Rare Earth and Trace Elements Composition of a Residual Clay from Sosan Akoko, Southwestern Nigeria: Implications for Weathering and Provenance

Abstract

The aim of this study is to determine the source area weathering and provenance of a residual clay samples overlying Precambrian basement complex in Southwestern, Nigeria. Fifteen representative clay samples were collected from three pits dug in three locations across the study area. The mineralogy and chemical composition of samples was analyzed using X-ray diffractometer (XRD) and inductively coupled plasma-mass spectrometer (ICPMS) techniques respectively. The results of mineralogical analyses indicates that kaolinite (1.4%) and nontronite (2.77%) are the major clay minerals present while the non-clay minerals include quartz, orthoclase, labradorite and albite. Chemical indices of alteration (CIA) and weathering (CIW) values of 76.02% and 89.9% respectively, low alkali and alkaline earth elements content derived from the samples implies a comparatively intense source area. Furthermore, plots of TiO2/Al2O3 indicate provenance of predominantly acidic rocks and high concentrations of Rubidium (Rb) and Strotium (Sr) in the samples with values ranging from 113.4-138.2 ppm and 218.3-229.2 ppm respectively suggests ongoing chemical weathering of the clay body. The findings from this research through mineralogical composition, rare earth elemental normalized patterns, and ternary diagrams plotted implies that these samples are derived from felsic sources.