Fluoride in groundwater and rocks, Mogwase and eastern North West region, 1993-1994

This dataset contains groundwater chemistry data collected for WRC project K5/526, which investigated the distribution of fluoride-rich groundwater in the Mogwase and eastern regions of the former Bophuthatswana, now part of North West and Limpopo provinces. Researchers from the Department of Geological Sciences at the University of Cape Town sampled about 320 sites in July and September 1993 and October 1994. Most sites were boreholes fitted with handpumps or windpumps in villages, schools and grazing areas, but some springs, rivers, pans and a mine seepage were also sampled. The researchers measured pH, total dissolved solids and total alkalinity in the field, measured fluoride with an ion-selective electrode, and determined major ions by ion chromatography at UCT. Trace elements (As, Mo, Al, Sr, Ba, Ni, Cr, V, Zn, Cu, Li, Cd, Co, Pb) were determined by ICP-AES on 57 acidified samples, and iodide on 51 samples. Fluoride ranged up to 69 mg/L, and about 45% of the analysed samples exceeded 1.5 mg/L. To identify fluoride sources, the team also collected 42 rock samples (with paired soils) across the main lithologies of the Bushveld Igneous Complex, Pilanesberg Alkaline Complex and Transvaal Supergroup in May and June 1994. These rocks were analysed by wavelength-dispersive XRF for major elements and fluorine, examined in thin section for fluorine-bearing minerals, and selected minerals (mica, amphibole, K-feldspar, carbonates and apatite) were analysed by electron microprobe. Whole-rock fluorine ranged up to about 80 000 ppm in fluorite ore from the Pilanesberg. The data were originally published only as printed appendices (A1, A2, A4 to A7, A9 and A10) of WRC Report No. 526/1/01. In 2026 they were harvested from the scanned report into machine-readable tables for the Water Research Observatory. OCR errors were corrected against the page images, site coordinates were converted to signed decimal degrees, and personal names in site descriptions were removed. Charge-balance and TDS consistency checks were also added. Totals of the rock and mineral analyses were recomputed to check the transcription. Thirty-six groundwater rows were found to carry ion values duplicated from other sites in the original report, and these were flagged as suspect rather than removed. Soil analyses were reported only as figures and were not included. Per-sample collection dates and the coordinate datum were not reported.