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Th-U-Pb zircon geochronology of the Palaeoproterozoic Hartley Formation porphyry by six methods, with age uncertainty approaching 1 Ma.

2016; Geological Society of South Africa; Volume: 119; Issue: 3 Linguagem: Inglês

10.2113/gssajg.119.3.473

1996-8590

David H. Cornell, Thomas Zack, T. Andersen, Fernando Corfú, Dirk Frei, Valby van Schijndel,

Geochemistry and Geologic Mapping

Research Article| September 01, 2016 Th-U-Pb zircon geochronology of the Palaeoproterozoic Hartley Formation porphyry by six methods, with age uncertainty approaching 1 Ma D. Cornell; D. Cornell Department of Earth Sciences, University of Gothenburg, Box 460 SE 40530, Sweden. email: cornell@gvc.gu.se; Thomas.zack@gvc.gu.se Search for other works by this author on: GSW Google Scholar T. Zack; T. Zack Department of Earth Sciences, University of Gothenburg, Box 460 SE 40530, Sweden. email: cornell@gvc.gu.se; Thomas.zack@gvc.gu.se Search for other works by this author on: GSW Google Scholar T. Andersen; T. Andersen Department of Geosciences, University of Oslo, Postbox 1047 Blindern, N-0316 Oslo Norway. email: tom.andersen@geo.uio.no; f ernando.corfu@geo.uio.no Search for other works by this author on: GSW Google Scholar F. Corfu; F. Corfu Department of Geosciences, University of Oslo, Postbox 1047 Blindern, N-0316 Oslo Norway. email: tom.andersen@geo.uio.no; f ernando.corfu@geo.uio.no 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. email: dirkfrei@sun.ac.za; Valby@sun.ac.za Search for other works by this author on: GSW Google Scholar V. van Schijndel V. van Schijndel Department of Earth Sciences, Stellenbosch University, Private Bag X1, 7602 Matieland, South Africa. email: dirkfrei@sun.ac.za; Valby@sun.ac.za Search for other works by this author on: GSW Google Scholar Author and Article Information D. Cornell Department of Earth Sciences, University of Gothenburg, Box 460 SE 40530, Sweden. T. Zack Department of Earth Sciences, University of Gothenburg, Box 460 SE 40530, Sweden. T. Andersen Department of Geosciences, University of Oslo, Postbox 1047 Blindern, N-0316 Oslo Norway. F. Corfu Department of Geosciences, University of Oslo, Postbox 1047 Blindern, N-0316 Oslo Norway. D. Frei Department of Earth Sciences, Stellenbosch University, Private Bag X1, 7602 Matieland, South Africa. V. van Schijndel Department of Earth Sciences, Stellenbosch University, Private Bag X1, 7602 Matieland, South Africa. email: cornell@gvc.gu.se; Thomas.zack@gvc.gu.se email: tom.andersen@geo.uio.no; f ernando.corfu@geo.uio.no email: dirkfrei@sun.ac.za; Valby@sun.ac.za Publisher: Geological Society of South Africa First Online: 20 Nov 2017 Online Issn: 1996-8590 Print Issn: 1012-0750 © 2016 September Geological Society of South AfricaGeological Society of South Africa South African Journal of Geology (2016) 119 (3): 473–494. https://doi.org/10.2113/gssajg.119.3.473 Article history First Online: 20 Nov 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation D. Cornell, T. Zack, T. Andersen, F. Corfu, D. Frei, V. van Schijndel; Th-U-Pb zircon geochronology of the Palaeoproterozoic Hartley Formation porphyry by six methods, with age uncertainty approaching 1 Ma. South African Journal of Geology 2016;; 119 (3): 473–494. doi: https://doi.org/10.2113/gssajg.119.3.473 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 Palaeoproterozoic Hartley Formation in the Olifantshoek Group was deposited in one of the rift-related Waterberg (sensu lato) red bed basins which formed on the Kaapvaal Craton after the 2.05 Ga Bushveld intrusions and coeval thermal event. The age of these basins is not well constrained due to the shortage of directly dateable rock types. The Hartley Formation contains rare quartz-porphyry lavas interbedded with the dominant basalts and these provide the means to date the formation by analyses of zircon. In this work zircon from one sample has been dated by six Th-U-Pb methods, namely Laser Ablation ICP Quadrupole Mass Spectrometry, Laser Ablation ICP High-resolution Mass Spectrometry, Laser Ablation ICP Multicollector Mass Spectrometry U-Pb (also Lu-Hf), Nordsim Ion probe U-Pb and Th-Pb; and Krogh method ID-TIMS. Our precise ages give a combined age of 1915.2 ± 1.1 Ma. Including one published ion probe date from the only other known occurrence of quartz porphyry, the results only agree if the quoted analytical errors are increased by 20%, which gives a combined result of 1915.6 ± 1.4 Ma. This is considered a reliable, precise and accurate age for the Hartley Formation and supersedes the published Kober method 207Pb/206Pb age of 1928 ± 4 Ma.The new Lu-Hf zircon data, supported by published whole rock Sm-Nd and Rb-Sr data, suggests that both the dominant basalts and the rare quartz porphyries of the Hartley Formation were derived from mafic source rocks which had been in the crustal domain from Archaean times.By contrast with the intracratonic rifts of the other Waterberg Basins, the Olifantshoek Supergroup reflects the development of a western passive margin as the Archaean Kaapvaal Craton rifted and drifted. This was followed by accretion of the Rehoboth Province along the Kalahari Line, accompanied by the development of the east-vergent Kheis Province thrust complex. This created a larger cratonic block against which the 1.2 Ga collisions of Namaqua-Natal terranes impacted. The Kheis Province now yields ~1.17 Ma cooling ages, reflecting the Namaqua collisions, but the true age of the Kheis event is still enigmatic. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.