The Tectono-Sedimentary evolution of the southern Free State Goldfield in the Witwatersrand Basin, with implications for the geodynamic evolution of the Kaapvaal Craton, South Africa

• Main Author: Friese, Andreas Eberhard Walter
• Format: Others
• Language: en
• Published: 2021
• Online Access: https://hdl.handle.net/10539/31055

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg in fulfilment of the requirements for the degree of Doctor of Philosophy, 2020 === An attempt was made to place the proposed tectono-sedimentary evolution of the Free State Goldfield and the Witwatersrand Basin into the context of the geodynamic evolution of the Kaapvaal Craton, including the Zimbabwe Craton and Limpopo Central Zone Terrane, as all share a common and linked geodynamic evolution since the Neoarchaean. This was achieved through a comprehensive compilation and synthesis of a large published and unpublished geoscientific dataset. The outcome is a plate-tectonic reconstruction of the geodynamic evolution of the Kaapvaal and Zimbabwe cratons(and the southern African lithosphere in general) in time and relative space, since their stabilisation as protocratons in the Neoarchaean at ~3.1 Ga until present time, is summarised pictorially in a series of palaeogeographic and palaeogeologic reconstruction ‘time-slice’ maps to provide a perspective not previously available (Appendices 20-A –20-Z). For each time period of the reconstructed sequential geodynamic evolution, these ‘time-slice’ maps show: (1) Archaean continental/cratonic crust, (2) the main structures that were active, (3) the lithostratigraphic units that were deposited, and (4) areas of juvenile crust formation within regions of magmatic-arc/back-arc basin development. Gaps indicate areas, of unknown extent, inferred to have been occupied by either oceanic crust or lost fragments of continental crust that separated the continental crust at the time. Note: Given their illegibility, all time-slice maps presented in A3 format as Appendices 20-A –20-Z are available digitally in PDF file format on the supplementary CD.A summary of geochronological ages used for the plate-tectonic reconstruction is divided into various epochs and/or orogenic cycles (i.e. Archaean, Palaeoproterozoic, Kibaran, etc.) for the Kaapvaal and Zimbabwe cratons, and the Limpopo Central Zone Terrane separately, and is presented in tabular format in Appendices 21-A –21-C respectively. A proposed correlation of Palaeoproterozoic-Mesoproterozoic (~2.6-1.45 Ga) stratigraphic units and tectonic events within the Kaapvaal, Rehoboth, Zimbabwe, Pilbara, Yilgarn, Singhbhum, Bastar and Dharwar cratons, as well as the Limpopo Central Zone Terrane, is provided in Appendix 22.Summariesof Palaeoproterozoic (syn-Transvaal Supergroup; ~2.49-2.41 Ga) formation and resetting ages reported from the Kaapvaal and Zimbabwe cratons and Limpopo Central Zone Terraneare presented in Appendices23-A and 23-B, respectively. A summary of Palaeo-to Mesoproterozoic (post-Transvaal Supergroup; ~2.1-1.0 Ga) deformation events reported from the area of the Witwatersrand Basin and Bushveld Complex (i.e., central Kaapvaal Craton) and their correlation with far field stress related to the Magondi and Okwa orogenies, Bushveld Complex emplacement, and Vredefort meteorite impact, as well as Kheis, Kibaran and Lomanian (Namaqua-Natal) orogeniesis presented in Appendix 24. Summaries of Palaeo-to Mesoproterozoic (post-Transvaal Supergroup; ~2.1-1.0 Ga) formation and resetting ages reported from the Kaapvaal Craton are presented in Appendices25-A and 25-B, respectively. A tectono-structural and terrane interpretation summary map for the Kaapvaal Craton, Limpopo Central Zone Terrane and Zimbabwe Craton, covering the countries of Botswana, Zimbabwe, South Africa, and parts of Mozambique, is presented in Appendix 26 === CK2021