Pre-Neoproterozoic basement evolution of southwestern Egypt

Abstract

ABSTRACTThe only surviving Archaean fragment of the Saharan Metacraton is exposed in the Uweinat-Kamil Mountains of Egypt, Libya, and Sudan. To expand our knowledge of this rare Archaean crustal fragment, we investigate protolith ages and the timing of metamorphic events associated with it via U-Pb zircon geochronology and geochemistry of 10 samples from the Egyptian part of the Uweinat-Kamil region. Our work confirms that the orthogneisses represent a tonalite, trondhjemite, granodiorite (TTG) and granite suite of Archaean-early Paleoproterozoic age (3.25–2.49 Ga). Late Paleoproterozoic rocks include 2.15–2.00 Ga paragneiss, 2.00 Ga metagranite and 1.99 Ga trondhjemitic leucosome. Neodymium isotopes from the 3.25 Ga orthogneiss record an entirely juvenile mantle signature, whereas the 2.91 and 2.49 Ga orthogneisses record significant juvenile mantle input, and 2.86–2.68 Ga orthogneisses reflects recycling of older crustal rocks. At c. 2.0 Ga, a magmatic and metamorphic event associated with anatectic partial melting occurred in northern Africa, assimilating both granitic and leucocratic gneiss of the Archaean TTG crust. Detrital input contributing to the paragneiss was mainly from Uweinat-Kamil TTG rocks and sources to the east-southeast. The oldest 3.42 Ga detrital zircon from the paragneiss probably reflects the conjoined Saharan Metacraton-Congo craton.