Mineralogy of the Middle Group Chromitite Cumulates at the Tweefontein Chrome Mine Section, Central Critical Zone, Eastern Bushveld Complex

The understanding of the silicate mineralogy in the Middle Group chromitite section of the central Critical Zone at Tweefontein in the eastern Bushveld Complex south of Steelpoort is essential for the investigation of the genesis of the cumulate rocks; in particular the crystallization history of the cumulus minerals and the development of the interstitial liquid are considered to be key parameters controlling the PGM distribution in those mafic rocks. The detailed ongoing investigation of the textural relationships and the mineral chemistry of the rock forming minerals may therefore assist in explaining the PGE distribution. Vertical geochemical and modal mineral distribution patterns are prime indicators of magmatic system conditions. The investigations will help to better understand the PGE distribution in a dynamic ultramafic to mafic system on the theoretical side, and will characterize the possibly variable PGE patterns of the different Middle Group chromitite sections within the Bushveld Complex. Practical conclusions such as PGE abundances and their occurrence in various minerals, as well as grain sizes and textures relations relevant for liberation are important for economic extraction processes.