A regolith-landform model for the Mt Gibson district describes relationships in terms of erosion and burial of complete and partly truncated profiles. Lateritization and post-lateritization processes responsible for the formation of a variety of regolith types are discussed. The pattern of regolith at Midway North which characterizes the district relates closely to the erosional and depositional modification of the deeply-weathered mantle. A total of 25 samples representing various regolith units were characterized petrologically, mineralogically, and geochemically. Systematic mineralogical and geochemical differences occur between transported and residual regolith units.
Hematite increases upwards in the residual weathering profile.
The Al content in goethite also tends to increase towards the top of the residual profile. Lateritic residuum is enriched in Cu, Pb, Zn, As, W, Ag, and Au which are associated with hematite and goethite. The calcareous clays overlying acid, plastic clays largely consist of dolomite, kaolinite with small amounts of hematite, calcite, halite, and palygorskite. These clays have low contents of chalcophile elements, but contain significant amounts of Au. However, the amounts of Au are very low in clays relative to the lateritic residuum.