Near‐surface boulders can pose serious challenges to opencast mining. They often introduce complexities, delays in drilling, blasting and excavation programmes, which subsequently decrease mining efficiency, increase mining risks and costs. The location of subsurface boulders and the identification of other geological features that may impact mining activities (e.g. fractures, the presence of iron‐rich ultramafic pegmatites and the variation in weathering across a mining region) are necessary to reduce the challenges posed by these geological features, therefore optimizing mining efficiency. In this study, magnetics, electrical resistivity tomography, seismic refraction tomography, ground penetrating radar and borehole data are integrated for boulder delineation and mapping of other geological features that may impact mining using an unmined section at Tharisa Mine, Bushveld Complex (South Africa), as a test site. The results obtained from the different geophysical techniques are found to complement each other and successfully delineate boulders, fractures, iron‐rich ultramafic pegmatites and the variation in weathering and layering across the area. The incorporation of geophysical results can thus improve mining efficiency, while reducing mining risks and costs.

The detection of mineral deposits and their related geological structures is of great importance to the mining industry as structures (such as dykes and faults) can affect the safety, cost and efficiency of mining. With the goal of testing cost-effective seismic methods for mineral exploration and mining, active and passive seismic experiments were conducted at Maseve platinum mine in the Bushveld Complex (South Africa) in 2020. The experiments involved surface-passive (using 5 Hz wireless nodes; single vertical component) and in-mine active reflection seismic surveys (using 4.5 Hz land streamer and 5 kg sledgehammer) to image geological structures and delineate economic platinum-group elements bearing Merensky and Upper Group-2 chromitite layers (known as reefs). This paper presents only the results from the in-mine active seismic experiments. The in-mine seismic surveys consisted of seven 2D reflection seismic profiles in the development tunnels, which were located ∼550 m below ground surface and a few tens of metres above known mineralizations: the Upper Group-2 and Merensky Reef. The data were carefully processed to enhance the reflections and suppress noise generated by mine infrastructure (e.g., equipment and ventilation). We successfully imaged the Merensky Reef and Upper Group-2 orebodies approximately 55 m and 124 m below the tunnel floor, respectively, and delineated faults and dykes that crosscut them. Furthermore, the seismic data reveal relatively strong amplitude and faulted reflections below the Upper Group-2 that may represent deeper chromitite-enriched orebodies. However, the economic value of these horizons can only be confirmed through drilling. The processed seismic data were combined with borehole data, synthetic modelling and geological models to constrain the interpretation. This study encourages the use of in-mine seismics for future mineral exploration, mine development and planning.

For underground mining, efficient groundwater management is one of the critical mining economics components. The region of interest, known as Tharisa Mine, is situated on the western limb of the Bushveld Igneous Complex, which is home to South Africa’s premier platinum-group metal resources. This work aimed to provide the findings from the investigation and imaging of the near-subsurface hydrogeological architecture in a shallow profile using stable isotopes of water (18O and 2H) and radioactive water isotopes (3H). Regarding isotope data, 18O varied from −3.5 to 1.5‰; 2H from −24 to 4.7‰; and 3H from 2.0 to 3.4 T.U. Utilizing combined geophysical techniques, the results were verified. Additionally, the geophysical methods, including seismic refraction tomography, multichannel analysis of surface waves, electrical resistivity tomography, and magnetics, helped identify the fluid’s pathways and lineaments during migration to verify the isotope results. The groundwater inflow volumes into the open pit were initially determined by integrating the following findings: the delineation of fracture systems/zones and fluid migration pathways; mining activities enhance the storage and transmission ability of the aquifer; and the main sources of water in the mine include mixing of surface and deep water sources, recycling of water possibly via lineaments, and tailings dam seepages.

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