Discussion
The rocks of the study area display characteristics features of Pan African and the MGC rocks of Nigeria. Field observation suggests that these rocks have undergone a high degree of alteration especially surface weathering, which implies that they are not I-type of granitic rocks (Chappell & White, 1974). The penetrative foliation of some of the gneisses resulted from the magmatic segregation of the mafic and felsic content of the rocks. Assuming foliation and other metamorphic fabrics, sample 1, 2 & 5 are categorized as igneous rocks.
The metamorphosed rocks display different kinds of foliation from slightly foliated rocks (granite gneiss), to strongly aligned porphyries in the porphyroblastic gneiss, and strongly foliated banded gneiss. These are metamorphic fabrics diagnostic of the migmatized basement complex rocks of Nigeria.
The granitic rocks plotted as quartz-rich granitoid and granodiorite on the QAP diagram. The older granite suites include such rocks as granodiorite, syenite, monzonite, charnockite, and other granites. The preponderance of the plagioclase among the feldspars as observed in thin section and XRF analysis confirmed the naming of this rock as granodiorite. The quartz-rich granitoid also has the highest quartz and SiO2 content both in thin section and from geochemical analyses.
High alumina content is consistent with the chemistry of Pan African rocks, which implied that the rocks of the study area are peraluminous and S-type granitic rocks. This high calc-alkaline content corroborates the description of Falconer, 1911, Burke et al., 1976, Turner, 1983, Odigi et al., 1993, Dada et al., 1995, Oyinloye, 1998 on other parts of the basement complex terrain of Nigeria. The high hypersthene content of the granites suggests they are charnokite affinities.