AFRICA WITHIN RODINIA SUPERCONTINENT: EVIDENCE FROM THE KIBARAN OROGENIC SYSTEM

The Mesoproterozoic Kibaran orogenic system of Africa has been ignored in most Rodinia reconstruction scenarios. This orogenic belt extends for >3000 km and is >400 km wide in Africa. It is the result of the convergence of Paleoproterozoic/Archaean cratonic blocks forming the Congo craton to the north and a mosaic including the Kalahari, Bangweulu, Tanzania and West-Nilian cratons (hereafter Kalahari craton) to the south. The orogenic system includes several segments with local names (from north to south): Karagwe-Ankolean, Burundian, Kibarides, Irumides, Choma-Kalomo, Ngamiland, Namaqua-Natal and Lurio belts. These segments define two major groups: (1) provinces affected by a long-lived Mesoproterozic plate convergence between ~1.4-1.0Ga. They host sedimentary basins affected by contractional deformation for the first time during the Mesoproterozoic. The supracrustal sedimentary units are intruded by large batholiths with peak magmatism/deformation at ca. 1.39-1.35 Ga (subduction) and 1.1-1 Ga (continental collision). Geochemical characteristics of 1.39-1.35 Ga mafic rocks suggest an active continental margin, although an ophiolitic complex formed in an oceanic arc has been documented. Strongly peraluminous Sn-Nb-W-REE bearing collisional granites were emplaced at ca. 1-0.96 Ga. (2) Archaean to Paleoproterozoic provinces representing older crust of the converging plates strongly reworked during the 1.1-1 Ga continental collision. Thin-skinned folds-thrusts define the main physiography of this orogen in central-eastern Africa and control the NE-SW structural grain of the belt.

The above new geological and geochronological data and interpretations suggest the convergence between the Kalahari craton and a composite Congo-Laurentia craton during the assembly of Rodinia, generating the Kibaran-Grenvillian-Llano belts. IGCP 440 geological and paleomagnetic data will be used to further constrain this interpretation.