Geostatistical surface modelling of radionuclide distribution patterns over gold tailings: the new machavie TSF case study

English: Motivated by an identified need for research specifically focused on providing industry with a better understanding of tailings impoundments, the project aimed to deliver a geostatistical 3D surface model of a typical tailings storage facility, which upon completion, would be capable of identifying radionuclide distribution patterns, for either prospecting or environmental assessment purposes. In an attempt to keep project expenses at a minimum, the 3D surface model was created using alternative methods of data acquisition, working in conjunction with a capable geostatistical-interpolator, as an alternative approach to more traditional geochemical sampling and laboratory analyses. Since the combination of portable X-ray fluorescence (PXRF) spectroscopy, natural gamma-ray spectrometry and Ordinary Prediction-based Kriging has not been tested for uranium exploration or environmental assessment over tailings impoundments before, the project, being the first of its kind, aimed to validate the viability of the approach. Evidenced by the successful identification of both radionuclide anomalies (potassium, thorium and uranium), as well as their respective migration pathways, results were found to validate the approach as a respectable alternative to conventional methods. Given the anionic and oxidative nature of the TSF in question, both analytical techniques identified changes in elevation, as being the dominant mechanism governing the distribution of mobilised radionuclides over the New Machavie TSF. While literature proposed the accumulation of radionuclides (K, Th and U) to the centre of the impoundments, results seemed to indicate the exact opposite, as radionuclides were found to migrate away from the top of the impoundments, before accumulating on the lower side slopes, following the natural flow direction of the TSF. With results stating the presence of uranium migration, geochemical indices were incorporated to quantify the extent of the migration. Despite literatures doubtfulness with regards to how radioactive disequilibrium would influence the results, both indices proved to be quite effective in verifying the radionuclide anomalies.