SYN-BREAK-UP DYKE GEOMETRY AND DISTRIBUTION AT THE INCIPIENT NAMIBIAN MARGIN – EXAMPLES FROM THE HENTIES BAY-OUTJO DYKE SWARM

Mafic dyke swarms are major components of the South Atlantic Large Igneous Province, which originated during the Cretaceous break up of Africa-South America. This contribution presents data on the dyke geometry and spatial distribution from the major Henties Bay-Outjo dyke swarm (HOD) in coastal and inland NW Namibia at the African margin, based on the mapping of dykes on digital aerial and satellite images. The dykes were emplaced in the crust at the NE-SW trending, Neoproterozoic Damara mobile belt. The dominant NE-SW strike of the HOD indicates the influence of the Damara Belt structural grain at a regional scale, but locally the dykes crosscut basement foliations and lithologic contacts. Coast-parallel dyke trends are also common. Statistics of dyke thickness, length, and distance between individual dykes are evaluated, in order to show potential clustering or fractal distribution of dyke fractures. These analyses will allow conclusions on fracturing processes of the lithosphere during dyke emplacement.