Morphological attributes, petro chemistry and origin of quartzite units in Ekiti, South-Western Nigeria

Abstract

This study presents lithologic and petrogenetic investigation of bedded quartzite from Okemesi and massive quartzites from Ado-Ekiti in southwestern Nigeria. Okemesi quartzite is extensive, thickly bedded and steeply dipping while quartzite from Ado-Ekiti is hummocky, ferruginous, fractured, and non-bedded. Analytical results reveal average SiO2 Okemesi (94.74 %) and Ado-Ekiti quartzite (93.88%). Similarly, average Rb/Sr are 0.74 and 1.22 while Sr/Ba are 0.89 and 0.69, respectively. These parameters portray them as supracrustal rocks of continental origin. Implying quartzites in Ekiti are non-schistose pelitic metasediments. Na2O/Al2O3 versus K2O/Al2O3 diagram revealed the quartzite units are sedimentary in origin and are compositionally similar to the Scottish metapelite and Igarra quartz mica-schist. Chemical Index of Alteration (CIA) of Okemesi quartzite (88 %) and Ado-Ekiti quartzite (91 %) which are relatively high signifies intense chemical weathering of their source rocks. Index of compositional variability (ICV) of Okemesi quartzite (0.83) and Ado-Ekiti quartzite (0.74) indicate the quartzites are immature pelite.