A Review of the Petrography and Geochemical Characteristics of the Pan African Granites in the Nigerian Precambrian Basement Complex

Abstract

 Ibe Chinedu Uduma*, Orunna Chidiebere and Aghaebita Ifeoma Chinwendu

A compilation and review of the grantoids within the Nigerian Precambriam Basement complex is presented. The granitoids or granitic rocks in the Nigerian Precambrian basement complex have been studied by several researchers for about sixty decades now. The studies had included their field relationship, petrography, and major element chemistry only. In recent times, detailed geochemical data, including major-, trace-and rare-earth elements have been obtained and used in assessing the petrogenetic and tectonic evolution of the granitoids. The rocks consist of porphyritic/porphyroblastic muscovite granites, biotite granites, hornblende-biotite granites/granodiorites, non porphyritic/non-porphyroblastic granites, aplites, granodiorites, diorites, quartz diorites, syenites/syenogranites, quartz-charnockite/charnockites. They are predominantly alkali-calcic to calc-alkalic and strongly peraluminous and were most likely derived from partial melting of crustal materials in an orogenic (post-collisional) tectonic setting. The granitoids are products of anatectic melting of the highest grade of amphibolite facies regional metamorphism of the surrounding peraluminous schists and gneisses. Some are, however, products of partial melting of hornblende-rich (igneous) crustal sources due to their metaluminous character. Radiometric age data reveal that they were emplaced at about 638 to 539 ± 8 Ma (Neoproterozoic-Pan-African).