The orebody at the Challenger gold mine shows remarkable down-plunge continuity, from the surface to some 1400 m vertical depth, which is geometrically equivalent to a down-plunge length of ~2800 m. However, at ~220 RL within the mine, the orebody is displaced by a 10-30 m wide zone of brittle faulting, known as the "79 Fault". This brittle fault zone appears to truncate not only the granulite facies metasedimentary gneisses that host the mineralisation, but also numerous mafic dykes that intrude the host rocks. In places the mafic dykes can be seen to be weakly foliated parallel to the plane of the brittle fault zone. The fault itself has inconsistent kinematic indicators observable in drill core, with slickenfibres that indicate both left lateral and right lateral senses of movement. The best indicator of the overall movement on the fault is the continuation of the gold mineralisation, which is displaced some 120 m in a left lateral sense. The fault zone itself is composed of clays and fault gouge, plus sections where there is intense brecciation and disruption of the gneissic wall rocks. Preliminary K-Ar isotopic characterisation of one whole rock sample taken from the fault gouge gave an apparent clay mineral crystallisation age of 1405±28 Ma. This age is consistent with the regional cooling history identified by previous thermochronology performed on samples from the Challenger mine. The preliminary K-Ar geochronological data suggest that the Challenger orebody's geological environment existed within the upper crust during a late period of tectonic activity across the Gawler Craton; however, further work will be required to conclusively determine the timing of the brittle faulting seen in the Challenger mine.