Mohamed Abd El-Wahed

Detailed geological mapping is the decisive key for mineral deposit prospecting, deciphering tectonic models, and outlining the main framework for most development programs and constructions. Without a doubt, various remote sensing datasets have introduced reliable lithological and structural mapping solutions. The main defect with remote sensing data is the curse of dimensionality, especially with hyperspectral data, where a lot of time is spent handling and selecting representative bands for various geological analyses. Consequently, and for the first time, our research is an attempt to resolve the complicated structural patterns (lineaments, folds, foliations, and cross-cutting relationships) and enhance lithological discrimination using a single band (of Sentinel 2 and ALOS PRISM data) and textural analysis. Through several trials over different pixel sizes (2.5 m and 10 m) and various kernels (3 × 3, 7 × 7, or 11 × 11), reasonable results are obtained, enabling lithological discrimination, in-depth structural analysis (foliations, faults, joints, and folds), shape recognition of systematic rock bodies, and delineation of quaternary deposits using single band analysis rather than time-consuming multiple band processing. Our results have been verified using intensive fieldwork and accurate visual interpretations using different datasets (e.g., previous geological maps, remote sensing data, etc.). Upon field verification and petrographical investigations of this research outcomes, we strongly recommend the adopted approach for the geological community, as it opens the doors for various applications utilizing single-band second-order statistics. We expect that this research could significantly help the geological community by reviving several previous studies and being applicable for future research, besides offering a reasonable approach for minimizing the time and efforts required for detailed field studies by highlighting micro-and mesoscale structures.

High-grade granitoid gneisses (740–710 Ma) and elongate bodies of amphibolite and hornblende schist with cm-scale layers of garnet pyroxenite form an overturned fold in the Gabal Um Gunud area, South Eastern Desert of Egypt. Whole-rock geochemical data combined with zircon U-Pb-Hf isotope data suggest that the metabasites represent relics of oceanic crust with an N-MORB affinity, which has been derived from partial melting (2.0–1.4 GPa; ~65- ~ 45 km depth) of a depleted mantle source beneath an intra-oceanic, spreading forearc basin. Such increment of melting degree resulted in small basaltic melt batches with transitional tholeiitic to boninitic affinities. Progressive slab subduction and partial melting of the tholeiitic amphibolite produced high-Al and low HREE melts for trondhjemite at av. T = 854°C and low-Al and high HREE melts for tonalite at higher temperatures (av. 949°C). The low Mg# of the trondhjemite-tonalite rocks may be attributed to limited contamination of subduction components, as evidenced by the weak lanthanide tetrad effects (TE1,3~1) and near-chondritic Zr/Hf, Nb/Ta, and Y/Ho ratios, while the garnet pyroxenite was the residuum produced in equilibrium with the trondhjemite-tonalite melts.

The present paper focuses primarily on the geology and petrography of the Neoproterozoic basement rocks encountered in the Wadi Arak-Wadi El Qash area which is located in the extreme western side of the Central Eastern Desert of Egypt. The Wadi Arak-Wadi El Qash area is occupied and dominated by the Hammamat molasses-type sediments which overlie unconformably upon a basement of ophiolitic, arc assemblages and Dokhan volcanic, and is intruded by felsites and late to posttectonic granites. Geological and petrographical examination revealed that the ophiolitic rocks form a NW-SE elongate belt of imbricate thrust sheets and slices of ultrabasic and basic association including serpentinites and Muweilih metabasalts together with sheared amphibolites and actinolite chlorite schist. The Arc assemblages comprise arc metavolcanic and Muweilih metaconglomerates. The island arc metavolcanic are commonly basic to intermediate with subordinate felsic composition and comprise metabasalts, metadolerite, metabasaltic andesite, metaandesite and metadacites together with their associated metaconglomerate rocks. The Muweilih metaconglomerates are intensely deformed, and their clasts were derived from pre-Dokhan volcanic rocks. The Dokhan volcanic are unmetamorphosed and embrace an association of basic to acidic lava flows together with their corresponding bedded pyroclastics. The Hammamat molasses sediments are dominated by red Igla Formation with subordinate green Shihimiya Formation. They are unmetamorphosed and classified into oligomictic and polymictic conglomerates, lithic arenites, feldspathic greywackes, siltstones, and mudstones. Felsites are characterized by plugs and dyke-like bodies and sharply intrude the Hammamat sediments. Late to post-tectonic granites are leucocratic of roughly syenogranite composition forming NW-trending pluton and intruding both Hammamat sediments and metavolcanics.

