2014 GSA Annual Meeting in Vancouver, British Columbia (19–22 October 2014)

Paper No. 247-2
Presentation Time: 1:25 PM

U-PB GEOCHRONOLOGY AND PALEOMAGNETISM OF THE WESTERBERG SILL, KAAPVAAL CRATON - SUPPORT FOR VAALBARA INTO THE PALEOPROTEROZOIC


DE KOCK, Michiel O.1, KAMPMANN, Tobias C.2 and SÖDERLUND, Ulf2, (1)Geology, University of Johannesburg, P.O. Box 524, Auckland Park, Johannesburg, 2006, South Africa, (2)Department of Geology, Lund University, Sölvegatan 12, Lund, S-223 62, Sweden, mdekock@uj.ac.za

Precise geochronology combined with paleomagnetism provides first-order information necessary for paleoreconstructions of crustal blocks and for revealing the history of supercontinent formation and break-up. These techniques are used here in an attempt to further constrain the apparent polar wander path of the Kaapvaal craton through the Neoarchean and Paleoproterozoic. A new baddeleyite U-Pb age of 2440.2 ± 5.9 Ma for the intracratonic Westerberg sill manifests a new event of mafic magmatism within the Kaapvaal Craton of southern Africa and falls in the center of a ca. 450 Ma gap in the paleomagnetic record, between 2.66 and 2.22 Ga. The Westerberg sill is coeval with the Woongarra sills on the Pilbara craton and intrudes into a remarkably similar sedimentary succession, hence supporting a coherent Kaapvaal-Pilbara block (i.e., Vaalbara) spanning the Archean-Proterozoic boundary interval. The coeval Westerberg-Woongarra igneous event may represent a large igneous province, here recognized for the first time on the Kaapvaal craton. The virtual geomagnetic pole obtained for the Kaapvaal craton for the Westerberg sill fits well into a large gap of the craton’s apparent polar wander path. Furthermore, combined with a coeval Pilbara pole, it allows for a reconstruction of Vaalbara that places Pilbara in relative close proximity and to the north of the Kaapvaal craton.
Handouts
  • De Kock 2014.pptx (8.7 MB)