Abstract Hydrogeochemical sampling during core drilling in the Bushveld Complex, South Africa, as part of the Bushveld Complex Drilling Project (BVDP) funded by the International Continental Scientific Drilling Program (ICDP), is challenging due to contamination risks associated with circulating fluids, which can lead to the dismissal of valuable data. This study investigated pragmatic procedures and integrated analytical methods (chemistry, stable isotopes, and end-member mixing analysis (EMMA)) to collect and interpret data from a deep exploration well in the Bushveld Complex despite potential contamination. Findings showed that shallower samples ( 450 mbgl) were more influenced by the drilling fluids, quantifiable through EMMA, showing a clear shift towards source water dominance (e.g. up to 100% source water at 935 mbgl) suggesting potential mixing or displacement effects at depth. Furthermore, a distinct calcium chloride (CaCl 2 ) water type with a peak electrical conductivity (EC) of approximately 8000 µS/cm was identified at 450 mbgl, indicative of saline fracture flow. The study demonstrates that hydrogeochemical data can be obtained through the application of best practices and integrated analysis in challenging drilling environments. It highlights the critical need for consistent, validated, and standardised protocols for this process.
Lubbe et al. (Wed,) studied this question.