The gold mineralization located in the southern Eastern Desert of Egypt mostly occurs
in characteristic geologic and structural settings. The gold-bearing quartz veins and the alteration
zones are confined to the ductile shear zones between the highly deformed ophiolitic blocks, sheared
metavolcanics, and gabbro-diorite rocks. The present study attempts to integrate multisensor remotely
sensed data, structural analysis, and field investigation in unraveling the geologic and structural
controls of gold mineralization in the Gabal Gerf area. Multispectral optical sensors of Landsat-8
OLI/TIRS (L8) and Sentinel-2B (S2B) were processed to map the lithologic rock units in the study
area. Image processing algorithms including false color composite (FCC), band ratio (BR), principal
component analysis (PCA), minimum noise fraction (MNF), and Maximum Likelihood Classifier
(MLC) were effective in producing a comprehensive geologic map of the area. The mafic index
(MI) = (B13-0.9147)  (B10-1.4366) of ASTER (A) thermal bands and a combined band ratio of S2B
and ASTER of (S2B3+A9)/(S2B12+A8) were dramatically successful in discriminating the ophiolitic
assemblage, that are considered the favorable lithology for the gold mineralization. Three alteration
zones of argillic, phyllic and propylitic were spatially recognized using the mineral indices and
constrained energy minimization (CEM) approach to ASTER data. The datasets of ALSO PALSAR
and Sentinel-1B were subjected to PCA and filtering to extract the lineaments and their spatial
densities in the area. Furthermore, the structural analysis revealed that the area has been subjected to
three main phases of deformation; (i) NE-SW convergence and sinistral transpression (D2); (ii) ~E-W
far field compressional regime (D3), and (iii) extensional tectonics and terrane exhumation (D4).
The gold-bearing quartz veins in several occurrences are controlled by D2 and D3 shear zones
that cut heterogeneously deformed serpentinites, sheared metavolcanic rocks and gabbro-diorite
intrusions. The information extracted from remotely sensed data, structural interpretation and
fieldwork were used to produce a gold mineralization potential zones map which was verified by
reference and field observations. The present study demonstrates the remote sensing capabilities
for the identification of alteration zones and structural controls of the gold mineralization in highly
deformed ophiolitic regions.

Metamorphic core complexes (MCCs) are a domed structures cored by high grade gneiss overlain by low grade supracrustal rocks. They are characterized by some common features such as extensional fabrics, ultra high-grade metamorphic facies, low angle normal fault (detachment fault), strike-slip shear zones surrounded the core complexes and ductile mylontitic shear zone (thrust zone) that separate the overlying low-grade rocks from the lower high-grade rocks. There is a debate about the presence or absence of metamorphic core complexes in the Arabian-Nubian Shield (ANS) especially in its northern part. The gneissic complexes in the ANS are considered as strike-slip core complexes like the Qazaz and Krish Domes whereas, those in the Egyptian Nubian Shield (ENS) are interpreted as antiformal stacks (e.g. Meatiq and Hafafit) formed during thrusting, or core complexes formed during orogen-parallel crustal extension. Some metamorphic core complexes are domes or contain gneiss domes within them, but not all gneiss domes possess the essential elements of a true metamorphic core complex. The most important points that negate the existence of MCCs in the ANS are absence of ultra-high grade metamorphic facies, absence of real low-angle normal faults, not all the gneisses have a domal structures, adjacent syn-extensional basins have fill that is older than the gneissic complexes, and models of ANS core complex exhumation include strike-slip faults with slip senses recently found to be inconsistent with the models. The gneissic complexes in the ANS differ from the Cordilleran-type or Aegean-type metamorphic core complexes. The origin of gneiss domes in the ANS is controversial, and many of them are presumably produced by mechanisms other than horizontal extension. During the oblique convergence of East and West Gondwana, the gneissic complexes in the ENS evolved from pure shear to simple shear-dominated transpression due to oblique convergence between East and West Gondwana along the Mozambique belt.

This chapter focuses on spectral features of hydrothermal alteration minerals and lithologies in the visible and near-infrared, shortwave infrared, and thermal infrared wavelength regions. The technical characteristics of multispectral and hyperspectral sensors, synthetic aperture radar, and unmanned aerial vehicles will be deciphered for detecting the alteration minerals and zones, lithological units, and structural features associated with ore mineralizations. Explanations about data acquisition for the remote sensing data, preprocessing techniques, image-processing algorithms, accuracy assessment techniques, interpretation of remote sensing data for alteration mineral detection, lithological mapping, structural analysis, and case studies will be discussed in this chapter.

