Reconnaissance paleomagnetic studies of Mesoproterozoic alkaline igneous complexes in the Kaapvaal craton, South Africa

Abstract We report paleomagnetic data from three different parts of a diffuse Mesoproterozoic alkaline igneous province in the eastern part of the Kaapvaal craton in South Africa. Except for the ∼1.3 Ga Pilanesberg dikes, these rocks have not previously been studied paleomagnetically. Isotopic dates from igneous rocks in the province generally indicate emplacement between 1.4 and 1.35 Ga, which falls in a time frame where the apparent polar wander path (APWP) for the Kaapvaal craton is poorly known. In order to help address this problem, we report paleomagnetic data for syenitic rocks in the large Pilanesberg Complex near the western limit of the alkaline province, two separate syenitic intrusions in the Pienaars River Complexes near Pretoria, and the Spitskop ijolite–nepheline syenite–carbonatite complex near the eastern limit of the province. These intrusive units yield poles that allow a tentative extension of the Mesoproterozoic Kaapvaal APWP back to 1.4 Ga. The data suggest a pronounced bend or cusp in the APWP at 1.1 Ga, which may record a major change in plate motion occurring at the same time as emplacement of the Umkondo large igneous province in southern Africa.