Zimbabwe Craton - Tokwe Segment

Tokwe Segment

This is the larger of two Early Archaean continental crustal fragments that stabilised in Zimbabwe before 3.3 Ga, extending for over 450 km between Shurugwi, Zvishavane and Masvingo. The much smaller northern fragment is known as the Rhodesdale Gneiss. Granitoids of the same and greater age as the 3.46 Ga Tokwe granitoid gneisses in the south central portion of the Zimbabwe craton are recognised in the central Midlands region, strongly suggesting synchronous formation of the two areas. This crustal block, also known as the Sebakwe Proto-craton, was fully stabilised by around 3.35 Ga with a later granitoid emplacement event around 3.2 Ga and provided the basement for the 3.0-2.6 Ga Late Archaean granite-greenstone magmatism. This second stage of evolution therefore resulted in the present predominance of these rocks, and occurred ca. 400 Ma after the initial stabilisation of the craton. The synchroneity and extent of the Tokwe Segment is considered strong evidence supporting a predominantly intra-cratonic origin for the Late Archaean greenstone belts of Zimbabwe and refuting an arc accretion origin for the craton.