Deforming belts in the Arabian‐Nubian Shield (ANS) are classified into (1) suture‐related belts, including arc–arc and arc‐continental, and (2) post‐accretionary systems, including N‐trending compression zones and NW‐trending strike‐slip faults. Terrane accretion took place in the ANS between 800 and 700 Ma, along arc–arc sutures. Such sutures are directed from E to NE in the northern part of the ANS, and from N to NE in the south, and are aligned in the north and east with N‐ or S‐verging ophiolitic nappes, or in the south with W‐verging nappes. The Asir, Hijaz, and Midyan terranes formed the Western Arabian shield by 715 Ma. The Afif terrane collided with the Hijaz and Asir terranes between 680 and 640 Ma, terminating the subduction along the Nabitah suture. Subduction began west of the Al Amar arc near the margin of the Ar Rayn terrane at 670 Ma. Afif and Ar Rayn terranes collided along the Al Amar‐Idsas suture about 640 Ma, producing the Idsas orogeny that initiated the major faulting and folding. Strike‐slip faults and upright folds related to oblique convergence between terranes and/or post‐accretionary systems deform the southern sutures. The eastern and western boundaries of the ANS are marked by arc‐continental sutures and characterized by N‐trending deformation belts that formed at 750–650 Ma when the ANS collided with East and West Gondwana. (a) The Gondwanaland supercontinent. The cratons comprising West Gondwana and those comprising East Gondwana. Neoproterozoic orogenic belts crisscross the supercontinent. Those associated with the final amalgamation of the supercontinent are the East African Orogen (750–620 Ma; blue), the Brasiliano‐Damara Orogen (630–520 Ma; dark red) and the Kuunga Orogen (570–530 Ma; red). Black arrows show inferred convergence and location of most intense continent–continent collision, (b) Map of the ANS showing the distribution of juvenile Neoproterozoic crust and adjacent regions of Archean–Mesoproterozoic crust and Cenozoic plate boundaries, Red Sea‐Gulf of Aden spreading centers, and the East African Rift system. CED, Central Eastern Desert; NED, North Eastern Desert; SED, South Eastern Desert; SES, South Ethiopian shield; WES, West Ethiopian shield, (c) Simplified evolution of the East Africa–Antarctic Orogen. Beginning with the break‐up of the supercontinent Rodinia (I), opening and closing of a wide ‘Mozambique Ocean’ with associated formation of juvenile crust (II), collision between continental fragments (III), and continued convergence and tectonic escape (IV). By the end of Neoproterozoic time, a new supercontinent ‘Greater Gondwana’ or ‘Pannotia’ came into existence.

Abstract This paper records the garnierite in Wadi Dubur Neoproterozoic serpentinites from the Central Eastern Desert of Egypt. Garnierite (Ni-Mg hydrous silicates) occurs in two types ( Type I and Type II ) of infillings in the weathered serpentinite that was displaced sinisterly by NNW-SSE trending strike-slip faulting and dextrally with NE-trending shearing. All recognized garnierites are serpentine-like (nepouite/pecoraite) existing in mixtures with the hosting serpentines. The Type I garnierite is Fe-richer [Mg 0.26-0.71 Ni 1.22-1.79 Fe 1.28-3.05 Al 0.0-0.02 Si 1.11-1.73 O 5 (OH) 4 ] showing zoning in a collomorph texture, while the Type II garnierite is homogenous with more Si and Mg [Mg 0.54-0.94 Ni 1.38-2.04 Fe 0.38-1.29 Al 0.0-0.01 Si 1.66-2.10 O 5 (OH) 4 ]. Raman spectra indicate that the substitution of Ni for Fe formed a poorly crystalline goethite. The serpentinization of the Dubur peridotite protolith and the associated alteration of chromite and Ni-sulfides were important for the early individualization of Ni. It is proposed that the unweathered serpentinites represent the bedrock, while the altered garnierite-bearing ones represent the saprock. The early weathering of serpentinites contemporaneous with a faulting activation caused in situ precipitation of Ni and Fe in veins (Type I garnierite). With the faulting repetition and progressive alteration maintenance Ni, Si and Mg were transferred to the percolating meteoric solutions, and moved downward through the weathering profile precipitating the Type II garnierite in gouges. Although the studied Ni-rich rocks represent a narrow mineralogical occurrence, they are remnants of a former lateritic regolith most probably formed by tropical or sub-tropical weathering during Cretaceous at the expense of Wadi Dubur Neoproterozoic serpentinites. The formed regolith has been subsequently largely eroded, buried and recently exhumed in arid climate.

