Abstract
M.Sc. (Geology)
The Karoo Supergroup of Botswana consists of substantial coal deposits of sub-bituminous to bituminous rank. Primarily preserved in the eastern margin of the Kalahari-Karoo Basin in Botswana, somewhat vague estimates of 212 billion tonnes of coal have been made. Though reconnaissance investigations were carried out to explore the Kalahari-Karoo Basin of Botswana, there is still a complete absence of petrographic information in the public domain. As a result, little is known about coal petrography of Botswanan coals.
Coal petrographic analyses (maceral group, vitrinite reflectance, and microlithotype analyses), along with chemical analyses (proximate, CV, and TS) provideda sound understanding of the Botswana coals.Five coalfields were assessed: Lechana, South Orapa, Morupule, and Takatokwane, and Tuli. The petrographic analyses were carried out using Zeiss Axio Imager m2m reflected light microscope fitted with Hilgers Diskus Fossil software.
The petrographic results revealed a wide variation of maceral composition and reflectance data. The Takatokwane, South Orapa, and Tuli coal samples are characterised by a high vitrinite content (37-91vol. %, 65-85 vol. %, and 76-88vol. % respectively, mineral matter free basis (mmf)). The Lechana samples were found to be borderline medium rank D to C, rich in either vitrinite or inertinite, with variable ash content and generally low sulphur content. The Takatokwane samples fall between the low rank A and medium rank D categories, with the South Orapa samples fall into the low rank A and medium rank B categories, and the Tuli samples into the medium rank D category. The samples from the aforementioned coalfields are characterised by variable ash content, and generally low sulphur content, with the exception of South Orapa and Tuli samples characterised by high sulphur content. The Morupule samples differ significantly from the rest in composition, rich in inertinite (74-91 vol. %, mmf), with variable ash content and low sulphur content. These samples fall into the medium rank D/C category...