Hydro-geochemical characterizations of a platinum group element groundwater system in Africa D. Pacome Ahokpossi * , Abdon Atangana, P. Danie Vermeulen Institute for Groundwater Studies, Faculty of Natural and Agricultural Science, University of Free State, 9300 Bloemfontein, South Africa article info Article history: Received 20 March 2017 Received in revised form 20 November 2017 Accepted 22 November 2017 Available online 24 November 2017 Keywords: Acid mine drainage Pyrrhotite oxidation Acid buffering Serpentinite Bushveld Groundwater quality Hydro-geochemical processes abstract Water is a scarce resource in the drylands of Africa and the Middle East and the identification of risks to aquifers is an important endeavor. There is a common and erroneous belief that only gold and coal deposits in Southern Africa are associated with acid-generating minerals. The study highlights the application the tools of geochemical analysis can reveal the classes of chemical reactions leading to the evolution of a shallow aquifer in an arid zone with active mining of sulfidic ore taking place. The prevailing hydro-geochemical processes were assessed at an open cast platinum mine. Major conclusions relate to the Acid Mine Drainage buffering within fractured aquifer system associated with the platinum deposit. The oxidation of pyrrhotite from in situ sources is the major contributing factor towards AMD formation. Neutralization of acid in the groundwater system has solved the pH problem but introduced a salinity problem. © 2017 Elsevier Ltd. All rights reserved. 1. Introduction Water is a scarce resource in the drylands of Africa and the Middle East and the identification of risks to aquifers is an impor- tant endeavor. The impact of acid mine drainage (AMD) on groundwater resource is one of the worse environmental concern associated with mining (Bell et al., 2001; Vermeulen and Usher, 2009). The mining industry forms the backbone of the South African Economy. According to the Mineral Commodity Summaries (2015), South Africa is the world's largest producer of chrome, manganese, platinum, vanadium and vermiculite; and the second largest pro- ducer of ilmenite, palladium, rutile and zirconium. The country is also one of the largest coal exporters. There is a common and erroneous belief that only gold and coal deposits in Southern Africa are associated with acid-generating minerals. This results in few investigations of the AMD potential of mining of Magmatic Sulfide Deposits in Bushveld Complex. The Platreef (Northern limb ore deposit in the BC) is known for its feldspathic pyroxenite-norite hosting one of the world class magnetic-type nickel, copper and platinum ground element (Kinnaird and McDonald, 2005). Since mid to late 1920's, the Plaatreef has become a site of platinum prospecting and mining (Buchanan, 1988). In the process of AMD, a number of hydro-geochemical pro- cesses occur. Some of these processes are: acid neutralization/ buffering, chemical precipitation, attenuation or dissolution of metals (Blowes et al., 1994). A sound hydro-geochemical conceptual model based on the site geology, hydrogeology, and mineralogy, is necessary for investigating the groundwater quality characteristics. One also needs to assess (test) the validity of each hypothetically conceived hydro-chemical reaction based on measured data. The study aims to investigate the hydro-geochemical processes within the catchment and how they directly impact overall groundwater quality. It highlights the application of (bivariate) scatter plots, and other diagnostic plots as complimentary tools to analyze the groundwater chemistry data collected in a typical Platinum Group Element groundwater system. It specifically uses groundwater monitoring data from an open cast platinum mine to describe different hydro-geochemical process which prevail in the monitored groundwater system. 2. Description of the study area The study area is located north-west of Mokopane town * Corresponding author. E-mail address: ahokposso@yahoo.fr (D.P. Ahokpossi). Contents lists available at ScienceDirect Journal of African Earth Sciences journal homepage: www.elsevier.com/locate/jafrearsci https://doi.org/10.1016/j.jafrearsci.2017.11.032 1464-343X/© 2017 Elsevier Ltd. All rights reserved. Journal of African Earth Sciences 138 (2018) 348e366