Ikhane PR, Akintola AI, Bankole SI, Oyebolu OO and Ogunlana EO
The knowledge of particle size distribution and the assemblages of heavy minerals in sedimentary rocks particularly in the Earth’s crust make it possible to effectively locate and use essential minerals to predict their dispersal pattern when they re-enter the natural environment. Particle size distribution of Sandstone facies exposed near Igbile, South western Nigeria were described to study the provenance and deduce the transportation history, environment of deposition and source area of the sediment. Twenty four (24) surface samples collected from the study area were subjected to granulometric analysis in order to determine their grain size distribution using sieves method of mesh size ranging from 1.00M to 90μm. Twelve samples were selected from the twenty four samples for heavy mineral studies to describe the heavy mineral make-up, using float and sink procedure with dense liquid, thin section studies was also done. Result of the granulometric studies of the sediments are medium to coarse grained, moderately sorted and finely skewed. The mean value ranges from 0.67-1.30, which suggests high to low energy of transportation, Inclusive standard deviation (sorting) ranges from 0.70-1.15, with more samples falling under moderately sorted, it suggest that the have been transported relatively farer away from their source with relatively low energy of transportation at a regular intervals that permitted fair hydraulic sorting at a lower course of a river. Inclusive graphic skewness ranges from 0.28-0.89. Only location 2B falls under finely skewed while the rest are severely finely skewed which exhibits sediments imput from various sources of tributaries and also implies a low velocity than normal. The heavy mineral assemblage shows the presence of opaque and non-opaque minerals such as zircon, tourmaline, rutile, stourolite, garnet, epidote, apatite, silimanite and kyanite. The calculated Zircon-Tourmaline-Rutile (ZTR) index shows that majority of the sample location have >50% ZTR index which suggest that almost all the location contain mineralogically immature sediments. Distribution bar chart of the ZTR index shows that majority of the sample locations have greater than 40% ZTR which is suggestive of texturally immature sediments. All locations except location 2B did not contain garnet and Kyanite heavy minerals which are indicative of metamorphic source. The mono-source characteristic could also be responsible for the moderately well sorted exhibited by particles deposited in the location. Also, all locations except location 4B is characterized by sediment input from volcanic source due to the presence of Apatite heavy mineral which is a source indicator.
Share this article