Feasibility of tailings retreatment to unlock value and create environmental sustainability of the Louis Moore tailings dump near Giyani, South Africa

SYNOPSIS The reprocessing of tailings resources to extract gold on an industrial scale has become common practice. While these projects are common in the Witwatersrand basin, similar low-technology processes are not operational in smaller goldfields. This study explores the possibility of reclaiming the tailings dump of the Louis Moore Mine in the Giyani Greenstone Belt, investigates potential hazards to communities in the vicinity, and identifies mitigation strategies. Auger samples were taken from the Louis Moore tailings at depths of up to 5 m. Aqua regia leach analyses show Au concentrations of up to 1 g/t. Inferred estimations based on ordinary kriging (OK) and inverse distance weighted (IDW) methods put the residual Au resource in the Louis Moore tailings dump at 0.20 t. Reworking the tailings is viable, although a potential environmental risk exists in the form of elevated arsenic concentrations. Further exploration is required to determine the mineralogical associations of Au and As. Tailings reworking would assist in raising funds for mine rehabilitation. The secondary tailings could potentially be repurposed, which would provide employment and facilitate community development, as well as deliver environmental benefits. Keywords: Louis Moore, tailings, gold, safety and health.

The Significance of Erosion Channels on Gold Metallogeny in the Witwatersrand Basin (South Africa): Evidence from the Carbon Leader Reef in the Carletonville Gold Field

Within the eastern portion of the Carletonville gold field, the gold- and uranium-rich Carbon Leader reef of the Central Rand Group (Witwatersrand Supergroup) is truncated by an erosion channel. This channel is asymmetrical and lenticular in shape, measuring 150 to 180 m in width and up to 100 m in depth. High-resolution seismic data show that the erosion channel cuts from the Carbon Leader reef into all older units of the Central Rand Group down to the Roodepoort Formation of the underlying West Rand Group. A total of seven bore-holes were drilled into the channel, revealing that it is composed of quartzite at its base (9 m thick), overlain by deformed (lower) and laminated (upper) chloritoid-bearing shale (21 m thick) and quartzite (18 m thick). The Carbon Leader reef is highly enriched in gold (5–40 g/t Au), whereas the gold tenor of the erosion channel fill is in general much lower (<1 g/t Au), although locally grades of as much as 3.8 g/t Au are reached. Detailed seismic, sedimentological, and petrographic analyses revealed that the channel was filled with locally sourced sediments from the Main Formation. A closed-system mass balance further demonstrates that gold in the erosion channel could have been entirely sourced from the Carbon Leader reef. Sediment load played a crucial role in the distribution of gold in the channel, thus supporting a stratigraphically controlled modified placer model for the origin of gold in the Carbon Leader reef.