No serious problems were encountered during mining through these features, and no significant displacements have been associated with them.

An airborne magnetic survey has identified several swarms of northeast-striking dolerite dykes. Underground dyke intersections are generally less than 10 m in width. Individual layers in the Upper Critical Zone can generally be correlated over several kilometers and as such, detailed local stratigraphic nomenclature can be established.ĭykes in this area are primarily composed of dolerite, which is generally fine-grained and of good competence, with associated areas of dense jointing and alteration. The UG3A and UG3B chromitite layers are approximately 0.1 m thick, occur approximately 5 m above the UG3 and are separated by approximately 0.3 m of pyroxenite. The UG3 chromitite layer is approximately 0.25 m thick and occurs approximately 15 m above the UG2. The UG1 chromitite layer occurs over 100 m below the UG2. The UG3, UG3A and UG3B chromitite layers are generally too thin and contain insufficient concentrations of PGE mineralisation to have any reasonable expectation to support economic extraction. However, concentrations in the UG1 chromitite layer in all areas of the RLS have been found to be subeconomic. Each of these chromitites carries varying concentrations of PGEs. The cyclic units are termed, from oldest to youngest the UG1, UG2, UG3 UG3A and UG3B. In the central portion of the eastern limb of the Bushveld complex, five chromitite layers have been identified in the Upper Critical Zone, each of which forms the base of a cyclic unit. However, a minimum of approximately 140 m of the Merensky Reef footwall units have been removed by erosion and therefore no Merensky Reef is preserved at the Smokey Hills project. In the Smokey Hills Project Area, the Merensky Reef is expected to occur approximately 300 m above the uG2. The Smokey Hills project is located in the central portion of the eastern limb of the Bushveld complex and is underlain by rocks of the upper critical zone, which hosts two of the more important PGE-bearing units in the Rustenburg Layered Suite: the Merensky Reef and the UG2.

Smokey hills