Resumen de Differential cryptic foreland exhumation of the c. 550 Ma East African/ Antarctic Orogen: a titanite fission-track approach
With a length of about 8000 km the East African/Antarctic Orogen forms one of the worlds largest orogenic belt, that resultedfrom the collision of E- and W- Gondwana during Late Neoproterozoic/Early Palaeozoic times at ca. 580 to 510 Ma (e.g. Stern, 1994; Jacobs et al., 1998). It stretches along East Africa into East Antarctica and is up to 1000 km wide. The East African/Antarctic Orogen has reworked large quantities of crust, recorded in the widespread occurrence o f K-Ar and Ar-Ar mica and hornblende ages in the marginal parts of the orogen and U/Pb zircon ages from high-grade rocks of the orogenic core. The eastern orogenic front is in many places sharply defined as a major shear zone, such as the Heimefront Shear Zone in East Antarctica (Jacobs et al., 1997; Golynsky 8 Jacobs, 2001). Major thrust nappes onto the Kalahari plate have been recorded in Zimbabwe and Mozambique (Grantham 8 Dirks, 1998). Remnants o f molasse deposits are recorded along the length of the orogen, the most voluminous being the Nubian Sandstone in northern Africa (Burke 8c Kraus, 1998). In southern Africa the molasse is represented as the c. 490 Ma Natal Group (Thomas et al., 1992). The Natal Group overlies different tectono-metamorphic units of the Kalahari plate. Our titanite fission track profile crosses the boundary o f the c. 1.1 Ga Natal Metamorphic province and the Archaean Kaapvaal Craton. We try to address the question, to what thermo-tectonic extend the Kaapvaal craton responded to the amalgamation of the ca. 1.1 Ga mobile belt to the south and especially whether the two different tectono-metamorphic units thereafter underwent similar exhumation histories during the foreland exhumation of the East African/ Antarctic Orogen at c. 550 Ma.
