Understanding the deep groundwater system and methane origins in the Bushveld Igneous Complex using environmental noble gas tracers

The ICDP-funded Bushveld Drilling Project (BVDP) aims to generate a continuous vertical stratigraphic sequence of the mineral and resources-rich Bushveld Igneous Complex (BIC) in South Africa. Within this framework, a specific focus is directed towards gathering water-related data, aimed at enhancing the understanding of deep groundwater systems in relation to water and energy security. The present project complements the already ongoing and funded collaborative activities between the Hydrogeology group of UniBas, the main partner's group at University of the Free State, and the BVDP, via the addition of state-of-the-art measurements of radio-noble gases dissolved in water. The determination of the radio-noble gas isotope concentrations of ³⁹Ar, ³⁷Ar, ⁸⁵Kr, and ⁸¹Kr, alongside the already planned analyses of classic environmental tracers [i.e., stable water isotopes (∂¹⁸O, ∂²H), atmospheric noble gas concentrations (He, Ar, Kr, Xe), and other ratio isotopes (³H,³He, and ⁴He)] will allow the characterization (i) of the residence times and flow dynamics of the suspected hundreds-of-thousands- to millions-of-years old deep groundwater, which in turn enables the assessment of the spatial extents and hydraulic properties of the different lithological units in the BIC, (ii) of the origins of suspected large amounts of dissolved CH₄, which in turn enables assessment of the potential for using CH₄ from the BIC for sustainable energy production, and (iii) enable estimating the quantity, quality, and vulnerability of groundwater and therefore the suitability for using it as a drinking water source.