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- Title
New age constraints on the tectogenesis of the Kheis Subprovince and the evolution of the eastern Namaqua Province.
- Authors
Moen, H. F. G.; Armstrong, R. A.
- Abstract
Mapping and stratigraphic analysis of the rocks adjacent in the Kaapvaal Craton east of Upington has suggested that the area previously defined as the Kheis Subprovince was deformed and metamorphosed not during the so-called Ebumean "Kheis Orogeny" but as the result of a considerably younger event. U-Pb zircon SHRIMP ages on sedimentary as well as volcanic and plutonic rocks show that the arenitic successions that dominate the area were derived from a provenance similar in geochronological make-up to the Kaapvaal Croton and laid down no earlier than -1.8 Ga ago. Deposition of the volcanosedimentary Wilgenhoutsdrif Group is dated at -1.3 Ga, confirming its unconformable relationship to the arenites and its co-magmatic relationship with the similarly-aged Kalkwert- Gneiss. The regional dynamothermal event is concluded to be early Namaquan, and its age is revealed by its post-Wilgenhoutsdrif character and Rb-Sr muscovite ages clustering around ~1.2 Ga. These findings confirm that the Kheis Subprovince contains no Ebumean orogenic signature and is, in fact, art integral part of the Namaqua Province. The post-tectonic Koras Group lies entirely within the subprovince and its <~1.t7 Ga age is consistent with the area's early Namaquan tectonic signature. It is separated from the ~1.1 to 1.0 Ga old Gordonia Subprovince by the Trooilapspan shear zone, a terrane boundary thought to indicate significant lateral displacement.
- Subjects
SOUTH Africa; OROGENY; ARENITES; GNEISS; METAMORPHIC rocks; SEDIMENTARY rocks; STRUCTURAL geology; CRATONS; NAMA (African people)
- Publication
South African Journal of Geology, 2008, Vol 111, Issue 1, p79
- ISSN
1012-0750
- Publication type
Article
- DOI
10.2113/gssajg.111.1.79