Geochemistry, mineralogy and thermal analyses of Cretaceous coals from the Benue Trough basin Nigeria: Reconnaissance assessments. (June 2021)

• Record Type: Journal Article
• Authors: Akinyemi, Segun A.; Nyakuma, Bemgba B.; Adebayo, Olajide F.; Kayode, Ayobami T.; Jauro, Aliyu; OlaOlorun, Olusola A.; Aturamu, Adeyinka O.; Madukwe, Henry Y.; Adegoke, Adebanji K.; Abdullah, Tuan Amran T.; Gitari, Wilson M.; Mudzielwana, Rabelani; Rabha, Shahadev; Saikia, Binoy K.; Hower, James C.
• Is Part Of: Journal of African earth sciences. Volume 178(2021)
• Publication Date: 2021-06
• Subjects: Geochemistry -- Mineral -- Trace elements -- Thermogravimetry -- Coal; Earth sciences -- Africa -- Periodicals; Earth sciences -- Middle East -- Periodicals; Geology -- Africa -- Periodicals; Geology -- Middle East -- Periodicals; Sciences de la terre -- Afrique -- Périodiques; Sciences de la terre -- Moyen-Orient -- Périodiques; Géologie -- Afrique -- Périodiques; Géologie -- Moyen-Orient -- Périodiques; Earth sciences; Geology; Africa; Middle East; Periodicals; Electronic journals; 556.05
• DOI: 10.1016/j.jafrearsci.2021.104167
• Languages: English
• ISSNs: 1464-343X

Abstract

Abstract: Selected coal samples from the Benue Trough Basin (Nigeria) were analysed by X-ray photoelectron spectroscopy (XPS), X-ray fluorescence (XRF), laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS), Fourier transform-infrared spectroscopy (FT-IR), and all the techniques used. The main minerals detected are clays (e.g., kaolinite and illite), quartz, feldspar, hematite and magnetite with traces of calcite, siderite, dolomite, orthoclase and graphite. The authigenic and detrital origins of the clay minerals detected were confirmed by FT-IR analysis. The XPS spectra identified elements similar to the mineral phases observed in the XRD spectra. The contents of Al2 O3, CaO, Fe2 O3, K2 O, Na2 O and P2 O5 were below the values reported for US and Chinese coals. The elemental indexes (e.g. Al2 O3 /TiO2, Co/Th vs. La/Sc, Cr/Th vs. Sc/Th) showed that the influence of intermediate-mafic materials derived from source-region sediments is negligible. The Ni/Co ratio showed that the coal forming marsh experienced comparatively mild redox conditions. The ratios of V/(V + Ni), Co/Ni, and Mo/Ni revealed marginal or non-existent marine effects. Trace metals ratios such as V/Ni, Sr/Ba, Rb/Sr, Sr/Cu and V/Zn showed evidence of a large degree of freshwater environment mainly in a humid climate. Maceral composition reflects fluctuations of dry and wet conditions in the forest swamp in a humid environment with an entry of marginal marine system and good plant tissue preservation. The rare earth elements (REE) in the coal samples studied are characterized by light-REE enrichment. Thermal decomposition resulted in the range of residual mass ( R M = 33.67%–61.28%) and mass losses ( M L = 38.72% - 66.33%), which attributed to the drying, devolatilization, and coke formation. Thermal reactivity followed the sample order A-5 > A-1 > A-6, which indicates A-5 is more thermally reactive. The results indicate that the coal samples could be exploited for electric power generation. Graphical abstract: Image 1 Highlights: Minerals are clays, quartz, feldspar, hematite and magnetite with traces of calcite, dolomite, siderite and graphite. Elemental ratios showed that the coal forming marsh undergone mild redox conditions and non-existent marine effects. Thermal reactivity followed the sample order A-5 > A-1 > A-6, which indicates A-5 is more thermally reactive.