The role of ground penetrating radar in bauxite resource evaluations

Bauxite, the primary source of aluminum occurs in both silicate (lateritic) and carbonate (karstic) forms throughout the globe. Each type of deposit presents unique challenges to resource evaluations due to the extreme variations in bauxite thickness, and the presence of a variable overburden. Lateritic bauxites, found in the tropics, are formed through a process of residual enrichment of Al₂O₃ through the dissolution of silicate parent rocks. Traditional resource definition approaches of closely-spaced drilling are costly and time consuming, have a negative environmental impact, and rarely converge on a reliable resource estimate due to the unpredictable nature of the lateritic weathering process. In recent years, GPR has proven to be an ideal complementary tool to map the ore zone at many deposits. Examples are provided demonstrating the technique´s viability in a variety of lateritic bauxites, as well as cases where conductive, diffusive or thick overburden has limited GPR´s effectiveness. Karstic bauxites (“pocket” deposits), are formed by the accumulation of intercalated clays by dissolution of the parent limestone. Karstic resources often occur within a series of small, steep-sided pits, with minimal surface expression. Examples are provided of GPR data from deposits in Europe and the Caribbean demonstrating GPR´s viability and limitations.