Neoproterozoic tectonothermal evolution of the Central Eastern Desert, Egypt: a slow velocity tectonic process of core complex exhumation

U–Pb ID-TIMS dating of igneous and metaigneous rocks from the El-Sibai area: time constraints on the tectonic evolution of the Central Eastern Desert, Egypt

“…Based on these postulated shear zones, they explained the gneiss complex as an exhumed gneiss dome resulting from orogen-parallel (NW-SE) extension caused by oblique collision, similar to the model proposed for the Meatiq gneiss dome (Abd Ell Wahed 2008;Fritz et al 1996Fritz et al , 2002Walbrecher et al 1993). Fowler et al (2007) rejected the existence of the so-called external strike-slip shear zones crucial to the exhumation model by Bregar et al (2002) and Fritz et al (2002) and explained the appearance of the El-Sibai gneisses as the result of synmagmatic deformation of tabular granitoid bodies contemporaneous with NW thrusting and nappe stacking. Fowler et al (2007) also reported NW-SE-trending open folds and subsequent NW-SE-directed extensional structures post-dating the NW thrusting, but emphasized that these structures pre-date development of semi-brittle to brittle strike-slip shear zones present in Wadi El-Shush (Fig.…”

“…The apparently old 40 Ar/ 39 Ar-hornblende ages of 623 Ma and 606 Ma from the Abu Markhat gneiss and amphibolites north of the El-Shush gneisses, respectively, were by Fritz et al 2002 interpreted to date either (1) early exhumation of the El-Sibai gneisses compared to the Meatiq and Megif-Hafafit gneiss domes ( 40 Ar/ 39 Ar-hornblende ages of c. 585 Ma); or (2) exhumation of the ElSibai gneisses from a shallower crustal level than the Meatiq and Megif-Hafafit gneiss domes. The latter explanation is consistent with the interpretation by Fowler et al (2007) and supports the interpretation that the El-Sibai gneiss complex is not a gneiss dome comparable to the Meatiq and Megif-Hafafit domes, but rather is part of the oceanic affined allochthon belonging to a higher structural level than the other, younger gneiss domes.…”

“…The highest metamorphic grade, with migmatization of metasediments and hornblende growth in metavolcanic rocks, is recorded in the island arc affined rocks associated with foliated metagabbro and granitoid intrusions (Fowler et al 2007). Fowler et al (2007) Bregar et al (2002) and Fritz et al (2002), respectively. Bregar et al (2002) and Fritz et al (2002) postulated the presence of two parallel sinistral strike-slip shear zones north-east and south-west of the El-Sibai gneiss complex, linked by a top-to-the-NW extensional shear zones in the north-west and a top-to-the-SE shear zone in the south-east.…”

“…Fowler et al (2007) Bregar et al (2002) and Fritz et al (2002), respectively. Bregar et al (2002) and Fritz et al (2002) postulated the presence of two parallel sinistral strike-slip shear zones north-east and south-west of the El-Sibai gneiss complex, linked by a top-to-the-NW extensional shear zones in the north-west and a top-to-the-SE shear zone in the south-east. These shear zones define together the boundaries of the gneiss complex.…”

“…Diapiric rise of late orogenic magmas is a third model which has been proposed to explain the Meatiq and El-Sibai gneissic complexes (Fritz and Messner 1999;Loizenbauer et al 2001;Neumayr et al 1998). Another group of authors explain the gneiss complexes as a result of orogen-parallel extension caused by oblique collision (Abd Ell Wahed 2008;Bregar et al 2002;Fritz et al 1996Fritz et al , 2002Walbrecher et al 1993).…”