The Whitehill Formation as a natural geochemical analogue to the Witwatersrand Basin's mine water issues, South Africa

Abstract

Mining activities within the Witwatersrand Basin, South Africa, have led to many studies, particularly focusing on the generation of acid mine drainage (AMD) in the basin and the associated environmental effects. This study assesses whether gypsum in the Whitehill Formation is connected to acid rock drainage (ARD) resulting from reactions between the pyrite-bearing shale and carbonaceous rocks. To investigate this, the geochemical, geological and palaeoclimatic settings were investigated and a laboratory experiment with Whitehill Formation rock samples was conducted. XRF data of the rocks and modal analysis were used to determine the mineral composition of the Whitehill Formation. In addition, pH-redox equilibrium (PHREEQC) modelling was used for simulations. The results of this study show that metals precipitated from the water-rock solution form various mineral phases like those of the Witwatersrand Basin. Large-scale dolomite dissolution might not be expected.

Keywords: Geochemical modelling; Mining influenced water (MIW); Natural analogue; Similar strata; Whitehill Formation; Witwatersrand Basin.