Preliminary review of the geology of the hornblende biotite gneisses of Obudu Plateau Southeastern Nigeria

Abstract

The Obudu Plateau, southeastern Nigeria is dominantly underlain by gneissose rocks with migmatitic characteristics, one of which is the hornblende-biotite gneiss. The gneisses are banded with quartz and plagioclase as the major minerals in the leucosome while hornblende and biotite occur in the palaeosome. Geochemically, the rocks are enriched in silica and alumina with an average of 71.6wt% and 14wt% respectively. Geochemical plots indicate that they are calc-alkaline to tholeiitic in character and derived from protholiths of igneous origin with minor sedimentary input.

Implications of tectonic anomalies from potential field data in some parts of Southeast Nigeria

“…Archaean, Eburnean and Pan-African ages have been gotten from rocks of this area (Ukwang et al, 2012). The relatively close match between the lithology of rocks and ages of the Southeast Nigeria, Northern Cameroon and Central African Fold Belt basement complexes (Ukwang et al, 2012) made researchers to infer that the existences of Nigerian Southeast basement evolutionary history is related to the Pan-African mobile belt in Central Africa (Agbi and Ekwueme, 2018). The Pan Central African belt in Central Africa is due to a continent-continent collision that involved the northern edge of the Congo Craton as the passive margin and the Adamawa-Yade and western Cameroon domain as the active margin (Agbi and Ekwueme, 2018;Toteu et al, 2004).…”

“…The Obudu Plateau which is an annex of the Bamenda Massif, is one of the Nigerian Precambrian basement outcrops in southeast Nigeria (Agbi and Ekwueme, 2018). The lithological disparities in the area involve high grade metamorphic rocks comprising predominantly of schists and gneisses that have been migmatized and intruded by unmetamorphosed dolerites, granites and quartzo-feldspathic veins (Agbi and Ekwueme, 2018). Also, associated with these rocks are insignificant occurrence of amphibolites, metaquartzites and metagabbros.…”

“…The relatively close match between the lithology of rocks and ages of the Southeast Nigeria, Northern Cameroon and Central African Fold Belt basement complexes (Ukwang et al, 2012) made researchers to infer that the existences of Nigerian Southeast basement evolutionary history is related to the Pan-African mobile belt in Central Africa (Agbi and Ekwueme, 2018). The Pan Central African belt in Central Africa is due to a continent-continent collision that involved the northern edge of the Congo Craton as the passive margin and the Adamawa-Yade and western Cameroon domain as the active margin (Agbi and Ekwueme, 2018;Toteu et al, 2004). The OP is dominated by migmatitic gneisses that have been grouped and described as garnet-sillimanite gneiss, garnet-hornblende gneiss, or simply as migmatite gneiss (Agbi and Ekwueme, 2018;Ukwang et al, 2003).…”

“…The Pan Central African belt in Central Africa is due to a continent-continent collision that involved the northern edge of the Congo Craton as the passive margin and the Adamawa-Yade and western Cameroon domain as the active margin (Agbi and Ekwueme, 2018;Toteu et al, 2004). The OP is dominated by migmatitic gneisses that have been grouped and described as garnet-sillimanite gneiss, garnet-hornblende gneiss, or simply as migmatite gneiss (Agbi and Ekwueme, 2018;Ukwang et al, 2003).…”

“…The evolution of the Nigerian Basement Complexes and Benue Trough were considered in the light of tectonothermal and global tectonic events respectively (Agbi and Ekwueme, 2018;Burke and Dewey, 1974). Over time, geologic structures in the Precambrian basement rocks were caused by the intrusions of Mesozoic calc alkaline ring complexes that is, younger granites (Woakes et al, 1987).…”