Description
The Kaapvaal craton covers an area of approximately 1,200,000 km2 (460,000 sq mi) and is joined to the Zimbabwe craton to the north by the Limpopo Belt. To the south and west, the Kaapvaal craton is flanked by Proterozoic orogens, and to the east by the Lebombo monocline that contains Jurassic igneous rocks associated with the breakup of Gondwana.
The Kaapvaal craton formed and stabilized between 3.7 and 2.6 Ga by the emplacement of major granitoid batholiths that thickened and stabilized the continental crust during the early stages of an arc-related magmatism and sedimentation cycle. The craton is a mixture of early Archean (3.0-3.5 Ga) granite greenstone terranes and older tonalitic gneisses (ca. 3.6-3.7 Ga), intruded by a variety of granitic plutons (3.3-3.0 Ga). Subsequent evolution of the Kaapvaal craton (3.0-2.7 Ga) is thought to be associated with continent–arc collision that caused an overlaying successions of basins filled with thick sequences of both volcanic and sedimentary rocks. This was then followed by episodic extension and rifting when the Gaborone–Kanye and Ventersdorp sequences were developed. Early Archean crust is well exposed only on the east side of the craton and comprises a collage of subdomains and crustal blocks characterized by distinctive igneous rocks and deformations.
Late Archean metamorphism joined the Southern Marginal Zone of the Kaapvaal craton to the Northern Marginal Zone of the Zimbabwe craton approximately 2.8-2.5 Ga by the 250 kilometres (160 mi) wide orogenic Limpopo Belt. The belt is an east-northeast trending zone of granulite facies tectonites that separates the granitoid-greenstone terranes of the Kaapvaal and Zimbabwe cratons.
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