The geological and economic legacy of the Pan-african Damara Belt and Lufilian Arc of south-central africa

Abstract

The Neoproterozoic belts of southern Africa, which include the Damara Belt and the Lufilian Arc, have had a significant impact on the understanding of the geology of Southern Africa and related regions. Above all, both belts are economically important as they host metallic and non-metallic mineral deposits of the Kalahari and Central African Copperbelt which are mined in Namibia, Democratic Republic of Congo (DRC), and Zambia respectively. The Damara Belt continues in a north-easterly direction into Botswana, where it continues below the Phanerozoic cover of the Karoo and Kalahari Supergroups to connect in the subsurface with the Lufilian Arc in western Angola and Zambia. The two belts record a full Wilson cycle and form part of a transcontinental suture zone which resulted from the collision between the Archean Congo and Kalahari cratons. The Damara Belt in Namibia, records a progressive increase in metamorphic grade and deformation intensity from sub-greenschist facies on the northern platform to HT/LP granulite facies in the core of the orogen. Similarly, the Lufilian Arc also records a gradual increase in metamorphic grade from sub-greenschist facies in the north (in the DRC) to amphibolite facies in the in the Domes Region in Zambia. Mineralization in these belts differs in style, shape, and size, which can be attributed to the differences in the nature and characteristics of the original sub-basins that formed during rifting, and subsequent deformation. In the Lufilian Arc, ore reserves for individual mines are in the order of 50–810 Mt of ore at 0.5–3 % Cu. This scale is simply not comparable to that in the Damara Belt with tonnages of up to 35 Mt with grades of 0.1–2 % Cu. Both regions also contain numerous smaller copper deposits. On the other hand, the Damara Belt hosts the world class Rossing and Husab uranium mines of Namibia (with grades of 310–450 ppm U) but no major uranium deposits occur in the Lufilian Arc. The Damara uranium deposits occur associated with syn-to post-tectonic granites in the core of the orogen where granite formation was initiated by anatexis of the metasedimentary rocks of the Swakop Group. In contrast, the associated Pb-Zn ± Cu mineralization in both belts appears to be remarkably similar, with comparable deposit sizes, grades, and estimated reserves. The legacy of these two orogenic belts is significant in that the Lufilian Arc serves as the standard or type locality for understanding sediment-hosted Cu-Co deposits globally, whereas the Damara Belt has been the key to understanding granite melt generation by anatexis and formation of granite-hosted uranium deposits in the world.