A U-Pb zircon LAM-ICP-MS age of 549 ± 11 Ma from the Stinkbank granite in the south Central Zone of the Damara belt represents the first robust age for the crystallization of a member of the regionally widespread suite of syntectonic Salem-type granites. This age confirms previous assertions that suggest that the main phase of crustal shortening related to the collision between the Congo and Kalahari Cratrons occurred between 550 and ~540 Ma in the south Central Zone, the leading edge of the Congo Craton. Ages from syntectonic granites reported in the literature from the north Central and the Northern Zone record progressively younger ages of ~530 to ~515 Ma and late-stage folding in the Northern Zone is suggested to have occurred between ~510 to ~500 Ma. The younging of ages that date the main collisional phase towards the north is interpreted to track the northward propagation of the deformation and metamorphic front from the main suture zone to the northern foreland of the Damara belt. Geochronological data are sparse, and the lack of detailed structural data precludes the retrodeformation of the fold-and-thrust belt along this 250 km long section. However, the age brackets suggest a migration of the orogenic front at a rate of at least 5 to 7 mm/a, but more likely in the order of several centimetre per year, if the internal strain is removed.

The Colenso fault is a major northwest to southeast trending fault zone in the Pan-African Saldania Belt of the Western Cape Province in South Africa that is spatially closely associated with granitoids of the ~550 to 510 Ma Cape Granite Suite. Most of these granites were previously considered to be largely post-tectonic intrusions, but structural data presented in this study demonstrate the synkinematic emplacement of granitoids into, and along, the Colenso Fault. The kinematic analyses of shear zones and granite fabrics together with previously published and new geochronological data are combined to provide constraints on the complex kinematic history of the fault and the tectonic evolution of the hitherto poorly understood Saldania Belt. Early, strongly gneissose granitoids of the composite Darling batholith (547 ± 6 Ma) were emplaced during sinistral strike-slip movement along the Colenso fault. Both the timing of emplacement and penetrative deformation of the Darling batholith suggest an intrusion of the pluton during the main Pan-African collisional event in the Saldania Belt. The younger Trekoskraal granite intrudes synkinematically into dextral strike-slip faults related to deformation along the Colenso fault. Single-zircon ages from synkinematic aplites constrain the timing of dextral strike-slip shearing to 539 ± 4 Ma. The emplacement of the late-kinematic Cape Columbine granite during dextral strike-slip faulting indicates that dextral strike-slip kinematics along the Colenso fault continued at least until ~520 Ma. These results point to a reversal of strike-slip motion along the Colenso fault at ~540 Ma that coincides with the onset of uplift of rocks of the Saldania Belt. The final exhumation of the belt at ~515 to 520 Ma is marked by the near-surface emplacement of the last phases of the Cape Granite Suite, related subaerial volcanism, sedimentation of the coarse-clastic, fault-bounded Klipheuwel Group, and the overlying fluvial to shallow-marine sequence of the Mid-Cambrian Cape Supergroup. The temporal and spatial overlap between igneous activity and rift-type sedimentation indicates that a substantial part of the Cape Granite Suite was emplaced in an overall transtensional and/or extensional setting. During this time, the voluminous plutonism of the Cape Granite Suite most likely represented a significant heat input that also contributed to a thermal weakening of the crust. In view of the Early Paleozoic extensional setting suggested here, we interpret Ar-Ar mineral ages of ~500 Ma and post-orogenic plutonism that are widely documented from Pan-African belts throughout southwestern Africa to reflect a thermal event related to crustal thinning and associated mantle upwelling that follows the main phase of Pan-African collisional tectonics.

The Navachab gold mine in central Namibia is situated in amphibolite-facies, marble-dominated metasediments of the Neoproterozoic Damara Sequence in the Pan-African Damara Belt. Gold mineralization is hosted by two main, and at least three minor, sets of auriferous quartz-veins that are developed on the subvertical northwestern limb of the regional-scale, shallow doubly-plunging anticline of the Karibib dome. The orientation, relative timing and progressive deformation of quartz veins indicate that veining occurred during folding and fold amplification of the Karibib dome. This deformation forms part of the main phase of northwest-directed collisional tectonics in the Damara belt at ~540 to 550 Ma. The two main vein sets include (1) bedding-parallel, shallowly-plunging ore lenses and shoots situated at the base of a prominent marble unit, and (2) a laterally extensive swarm of shallowly-dipping quartz veins that truncate the host rocks at high angles. The bulk of the bedding-parallel lenses represent dilational jogs that opened during flexural flow along bedding-parallel slip planes during the amplification of the Karibib dome. Flexural flow and associated bedding-parallel fluid infiltration were concentrated close to the contact between marbles and the underlying siliciclastic formations. This lithological contact, in particular, represented a pronounced rheological contrast resulting in increased slip rates during fold amplification. The highly discordant sets of shallowly-dipping, sheeted quartz veins were emplaced during the fold lock-up stage of the Karibib dome. Quartz veining occurred when the northwestern limb of the dome was rotated to subvertical attitudes, so that bedding-parallel flexural slip ceased to be active. Extensional fracturing and veining was facilitated by the presence of transiently supralithostatic fluid pressures. The high-amplitude fluid pressure cycling associated with extensional fracturing is likely to have triggered gold precipitation in the shallowly-dipping veins. Although bedding-parallel veins and discordant veins are broadly contemporaneous, related to the regional-scale D2 phase of fold-and-thrust tectonics, cross-cutting relationships between the two main vein systems indicate that the two vein sets have represented separate entities and succeeded each other rather than forming an interconnected fracture mesh.

U-Pb zircon and monazite ages from the oldest and youngest granite phases of the composite Stinkbank pluton in the south Central Zone of the Pan-African Damara belt in Namibia indicate a timing of emplacement of the composite pluton between 547.5 ± 4.7 Ma and 529.4 ± 4 Ma. This documents the assembly of the sheet-like pluton over a period of 17 ± 7 Ma (2σ ) in the lower Cambrian. Intrusive relationships, the folding of all granite phases and the pervasive development of magmatic and solid-state foliations indicate the syn-tectonic emplacement and deformation of the pluton during northwest-southeast shortening (D3) over a protracted time between >550 Ma and 50 Ma in the south Central Zone, between >560 Ma and at least 500 Ma. We suggest that previously identified deformation episodes do not represent distinct deformational phases related to changes in regional stress fields or plate kinematics. Instead, different kinematics and the seemingly different timing of deformational episodes are the result of variations of the strength of the Central Zone during high-angle convergence. Mid- and lower-crustal levels are decoupled from the upper crust, forming a ductile, partially molten orogenic infrastructure beneath a rheologically stronger, upper-crustal superstructure. Variations in crustal rheologies are brought about by regional high-T metamorphism and, in particular, partial melting of mid- and lower crustal levels. The presence of melts and advective heat transport through granite plutons has resulted in a similar weakening of even upper crustal levels, although spatially restricted to the intrusions and immediate wall rocks. The orogenic superstructure-infrastructure also implies that the correlation of deformational events through seemingly syn-, late- and post-tectonic granite intrusions from different parts and levels of the orogen may lead to erroneous interpretations of the actual timing of events.