The gold mineralization located in the southern Eastern Desert of Egypt mostly occurs in characteristic geologic and structural settings. The gold-bearing quartz veins and the alteration zones are confined to the ductile shear zones between the highly deformed ophiolitic blocks, sheared metavolcanics, and gabbro-diorite rocks. The present study attempts to integrate multisensor remotely sensed data, structural analysis, and field investigation in unraveling the geologic and structural controls of gold mineralization in the Gabal Gerf area. Multispectral optical sensors of Landsat-8 OLI/TIRS (L8) and Sentinel-2B (S2B) were processed to map the lithologic rock units in the study area. Image processing algorithms including false color composite (FCC), band ratio (BR), principal component analysis (PCA), minimum noise fraction (MNF), and Maximum Likelihood Classifier (MLC) were effective in producing a comprehensive geologic map of the area. The mafic index (MI) = (B13-0.9147) × (B10-1....

The Arabian-Nubian Shield (ANS), the northern extension of the East African Orogen (EAO), consists of a number of amalgamated island-arc tectonic terranes, separated along suture zones, major shear zones and cryptic major high strain zones. The Allaqi-Heiani-Oneib-Sol Hamid-Yanbu Suture separates the Eastern Desert-Midyan terrane from the Gabgaba-Gebeit-Hijaz terrane. The latter terrane juxtaposes Haya-Jiddah terrane along the Nakasib-Bir Umq Suture which is the longest ophiolite-decorated shear zone allover the ANS. The Haya-Jiddah terrane is separated from the Nakfa-Asir terrane along Baraka-Al-Damm Fault Zone. The previously mentioned Hijaz-Jiddah-Asir borders the continental Afif terrane through the Hulaifa-Ad-Dafinah-Ruwah sinistral transpressional zone. Ad-Dawadimi and Ar-Rayan terranes occupy the eastern part of the Arabian Shield, being separated from the Afif terrane and from each others along the Halaban and Al-Amar Sutures. The smallest terrane in the ANS is the Ha’il terrane. This chapter reviews some of the major shear zones existed inside the Eastern Desert of Egypt (The Egyptian Nubian Shield; ENS). It addresses also the Allaqi-Heiani Suture which is regarded as the western segment of the enormous arc-arc Allaqi-Heiani-Oneib-Sol Hamid-Yanbu Suture Zone. The shear zones are dealt with through two main groups; syn-accretion- and post-accretion shear zones. The first group is manifested by the NNE-oriented Hamisana Shear Zone, whereas the second group is typified by the Najd-related NW-trending Shear Zones, such as Hodein-Karite-, Nugrus- and Atallah-Shear Zones, as well as by the relatively younger ENE- (to E-) trending shear zones and shear belts, such as Mubarak-Barramiya Shear Belt and Abu Dabbab Shear Zone. The shear zone-related mineralizations (particularly gold) is dealt in the last section.

The tectonic evolution of the Arabian–Nubian Shield (ANS), the northern continuation of the East African Orogen (EAO), is enigmatic and a matter of controversy. The EAO is observed as a N–S trending major suture zone separating East and West Gondwanaland. It documents a prolonged tectonic history bracketed by the fragmentation of Rodinia Supercontinent and the amalgamation of Gondwana. The ANS is dominated by Neoproterozoic juvenile continental crust (i.e., crust formed directly from the mantle), formed by magmatic arc accretion and subsequent post-tectonic magmatism, and includes a mosaic of tectonic terranes juxtaposed along ophiolite-decorated megashears (suture zones). Among them is the Eastern Desert terrane (namely, Aswan or Gerf terrane in some literatures) which is regarded as the western extension of Midyan terrane in Western Arabian and shows most of the polydeformed history of the ANS. This chapter is devoted to discuss the Neoproterozoic crustal evolution of the Pan-African belt of the Eastern Desert terrane in an attempt to understand the tectonic setting of the ANS. Main points to be discussed in this chapter are: (1) infracrustal–supracrustal rocks, (2) thrusting, shearing, and folding relations; (3) gneiss domes versus metamorphic core complexes; (4) the conjugate pairs of Najd-related shears; (5) role of Najd Fault System in tectonic evolution of gneiss domes; (6) rates and transport directions of metaultramafic nappes; (7) the voluminous intrusives in northern Eastern Desert; (8) the post-amalgamation Hammamat sediments and their relation to Dokhan Volcanics; and (9) the northward decrease in intensity of deformation in the entire Eastern Desert.

