Mineralogical evaluation of clay deposits of Nanka formation in parts of South-eastern Nigeria

Abstract

Detailed field geology and laboratory studies of the Eocene Nanka Formation were carried out where they outcropped in places like Ogbunike, Umunya, Nanka, Ekwulobia and Ogbu all in Anambra State, South-eastern Nigeria to determine their mineralogical composition. Samples of clay and unconsolidated sands were collected from outcrop locations within the formation and subjected to Xray diffraction and granulometric analyses respectively. The results of the X-Ray diffraction analysis (XRD) analysis indicated the presence of Quartz, Muscovite, Kaolinite and Hematite. Quartz ranges from 30.1 to 99.7% with an average of 53.68%, while Muscovite ranges between 62.6 and 69.6% with an average of 66.1%. Kaolinite and Hematite averages were 72.05 and 7.6%, respectively. The results of the granulometric analysis of sand samples revealed that the mean size value ranges from 2.33 to 3.295 which are indicative of fine to medium-grained to coarse-grained sandstone. Sorting ranged from 1.251 to 1.817 mm, showing that the sands were poorly to well sorted, while skewness and kurtosis range from 0.005 to 0.826 and 1.365 to 2.15, indicating symmetrical to very fine skewed and leptokurtic to very leptokurtic respectively. The sands and some clay minerals are abundant in the study area and they are good industrial minerals.