The geology of the area east of Pofadder with emphasis on shearing associated with the Pofadder lineament, North West Cape

Master Thesis


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University of Cape Town

To the east of Pofadder in Bushmanland, N.W. Cape, an area of some 3600 km² has been geologically mapped. Emphasis has been placed on the role of shearing in the deformation history of the area. The study area occurs within the Namaqualand Metamorphic Complex and consists of gneisses, schists and quartzites. These rocks are overlain to the south by the Dwyka Formation of the Karoo Sequence. The rocks of the Namaqualand Metamorphic Complex have undergone polyphase deformation and have been mapped according to their fabric and composition. The Bushmanland Group consists of supracrustal rocks and the following lithologies have been mapped: quartzite (granular and glassy varieties), muscovite-quartz schist, calc-silicate gneiss, quartzo-feldspathic rocks (quartzo-feldspathic gneiss, leucogneiss and leptite), para-amphibolite gneiss and pelitic gneiss. Pre-tectonic intrusive rocks consist of the Nouzees Gabbronorite Suite, a mafic granulite, amphibolite and alkali-feldspar granitic gneisses. Syn to post-tectonic intrusive rocks include a granodiorite-tonalite suite, diorite, pegmatite and vein quartz. Dolerite is post-tectonic, most likely of Karoo age and occurs as sills and remnant hillocks. Non-diamondiferous kirnberlite pipes occur in the west and their emplacement appears to have been structurally controlled, being situated along the Nouzees shear zone.

Bibliography: pages 110-117.