The Wadi Mubarak belt, Eastern Desert of Egypt: a Neoproterozoic conjugate shear system in the Arabian?Nubian Shield

Shalaby, Ahmed; Stüwe, Kurt; Makroum, Farid Mahmoud; Fritz, Harald; Kebede, Tesfaye; Klötzli, Urs

doi:10.1016/j.precamres.2004.09.005

Cited by 113 publications

(71 citation statements)

References 24 publications

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“…(El-Ramly 1972) and the geological map of Quseir (Klitzch et al 1987). Major structures are after Akaad et al (1993, Bregar et al (2002), Shalaby et al (2005), and Abd El-Wahed (2007 The performed structural observations and measurements are in complete agreement with that presented by Fowler and Osman (2001) for Wadi Um Had area, including Wadi Hammamat basin.…”

Section: Wadi Hammamat Basinsupporting

confidence: 81%

The role of the Najd Fault System in the tectonic evolution of the Hammamat molasse sediments, Eastern Desert, Egypt

El‐Wahed

2009

Arab J Geosci

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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 Neoproterozoic time. Supply 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 granites (610-550 Ma). The late Neoproterozoic structures in the molasse sediments include: (1) NNWdirected thrusts due to NNW-SSE shortening (650-640 Ma), indicated by the presence of NE-, ENE-, and WSW-trending folds and NNW-directed thrusts.(2) SWand NE-directed thrusts due to ENE-WSW constriction during oblique convergence and arc accretion at around 640-620 Ma. Many of the map-and mesoscopic-scale NWtrending folds in the core complexes, the molasse sediments, and the Neoproterozoic nappes in the Eastern Desert are related to this event. Sinistral shearing along the Najd Fault System (650-540 Ma) resulted in the development of subvertical foliation, subhorizontal stretching lineation, and NW-trending tight folds overprinting earlier folds. Stretched pebbles are oriented NW-SE and WNW-ESE in the molasse basins localized within the Najd Fault System, and NE-SW in the basins outside the influence zone of this NW-trending fault system. Strain estimated using pebbles from nine molasse basins indicate that the amount of strain differs from one basin to another and from one place to another within the same basin. Weak tectonic strain (Rs=2.16-2.24) is obtained from post-orogenic basins; moderate strains are reported from foreland basins (Rs=2.37-3.18), whereas moderate to high tectonic strains are recorded from the intermontane basins (Rs=2.40-4.36). The obtained tectonic strain and K values indicate that the flattening strain prevails in the post-orogenic and foreland basins, whereas as both constrictional and flattening strains are recorded in intermontane basins. Strain variation from one basin to another and within the individual basin is attributed to presence of thrust and sinistral shear zones. Away from the deformed zones, the pebbles show no significant stretching. Two phases of thrusting and an episode of transpressional sinistral shearing are the latest structure features of the East African orogeny in the Arabian-Nubian Shield.

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Section: Wadi Hammamat Basinsupporting

confidence: 81%

The role of the Najd Fault System in the tectonic evolution of the Hammamat molasse sediments, Eastern Desert, Egypt

El‐Wahed

2009

Arab J Geosci

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“…The appearance and formation of the gneiss domes are interpreted to be closely linked to tectonic activity along the northward continuation of the Najd Faults System (e.g. Shalaby et al 2005), a major NW-trending, dominantly sinistral strike-slip system in Saudi Arabia (Brown and Coleman 1972;Stern 1985), where it extends for almost 2,000 km. The amphibolite grade, granitoid-dominated gneisses in the domes lie beneath a thrust sheet of eugeoclinal rocks dominated by greenschist grade ophiolitic and island arc assemblages referred to as the ''Pan-African Nappes'' (Ries et al 1983;Habib et al 1985a, b;El-Gaby et al 1988).…”

Section: Introductionmentioning

confidence: 99%

“…800 Ma to ca. 600 Ma, thus indicating a complex and prolonged magmatic history for this part of the East-African Orogen (Stern and Hedge 1985;Kröner et al 1994;Loizenbauer et al 2001;Bregar et al 2002;Shalaby et al 2005). Post-tectonic intrusives (''Younger Granites'') range in age from ca.…”

Section: Introductionmentioning

confidence: 99%

U–Pb TIMS age constraints on the evolution of the Neoproterozoic Meatiq Gneiss Dome, Eastern Desert, Egypt

Andresen

El-Rus

Myhre

et al. 2007

Int J Earth Sci (Geol Rundsch)

173

121

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Ages are used to constrain the temporal evolution of the Meatiq Gneiss Dome, Eastern Desert, Egypt, by dating (ID-TIMS) pre-, syn-, and post-tectonic igneous rocks in and around the dome. The Um Ba'anib Orthogneiss, comprising the deepest exposed structural levels of the dome, has a crystallization age of 630.8 ± 2 Ma. The overlying mylonites are interpreted to be a thrust sheet/ complex (Abu Fannani Thrust Sheet) of highly mylonitized metasediments (?), migmatitic amphibolites, and orthogneisses with large and small tectonic lenses of lessdeformed intrusives. Two syn-tectonic diorite lenses in this complex have crystallization ages of 609.0 ± 1.0 and 605.8 ± 0.9 Ma, respectively. The syn-tectonic Abu Ziran diorite, cutting across the tectonic contact between mylonite gneisses of the Abu Fannani Thrust Sheet and a structurally overlying thrust sheet of eugeoclinal rocks (''Pan-African nappe''), has a magmatic emplacement age of 606.4 ± 1.0 Ma. Zircons from a gabbro (Fawakhir ophiolite) within the eugeoclinal thrust sheet yielded a crystallization age of 736.5 ± 1.2 Ma. The post-tectonic Fawakhir monzodiorite intrudes the ophiolitic rocks and has an emplacement age of 597.8 ± 2.9 Ma. Two other post-tectonic granites, the Arieki granite that intrudes the foliated Um Ba'anib Orthogneiss, and the Um Had granite that cuts the deformed Hammamat sediments, have emplacement ages of 590 ± 3.1 and 596.3 ± 1.7 Ma, respectively. We consider formation of the Meatiq Gneiss Dome to be a young structural feature (\631 Ma), and our preferred tectonic interpretation is that it formed as a result of NE-SW shortening contemporaneous with folding of the nearby Hammamat sediments around 605-600 Ma, during oblique collision of East and West Gondwana.

