Pan-African structures, ophiolites and mélange in the Eastem Desert of Egypt: a traverse at 26°N

Ries, A. C.; Shackleton, Robert; Graham, Rod; Fitches, W. R.

doi:10.1144/gsjgs.140.1.0075

Cited by 279 publications

(129 citation statements)

References 25 publications

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“…Ries et al 1983;Wilde & Youssef 2002;Abdeen & Greiling 2005;Eliwa et al 2010;Johnson et al 2011;Bezenjani et al 2014). Proposed depositional ages lie close to the time of the Pan-African Orogeny, and both pre-collisional and postcollisional settings have been proposed.…”

Section: The Hammamat Formationmentioning

confidence: 88%

“…The Hammamat Formation rocks' depositional environments, and their relationship to the PanAfrican Orogeny is of some debate (e.g. Ries et al 1983;Wilde & Youssef 2002;Abdeen & Greiling 2005;Eliwa et al 2010;Johnson et al 2011;Bezenjani et al 2014); the sediments are arguably (as described in the above-cited studies and references therein) considered to be pre-collisional, syn-collisional or post-collisional, and either locally sourced and deposited in isolated basins, or of distant provenance deposited from a major fluvial system of continental proportions.…”

Section: The Arabian-nubian Shieldmentioning

confidence: 99%

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A detrital record of the Nile River and its catchment

Fielding

Najman

Millar

et al. 2016

JGS

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This research uses analyses from Nile catchment rivers, wadis, dunes and bedrocks to constrain the geological history of NE Africa and document influences on the composition of sediment reaching the Nile delta. Our data show evolution of the North African crust, highlighting phases in the development of the Arabian-Nubian Shield and amalgamation of Gondwana in Neoproterozoic times. The Saharan Metacraton and Congo Craton in Uganda have a common history of crustal growth, with new crust formation at 3.0 -3.5 Ga, and crustal melting at c. 2.7 Ga. The Hammamat Formation of the ArabianNubian Shield is locally derived and has a maximum depositional age of 635 Ma. By contrast, Phanerozoic sedimentary rocks are derived from more distant sources. The fine-grained (mud) bulk signature of the modern Nile is dominated by input from the Ethiopian Highlands, transported by the Blue Nile and Atbara rivers. Detrital zircons in the Nile trunk are predominantly derived from Phanerozoic cover rocks. Most detritus from the upstream White Nile is trapped in the Sudd marshes and contributes little to the Nile trunk. Therefore, the White Nile downstream is dominated by locally derived Phanerozoic cover. The White Nile proximal to the Gezira Fan is influenced by the fan's Blue Nile signature.

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Section: The Hammamat Formationmentioning

confidence: 88%

Section: The Arabian-nubian Shieldmentioning

confidence: 99%

A detrital record of the Nile River and its catchment

Fielding

Najman

Millar

et al. 2016

JGS

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“…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). Based on the nature and structural position of ophiolites and associated island arc sequences we prefer to group them together and use the term the eugeoclinal thrust sheet/complex.…”

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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“…Many are allochthonous ophiolitic melanges according to Ries et al (1983) who give the best general account of the geology and state that they have no evidence as to the original environment of crystallisation of the ophiolites, whether mid-oceanic ridge or other setting. This account aims to provide some indication.…”

Section: Introductionmentioning

confidence: 99%

Compositional variation in chromite from the Eastern Desert, Egypt

1992

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Electron microprobe analyses of chromite ores from Baramiya, Seifein, Siwigat, Ashayer, Um Salatit and Ras Shait, Egypt, reveal two compositional groups. The unaltered chromites from Baramiya and Seifein have high Al and low Cr contents [Cr/(Cr + AI) = 0.56] whereas the remainder have low Al and high Cr contents [Cr/(Cr + A1) = 0.73]. Such bimodality characterises Alpine-type peridotites. The second group probably crystallised at higher T and lower P than the first group and has a composition characteristic of a type III alpine-type peridotite, i.e. of arc or possibly ocean plateau origin but not of mid-ocean ridge origin. The crystallisation setting of the first group is less certain but not inconsistent with the same environment as the second group so that considering the likely higher pressure of crystallisation of the first group overall favours plutonic crystallisation in the roots of an arc for both groups.Rim, patchy and fracture alteration of the chromite occurred possibly partly of late magmatic (deuteric) origin but mainly connected with fluid movements, serpentinisation and tectonism. The final composition of the resultant ferritchromite is variable and depends largely on the original chromite composition; the composition of the ferritchromite developed in highly cataclased chromites deviates markedly from that of the original chromite presumably due to unmixing and migration.

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Pan-African structures, ophiolites and mélange in the Eastem Desert of Egypt: a traverse at 26°N

Cited by 279 publications

References 25 publications

A detrital record of the Nile River and its catchment

A detrital record of the Nile River and its catchment

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

Compositional variation in chromite from the Eastern Desert, Egypt

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