Palaeo- Meso- and Neoarchaean Granite-Greenstone Basement Geology and Related Rocks of the Central and Western Kaapvaal Craton, South Africa

Abstract

The Kaapvaal Craton, one of the oldest well-preserved crustal fragments on Earth, enables an understanding of the development of the early Earth. The craton comprises an older eastern component (Witwatersrand Block) ranging in age from ca. 3660 to 2700 Ma and a ca. 3174 to 2782 Ma western domain (Kimberley Block). This contribution deals with the geological nature of the central and western sectors of the Kaapvaal Craton where Archaean basement granite-greenstone rocks occur as inliers surrounded by younger cover formations. Three main areas discussed include the Johannesburg and Makoppa domes and the Kraaipan terrane. Also described are the Marydale terrane, the Rand Anticline, the linear Colesberg magnetic anomaly, and the Modipe Gabbro and Gaborone Granite complexes. Geophysical and geochronological findings suggest that the Kimberley Block is a younger terrane accreted onto the older eastern or Witwatersrand Block along or near the Colesberg Lineament—this despite meagre physical evidence of a collisional zone. Geophysical, petrological and geochemical techniques have helped to understand the crustal structure and depth extent of the roots of the craton. Findings suggest the keel extends to depths of 250–300 km, important for the stability field of diamonds.