Characterisation and tectonic implications of the Early Cretaceous, Skeleton Coast Dyke Swarm, NW Namibia

Abstract

The Early Cretaceous, Skeleton Coast Dyke Swarm (SCDS) was intruded into Permo-Carboniferous sediments of the Karoo Supergroup, Pan-African granites, Neoproterozoic metasediments, and Archean to Mesoproterozoic gneisses of the Kaoko Belt, NW Namibia. Aeromagnetic data and satellite imagery has been used to map the distribution of the generally coast parallel mafic dykes along with a significant number of dykes that cut across Pan-African structures of the Kaoko Belt. Dykes of the SCDS were mapped for some 500 km along the Skeleton Coast of NW Namibia and up to 200 km inland, and with a likely continuation into Angola. The geochemistry and published geochronological data suggest that the majority of the dykes are related to the Etendeka volcanics. These volcanics, together with the basalt and rhyolite lava flows and associated mafic dyke swarms of S-SE Brazil, form the Parana-Etendeka magmatic province of Early Cretaceous age. Geochemical analysis of 26 dykes show that the majority of the dykes are Low-TiO2 quartz tholeiites of two types: 1) qtz-tholeiites enriched in LREE [(La/Yb)N - 3.43 to 6.46]; & 2) qtz-tholeiites with REE patterns similar to E-MORB [(La/Yb)N