The 2055 Ma Bushveld Complex, South Africa, is well known for the occurrence of discordant bodies within the Rustenburg Layered Suite (RLS). Many discordant bodies disrupt mining of layered reefs, but a few have been successfully exploited, including the well known platiniferous dunite pipes. The Kennedy's Vale discordant body, situated in the Steelpoort Valley section of the Eastern Limb, has been almost entirely mined out for a central core of vanadium-rich Ti-magnetite. Discordant bodies are particularly abundant in this area which is severely disrupted by syn-Bushveld doming and faulting. The three-dimensional shape of discordant bodies in the RLS is highly variable, most are pipe-like, but Kennedy's Vale is unusual in that it constitutes an elongate, dyke-like body. The Kennedy's Vale occurrence is emplaced within gabbroic-anorthositic wall rocks of the Lower Main Zone, at a stratigraphic height of several thousands of metres below the Ti-magnetite layers. A broad zonation is recognised and the central core of massive Fe-Ti oxides is enclosed by an inner sheath of iron-rich wehrlite pegmatite and an outer sheath of iron-rich clinopyroxenite pegmatite. The sheath contains disseminated Fe-Ti oxides. An irregular and diffuse reaction rim has been identified between the outer sheath and the wall rocks.
Kennedy's Vale is part of the iron-rich ultramafic pegmatite (IRUP) group of discordant bodies, highly unusual rocks characterised by the absence of plagioclase and being more differentiated than the wall rocks in which they are emplaced. The composition of the olivine in the outer sheath at Kennedys' Vale (Fo49.6-46.5) is typical of the IRUP at this stratigraphic height, but considerably more differentiated than the pyroxene in the wall rocks. The reaction rim to the dyke includes relic grains of extremely calcic plagioclase and symplectites, indicative of high-temperature reactions. Symplectites formed due to reaction between the primocrysts in the gabbroic wall rocks and Fe-Ti melts. Kennedy's Vale crystallized from dense, immiscible Fe-Ti oxide-rich melts that drained downward within the RLS into the underlying cumulates with which they reacted. The relatively high vanadium content of the Ti-magnetite in the Kennedy's Vale orebody (average of 2.0 to 2.2 weight % V2O5) is consistent with melts sourced from the lowermost group of Ti-magnetite layers in the Upper Zone. The internal zonation of the dyke is ascribed to contamination of melt with distance from the conduit. The core-zone of massive Fe-Ti oxides was the last component to form as it required a persistent supply of Fe-Ti oxide melt. The absence of core parts of massive Fe-Ti oxides from some bodies of IRUP can be explained by their relatively low stratigraphic height or the relative paucity of introduced melt.