THE KUNENE COMPLEX, ANGOLA NAMIBIA - A COMPOSITE MASSIF-TYPE ANORTHOSITE COMPLEX

The c. 15000 km2, c. 2 Ga Kunene complex of southern Angola and northe rn Namibia is one of the world's largest occurrences of anorthositic r ocks, rivalled only perhaps by the Lac St Jean massif of the Grenville Province in Quebec. We report here the results of a detailed field an d laboratory study of a 100 km2 area in the northern part of the compl ex. Coarse grained (av. 1-2 cm) anorthosite and leucotroctolite are th e predominant rock types, although colour index varies between 0 and 5 0, averaging about 10. Ultramafic rocks are totally absent. Typical mi neralogy is: plagioclase (An57-76) + olivine(Fo64-71) + orthopyroxene( En65-74) + clinopyroxene +/- Fe-Ti oxides +/- apatite. Textures are do minantly massive, although weak, impersistent, magmatic lamination wit h near-vertical dip and unsystematic strike is also present. Other mag matic features include plagioclase and orthopyroxene megacrysts, block structure, mortar texture, and anorthositic dykes. Metamorphic effect s are minimal or absent. All of these attributes are similar to those found in typical massif-type anorthosites. Since comparable features a re present over large areas elsewhere in the complex, we suggest that Kunene should be considered analogous to a large, composite, massif-ty pe anorthositic intrusive complex, rather than to a large, single or c omposite mafic layered intrusion such as Bushveld, as has been previou sly suggested or assumed. This interpretation is supported by satellit e imagery, which shows the outlines of several individual anorthositic plutons, one of which clearly encompasses our field area.