| Summary: | The ~132 Ma Paraná-Etendeka Large Igneous Province consists of an extensive succession of bimodal flood volcanic rocks and intrusions across Brazil, Paraguay, Uruguay, Argentina, Namibia and southern Angola. This magmatism has been attributed to the impact of the Tristan mantle plume and the associated opening of the South Atlantic Ocean, during the Early Cretaceous breakup of West Gondwana. In southern Africa, this is preserved as the Etendeka flood volcanic succession and dyke suites, and the Damaraland Intrusive Suite, a series of subvolcanic intrusions that occur in a north-east-trending band within the Neoproterozoic Damara Orogenic Belt. The Doros Gabbroic Complex is a relatively small (~3.5 km x 7.5 km) layered mafic intrusion that forms part of the Damaraland Suite in north-western Namibia. It is hosted by deformed Damaran metaturbidites, Damaran granitoids and Karoo-age metasedimentary strata in the Southern Kaoko Zone of the Damara Belt. The intrusion is a shallow lopolith, with an estimated thickness of at least 500 m, which consists of a sequence of roughlyconcordant, sill-like gabbro layers, dipping in towards the centre, cross-cut by dolerite and bostonite dykes. It is undeformed and unmetamorphosed. The fundamental mineralogy is essentially the same throughout the main body of the intrusion (plagioclase + calcic clinopyroxene + oxy-exsolved Fe-Ti oxides ± olivine). However, variations in the modal proportions of these minerals, and in the mineral and rock textures and compositions, define a series of layers. The stratigraphy broadly comprises: 1) a fine-grained gabbroic sill with chilled margin, present mostly as subcrop; 2) a sequence of massive, olivine-cumulate melagabbros (the Lower Zone), with a basal chilled margin, that form the outer ring of the complex; 3) a massive, plagioclase-cumulate olivine gabbro (the Intermediate Zone), comprising the inner ring of the complex; and 4) a sequence of variable, strongly foliated, plagioclase-, olivine- or magnetitecumulate gabbros (the Upper Foliated ...
|
|---|