A 3D geometrical and geometallurgical model of a chromite mine

This contribution introduces a 3D geometallurgical model that has been developed to assess the resource potential of PGE (+Ni and Cu) recovery at the Thaba chromite mine, South Africa. The Thaba Mine is located on the northwestern limb of the Bushveld Complex and is operated by Cronimet SA. The geometallurgical model is based on a structural model and geostatistical interpolation of primary geometallurgical properties, obtained from mineral liberation analysis (MLA) and geochemical exploration data.

More than 250 MLA samples and 750 geochemical measurements cover four target seams (lower group chromitite seams: LG 6 and LG6a; middle group chromitite seams: MG1 and MG2). The data provides information about chemistry, modal mineralogy and micro-fabric from the platinum group minerals and associated base metal sulfides.
The 3D model is based on the geometry and lithological interpretations of 300 drill cores and the known main faults in the study area and covers all stratigraphic units. The MLA measurements are linked to the 3D geometry of the target seams by the sampling positions in the associated boreholes. This allows to interpolate the information based on the MLA measurements over the horizontal extension of the target seams. The model can be enhanced with further information, e.g the distance to a volume of alterated silicate host rock. The final step is to transfer the geometallurgical model to a block model, that allows to predict for each block the parameters for an optimized processing.
Our approach shows how the different ore types are spatially related to geological features and that a separate extraction of different geometallurgical ore types would be sensible.