deformational episode have been recognized D1, D2 and D3 with pinch and swell, ptygmatic and ghost structures in the rocks of this area. These small scale geological structures are in conformity with the orientation of Mbe Mountain which is a major topographical feature in the area. These structural imprints on the rocks in the study area are indicative of Pan-African orogeny in an extensional tectonic environment. The minor NW-SE trends are interpreted as signets of pre-Pan-African deformational events in the Kanyang area. The area is characterized by high temperature and pressure rocks which appear mainly as banded medium to coarse grained metamorphic rocks such as granulite, eclogite, schist, quartzite and ironstone. There is also unmappable dolerite intrusion in the area. Minerologically, the average modal composition shows that the rocks in the area consist of quartz, k-feldspar, plagioclase, sillimanite, augite, omphacite, and almandine garnet, as the major minerals while opaque are accessory minerals.

Keywords: Rocks deformation, metamorphism, magmatism, structural features, Pan African, Kanyang, SE Nigeria