The intracratonic Irumide Belt of Zambia and its bearing on collision orogeny during the Proterozoic of Africa

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Abstract
Summary: The Irumide Belt of Zambia is often quoted as being typical of African intracratonic mobile belts which involve no crustal shortening or major displacements. This belt is shown here to include the NW-facing foreland fold and thrust zone of the Southern Moçambique Belt and to have involved considerable crustal shortening. A crustal scale ‘pop-up’ structure separates this foreland from the internal higher-grade granulite-facies rocks of Malawi and Moçambique where major SE-facing nappe structures of Irumide age have been described. Several possible suture zones are identified and the Irumide-Moçambique Belt is interpreted as resulting from collisional processes during the Mid-Proterozoic. The adjacent Ubendian Belt represents a continental transform fault zone associated with crustal shortening across the Irumide Belt. The implications of these interpretations regarding the onset of plate tectonics in the Proterozoic and Archaean are briefly discussed.