Numerical modeling of impact heating and cooling of the Vredefort impact structure

Abstract

Large meteorite impacts, such as the one that created the Vredefort structure in South Africa ~2 Ga ago, result in significant heating of the target. The temperatures achieved in these events have important implications for post-impact metamorphism as well as for the development of hydrothermal systems. To investigate the post-impact thermal evolution and the size of the Vredefort structure, we have analyzed impact-induced shock heating in numerical simulations of terrestrial impacts by projectiles of a range of sizes thought to be appropriate for creating the Vredefort structure. When compared with the extent of estimated thermal shock metamorphism observed at different locations around Vredefort, our model results support our earlier estimates that the original crater was 120-160 km in diameter, based on comparison of predicted to observed locations of shock features. The simulations demonstrate that only limited shock heating of the target occurs outside the final crater and that the cooling time was at least 0.3 Myr but no more than 30 Myr.