Impact-Generated Permeability and Hydrothermal Circulation at the Vredefort Impact Structure, South Africa
- Author(s)
- S. Marchi, A. Alexander, A. Trowbridge, C. Koeberl
- Abstract
The 2.02 billion year old Vredefort impact structure in South Africa offers a unique opportunity to study large-scale impact processes on Earth. Vredefort's large size (∼250 km in diameter) and eroded topography provides the opportunity to study the effects of shock physics at depth and post-formation hydrothermal alteration. In this work, we simulate the formation of the Vredefort structure building upon recent shock physics (iSALE) simulations. We expand those simulations to cover a wider range of input conditions, and compute impact-driven porosity and permeability. The latter quantities are used to perform fluid mobility simulations (HYDROTHERM). We find that the Vredefort event produced significant impact-generated porosity (up to 30%) in an annulus from about 50 to 100 km from the center and up to several kilometers in depth. The corresponding estimated permeability (up to 10−12 m2) would have allowed for large scale subsurface fluid flows. Our hydrothermal calculations show that the Vredefort impact event could have generated a complex crustal fluid pattern within the crater rim that lasted for hundreds of thousand years, with localized flow concentration regions, opening a new interpretation for the mobilization and location of the ore deposits in the Witwatersrand basin. The combined approach utilizing impact and hydrothermal simulations constitute a powerful tool to understand geochemical processes at Vredefort, as well as to assess the ability of large impacts to drive crustal chemistry with far-reaching consequences for the prebiotic evolution of the early Earth.
- Organisation(s)
- Department of Lithospheric Research
- External organisation(s)
- Southwest Research Institute, University of Colorado, Boulder, NASA Postdoctoral Fellow
- Journal
- Earth and Space Science
- Volume
- 11
- DOI
- https://doi.org/10.1029/2023EA003065
- Publication date
- 01-2024
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 105105 Geochemistry
- ASJC Scopus subject areas
- Environmental Science (miscellaneous), General Earth and Planetary Sciences
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/cbaeff8c-1ef3-447f-b066-5bae2bee9f57