الفهرس 
INTRODUCTION AND BACKGROUNDOnly 14 pages are availabe for public view
Abstract
The Abu Swayel Allochthon is located at the western part of the Allaqi-Heiani Suture (AHS), consisting of NW-trending metavolcanic and metasedimentary belts. These two belts are overthrusted along an SW-trending low-angle thrust fault and are separated by the NW-trending Allaqi Shear Zone. The metasediments in the study area are mainly pelitic with subordinates psammitic and carbonates. The greater Abu Swayel area undergone low grade of regional metamorphism (LP/LT), and the mineral assemblages recorded from these rocks are biotite and cordierite as index minerals of low grades. This is the first time to map cordierite mica schist from this area, and this is evidence for the pelitic protolith for this rocks. Diopside marble, black marble, and quartz marble are the main categories recorded from Abu Swayel area. Depending on Sm-Nd isotope data the metasediments source rock is juvenile Neoproterozoic rather than the pre-Neoproterozoic crust and the same situation for the metavolcanics and finely grained granitoids. The Juvenility of the protolith for the metamorphic belts revealed a confined subduction zone, which is restricted only for the ANS terranes.
Three Neoproterozoic (c. 700, c. 690 and 630-620 Ma) tectono-magmatic events are recorded in Abu Swayel area as revealed by U-Pb zircon age and Hf analysis, without any evidence for any pre-Neoproterozoic crust. The first event is the magmatic emplacement of a post-obduction gabbro-diorite pluton (702 ± 10 Ma) at Gabal Shilman, with depleted mantle Hf isotopic composition (mean εHf(t) = +9.13). The second magmatic event occurs at c. 680 Ma with the crystallization of the Um Shilman granodiorite (687 ± 16 Ma), and the Wadi Haimur granite (676 ± 14 Ma), both with a juvenile, but lower mean εHf(t) values of +8.80 and +6.59 respectively. The third magmatic event occurs at c. 630 Ma with the emplacement of the Wadi Shilman granite (630 ± 18 Ma) with lower again εHf(t) values of +5.49 to +7.49 (mean = +6.08) and the Magal Gebreil biotite granite (619 ± 4 Ma). This new U-Pb zircon and Hf isotopic data suggest that all of these synorogenic pulses are consanguineous, with a Tonian depleted mantle source. Juvenile depleted mantle source is supported by the mafic xenoliths recorded from Um Shilman batholith, and the direct proportion between εHf(t) values, and rock age suggesting the incorporation of previous Neoproterozoic juvenile rocks in later magmas. Mafic. Our data suggest the emplacement of ophiolites in Abu Swayel area and the accretion of terranes occurred earlier than 702 ± 10 Ma.
The proposed evolutionary tectonic model for the western part of the Allaqi-Heiani Suture is the congested oblique subduction model.