Microbeam U-Pb Zircon dating of the Makwassie Formation and underlying units in the Ventersdorp Supergroup of South Africa

Abstract

Research Article| December 01, 2017 Microbeam U-Pb Zircon dating of the Makwassie Formation and underlying units in the Ventersdorp Supergroup of South Africa D.H. Cornell; D.H. Cornell Department of Earth Sciences, University of Gothenburg, Sweden e-mail: cornell@gvc.gu.se Search for other works by this author on: GSW Google Scholar P.G. Meintjes; P.G. Meintjes Department of Earth Sciences, University of Gothenburg, Sweden e-mail: pgm@pgmmanagement.co.za Search for other works by this author on: GSW Google Scholar W.A. van der Westhuizen; W.A. van der Westhuizen Department of Geology, University of the Free State, South Africa willemvdw1950@gmail.com Search for other works by this author on: GSW Google Scholar D. Frei D. Frei Department of Earth Sciences, Stellenbosch University, Private Bag X1, 7602 Matieland, South Africa Present address: Department of Earth Sciences, University of the Western Cape, Private Bag X17, 7530 Bellville, South Africa e-mail: dirkfrei@uwc.ac.za Search for other works by this author on: GSW Google Scholar Author and Article Information D.H. Cornell Department of Earth Sciences, University of Gothenburg, Sweden P.G. Meintjes Department of Earth Sciences, University of Gothenburg, Sweden W.A. van der Westhuizen Department of Geology, University of the Free State, South Africa D. Frei Department of Earth Sciences, Stellenbosch University, Private Bag X1, 7602 Matieland, South Africa Present address: Department of Earth Sciences, University of the Western Cape, Private Bag X17, 7530 Bellville, South Africa e-mail: cornell@gvc.gu.se e-mail: pgm@pgmmanagement.co.za willemvdw1950@gmail.com e-mail: dirkfrei@uwc.ac.za Publisher: Geological Society of South Africa First Online: 23 Apr 2018 Online Issn: 1996-8590 Print Issn: 1012-0750 © 2017 December Geological Society of South AfricaGeological Society of South Africa South African Journal of Geology (2017) 120 (4): 525–540. https://doi.org/10.25131/gssajg.120.4.525 Article history First Online: 23 Apr 2018 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation D.H. Cornell, P.G. Meintjes, W.A. van der Westhuizen, D. Frei; Microbeam U-Pb Zircon dating of the Makwassie Formation and underlying units in the Ventersdorp Supergroup of South Africa. South African Journal of Geology 2017;; 120 (4): 525–540. doi: https://doi.org/10.25131/gssajg.120.4.525 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySouth African Journal of Geology Search Advanced Search Abstract The Archaean Ventersdorp Supergroup is the most widespread volcanosedimentary cover sequence on the Kaapvaal Craton. It unconformably overlies the Witwatersrand Supergroup and is unconformably overlain by the Transvaal Supergroup. Due to exploration drilling for Witwatersrand gold, the Ventersdorp Supergroup is the globally most extensively drilled sequence. Early efforts to date its volcanic units have commonly been thwarted by pervasive 2.3 to 2.0 Ga alteration. In situ U-Pb zircon dating promises a panacea, but the effects of lead mobility and high common lead remain potential pitfalls. The ages of the 'type' formations of the Ventersdorp Supergroup sensu stricto are still not well established and much of the published data is on units only considered to be correlated with the 'type' formations.Quartz porphyry rhyolites of the Makwassie Formation in the Platberg Group are reliably dated by the laser ablation ICPMS U-Pb zircon method on four samples with a combined age of 2720 ± 2 Ma. This supercedes the first ion probe date of 2709 ±4 Ma which is now regarded as a minimum age due to probable ancient lead loss and associated high common lead. The published 2714 ±16 Ma age for the stratigraphically lower Klipriviersberg Group was affected by similar problems. The Makwassie Formation is the only formation of the Ventersdorp Supergroup sensu stricto for which an accurate and reliable date has now been established by more than one precise age determination.Two samples considered to be from the Goedgenoeg Formation, which underlies the Makwassie Formation, were investigated. The formation is best dated by a 2746 ± 9 Ma age on a feldspar porphyry borehole sample from near Wolmaransstad. A sample from a similar rock type also assigned to the Goedgenoeg Formation, which underlies the Makwassie Formation in Wesselton Mine at Kimberley, gave an age of 2781 ± 5 Ma. A 30 Ma period of Goedgenoeg volcanism is considered to be unlikely. The older sample may rather be a time-correlate of a stratigraphically lower unit such as the 2785 ± 2 Ma Kanye Formation or the 2769 ± 2 Ma Derdepoort Outlier. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.