Alteration, heat, and Witwatersrand gold: 111 years after Harrison and Langlaagte

Abstract

The Witwatersrand Basin records evidence of widespread alteration within the Central Rand Group in all goldfields and well into the central part of the basin, and also within mineralized portions of the West Rand Group. This alteration has affected all rock types and is characterized by assemblages of pyrophyllite-chloritoid-chlorite-muscovite-pyrite-rutile-tourmaline-quartz, or combinations of these minerals, plus variable albite, paragonite, margarite, kaolinite, kyanite, sudoite, and pyrrhotite. Alteration assemblages are spatially related to mineralization, with both being best-developed in the Central Rand Group, and within the goldfields. An approximate estimate of the volume of rock i..