Osun River Basin Sediments Heavy Mineral Distribution.

Heavy mineral assemblage of sediments in Osun River basin has been studied in five states in Southwestern Nigeria to determine their concentrations and provenance. Twenty-five sediment samples were analyzed for heavy mineral assemblage determinations. The separation of these minerals was carried out using bromoform (specific gravity 2.85) and slide examination under the petrographic microscope. The heavy minerals assemblages of Zircon, Tourmaline, Rutile, Silimatate, Garnet, Epidote, and Staurolite indicated its derivation from mixed sources of acid igneous rock to medium and high grade metamorphic rocks. The calculated ZTR % values varied between 21.1% in Ekiti to 56.7% in Lagos State and the mean ZTR (Zircon, Tourmaline, Rutile) percentage indices was 36.4%. The two most abundant were Staurolite and Rutile with 43.92% and 11.95%, respectively. We found that their concentrations and sizes increase from Ekiti state in the upper section of the Osun basin to Lagos in the Southern part of the basin according to coastal drift. (Keywords: heavy minerals, river sediments, activity concentration, provenance, mineralogical component, Osun River, zircon, tourmaline, rutile, silimatate, garnet, epidote, staurolite)