Investigation of the Geochemical Composition and Paleo-Depositional Environment of Ubo and Ikpeshi Marble Deposit, Southwestern Nigeria: A Comparative Study

Abstract

The marble deposits at Ubo and Ikpeshi areas of Edo state, Southwestern Nigeria, were studied in order to determine the major elements and the paleo-depositional environment of the original sediments using standard methods.  Results obtained using test of difference between Ubo and Ikpeshi marbles showed that CaO (51.977±0.922 & 54.726±0.23), MgO (3.034±0.829 & 0.499±0.115), Na₂O (1.7±0.73 & 0.024±0.008), MgCO3 (6.337±1.734 & 1.034±0.238), Cu (24.589±0.692 & 27.447±0.711), Ni (23.907±0.854 & 30.979±0.494), all for Ubo and Ikpeshi respectively; with Ni showing highest significance with P<0.01. The Ubo marble deposit occurs as a lensoid body within the younger metasedimentary sequence. The major element composition reveal a mean chemical composition of CaO (51.97 and 54.73 %), MgO (3.0 and 0.49 %), SiO₂ (0.74 and 0.70%), K₂O (0.08 and 0.04%), Na2O (1.70 and 0.02%), Al₂O₃ (0.75 and 0.25%), Fe₂O₃ (0.34 and 0.25%), and Loss on Ignition - L.O.I (43.34 and 49.31%) in Ubo and Ikpeshi marbles respectively, which is indicative that the marble samples were all calcitic. The low values of the total alkali content in the marble samples from the two locations indicate that the environment of deposition of the original carbonate materials that metamorphosed into marbles from both locations must have  been a shallow, highly saline environment with probably little influx of salty brine water in the basin. Silica was used as an abscissa in these plots because it shows substantial variations among the marbles with most of the linear relationship between silica and the  various oxides showing negative correlation, this probably reflects the admixture of the carbonates with chert. The trend of the plots of  Na₂O + K₂O vs. SiO₂ for the marbles from both locations show a variation in the salinity.

Keywords: Ubo, Ikpeshi, Marble, Marine Environment, Metasedimentary