EVALUATION OF LIMESTONE TEXTURAL AND GEOCHEMICAL COMPOSITION IN ONIGBEDU, OGUN STATE, IN RELATION TO ITS INDUSTRIAL USAGE AND DEPOSITIONAL ENVIRONMENT

Field relationship, petrographical studies and geochemical analysis were combined in investigating the depositional environment and industrial viability of limestone beds in Purechem’s quarry at Onigbedu. Field observation indicates a homogenous lithology of the beds with variation in textural and clastic composition. Petrographic study revealed that the limestone falls under the Biospamicrite and Wackestone classification based on the works of Folks, (1959) and Dunham, (1962) respectively. The geochemical analysis which involves the use Atomic Absorption Spectrophotometer (AAS) to determine the major and minor oxides and the LOI constituent of the six (6) limestone beds reveals that; the CaO concentrations ranges between 48.75 and 54.24% with a mean value of 52.63%. The silica SiO2 contents range between 1.26 – 8.33 % with a mean value of 2.98% and Fe2O3 between 0.55 – 1.11% with mean of 0.74%, MgO and Al2O3 contents vary between 0.58 – 1.11% and 0.52 – 1.25% with equal mean values of 0.79%. The limestone is highly fossiliferous with the identified fossils indicating deposition in an open shelf environment. Moreover, the limestone deposit was equally observed to be principally mud supported which is indicative of rocks deposited in quiet water and a low energy environment, therefore from all indication, the limestone was deposited under low to high energy condition. Interpretation of these results suggest a shallow marine environment. The observed compositional features of the limestone makes it a very viable industrial raw material because it certifies the specifications of the Morroccan Standard NM 10.1.004, and the American Construction Code, in the use of limestone for various industrial purposes.