Abstract The formation of the Kamanjab Inlier (KI) in NW Namibia is poorly known and constrained to Palaeoproterozoic times. With the Epupa complex (EC) and Grootfontein Inlier (GI), the KI marks the southwestern Congo craton margin. Our new geochemical data for granitoids and orthogneisses indicate formation along an active continental margin. Single zircon ages frame granitoid emplacement to 1.86–1.83 Ga, roughly 75 myr older than ages from the northern EC and approximately 100 myr younger than from the GI. The southern EC is the only known Archaean Namibian basement with ɛNd 1.85 Ga of −10.2 to −6.3, in contrast to northern EC (−1.8 to 4.4) and KI (−6.2 to 2.6). Thus, earlier speculation that the southern EC is an exotic terrane, among the Namibian basement complexes, is supported by our data. In contrast, the KI is geochemically comparable to the northern EC and GI. The c. 2.0 Ga Lufubu metamorphic complex roughly 1000 km further east shows similar geochemistry, and a common evolution in the Kamanjab–Bangeweulu magmatic arc has already been proposed. Therefore, our new data point to a major Palaeoproterozoic crustal growth event at the southwestern margin of the Congo Craton starting in the present east and gradually moving towards the present NW.

Evidence is presented relating to the tectonic evolution of the Limpopo Belt of southern Africa. It is demonstrated that this evolution was protracted, lasting at least 700 m.y. between ca. 2.7 and ca. 2.04 Ga, and comprised the complex assembly of terranes along shear zones through processes involving compression, extension, and strike-slip strain (transpression and transtension). It is argued that this evolution is more akin to Turkic-type craton building than to Himalayan- or Alpine-type collision between the Kaapvaal and Zimbabwe cratons at either ca. 2.7 Ga or ca. 2.04 Ga, to which most earlier workers have subscribed. The steeply dipping shear zones separating terranes are tens of kilometers wide with gradational contacts, as opposed to narrow (<1 km) shear zones with relatively sharp contacts that characterize the Himalayas and Alps. Ductile deformation with both subvertical and horizontal transport directions is common in the Turkic-type orogenesis rather than thin skin, thrust tectonics. The shear zones are interpreted to be artifacts of long-lived subduction zones. Relics of calc-alkaline (I-type) magmatic arcs that formed both on continental and oceanic crust are identified and are related to subduction-accretion of the various terranes. In contrast, S-type magmatism (melts derived from sedimentary protoliths) characterizes deformation after continent-continent collision in the Alps and Himalayas. Individual terranes are characterized by distinct P-T-time (pressure-temperature) paths that show they experienced different tectonic histories under high-grade amphibolite- to granulite-facies conditions instead of lower-grade, greenschist- to amphibolite-grade conditions, which are more common in the Alps and Himalayas. Individual terranes also have distinct metallogenic signatures.

Abstract The East African–Antarctica Orogen resulted from the continent–continent collision of East and West Gondwana, or parts thereof, during the Pan-African event at c . 650–510 Ma. The collision overprinted large areas of older, mainly Mesoproterozoic, crust up to granulite facies grade in East Antarctica. The collision history is well documented by folding and thrusting, isothermal decompression and metamorphic zircon growth at c . 580–560 Ma (Pan-African I). The convergence was succeeded by an extensional phase, probably representing orogenic collapse. This Pan-African II event at c . 530–510 Ma is characterized by large-scale extensional structures, finally resulting in the post-tectonic intrusion of voluminous A2-type granitoids. In central Dronning Maud Land the Pan-African II event started with the intrusion of syntectonic igneous rocks within an overall extensional setting. Two new SHRIMP data from gabbro zircons of the Zwiesel Gabbro give ages of 521±5.6 and 527±5.1 Ma. These ages are interpreted as crystallization ages and confirm the interpretation that the gabbro was emplaced early during the Pan-African II event. The gabbro was intruded by a network of leucogranite dykes and veins. Whereas the gabbro appears entirely undeformed, the leucogranite dykes are strongly mylonitized along extensional shear zones, indicating pronounced strain partitioning of the gabbro complex. Within the leucogranite mylonites, large tension gashes developed during mylonitization, indicating very high strain rates. Quartz c-axis orientations from quartz of the tension gashes show a distinct cross-girdle that formed during pure shear deformation. Fluid inclusion data from the leucogranite mylonites and the associated tension gashes mainly reveal recrystallization-related intracrystalline CO 2 -dominant inclusions with relatively low densities of < 1 g cm −3 . The fluid inclusion data are interpreted to represent the last stages of a retrograde P–T path that is characterized by simultaneous cooling and decompression during extensional exhumation, probably succeeding the collapse of overthickened crust. A comparable orogenic collapse of the East African–Antarctic Orogen is reported from other parts of the orogen, such as from western Madagascar and the northern Arabian–Nubian Shield.