Amalgamation in the Central African Shield (CAS) by the Kibaran orogen: New hypothesis and implications for the Rodinia assembly

Abstract

The Central African Shield has been built in the Mesoproterozoic time coevally with the “Rodinia assembly”. By the beginning of the Neoproterozoic, this Rodinia supercontinent was dispersed to a new assembly (the Gondwana supercontinent) built during the Neoproterozoic by the Brasiliano-Pan-African belts. During the Rodinia assembly, the western and eastern previous blocks (Congo Craton, Tanzanian Craton and Bangweulu Block) were amalgamated by the Kibaran Belt. The aim of this paper is to better understand the collage of blocks (or cratons), which constitute the Central African Shield during the Kibaran orogeny, which leads to the Kibaran belts by the Middle and Upper Mesoproterozoic time (1400-1000 Ma). The cratons involved in this Mesoproterozoic collage are: the Congo Craton, the Tanzanian Block and the Bangweulu Block themselves made by the amalgamation of Archean and Paleoproterozoic terranes. However, this collage was the result of a long geodynamic evolution with at least three Kibaran orogenic events (ca.1400-1375, 1375-1180 Ma and 1180-1000 Ma). Each orogenic event comprised: deposition of sediments, tectono-metamorphic events with granitic intrusions and extensive to compressive tectonic events with molassic deposits. The early event (ca.1400-1375 Ma) leads to a “triple junction rifting” hypothesis. Consequently, this geodynamic history has a regional impact on the Rodinia evolution, on the following Neoproterozoic belts and likely on the geometry of the African rift.