Late orogenic basin evolution, deformation and metamorphism in the Pan-African Basement, Wadi Queih, Eastern desert of Egypt

The present volume presents the latest contributions to the geoscientific cooperation project between the Egyptian Geological Survey and Mining Authority (EGSMA), Cairo, Arab Republic of Egypt, and the Geologisch-Paläontoloplsches Institut (GPI), Ruprecht-Karls-Universität, Heidelberg, Federal Republic of Germany. This International cooperation project is sponsored by the Federal Ministry for Education, Science, Research and Technlogy (BMBF), Bonn, through the International Bureau of Forschungszentrum Jülich. The overall objectives are to assess the structural and tectonic evolution, orogeny and terrane boundaries with particular emphasis on thelocation, nature and geometry of ore deposits. Ultimately, these cooperative efforts should lead to the comprehensive assessment and effective mining of economic minerals. The cooperat ion project has also turned attention to the very low-grade metamorphic rocks of the Hammamat Group and adjacent low-grade volcano-sedimentary sequences which host a number of important mineral deposits. These rock associations represent late-Pan-African molasse-type deposits and associated igneous rocks, which probably represent the late-tectonic stage of extensional collapse. Consequently, the Hammamat Group is represented by thick, coarse clastic sequences fining upwards into arkoses, sandstones, siltstones and mudstones. These rocks are usually conside red as being deposited in discrete sedimentary basins, commonly referred to as Hammamat Basins

Minimizing labeling ambiguity during classification process of the geological units covering the central part of the Suez Canal Corridor, Egypt using their radar scattering response

Deriving information about the geometrical and dielectrical characteristics of objects using optical and radar satellite sensors is valuable for delineating and classifying surficial sediments. In the present study, unsupervised and supervised classifications of the Landsat-8 and the full-polarimetric Radarsat-2 data were used to map the different geological units and to reduce labeling ambiguity during classification processes. The study covers the central part of the Suez Canal Corridor in northeast Egypt. The full-polarimetric Radarsat-2 image was decomposed, filtered and geo-referenced to extract the scattering response of the different land cover and geological units covering the study area. In addition, polarimetric target decomposition and Wishart unsupervised classification with 5 classes were performed. The extracted polarization signatures show significant correlation with the obtained classes in terms of their geometrical (surface roughness) and dielectrical (mineral composition) characteristics. These characteristics are related to physical properties and to some extent, to the grain size and degree of weathering. The results show that the integration between the radar scattering responses and the optical reflectance information of the classified land cover and rock units is appropriate for precise objects discrimination. Keywords: Radarsat-2, Full-polarimetric SAR, Landsat-8, Scattering response, Classifications, Geological mappin

Structural Evolution of the Neoproterozoic Western Allaqi-Heiani Suture, Southeastern Egypt

The Neoproterozic Allaqi-Heiani suture in southeastern Egypt is the western extension of the Allaqi-Heiani-Onib-Sol Hamed-Yanbu suture that represents one of arc-arc sutures in the Arabian-Nubian Shield. It extends for more than 250 km from the N-trending Hamisana Shear Zone in the east to Lake Nasser in the west. It separates the 750-Ma-old Southeastern Desert terrane in the north from the 830-720-Ma-old Gabgaba terrane in the south. Structural studies supported by remote sensing investigations including Landsat Thematic Mapper (TM) images show that the western part of Allaqi-Heiani suture zone constitutes three S- to SW-verging nappes in the north overriding an autochthonous block to the southwest. SW-verging, low-angle thrust sheets and folds, forming a 10-km wide imbrication fan, dominate the northern upper nappe (northern allochthon). These folds and thrusts deform shelf metasedimentary rocks including psammitic metasediments, marble and subordinate conglomerate. Volcanic rocks including rhyolites and felsic tuffs dominate the upper part of the northern allochthon. The contacts between the metasedimentary rocks on the one hand and the rhyolites and felsic tuffs on the other hand are extrusive. This allochthon overrides an internally deformed nappe (central allochthon) dominated by arc and ophiolitic assemblages now preserved as felsic and mafic schist, talc schist, serpentinites, and metagabbros. This allochthon is characterized by NW-trending, upright folds, which deform the earlier sub-horizontal structures. The structurally lower nappe (southern allochthon) is dominated by NNE-trending folds which deform amphibolite facies schistose metavolcanic and metavolcanoclastic rocks. The NNE-trending folds deform earlier NW-trending folds to produce crescentic dome interference pattern with well-developed NE-trending axial planar cleavage, consistent with ESE-WNW bulk shortening. The southernmost structural unit is an autochthonous block dominated by arc-related volcanic and volcanoclastic rocks. This block has suffered only minor deformation compared to the nappes to its north. The consistent SW-vergence of the structures indicates tectonic transport from northeast to southwest, followed by ESE-WNW shortening similar to that found in the Hamisana Shear Zone, further east. Collision between the Gabgaba-Gebeit terrane and the Southeastern Desert terrane along the Allaqi-Heiani suture, after the consumption of a marginal basin probably over an N-dipping subduction zone, led to the formation of EW- to NW-trending folds and thrusts. This was followed by ESE-WNW tectonic shortening to form NNE-trending folds, which are found to be overprinting the earlier structures. This latest shortening might be due to collision between the Arabian-Nubian Shield and the Saharan Metacraton along an N-trending arc-continent suture represented farther south by the Keraf suture

The Nubian Swell

We use the name Nubian Swell to refer to a complex, east-west trending structural high in southern Egypt and northern Sudan. This 500 km wide zone of uplifted Neoproterozoic crystalline basement and Paleozoic sediments and parallel troughs extend westward for more than 800 km from the flanks of the Red Sea Hills. The Nile in this region is called the Cataract Nile and is in a youthful stage, particularly in northern Sudan where it is incised in the Neoproterozoic crystalline basement. The northern Cataract Nile flows through the rapids of the Batn el Hajar or \u27Belly of Stones\u27 region, characterized by structurally controlled 90⁰ turns, frequent bifurcation and disruption by several cataracts, and near-absence of floodplains. Orbital imaging radar has advanced our understanding of the Nubian Swell, through the discovery and mapping of paleochannels and faults that indicate tectonic uplift during Cenozoic time. Earthquakes in southern Egypt during the early 1980s provide evidence that portions of the Nubian Swell are still tectonically active, with recent seismic activity concentrated where E-W trending structures intersect N-S trending structures of the Aswan corridor. We conclude that the Nubian Swell is an important tectonic feature of North Africa, with episodic but continuing uplift