MESOPROTEROZOIC TECTONIC EVOLUTION OF THE KALAHARI CRATON: IMPLICATIONS FOR RODINIA RECONSTRUCTIONS

The Kalahari craton was stabilized following 2.0–1.8 Ga orogenesis in southern Africa and originally contiguous parts of Antarctica. Crust that formed or was reworked at 1.4–1.0 Ga occurs along all of its margins, partly as inliers in younger, ~550 Ma (Pan-African) belts. Along the southern craton margin, the Namaqua–Natal–Maud belt underwent arc magmatism, terrane accretion, polyphase amphibolite- to granulite-grade contractional/transpressional deformation, and late-syntectonic granite intrusion at 1.38–1.0 Ga. A largely buried orogen along the western craton margin records amphibolite-grade deformation and granitoid plutonism at 1.35–1.2 Ga and is inferred to connect with the Namaqua belt to the south. 1.1–1.0 Ga granitoid orthogneisses within Pan-African belts along the northern and eastern craton margins are associated in one area with a 1.4 Ga ophiolite/arc terrane. The orthogneisses form part of an extensive region north of the Kalahari craton and east of the Congo craton that includes large amounts of 1.15–1.0 Ga arc-type rocks containing juvenile crustal components. This region may represent one of the main convergent zones active during Rodinia assembly, although its original relations are obscured by intense Pan-African overprinting. Widespread intraplate magmatism affected much of the Kalahari craton at 1.1 Ga and is inferred to record impact of a mantle plume inboard of the Namaqua–Natal–Maud belt. Critical questions that bear on Rodinia configurations include the following: (1) Which of the 1.4–1.0 Ga orogenic belts on the margins of the Kalahari craton can be paired with coeval belts in other parts of Rodinia? (2) Can the 1.1 Ga intraplate magmatism be correlated directly with widespread coeval magmatism within Laurentia? (3) Did the Kalahari and Congo cratons collide during Rodinia assembly, or were they first juxtaposed during assembly of Gondwana at the end of the Neoproterozoic? The answer to the last question depends on whether the transcontinental, ~550 Ma Damaran-Lufilian-Zambezi orogen separating the two cratons represents a Himalayan-style collisional belt formed by consumption of a wide ocean, or whether it records closure of narrow Neoproterozoic basins developed across previously assembled parts of Rodinia.