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“…These shear zones mark the external boundaries of the core complexes (e.g., Sibai, Meatiq, Hafafit) and control the main deformation events in the CED (Fritz et al 1996Shalaby et al 2005Shalaby et al , 2006Abd El-Wahed 2006. Sinistral shearing along the NFS was active in the period 650-540 Ma.…”

Section: Relation Between Wfsz and The Najd Fault Systemmentioning

confidence: 99%

“…The first model considers the gneiss-cored domes as metamorphic core complexes formed during transpression combined with lateral extrusion along the NW trending zones bounded by sinistral strike-slip shears of the NFS with the formation of synextensional plutonism (e.g., Fritz et al 1996 andBregar et al 2002;Abd El-Wahed 2008). This model highlights the importance of the NFS during the tectonic evolution of the Eastern Desert of Egypt (e.g., Fritz and Messner 1999;Unzog and Kurz 2000;Loizenbauer et al 2001;Makroum 2001;Abdeen and Greiling 2005;Shalaby et al 2005Shalaby et al , 2006Abd El-Wahed 2006Abdeen et al 2008). The second model argues against the presence of core complexes in the Eastern Desert of Egypt and explains the development of gneiss-cored domes by an overlap between NW-SE complex folding and NW-SE extension parallel to the fold hinges (e.g., Fowler and Osman 2001;Fowler et al 2007;Andresen et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Synoblique convergent and extensional deformation and metamorphism in the Neoproterozoic rocks along Wadi Fatira shear zone, Northern Eastern Desert, Egypt

El‐Wahed

Anbar

2008

Arab J Geosci

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The Wadi Fatira area occurs at the southern margin of the Northern Eastern Desert (NED) of Egypt and is occupied by highly sheared metavolcanics tectonically alternated with banded iron formations and intruded by Barud tonalite-granodiorite, post-tectonic gabbroic and granitic intrusions. Detailed structural investigation showed that the schists and migmatitic amphibolites are formed by shearing in metavolcanics and syntectonic Barud tonalitegranodiorite due to movement along the Wadi Fatira shear zone (WFSZ). This shear zone starts as a NW-SE striking fault along Wadi Barud Al Azraq and the Eastern part of Wadi Fatira and turns to a E-W trending fault to the north of Wadi Fatira. Microstructural shear sense indicators such as asymmetric geometry of porphyroclasts such as σ-type and asymmetric folds deforming fine-grained bands which are frequently found around porphyroclasts indicate sinistral sense of shearing along the WFSZ. This shear zone is characterized by transitions from local convergence to local extension along their E-W and NW-SE trending parts, respectively. The NW-SE part of the WFSZ is of about 200 m in width and characterized by synmagmatic extensional features such as intrusion of synkinematic tonalite, creation of NE-SE trending normal faults, and formation of migmatitic amphibolites and schlieric tonalites. This part of the shear zone is metamorphosed under synthermal peak metamorphic conditions (725°C at 2-4 kbar). The E-W compressional part of the WFSZ is up to 3 km in width and composed of hornblende, chlorite, actinolite, and biotite schists together with sheared intermediate and acidic metatuffs. Contractional and transpressional structures in this part of the WFSZ include E-W trending major asymmetrical anticline and syncline, nearly vertical foliation and steeply pitching stretching lineations, NNE dipping minor thrusts, and minor intrafolial folds with their hinges parallel to the stretching lineation. P-T estimates using mineral analyses of plagioclase and hornblende from schists and foliated metavolcanics indicate prograde metamorphism under medium-grade amphibolite facies (500-600°C at 3-7 kbar) retrogressed to low-grade greenschist facies (227-317°C). The foliation in Barud tonalite-granodiorite close to the E-W part of the WFSZ runs parallel to the plane of shearing and the tonalite show numerous magmatic flow structures overprinted by folding and ductile shearing. The WFSZ is similar to structures resulted from combined simple shear and orthogonal shortening of oblique transpressive shear zones and their sense of movement is comparable with the characteristics of the Najd Fault System.

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The Wadi Mubarak belt, Eastern Desert of Egypt: a Neoproterozoic conjugate shear system in the Arabian?Nubian Shield

Cited by 113 publications

References 24 publications

The role of the Najd Fault System in the tectonic evolution of the Hammamat molasse sediments, Eastern Desert, Egypt

The role of the Najd Fault System in the tectonic evolution of the Hammamat molasse sediments, Eastern Desert, Egypt

U–Pb TIMS age constraints on the evolution of the Neoproterozoic Meatiq Gneiss Dome, Eastern Desert, Egypt

Synoblique convergent and extensional deformation and metamorphism in the Neoproterozoic rocks along Wadi Fatira shear zone, Northern Eastern Desert, Egypt

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