Thermal History and Tectonic Setting of the Namaqualand Granulites, Southern Africa: Clues to Proterozoic Crustal Development

Mesoproterozoic rocks of Namibia and their plate tectonic setting

“…1), where they are precisely dated at 1060-1030 Ma. This metamorphic event is characterized by an anti-clockwise P-Tt path (Waters, 1989(Waters, , 1990Robb et al, 1999). (8) The timing of magmatic activity in the NMC is poorly constrained.…”

Shrimp Zircon Ages and Petrology of Lower Crustal Granulite Xenoliths From the Letseng-La-Terae Kimberlite, Lesotho: Further Evidence for a Namaqua-Natal Connection

“…The abundance of A-type granites emplaced during this event has been used to postulate significant lower crustal melting in the Natal terranes and has also been correlated with emplacement of similar granites formed during low-P and high-T midcrustal metamorphism in the western the Namqua Belt Robb et al, 1999). A significant component of advective heat associated with the emplacement of mafic magmas at the base of the crust is necessary to form mid-crustal granulites (Waters, 1990;De Yoreo et al, 1991). Remarkably, no granites ranging in age between ~1.0 and ~1.1 Ga have been found at the surface in the Tugela terrane nor are there such xenoliths within kimberlites of the Letseng-la-Terae Mine.…”

“…The calculated thickness of the magmatic underplate is based on thermal modelling and is required to produce the peak thermal gradient in the granulite-and upper amphibolite-facies (Waters, 1990). The general difference in crustal thickness between Archaean and Proterozoic crust has been interpreted as a consequence of different mantle lithospheric compositions.…”

Geochemistry and tectonic significance of the Mesoproterozoic Kgwebe metavolcanic rocks in northwest Botswana: implications for the evolution of the Kibaran Namaqua-Natal Belt

“…The granulites in the Namaqualand equilibrated at c. 6-7 kbar/ 800-900°C (Jackson, 1976;Waters, 1990;Willner, 1995) and suggest exhumation of mid-crustal crust. These c. 1060-1030 Ma old granulites record an anticlockwise P-T-t path and suggest extensional collapse (Waters, 1990).…”

“…The granulites in the Namaqualand equilibrated at c. 6-7 kbar/ 800-900°C (Jackson, 1976;Waters, 1990;Willner, 1995) and suggest exhumation of mid-crustal crust. These c. 1060-1030 Ma old granulites record an anticlockwise P-T-t path and suggest extensional collapse (Waters, 1990). It should be stressed that extensional collapse related strike-slip faults cannot be compared with the wrench and transpressional faults developed during the Himalayan-type indentation tectonics as documented by Jacobs, Thomas & Weber (1993).…”