Age, origin and palaeogeography of the Southern Irumide Belt, Zambia

The Southern Irumide Belt (SIB) records over one and a half billion years (c. 2000-500 Ma) of tectonic evolution along the southern Congo Craton margin. To understand this evolution we present U-Pb, Lu-Hf, REE zircon and structural data for the SIB of Zambia, which are used to investigate its formation, evolution and relationship to the Irumide Belt of the southern Congo Craton. Orthogneiss in the Chewore-Rufunsa and Chipata terranes yields ages between c. 2040 and 2000 Ma. This implies the presence of Paleoproterozoic basement throughout the SIB, similar to basement rocks within the Irumide Belt. Detrital zircon data from the Chipata Terrane yield age populations and epsilon(Hf)(t) values that are equivalent to those for samples from other SIB terranes and the Irumide Belt. The similarities between basement units and overlying sedimentary sequences in the SIB and Irumide Belt indicate that the SIB formed an integral part of the southern Congo margin since the Paleoproterozoic, rather than accreting to this margin during the late Mesoproterozoic. Subsequent structural deformation in this region occurred as two phases, a north-south-directed compression during the late Neoproterozoic to Cambrian, and a weaker east-west-directed compression during the Phanerozoic.