Major Oxide Composition of Selected Coals From Anambra Basin, Southeastern Nigeria: Implications for ASH Deposition Tendency, Paleoenvironment Reconstruction and Tectonic Setting

The study on major oxide geochemistry of coal is vital to the determination of ash deposition tendencies, paleoclimatic and paleoredox condition reconstruction, hydrothermal influence and tectonic setting of coal. Geochemical analysis for Eha-Alumona and Ehandiagu coals was performed by X-ray fluorescence (XRF) Spectroscopy techniques with values in the range as follows SiO2 (47.39-51.64%), Al2O3 (29.38-33.32%), Fe2O3 (6.50 -10.36%), and TiO2 (1.22–1.98%), MgO (0.045–0.11%), CaO (0.25– 0.50%), Na2O (0.020–0.040%), and of K2O (0.13-0.027). Major oxides such as SiO2, Al2O3 and Fe2O3 constitute greater than 86% of the bulk compositions of both coals. The ash deposition indices suggest a low slagging and fouling propensity which means the coals are non-problematic during combustion. Results from the computed values of major oxide geochemical indices and bivariate plots revealed that the coals are sub-bituminous in rank, a semi-arid palaeoclimatic climatic condition prevailed at the time of deposition, an oxic to sub-oxic paleoredox condition. The coal samples are derived mainly from terrestrial sources. The tectonic setting of the source material for forming coal is from an active continental margin related to the subduction of oceanic crust beneath the continental crust