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Comparing and contrasting Cretaceous brittle deformation structures in the upper continental crust of west and east coast regions of southern Africa: dyke geometry along the incipient Namibian margin (Henties Bay-Outjo Dyke Swarms) and joint systems in the Table Mountain Group and Karoo intrusions flanking the Cape margin Muedi T1,3, de Wit M.J2 and Reinhard R.O3 1) AEON (Africa Earth Observatory Network), and Department of Geosciences, Faculty of Science, Nelson Mandela Metropolitan University, South Africa, Email: [email protected] 2) AEON (Africa Earth Observatory Network), Faculty of Science, Nelson Mandela Metropolitan University, South Africa, Email: [email protected] 3) Karlsruhe Institute of Technology, Karlsruhe, Germany, Email: [email protected] ABSTRACT Mafic dyke swarms are a major component of the South Atlantic Large Igneous Province that originated during the break-up of Africa and South America ca. 130 Ma. We examined Cretaceous dyke geometry, brittle deformation and geometric patterns of the Henties Bay-Outjo Dyke Swarm (HOD), Namibia. We also investigated the relationship between the HOD and Ponta Grossa Dyke Swarm (PG) of Brazil intruded during West Gondwana break-up. This was achieved by reconstructing Gondwana plates containing the PG and HOD swarms, using ArcGIS and Gplates software. We also investigated joints systems in the Table Mountain Group quartzite (TMG) and Golden Valley Sill (GVS) a major Karoo mafic intrusion, both in the Eastern Cape Province, South Africa to compare geometric patterns and brittle structures with those of the HOD Swarm. Mapping of the dykes was carried out by remote sensing using digital aerial and satellite images. The fractal analysis conducted within the HOD indicates a fractal dimension of Df =1.7, while analysis of the TMG and GVS joint systems indicates an averaged fractal dimension of Df=1.8. For that reason it appears that analysed fractal geometry in the HOD, TMG and GVS originated under different tectonic stress conditions. The HOD and GVS dominant orientations of NNE/NE seem to have undergone similar tectonic stress regime during Gondwana break-up. We can determine that the HOD dykes are not always related to joints during continental break-up; but rather that the dykes initiate fracture systems into which they subsequently migrate during intrusion. KEYWORDS: Dyke swarm, joints, tectonic stress, Gondwana and fractals