Granular zircon from Vredefort granophyre (South Africa) confirms the deep injection model for impact melt in large impact structures

Researchers have discovered 'former reidite in granular neoblastic' (FRIGN) zircon within granite clasts trapped in the Vredefort granophyre dikes, South Africa. This finding provides the highest-pressure shock estimates (≥30 GPa) yet recorded in the Vredefort structure and supports the deep injection model for impact melt in large craters. The study suggests that these clasts were captured near the top of the impact melt sheet during a 2.02-billion-year-old meteorite impact, then transported downward through fractures, traveling approximately 8–10 km to the lowest stratigraphic levels of the structure. By analyzing shocked minerals within supracrustal xenoliths, the researchers constrained the emplacement history and conditions affecting target rocks near the impacted surface, offering new insights into the dynamics of large impact structures.

Kovaleva, E., Zamyatin, D. A., & Habler, G. (2019). Granular zircon from Vredefort granophyre (South Africa) confirms the deep injection model for impact melt in large impact structures. Geology, 47(8), 691–694. https://doi.org/10.1130/g46040.1