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

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.