Genesis of the mafic granophyre of the Vredefort impact structure (South Africa): Implications of new geochemical and Se and Re-Os isotope data

New geochemical and isotopic data reveal that the mafic granophyre at the Vredefort impact structure, South Africa's largest confirmed crater, likely formed through assimilation of mafic country rock—primarily epidiorite—into felsic impact melt. Contrary to a two-stage emplacement model, this study supports a single intrusive phase where mafic components were incorporated into the dominant felsic granophyre. High-precision analyses of highly siderophile elements (HSEs), Re-Os isotopes, and first-ever Se isotope data, alongside comparisons with Dominion Group meta-lava and epidiorite, provide robust evidence for this process. These findings challenge previous interpretations and refine our understanding of impact melt dynamics in large craters.

Reimold*, W. U., Schulz, T., König, S., Koeberl, C., Hauser, N., Wannek, D., & Schmitt, R.-T. (2021). Genesis of the mafic granophyre of the Vredefort impact structure (South Africa): Implications of new geochemical and Se and Re-Os isotope data. Large Meteorite Impacts and Planetary Evolution VI, 235–254. https://doi.org/10.1130/2021.2550(09)