Bibliography: leaves 112-120.Metamorphism observed in the Vredefort structure increases in grade on a regional scale from lower greenschist facies in the outer perimeter of the Potchefstroom syncline, throughupper greenschist and amphibolite grades within rocks of the Witwatersrand Supergroupand Dominion Group in the collar of the Vredefort dome, to granulite grades in the core ofthe dome. In the collar, two metamorphic assemblages have been identified, one representing a peak metamorphic event pre-impact in age and constrained to temperatures >420-620°C at 3.0-4.0 kbar, and a younger retrograde event, constrained to 500-540 ± 15°C, which overprints the latter assemblage and overgrows pseudotachylite in a small number of samples
