Rollinson, H. and Blenkinsop, Thomas G. ![]() |
Abstract
The Northern Marginal Zone of the Limpopo Belt in southern Africa comprises a Plutonic Assemblage of granitoids including a distinctive suite of porphyroclastic granites. and a much less abundant Supracrustal Assemblage of metabasites and iron formations. These rocks are at granulite facies above a normal thickness of continental crust. Most of the Plutonic Assemblage are intrusive rocks that crystallized from dry melts from 2800 to 2600 Ma, with a relatively simple thermal history. They may have been derived from partial melting of a mafic source. Some supracrustal rocks have experienced two thermal events at granulite facies. A reverse-sense shear zone forms the boundary of the Northern Marginal Zone with the Zimbabwe craton. The southern boundary is the Triangle shear zone, which is proven as a continuous structure along a much greater strike length than previously documented. A widespread sub-vertical foliation in the Northern Marginal Zone and the reverse shear zone formed during progressive NNW-SSE shortening. Crustal thickening occurred both magmatically and tectonically in the late Archaean, and was accompanied by synchronous uplift. Protracted magmatism provides a mechanism to incorporate supracrustal rocks into the lower crust, and can explain the occurrence of more than a single thermal event.
Item Type: | Article |
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Date Type: | Publication |
Status: | Published |
Schools: | Earth and Environmental Sciences |
Subjects: | Q Science > QE Geology |
Uncontrolled Keywords: | Archaean; granulites; Limpopo Belt; Zimbabwe |
Publisher: | Geological Society of London |
ISSN: | 0016-7649 |
Last Modified: | 24 Oct 2022 12:08 |
URI: | https://orca.cardiff.ac.uk/id/eprint/50649 |
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