Granulite facies metamorphism in the Central and Southern Marginal Zones of the Limpopo Belt, South Africa

Tsunogae, T. and Miyano, T. (1989) Journal of the Geological Society of Japan, 97, 1-16.


Abstract

The Limpopo Belt is an intensely deformed and highly metamorphosed Archean terrane in South Africa. Most part of this belt has suffered granulite facies metamorphism. Metamorphic conditions of the Central and Southern Marginal Zones of the Limpopo Belt were estimated on the basis of mineralogic and petrologic data, using available geothermometers and geobarometers. Two different metamorphic P-T trajectories (paths) are proposed for the studied area. They may show two different retrogressive episodes, following peak metamorphism. Accordingly, the pressure in the Central Zone decreased from about 10 kb (kyanite zone) to 4 kb (sillimanite zone) at about 800C, probably reflecting an isothermal and rapid uplift. On the other hand, the P-T path of the Southern Marginal Zone has a gentle slope relative to that of the Central Zone. It indicates pressure variation from 6-7 kb at 680-730C to 1-3 kb at 450-500C. The difference in the P-T trajectories may be related to the formation of the Palala Shear Zone, which bounds the two Zones. Consequently, the Southern Marginal Zone has been slipped along the shear zone against the Central Zone, delaying the uplift of the former.