The Hammamat molasse sediments of the Eastern Desert of Egypt were deposited in isolated basins formed during an initial stage of orogen parallel N‐S extension (650‐580 Ma) in the late Precambrian. Delivery of sediments to the molasse basins began after the eruption of Dokhan volcanics (602‐593 Ma), exhumation of core complexes (650‐550 Ma) and intrusion of late tectonic younger granites (610‐550 Ma). Strain ratios estimated using pebbles from nine selected molasse basins indicate that the amount of strain differs from one basin to another. Weakly strained pebbles (Rs= 2.22‐2.39) are obtained from Wadi Abu Gheryan and Wadi El‐Qash basins. Relatively high strain is recorded from Wadi Umm Seleimat basin (Rs= 4.00‐4.44), while moderate tectonic strains are estimated at Wadi Igla, Wadi Kareim, Wadi Hammamat, Wadi Queih, Wadi Abu Sheqeili and Umm Tawat basins (Rs= 2.42‐3.00). The late Pan‐African structures in the molasse sediments include: (i) NNW‐ward thrusting (D1) due to NNWSSE short...

In late Triassic time, Al Jabal Al Akhdar basin originated at an active continental on the African plateform. It extends for about 355km long with 75 km width between Gulf of Sirt to the west, Gulf of Bomba to the east. Thick succession of carbonate rocks was deposited from Upper Cretaeous to Eocene. Al Jabal Al Akhdar is one of the structural belts that are characterized by intra-Senonian compressional structures therefore it is part of the Syrian Arc belt that extends from northwestern Libya to Syria including the northern Egypt and the Palmyrides in Syria. In the Cyrenaica an inverted E-W to NE-SW-trending fold belt formed by the Santonian and was slightly accentuated by the Tertiary In Upper Cretaceous and during the Alpine compressin Al Jabal Al Akhdar basin was structurally inverted from normal faulting to Wrench system and development of right-handed, left-handed strike-slip faults, different generations of folds as well as normal faulting and joints. There is a clear junctio...

Wadi El Qash area is located in the Central Eastern Desert along the western border of the Precambrian rocks exposed along Qift-Qusier road. The area is occupied by ophiolites, Island arc metavolcanics, Muweilih metaconglomerates, Dokhan Volcanics, Hammamat sediments, post-Hammamat felsites and post tectonic granites (Phase I) as well as post granite dikes. The area is characterized presence of both pre- and post-rift structures. The pre-rift structures are preserved in ophiolites and Muweilih metaconglomerate and include thrusting of Muweilih ophiolites in NE direction along low angle thrust fault trending NW-SE and dipping to SW and formation of passive NW-SE foliation in Muweilih metaconglomerate. Post-rift structures were developed through four phases of deformation including three compression phases and final phase of extension and wrenching. D1 is manifested by thrusting of Hammamat conglomerate over Muweilih ophiolitic metabasalts and consequently thrusting of Igla sediment o...

ABSTRACT The Wadi El-Shush area in the Central Eastern Desert (CED) of Egypt is occupied by the Sibai core complex (SCC) and its surrounding Pan-African nappe complex (PNC). The SCC consists of four groups of granitoid rocks formed during island arc accretion and orogen parallel extension. The SCC and the PNC were developed through four successive deformational events (D1 to D4) and accompanied by three metamorphic events (M1 to M3). The first deformational event (D1) is only recognized in the amphibolites representing an old oceanic crust (900-740 Ma). The first metamorphic episode (M1) is a high temperature (>750oC) metamorphism led to the formation of amphibolite. Between 740Ma and 660Ma, oblique island arc accretion and plate convergence formed the PNC and the El-Shush gneissic tonalite that intruded at about 680±10 Ma and had been affected by thrusting and folding during D2. (N)NW-directed thrusting of the PNC led to the development of sub-horizontal thrusts and NNE-trending recumbent fold in the El- Shush gneissic tonalite. Presence of imbricate structures in the PNC and a NNE-trending recumbent fold in El-Shush gneissic tonalite suggest the presence of crustal thickening. Furthermore, an absence of highpressure metamorphic rocks on both sides of the thrust may indicate limited presence of lithospheric thickening. Continuation of such thrusting produced imbricate structures and thrust duplexes in the PNC. D2 thrusting in the CED usually took place under greenschist facies metamorphic conditions. In Sibai core complex, the second metamorphic event (M2P) occurred in the range of greenschist facies and under PT conditions of 480-525oC at 2-4.5 kbar. A continuation of oblique island arc convergence initiated renewed magmatic activity and deformation along NW-trending Najd-related strike-slip shear zones and NE-SE low angle normal faults (D3). D3 (660-560 Ma) consists of two stages, namely transpression and transtension, accompanied by the emplacement of three groups of granitoids, development of NNWtrending major asymmetrical anticline (F3a) and NE-trending open folds (F3b) as well as minor asymmetric, overturned and partly recumbent shear-folds in PNC. The tectonic transport direction during D3 was toward the northwest. Mylonitic fabrics within strike-slip shear zones were developed under retrograde greenschist facies metamorphism in the range of 222-321ºC in PNC and 202-230oC in the gneissic tonalite. Presence of retrograde metamorphism supports the slow exhumation of Sibai core complex under brittle-ductile low temperature conditions. Arc-accretion caused thrusting, imbrication and crustal thickening whereas gravitational collapse of a compressed and thickened lithosphere initiated the sinistral movement along transcurrent shear zones and low angle normal ductile shear zones and consequently development and exhumation of Sibai core complex.

