Assessment of Bituminous Sand from Agbabu, Southwestern Nigeria Using Geochemical and Sedimentological Approach

Abstract

Bituminous sands consists of sand and other associated clastic rocks which are impregnated with heavy hydrocarbon (bitumen), chemically similar to conventional oils but which have high densities or low API gravities (<120 API) and high viscosities. A total of ten (10) samples were collected from the study areas and used for geochemical and sedimentological analysis. The order of the mean concentrations of tested heavy metals in the sampled bitumen within the area are; Mn>Ba>Pb>Cr>Cd>Cu>Co>Ni>. Based on the Geo Accumulation Index (Igeo), the study areas are generally classified as unpolluted with regards to the measured heavy metals. From the interpretation of the analysis, the values of the mean, standard deviation, skewness and kurtosis were found to range between 1.1- 2, 0.89- 1.753, -0.454 - (-0.1866), 0.84- 1.548. The mean and standard deviation signifies that the sediment was generally medium grain size and moderately sorted which implies that the sands have undergone a fairly long transportation history. The values of skewness and kurtosis signify that the sample are generally coarse skewed and leptokurtic. Results of bitumen saturation analysis revealed that the average percentage weight of the bitumen in the surface samples ranged between 23.68% and 96.54% with an average bitumen saturation of over 40%. The presence of heavy mineral suites of Zircon, Tourmaline and Rutile in all the samples indicates that the sediments were derived from igneous and metamorphic rock of nearby basement rocks but their accumulation was strongly controlled by mechanical process of sedimentation.