Erosional reservoir for the northern segment of the Arabian-Nubian shield: Constrains from U-Pb geochronology of the lower palaeozoic succession, North Eastern Desert, Egypt

Abstract

Zircon U-Pb geochronology of detrital sedimentary rocks is a precious and unique tool to explore older eroded crust which, frequently, no longer exists. This is because the clastic sedimentary rocks represent a detritus reservoir for the surrounding eroded region. A total of 207 (196 concordant ages) zircon grains from the Lower Palaeozoic Araba and Naqus formations were analysed to investigate the possible rock provenances and examine the different components of the Arabian-Nubian Shield in the region before being intensively eroded between the Cambrian and the Carboniferous. Somr El-Qaa area in the North Eastern Desert (NED) contains one of the rare remnant exposures of the Lower Palaeozoic sediments where the catchment area is expected to be extended through the NED and Southern Sinai. Three main chronological provenances sources were represented: (1) Pre-Pan-African (Pre-Cratonization) source, represented by ca. 35% of Araba Formation and ca. 10% of Naqus Formation total populations (44 grains) with ages varies between 2289 ± 113 Ma and 907 ± 45 Ma, indicates a probable pre-Pan-African crust palaeo-existence in the region. (2) Pan-African (Cratonization) source, represented by ca. 58% of Araba and ca. 76% of Naqus dated zircons (137 grains) with ages varying between 887 ± 44 Ma and 501 ± 25 Ma. Surprisingly, nearly half of the dated grains belong to the age zones of the island arc and syn-orogenic suites which suggests their palaeo-dominance in the NED and being intensively eroded. (3) Post-Pan-African (Post-Cratonization) source, represented by ca. 3% of Araba and ca. 12% of Naqus total analysed grains (15 grains) with ages ranging from 489 ± 24 Ma to 312 ± 16 Ma which refers to probable unidentified magmatic events during the Cambrian-Silurian along with the Hercynian tectonic event. Furthermore, it documents being the so-called Lower Palaeozoic system open in the studied region until Pennsylvanian time.