ABSTRACT The studied area is located between the central and southern parts of the Eastern Desert of Egypt and occupies the northern part of Wadi Hafafit. Field geology, structural criteria, petrography and mineral chemistry have been used to construct the origin and tectonic evolution of this area. The rocks are mapped and classified lithologically into foliated metagabbro, foliated tonalite, mylonitic unit and deformed granite, together with slices of metamorphosed ultramafics along tectonic faults. An outline of the kinematics is presented in order to show the interaction of the major magmatic, structural and metamorphic events. Four deformational events have been recognized in the studied rocks (D1-D4). D1 event is manifested by a major F1 oval-shaped closed fold in foliated tonalite and metagabbro with the axes plunging 19o/ N32oW and 10o/S30oE. During D2, minor folds were formed with the axes plunging 30o/S40oW. D1 and D2 represent two successive but continuous phases of deformation and appear to be responsible for the domal structure in the studied area. D3 resulted in a major thrusting and mylonitic foliation. The axes of minor F3 folds with the axes plunge 12o/S6oE and 16o/N5oW. D4 is a consequence of later thrusting, major and local strike slip faults and shearing. Three metamorphic phases synchronous with the four deformational events have been recognized. Syn-D1 and D2 regional metamorphism (M1) and migmatization occurred under upper amphibolite and granulite facies conditions. Local dynamo-thermal metamorphism (M2) synchronous with D3, which overlapped or ended by the intrusion of the deformed granite. Late retrograde metamorphism (M3) occurred during D4 later shearing. The P-T conditions of magmatic and metamorphic processes have been estimated using mineral chemistry and geothermobarometry of plagioclase, pyroxene and amphibole, muscovite, biotite, garnet and chlorite. The first metamorphic event (M1) of the foliated metagabbro records a peak metamorphism at about 800oC and 7.5 kbar, corresponding to upper amphibolite to lower granulite facies metamorphism, under which the tonalite is suggested to have been formed by partial melting of lower crustal gabbroic rocks. This melt has ascended and was syntectonically emplaced into middle crustal levels where it crystallized at relatively low T (550oC) and P (6.2 kbar). The mylonitic unit has undergone dynamo-thermal metamorphism (M2) under greenschist to lower amphibolite facies conditions (T 550oC and P 3-4 kbar). The deformed granite was most probably formed by partial melting of lower to middle crustal protoliths under P-T conditions of 770oC and 4-8 kbar, which was later emplaced and crystallize at relatively low T (550oC). M3 retrograde metamorphism occurred during D4 under temperature range of 170o-227oC. The studied rocks are the consequence of tectono-magmatic and tectono-metamorphic processes. They were formed during the orogenic compressional phase of the Pan-African orogeny in an active continental margin tectonic setting. Later tectonics and uplift were followed by deep-erosion which led to the exhumation and exposure of the deep-seated rocks.

