Zircon geochronology and Sr, Nd, Pb isotope geochemistry of granitoids from Bayuda Desert and Sabaloka (Sudan): evidence for a Bayudian event (920-900 Ma) preceding the Pan-African orogenic cycle (860 - 590 Ma) at the eastern boundary of the Saharan Metac
Earth and related Environmental sciences
Geodynamics and mineral resources
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Results of zircon geochronology and Sr, Nd and Pb isotope investigations carried out on granitoid rocks from the boundary of the Saharan Metacraton with the Arabian-Nubian Shield (ANS) reveal a protracted, partly pre-Pan-African geodynamic evolution and the existence of crustal terranes of different ancestries. (Meta)granitoids and gneisses in north-central Bayuda Desert record a 920-900Ma orogenic event, hitherto unrecognized in northeastern Africa. This early Neoproterozoic Bayudian event is restricted to a pre-Pan-African crustal terrane which appears only slightly affected by Pan-African tectogenesis and deformation, named here the Rahaba-Absol terrane. Within this terrane, amphibolite-facies metamorphism occurred at 921±10Ma in the El Melagi muscovite-biotite gneiss of the Rahaba Series, probably during a collisional phase; followed by the intrusion of the Absol medium-K granite-granodiorite pluton discordantly emplaced at 900±9Ma into high-grade schists and amphibolites of the metavolcanosedimentary Absol Series. Nd TDM model ages (2040-2430 Ma) and ages of rounded zircon cores (1060, 1980, 2540 and 2675 Ma) of the El Melagi gneiss indicate a predominantly late Archaean to Palaeoproterozoic source region and suggest a latest Mesoproterozoic to early Neoproterozoic depositional age of its pelitic precursor sediment. The post-collisional Absol pluton has isotope characteristics (Nd-Sr-Pb) indicating assimilation of old pre-Neoproterozoic crust. The Rahaba-Absol terrane is part of the Saharan Metacraton and is in tectonic contact with the high-grade metamorphic Kurmut terrane of eastern Bayuda Desert. The Kurmut terrane has juvenile Neoproterozoic isotope characteristics, its granitoids record only Pan-African orogenic events and it is therefore considered a part of the Arabian-Nubian Shield. Both the Rahaba-Absol and the Kurmut terrane of the Bayuda Desert are intruded by post-collisional high-K granitoid magmatism of late Pan-African age, with no intermediate events recorded.
CitationKüster, D; Liégeois, J.P.; Matukov, D; Sergeev, S; Lucassen, F (2008). Zircon geochronology and Sr, Nd, Pb isotope geochemistry of granitoids from Bayuda Desert and Sabaloka (Sudan): evidence for a Bayudian event (920-900 Ma) preceding the Pan-African orogenic cycle (860 - 590 Ma) at the eastern boundary of the Saharan Metac. , Precambrian Research, Vol. 164, 16-39, Elsevier, DOI: 10.1016/j.precamres.2008.03.003.