MODELING CRUSTAL STRUCTURE OF THE BUSHVELD COMPLEX USING RECEIVER FUNCTIONS

The Bushveld Complex in South Africa is the world’s largest layered mafic intrusion, containing more than 70% of the world’s platinum group elements. This intrusion is exposed in several outcrops, but they are not connected at the surface and it is still debated whether or not they are connected at depth. A published gravity model suggests that the lobes are connected. The goal of this study is to determine if Receiver Functions show a signature diagnostic of the mafic layer of the Bushveld Complex and the Transvaal Sediments underneath. If Receiver Functions are a reliable method, they will then be used to model structure in the center of the Bushveld. To produce Receiver Functions, teleseismic events of magnitude >5.5 that occurred 30-90 degrees from the seismic station were used. The receiver functions were used to create crustal models with an Interactive Receiver Function Forward Modeller (IRFFM). The IRFFM models the crustal layering through manipulation of the Vp/Vs, layer thicknesses, and Vs to produce a synthetic receiver function that matches the observed receiver function. The receiver functions obtained begin with a P-wave arrival, followed by a 2-second backswing caused by the Transvaal Sediments underneath the high velocity layer of the Bushveld Complex, and then a positive amplitude around 6 seconds indicating the Moho. The IRFFM models suggest a crustal thickness of 40 km. The Receiver Functions method can image the signatures of the Bushveld Complex and the Transvaal sediments and will be used to model the center of the Bushveld Complex.