Geochemo-Petro-BiomarkerAnalysis of the Mid CretaceousAwgu Coal inNigeria's Central BenueT

Abstract

Due to its enormous coal resources with the potential for oil and gas, the Central Benue Trough is the focus of geological study. The current study's goal is to investigate the origins and depositional settings of the chosen coals. Inductively Coupled Plasma Mass Spectrometry (ICPMS), petrographic, and Gas Chromatography-Mass Spectrometry (GC/MS) investigations were used to investigate field coal samples from Jangwa/Shankodi and the surrounding regions. The examined coals' Ni/Co vs V/Cr, Cu/Zn, V/Ni, V/Mo, V/(Ni+V), (Cu+Mo)/Zn, V/(V + Cr), U, and Mo concentrations suggest oxic depositional settings, whereas the contents and ratios of Ni/Co, V/Cr, U, and Th show marine-terrestrial oxic-dysoxic conditions existed during deposition. An oxic depositional environment is further supported by the authigenic U values and Ce/Ce* ratios. The intricate interaction of terrestrial and marine forces during deposition can be seen in the V/Mo ratios, Sr/Ba ratios, and Y/Ho ratios. The coal facies, vitrinite constitutes, on average 59.9 %, liptinite 0.27 %, inertinite 10.54 % and mineral matter 52.43 respectively. The examined coals' maceral components and mineral matter (≥10%) indicate that they were deposited in habitats with planar margin mires and a river system with planar margin mires, respectively. The values and cross plots of gelification index (GI), tissue preservation index (TPI), ground water index (GWI), vegetation index (VI), and wood index (WI) showed deposition in a wet forest swamp to lower deltaic marsh environment in an ombrotrophic paleomire. The maceral component's ternary diagrams indicate deposition in a wet moor environment with sporadic moderate-to-high flooding occurrences. The limno-telmatic and telmatic zones in the depositional habitats originated in a continuously flooded setting with shallow water, where the examined coals were deposited by the river. Nalkanes with a C13–C35 range are indicative of both marine and terrestrial biological compounds. The Pr/Ph ratios are consistent with the deposition of terrestrial plant debris in an aerobic (oxic) condition in lacustrine–fluvial/deltaic depositional environment. Overall, this study's utilization of integrated petrologic, geochemical, and biomarker data offers a trustworthy method for evaluating coal depositional settings.

Publication Info:

Author: Adamu, M.L.1/2*, Obaje, G.N.2, Adeoye, J.A.2 and Oladimeji G

Volume: 59

Issue: September

Published By: Journal of Mining and GeologyVol. 59(2) 2023. pp. 131 - 156, 2023-09-01