GEOCHEMISTRY AND ORIGIN OF THE ARCHEAN BEIT BRIDGE COMPLEX, LIMPOPO BELT, SOUTH-AFRICA

The Beit Bridge complex (BBC) in the Central Zone of the Limpopo Belt includes metasedimentary rocks of Archaean age, amphibolites and granitoids which comprise ≥50% of the complex. BBC metapelites have negative Eu anomalies and other immobile element distributions similar to Phanerozoic shales. One group of metapelites that shows significant depletion in Ca, Na and Sr appears to have been derived from intensely weathered sources. The negative Eu anomalies in BBC metapelites suggest intracrustal melting of their sources and thus the presence of evolved continental crust in this part of Southern Africa by about 3000 Ma. BBC banded iron formation (BIF) is similar to other Archaean BIF and shows large positive Eu anomalies. BBC carbonates are dolostones depleted in REE, HFS elements, U, Th, Ba, Sr, Ni, Se, V and Y and enriched in Fe, Mn, Na, Rb and Cs relative to Phanerozoic marine carbonates. -from Authors