Coal Occurrence and Quality at Mushithe Area, Soutpansberg Coalfield, South Africa

Abstract

South Africa is the 7th largest coal producer in the world and continues to rely on coal as its primary energy source, owing to its abundant availability and low cost. The Mushithe coal occurrence, located within the Pafuri basin of the Soutpansberg Coalfield, has been overlooked compared to other coal occurrences in the Tshikondeni area. The coal occurrence at Mushithe outcrops at Mbodi River. The study aims at establishing the geological setting, mode of occurrence, coal quality and economic value of the Mushithe coal occurrence. Geological mapping and sampling, petrography, and geochemical analysis were done on 14 host rock and 6 coal samples. Coal bearing rocks at Mushithe are occurring as a valley isolated from the Pafuri Basin. The outcropping seam at Mushithe is exposed along the Tshamatsha Fault. The coal measures contain four to seven seams, ranging from 0.35 m to 11.38 m in thickness. Pink and red quartzite, mudstone, basalt, quartz vein, sandstone, shale, carbonaceous shale, and calcrete were identified as associated rock types. The general strike is northeast, and the dip direction is northwest, with an average dip angle of 23°. Mushithe coal is dominated by vitrinite (65.77%) and inertinite (34.23%), with no liptinite detected. The high presence of vitrinite suggests that the coal is formed in a wet swamp environment. Additionally, signs of weathering such as cracks, fissures, and oxidation rims were observed in the coal. Coal quality belongs to bituminous C on UNECE 1998 classification, being characterised by low sulphur content (0.23 to 0.38 wt %) and high moisture (6.07 to 10.94 wt %), ash yield (16.7 to 41.9 wt %), volatile matter (29.7 to 35.8 wt %), fixed carbon (25.25 to 50.49 wt %) and calorific value (12.97 MJ/kg to 23.35 MJ/kg). Mineral matter constitutes approximately 5.7 to 35.8 wt %, predominantly quartz with varying proportions of clay (kaolinite), as well as minor carbonates (siderite) and sulphides (pyrite). The geochemistry is characterised by high values of Al2O3 from 7.56 to 15.83 wt %, SiO2 (9.76 to 20.04 wt %), and MgO (0.26 to 2.80 wt %). The outcropping seam was found to be of economic value and suitable for use as thermal coal for electricity generation.