1170 Ma SHRIMP age for Koras Group bimodal volcanism, Northern Cape Province

Abstract

Research Article| March 01, 2000 1170 Ma SHRIMP age for Koras Group bimodal volcanism, Northern Cape Province J. Gutzmer; J. Gutzmer Department of Geology, Rand Afrikaans University, P.O. Box 524, Auckland Park, 2006 Republic of South Africa, E-mail: jgutzmer@uni-muenster.de; njb@na.rau.ac.za Search for other works by this author on: GSW Google Scholar N.J. Beukes; N.J. Beukes Department of Geology, Rand Afrikaans University, P.O. Box 524, Auckland Park, 2006 Republic of South Africa, E-mail: jgutzmer@uni-muenster.de; njb@na.rau.ac.za Search for other works by this author on: GSW Google Scholar A. Pickard; A. Pickard Centre for StrategicMineral Deposits, DepartmentofGeology and Geophysics, The University of Western Australia, Nedlands, Western Australia, Australia, E-mail: apickard@geol.uwa.edu.au; mbarley@geol.uwa.edu.au Search for other works by this author on: GSW Google Scholar M.E. Barley M.E. Barley Centre for StrategicMineral Deposits, DepartmentofGeology and Geophysics, The University of Western Australia, Nedlands, Western Australia, Australia, E-mail: apickard@geol.uwa.edu.au; mbarley@geol.uwa.edu.au Search for other works by this author on: GSW Google Scholar South African Journal of Geology (2000) 103 (1): 32–37. https://doi.org/10.2113/103.1.32 Article history accepted: 22 Feb 2000 first online: 07 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation J. Gutzmer, N.J. Beukes, A. Pickard, M.E. Barley; 1170 Ma SHRIMP age for Koras Group bimodal volcanism, Northern Cape Province. South African Journal of Geology 2000;; 103 (1): 32–37. doi: https://doi.org/10.2113/103.1.32 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 bimodal volcanic and coarse siliciclastic sedimentary rocks of the Koras Group are virtually undeformed and weakly metamorphosed, and overlie the highly metamorphosed and strongly deformed rocks of the Kheis subprovince of the Namaqua—Natal Metamorphic Province with a sharp erosional unconformity. Zircons from the Swartkopsleegte quartz porphyry, close to the base of the Koras Subgroup, have been dated at 1171 ±7 Ma by SHRIMP. This age is in good agreement with, but far more precise than, previously published ages for the Koras Group. The new age defines the onset of bimodal volcanism in the Koras Group and also indicates that the compressional Kibaran Orogeny in the Namaqua—Natal Province ended before or at ~1170 Ma. The main phase of Kibaran deformation, uplift, and erosion in the Namaqualand sector of the orogen took place in the period between the extrusion of the Wilgenhoutsdriflavas at ~1330 Ma and deposition of the Koras Group at 1171 Ma. Younger ages for peak metamorphism and post-tectonic intrusions (1060 to 1030 Ma) in the Namaqua—Natal Province clearly post-date Kibaran compressional tectonics and magmatic activity by more than 100 Maand are related to a subsequent magmatic event in the orogen. The Koras Group in Namaqualand is widely regarded as a typical representative of the ~1105 Ma Umkondo igneous province, a group of volcano—sedimentary successions and igneous bodies which post-date the Kibaran Orogeny in southern Africa. However, extrusion of the Koras lavas predates the Umkondo suite in Zimbabwe and coeval lavas in Botswana andNamibia by 60 Ma. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.