Archaean Crustal Growth, Proterozoic Terrane Amalgamation and the Pan-African Orogeny, as Recorded in the NE African Sedimentary Record.

Monday, 14 December 2015
Poster Hall (Moscone South)
Laura Fielding1, Yani Najman2, Ian Millar3, Peter Butterworth4, Sergio Andò5, Marta Padoan5, Dan N Barfod6 and Benjamin C Kneller7, (1)Lancaster University, LEC, Lancaster, United Kingdom, (2)University of Lancaster, Lancaster Environment Centre (LEC), Lancaster, United Kingdom, (3)British Geological Survey, NERC Isotope Geosciences Laboratory, Nottingham, United Kingdom, (4)BP Egypt, Cairo, Egypt, (5)University of Milano-Bicocca, Department of Earth and Environmental Sciences, Milan, Italy, (6)University of Glasgow, Glasgow, United Kingdom, (7)Aberdeen University, Department of Geology, Aberdeen, United Kingdom
The cratons of Central Africa are formed of various blocks of Archaean and Palaeoproterozoic crust, flanked or truncated by Palaeoproterozoic to Mesoproterozoic orogenic belts. The geology of east Africa has largely been shaped by the events of the Pan-African Orogeny when east and west Gondwana collided to form ‘Greater Gondwana’ at the end of the Neoproterozoic. The Pan-African orogeny in NE Africa involved the collision of Archaean cratons and the Saharan Metacraton with the Arabian Nubian Shield, a terrane comprising Neoproterozoic juvenile oceanic island arcs. Phanerozoic cover sedimentary rocks, eroded from the Pan-African orogenies, blanket much of NE Africa. Detrital data from these Phanerozoic cover sedimentary rocks, and modern rivers draining both the cover the basement, provide a wealth of information on basement evolution, of particular relevance for regions where the basement itself is poorly exposed due to ancient or modern sedimentary cover. From samples collected in Uganda, Ethiopia, Sudan and Egypt, we provide combined U-Pb and Hf-isotope zircon, U-Pb rutile and Ar-Ar mica datasets, heavy mineral analyses, and bulk trace element data, from Archaean basement, Phanerozoic cover and modern river sediment from the Nile and its tributaries to document the evolution of the North African crust. The data document early crust-forming events in the Congo Craton and Sahara Metacraton, phased development of the Arabian Nubian Shield culminating in the Neoproterozoic assembly of Gondwana during the Pan African Orogeny, and the orogen’s subsequent erosion, with deposition of voluminous Phanerozoic cover.