The Proterozoic Bushveld Catastrophe, South Africa

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This research is focused on (1) unique chemistry and quench textures of Rooiberg Felsite, the earliest member of the giant Bushveld Complex. (2) progressive recrystallization (T1,200oC) of intensely strained quartzose sediments below the Rooiberg Felsite into a network of tridymite needles and (3) structure and evolution of the Bushveld-Vredefort system. Present data suggest that multiple impacts of a disintegrating asteroid or comet caused the Bushveld-Vredefort catastrophe; endogenic alternatives are possible but involve novel and unverified processes. Vredefort rocks furnish evidence for shock in the form of planar features in quartz, shatter cones, pseudotachylite, coesite and stishovite. Rocks in equivalent structural positions are not exposed in the Bushveld Complex; elsewhere, recrystallization and incipient melting have destroyed earlier textures and minerals. Nevertheless, a search for shock features will continue in favorable localities, other field work will be carried out, and detailed petrologic and geochemical studies will be made. This study has the potential to completely change long standing ideas as to the origin of the world's largest layered mafic complex and its very extensive ore deposits.