The Belingwe Greenstone Belt: Ensialic or Oceanic?

Abstract

The Belingwe belt in Zimbabwe is probably the best preserved late Archaean greenstone belt known. The basal unit that rests unconformably on upto 3.5 Ga old granitoid gneisses and Mtshingwe Group rocks, consists of fluvial to shallow-marine sedimentary rocks, and is similar to cratonic cover successions. The overlying volcanic unit is a submarine lava plain sequence of massive and pillow basalts with komatiites near the base and andesites near the top. Many workers have interpreted the Zimbabwe craton as vertically accreted crust. Coherent units of volcano–sedimentary rocks were laid down in rifts on top of older continental basement (ensialic model) and underwent little deformation until the late-stage emplacement of granite-gneiss complexes. The Belingwe greenstone belt is situated in the southern part of the Zimbabwe craton, north of the Limpopo belt and east of the Great Dyke. It contains a well preserved, 2.9–2.65 Ga old volcano–sedimentary sequence which is surrounded by granitoid–gneiss terrains, the 3.5 Ga Shabani gneiss complex to the east and the 2.9 Ga Chingezi gneiss complex to the west.