Abstract This paper records the garnierite in Wadi Dubur Neoproterozoic serpentinites from the Central Eastern Desert of Egypt. Garnierite (Ni-Mg hydrous silicates) occurs in two types ( Type I and Type II ) of infillings in the weathered serpentinite that was displaced sinisterly by NNW-SSE trending strike-slip faulting and dextrally with NE-trending shearing. All recognized garnierites are serpentine-like (nepouite/pecoraite) existing in mixtures with the hosting serpentines. The Type I garnierite is Fe-richer [Mg 0.26-0.71 Ni 1.22-1.79 Fe 1.28-3.05 Al 0.0-0.02 Si 1.11-1.73 O 5 (OH) 4 ] showing zoning in a collomorph texture, while the Type II garnierite is homogenous with more Si and Mg [Mg 0.54-0.94 Ni 1.38-2.04 Fe 0.38-1.29 Al 0.0-0.01 Si 1.66-2.10 O 5 (OH) 4 ]. Raman spectra indicate that the substitution of Ni for Fe formed a poorly crystalline goethite. The serpentinization of the Dubur peridotite protolith and the associated alteration of chromite and Ni-sulfides were important for the early individualization of Ni. It is proposed that the unweathered serpentinites represent the bedrock, while the altered garnierite-bearing ones represent the saprock. The early weathering of serpentinites contemporaneous with a faulting activation caused in situ precipitation of Ni and Fe in veins (Type I garnierite). With the faulting repetition and progressive alteration maintenance Ni, Si and Mg were transferred to the percolating meteoric solutions, and moved downward through the weathering profile precipitating the Type II garnierite in gouges. Although the studied Ni-rich rocks represent a narrow mineralogical occurrence, they are remnants of a former lateritic regolith most probably formed by tropical or sub-tropical weathering during Cretaceous at the expense of Wadi Dubur Neoproterozoic serpentinites. The formed regolith has been subsequently largely eroded, buried and recently exhumed in arid climate.

Near the summit of Sleza Mt were discovered by M A. Wahed, co-author of this publication, three zones of mineralization ilmenitowo vanadium (BB zone, C and DD). These zones are an important complement to the AA zone discovered in 1986. By Jamrozik. The arrangement of these zones marked on Fig. 1 suggests that mineralization fills the structure en echelon, therefore mineralization occurred at the time when the interior of the gabbro massif was still able to Magma, or is secondary ore mineralization, hydrothermal or pneumatolityczny. At the western end there is a great BB zone pegmatite with radially arranged uralitized gabbro crystals, having a length of 50 m. The presence of this speaks to the validity of an opinion on the secondary nature of the mineralization. The content of Ti02 is more than 5% by weight. vanadium and about 1700 ppm.

The Um Luseifa composite metavolcanics are composed originally of mafic and felsic tuffaceous lavas and their equivalent pyroclastics, which subsequently deformed and polymetamorphosed. These metavolcanics are separated and mapped into three lithologic divisions: mafic rocks, felsic rocks and mafic-felsic rocks. El Delhemi granite and Um Shaddad granite plutons were intruded into the studied rocks on the west and southwest respectively. Two ductile phases of deformation (D1-D2) accompanied by two metamorphic events (M1-M2) as well as later brittle deformation (D3) have operated the studied rocks. DI and D2 represent a single period of progressive deformation and are mainly ductile. DI is manifested by tight to open folding (F1), penetrative foliation (SI) parallel to the original banding and lamination and mineral elongation within S1 (LI). D2 is indicated by thrusting and associated folding (F2), crenulation foliation (S2), and lineation (L2), which is represented by the crenulatio...

The change from compressional to extensional tectonic regimes at the end of the Pan-African orogeny is accompanied by a transition from syn-collisional calc alkaline plutons to post-orogenic alkaline granites.It is indicated that a depleted upper mantle origin of calc alkaline magma, was gradually changed into alkaline type throughout dehydration and contamination from the subducted oceanic crust. The original upper mantle is changed by progressive distentional movement during collision creating successive intrusions of granitic rocks that exhibiting variant thermobarometric and depth conditions. Egyptian granites of the Central Eastern Desert formulate a perfect example showing a successive array starting from relatively deep calc alkaline granite (Katazonal granite) formed at a depth of 9.5 km. to proper alkaline granite at relatively shallower (Telezonal granite) depth of 1.2–1.5 km. Between the two extremes, transitional granitic rocks were emplaced at different levels of depth ...

