Granulometric Characteristics and Heavy Mineral Composition of Igbokoda Beach Sands, Ondo State, Southwestern Nigeria

Abstract

Analysis of grain size distribution has been widely used by sedimentologists to classify sedimentary environments and elucidate transport dynamics. Grain size and heavy mineral content analysis of Igbokoda beach sands, Ondo State, Southwestern Nigeria was carried out to determine the provenance, maturity, industrial and economic significance as well as the economic prospect of the heavy minerals present in the beach sands. For the purpose of this study, a total number of ten (10) beach sand samples were collected along the beach sides in Igbokoda for laboratory analyses. For grain size and heavy mineral content analyses, granulometric and heavy mineral content analyses were carried out on the samples. Grain size analysis was determined by dry sieving the sediments. Granulometric analyses of Igbokoda beach sands showed that Igbokoda beach sands are predominantly fine-medium, clay-free, well-sorted, near symmetrical-fine skewed beach sands with mesokurtic-leptokurtic types ranging from 2.000 mm to 0.063 mm.  From the provenance study, the samples were observed to be mature and predicted to have been sourced from a distal source. Heavy mineral content investigation was carried out using heavy mineral separation techniques, which involve using separating funnels and tetrabromoethane, which make up 6-15% of the weight of Igbokoda beach sands. For the purpose of this study, samples were collected from the various sections of the Igbokoda beach sides. For the first section of the beach side, the percentage of concentration of ilmenite is the highest, followed by zircon, pyroxene, rutile, with subordinate amounts of epidote, augite, garnet, apatite, spinel, staurolite and tourmaline. In the second section, almost similar results to the first section were obtained, except in some cases, that is, the concentration of ilmenite and magnetite is lesser, covellite and kyanite are present. From the results, Igbokoda beach sands are predicted to have been sourced from a continental environment and consist of intrusive granitic, metamorphosed and partly sedimentary rock types. However, the beach sands are derived predominantly from intermediate source(s), probably granodiorite. The presence and abundance of heavy minerals like augite, rutile, tourmaline, pyroxene, zircon and others in the bulk composition of the beach sands supports the influence of granitic, gneissic, granodioritic and schistosity sources from nearby crystalline basement complex. Igbokoda beach sands serve various industrial purposes such as filtration, production of glassware and construction.