Petrologic and Structural Features of Basement Rocks of Parts of Mukuru Area, Southeastern Nigeria

Abstract

Field investigations in the western part of Mukuru area indicate intense structural imprints and high HT/HP metamorphism, and some magmatism. The rock units in the area include migmatitic gneisses, granulites, amphibolites, schists, charnockites, epidiorites and granites. The charnockites which are common in the shear zone and boundary areas appear to mark the end of magmatism. However, relicts of magmatic rocks mapped at Ubong Community in the study area suggest earlier magmatism. The metamorphic rocks are strongly deformed in a N-S to NE-SW direction with ghost structures, pinch and swell structures, ptygmatic veins, showing evidence of extensional tectonics. No visible contact relationship between the migmatitic gneisses and schists was observed. Diagnostic metamorphic structures like fine banding/layering of alternating dark- and light-coloured layers are conspicuous in gneisses and some amphibolites while schistosity and deep weathering are present in schists. The geodynamic features prevalent in Mukuru area are deformation and metamorphism. They indicate a possible petrogenetic link to southern Obudu Plateau in the north, western Cameroon in the east than Bansara in the west.