Wadi Dubur metasediments occur in three localities named East Dubur, West Dubur and Nuweibi. They are composed mainly of chlorite-biotite schist, chlorite schist, garnet-mica schist, amphibole schist and metagreywacke. They are intruded and faulted against metagabbro-diorite complex, older granites and younger granites. Structural analysis of major, minor and micro structures and P-T estimates indicate that these metasediments have been tectonically evolved through four phases of deformation (D1-D4). DI is a weak ev*.nt represented by F1 minor tight folds trending N80°W and plunging 10°WNW recorded only in Nuweibi metasediments. Si strikes N75°-8O 'W and dips 60°-85°NNE and rarely SSW, whereas L1 plunges WNW. D2 is synchronous with D1 and is represented by F2 macroscopic and mesoscopic anticlinal folds trending NW-SE and NNW-SSE and plunge NW in East Dubur and SE in West Dubur. S2 strikes N10°-35°W and dips 600-700 NE and SW. L2 lineation plunges 10°-15°NW. D3 is the main deform...

Feiran gneisses and amphibolites occur in the southwestern part of Sinai around Wadi Feiran. Petrographically, they consist mainly of gneisses, migmatites and amphibolites. The gneisses are mainly biotite hornblende gneisses, hornblende gneisses and biotite gneisses. Migmatites are mainly migmatitic gneisses whereas the amphibolites are hornblende and biotite amphibolites that are mainly massive and foliated, fine to coarse-grained. Major and trace elements geochemistry indicate an igneous origin for gneisses and amphibolites. The gneisses range in composition from tonalite to granodiorite. The parental magma of the gneisses has calc-alkaline, metaluminous and I-type characteristics, derived from volcanic arc- syn collision setting at a depth of 23-30 km. The crystallization temperature of the parent rocks ranges between 670 and 720T at <10 kb. The spider diagram of the gneisses shows great similarities to the continental crust. The amphibolites are of basaltic composition, deriv...

The Hammamat molasse sediments of the Eastern Desert of Egypt were deposited in isolated basins formed during an initial stage of orogen parallel N‐S extension (650‐580 Ma) in the late Precambrian. Delivery of sediments to the molasse basins began after the eruption of Dokhan volcanics (602‐593 Ma), exhumation of core complexes (650‐550 Ma) and intrusion of late tectonic younger granites (610‐550 Ma). Strain ratios estimated using pebbles from nine selected molasse basins indicate that the amount of strain differs from one basin to another. Weakly strained pebbles (Rs= 2.22‐2.39) are obtained from Wadi Abu Gheryan and Wadi El‐Qash basins. Relatively high strain is recorded from Wadi Umm Seleimat basin (Rs= 4.00‐4.44), while moderate tectonic strains are estimated at Wadi Igla, Wadi Kareim, Wadi Hammamat, Wadi Queih, Wadi Abu Sheqeili and Umm Tawat basins (Rs= 2.42‐3.00). The late Pan‐African structures in the molasse sediments include: (i) NNW‐ward thrusting (D1) due to NNWSSE short...

In late Triassic time, Al Jabal Al Akhdar basin originated at an active continental on the African plateform. It extends for about 355km long with 75 km width between Gulf of Sirt to the west, Gulf of Bomba to the east. Thick succession of carbonate rocks was deposited from Upper Cretaeous to Eocene. Al Jabal Al Akhdar is one of the structural belts that are characterized by intra-Senonian compressional structures therefore it is part of the Syrian Arc belt that extends from northwestern Libya to Syria including the northern Egypt and the Palmyrides in Syria. In the Cyrenaica an inverted E-W to NE-SW-trending fold belt formed by the Santonian and was slightly accentuated by the Tertiary In Upper Cretaceous and during the Alpine compressin Al Jabal Al Akhdar basin was structurally inverted from normal faulting to Wrench system and development of right-handed, left-handed strike-slip faults, different generations of folds as well as normal faulting and joints. There is a clear junctio...

Wadi El Qash area is located in the Central Eastern Desert along the western border of the Precambrian rocks exposed along Qift-Qusier road. The area is occupied by ophiolites, Island arc metavolcanics, Muweilih metaconglomerates, Dokhan Volcanics, Hammamat sediments, post-Hammamat felsites and post tectonic granites (Phase I) as well as post granite dikes. The area is characterized presence of both pre- and post-rift structures. The pre-rift structures are preserved in ophiolites and Muweilih metaconglomerate and include thrusting of Muweilih ophiolites in NE direction along low angle thrust fault trending NW-SE and dipping to SW and formation of passive NW-SE foliation in Muweilih metaconglomerate. Post-rift structures were developed through four phases of deformation including three compression phases and final phase of extension and wrenching. D1 is manifested by thrusting of Hammamat conglomerate over Muweilih ophiolitic metabasalts and consequently thrusting of Igla sediment o...