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ABSTRACT
This study was carried within the Anambra Basin with the aim of determining the chemical composition and basic geotechnical and physical characteristics of Ogiso and Okhoro clay deposits in Edo State, Southern Nigeria. In this study, ten (10) fresh clay samples were randomly collected, three (3) from Okhoro and seven (7) from Ogiso and were subjected to X-ray-Diffraction (XRD), X-ray-Fluorescence (XRF) and geotechnical analysis to determine their mineralogy, chemical composition and engineering behaviour so as to evaluate their economic potential. The XRD analysis revealed that the basic mineralogy of the samples studied is made up of kaolinite, quartz and hematite with traces of zircon, illite and anatase occurring in minor amounts in some of the samples. The XRF analysis revealed the occurrence of 10 elemental oxides and 10 elemental trace elements. The major elemental oxides include SiO2 with a range of 55.82 – 61.41wt %, Al2O3 with a range of 21.12 – 24.42% and Fe2O3 with a range of 6.05 – 9.06% while the major elemental trace elements are zircon with a range of 0.89 – 1.78wt%, zinc with a range of 0 – 1.51%, copper with a range of 0 – 1.39wt% and chromium with a range of 0.01 – 0.11wt%. The geotechnical analysis revealed that the samples are of low to medium plastic inorganic clay with percentage fines fraction of 76.84 – 78.45%. The high chemical index of alteration (CIA) values, high chemical index of weathering (CIW) values and moderate ratio of TiO2/Zr suggest an intense weathering source area. The mineralogical composition, the elemental trace element, main element discrimination diagram and elemental ratios of these samples such as TiO2/Al2O3 suggest a provenance mainly of intermediate source. The results from the analysis further indicate the clay samples from the study areas are mainly kaolinitic clay and categorized as commercial ball clays. It is a fairly good construction material based on the moderate plasticity index.
