## 2 Geological Settings  
The Tuli Basin is thought to be a small intracratonic, east-west-trending fault-controlled basin with a preserved width of approximately 80 km [1]. The basin is present in the northernmost part of the Limpopo Province in South Africa, extending into Eastern Botswana and Southeastern Zimbabwe (Figure 1). These sediments of the Tuli Basin form part of the Limpopo Karoo Supergroup, and they were deposited contemporaneously with the main Karoo Basin sediments, forming an isolated and fault-controlled basin. The Tuli Basin was formed from approximately Late Carboniferous to Middle Jurassic in a continental tectonic setting [12]. According to [2], two broadly different tectonic settings were involved in the deposition of the Karoo Supergroup. The Tuli Basin forms the Limpopo part of Karoo-age basins. It has been proposed that the Limpopo area forms the western arm of a failed rift triple-junction [13], which later extended in a north-south direction and from the Save Basin in Zimbabwe to the Lebombo Formation in South Africa. Two distinct tectonic regimes that were sourced from the southern and northern margins of Gondwana led to the advancement of the Karoo Supergroup [14]. The authors of [15] reported that the Limpopo area, Karoo-age basins are made up of the following basins: Tuli Basin, Tshipise Basin (South Africa, partly Zimbabwe), and Nuanetsi Basin (Zimbabwe). According to the Tuli Basin, which trends approximately 1300 km east-west in the shared border region of South Africa, Zimbabwe, and Botswana, preserves an estimated thickness of 450-500 m of strata [2; 12]. It has been interpreted as the down-dropped western arm of a failed triple junction related to the break-up of Gondwana [16; 17]. However, an episode of Middle-Jurassic rifting and associated subsidence fails to accommodate the substantial record of pre-Jurassic strata preserved in the basin. According to [18], the main Karoo Basin consists of four major groups, which are Dwyka Group (Late Carboniferous-Early Permian), Eeca Group (Permanian), Beaufort Group (Late Permian-Triassic), and the Stormberg Group (Late Triassic-Early Jurassic). About 183 Ma, the Karoo sedimentary sequence was intruded by the Early Jurassic dolerites. The Tuli Basin consists of three formations, namely, the Madzaringwe Formation, Mikambeni Formation, and Fripp Formation. The aforementioned formations are the equivalents of the Eeca Group in the main Karoo Basin [2] (Figure 3). The sedimentary succession of the Tuli Coalfield consists of the Tshidzi Formation at the base and is mostly composed of diamictite and sandstones. The Tshidzi Formation is equivalent to the Dwyka Group in  
Figure 2: Local geology of Vele Mining Right area (after [8]). the main Karoo Basin. The Madzaringwe Formation forms the base of the Ecca Group and overlies the diamictites of the Tshidzi Formation [19]. It consists of sandstone, siltstone, and shale with thin coal seams with a maximum stratigraphic thickness of nearly 120 m [19]. As documented by [20], the Madzaringwe Formation in Tuli Basin, which is the focus of this study, consists of an alternating succession of feldspathic, cross-bedded conglomerates, sandstone, siltstone, and shale comprising some coal seams [20]. Furthermore, they reported that this formation was deposited on top of the Tshidzi Formation. The coal series found in the Madzaringwe Formation are located at a depth of less than 50 m along the southern margin. The coal series can reach a depth of over 300 m close to the Limpopo River [2]. The two major seams which are represented as flat-lying coal have a thickness of about 1.6 m and 1.2 m [2]. These seams are overlain by mudstones and minor sandstones. The economically important coal succession in Madzaringwe Formation is interbedded with mudstones [12]. Succeeding the Madzaringwe Formation is the Mikambeni Formation, which is about 60 m thick, consisting of shale, sandstone, and coal.