Reference Work Entry

Encyclopedia of Astrobiology

pp 885-885

Kaapvaal Craton, South Africa

  • Nicholas ArndtAffiliated withMaison des Géosciences, LGCA, Université J. Fourier Email author 

Definition

The Kaapvaal craton in South Africa is, along with the Pilbara craton of Western Australia, the only areas where mid-Archean (3.6–2.5 Ga) volcanic and sedimentary rocks are relatively well preserved. The craton covers an area of about 1.2 × 106 km2 and is made up of several strongly deformed early Archean (3.0–3.5 Ga) greenstone belts intruded by tonalitic gneisses (ca. 3.6–3.7 Ga), and a variety of granitic plutons (3.3–3.0 Ga). The craton formed and stabilized between about 3.7 and 2.6 Ga when major granitoid batholiths intruded, and deformation thickened the crust. At the same time, a thick, stable harzburgitic (olivine-orthopyroxene peridotite) keel formed the lower part of the lithosphere. Subsequent evolution from 3.0 to 2.7 Ga involved collision with surrounding cratons and the development of basins filled with thick sequences of both volcanic and sedimentary rocks. Similarities of rock records of the Kaapvaal and Pilbara cratons suggest that they were once p ...

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