Geochemical characterization of Egbetua stream sediments, southwestern Nigeria: implication for provenance and depositional conditions

Abstract

The aim of this work is to determine the provenance, chemical index of alteration, elemental spatial distribution in the stream sediments, stream flow energy and the depositional conditions in the study area. The study area is located in Egbetua area in Akoko Edo Local Government Area of Edo State, Southwestern Nigeria. It is located on latitudes 07º 21’30’’N and 07º 22’N longitudes 06º 15’ 30” E and 06º 17’E and average elevation of 182 metres. Standard field and laboratory procedures were used in the study. Geochemical analysis was carried out using x-ray fluorescence method. Average concentrations of SiO2 (78.24 wt. %), Al2O3 (ca. 12.15 wt. %) and the chemical index of alteration (CIA) values of 68.90% indicate felsic granitic source rocks. Ce/Ce*, Eu/Eu* and (La/Yb)n ratios were used to deduce the prevailing reducing-oxidizing depositional environment of the sediments. Ce/Ce* (0.80) confirmed an oxidizing environment of deposition with low stream flow energy, while Eu/Eu* (0.07) corroborated an oxidizing environment with felsic source rock. (La/Yb)n (5.95) indicated an oxidizing environment in a low stream energy flow with coarse-grained and clay size sediment input.