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Photomicrographs of the main rock types. (a) The poor mineral assemblage of the quartzofeldspathic gneisses, (b) Clinopyroxene of sample F39 is highly deformed and aligned along the S1 foliation. (c) Hornblende porphyroblast of sample F39 has inclusions of clinopyroxene. (d) Metamorphic foliation (parallel crystals of the hornblende) of sample F1. (e) Backscattered-electron image showing two different phases of amphibole, where the high temperature hornblende was replaced by low temperature actinolite. (f) Garnet porphyroblast of sample F93d. This porphyroblast has biotite, plagioclase, quartz and chlorite inclusions. (g) Deformed garnet crystal of sample F93d with long axes parallel to the matrix foliation. (h) Cordierite porphyroblast of sample F93d with sigmoidal shape.
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The Feiran–Solaf metamorphic complex of Sinai, Egypt, is one of the highest grade metamorphic complexes of a series of basement domes that crop out throughout the Arabian-Nubian Shield. In the Eastern Desert of Egypt these basement domes have been interpreted as metamorphic core complexes exhumed in extensional settings. For the Feiran–Solaf comple...
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... rock types of the Feiran-Solaf complex can be grouped into four major types: (i) migmatitic biotite and hornblende gneisses (migmatites); (ii) hornblende gneisses; (iii) quartzofeldspathic gneisses and (iv) calcsilicates. The quartzofeldspathic gneisses have a very simple mineralogy ( Fig. 4a) consisting of biotite, quartz, plagioclase and Fe-Ti oxides and will not be discussed further. The calcsilicates have a complicated fluid history and are studied separately (Abu-Alam & Stu¨weStu¨we, Unpublished data). Here, we concentrate on the migmatites, the hornblende gneisses, and the minor but nevertheless important ...
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... 2009 Blackwell Publishing Ltd clinopyroxene (in order of abundance) along with minor titanite, magnetite and epidote. Clinopyroxene occurs as anhedral elongated crystals up to 0.3 · 0.7 mm which are highly deformed and dyna- mically recrystallized in the S 1 foliation (Fig. 4b). Hornblende occurs as both small grains (<0.5 mm) and porphyroblasts (>1.5 mm). The small crystals are highly deformed, parallel to S 1 foliation and in equi- librium with the clinopyroxene. The porphyroblasts are subhedral to anhedral weakly deformed grains. These porphyroblasts have inclusions of clinopyroxene ( Fig. 4c). The long ...
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... in the S 1 foliation (Fig. 4b). Hornblende occurs as both small grains (<0.5 mm) and porphyroblasts (>1.5 mm). The small crystals are highly deformed, parallel to S 1 foliation and in equi- librium with the clinopyroxene. The porphyroblasts are subhedral to anhedral weakly deformed grains. These porphyroblasts have inclusions of clinopyroxene ( Fig. 4c). The long axes of the hornblende porphyro- blasts are sub-parallel to the S 1 foliation. The horn- blende crystals are overgrown by actinolite. Plagioclase occurs as subhedral to anhedral equant crystals attaining 0.75 mm in diameter and highly altered to epidote. Quartz with undulose extinction occurs interstitially between the ...
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... altered to epidote. Quartz with undulose extinction occurs interstitially between the plagioclase, hornblende and the clinopyroxene crystals. The magnetite occurs as euhedral crystals (0.3 mm) that overgrow the S 1 foli- ation. Titanite occurs as small euhedral inclusion crystals (<0.01 lm) in hornblende porphyroblasts within S 1 foliation ( Fig. ...
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... to subhedral elongated crystals attaining 0.35 · 0.7 mm. The plagioclase crystals show albite and albite-Carlsbad twinning, but untwined crystals are observed too. The plagioclase crystals are highly retrogressed to epidote. Hornblende is a green colour and strongly pleochroic. Hornblende occurs as anhedral elongated crystals (1.63 · 0.68 mm) (Fig. 4d). Hornblende is retrogressed to actinolite, chlorite and titanite (Fig. 4e). Quartz occurs as anhe- dral to subhedral crystals that lie interstitially between the plagioclase and the hornblende crystals. It fre- quently exhibits undulose extinction. The long axes of the plagioclase and the hornblende crystals are parallel to the ...
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... crystals show albite and albite-Carlsbad twinning, but untwined crystals are observed too. The plagioclase crystals are highly retrogressed to epidote. Hornblende is a green colour and strongly pleochroic. Hornblende occurs as anhedral elongated crystals (1.63 · 0.68 mm) (Fig. 4d). Hornblende is retrogressed to actinolite, chlorite and titanite (Fig. 4e). Quartz occurs as anhe- dral to subhedral crystals that lie interstitially between the plagioclase and the hornblende crystals. It fre- quently exhibits undulose extinction. The long axes of the plagioclase and the hornblende crystals are parallel to the metamorphic foliation (Fig. 4d). K-feldspar occurs as very small (apparent only ...
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... is retrogressed to actinolite, chlorite and titanite (Fig. 4e). Quartz occurs as anhe- dral to subhedral crystals that lie interstitially between the plagioclase and the hornblende crystals. It fre- quently exhibits undulose extinction. The long axes of the plagioclase and the hornblende crystals are parallel to the metamorphic foliation (Fig. 4d). K-feldspar occurs as very small (apparent only under the scanning electron microscope) anhedral equant crystals, which lie interstitially between the plagioclase, the quartz and the hornblende crystals. Ilmenite grows over magnetite as lamellar ...
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... peak assemblage is identified by a continuous metamorphic foliation, which is defined by parallel crystals of hornblende, plagioclase, quartz and iron oxides (Fig. 4d). The retrogression of plagioclase to epidote and hornblende to actinolite, chlorite and titanite as well as the presence of albite identify the retrograde assemblage. The large difference between the crystal size of the K-feldspar and the surrounding minerals, the anhedral shape of the K-feldspar crystals as well as the presence of ...
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... fig. 3a). Because these rocks prove to be petrologically useful (see below), they are described in detail here although they are quite rare in the FSMC. The rocks contain biotite, garnet, cordierite, plagioclase, quartz, chlorite, ilmen- ite and rutile. Muscovite and K-feldspar are notably absent. Garnet and cordierite occur as porphyroblasts (Fig. 4f). Garnet porphyroblasts are subhedral to anhedral equant grains up to 5 mm in diameter with inclusions of quartz, plagioclase, biotite, chlorite and ilmenite. The inclusions define linear trails that are oblique to the matrix foliation (S 1 ) giving relic evi- dence to an earlier deformation phase prior to D 1 . Some garnet is ...
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... ilmenite. The inclusions define linear trails that are oblique to the matrix foliation (S 1 ) giving relic evi- dence to an earlier deformation phase prior to D 1 . Some garnet is idiomorphic and has straight crystal boundaries against biotite in the matrix. Other garnet crystals are highly deformed with long axes parallel to the matrix foliation (Fig. 4g). The cordierite por- phyroblasts are anhedral, highly altered grains 0.5 mm and 3 mm in diameter. The cordierite crystals are equidimensional porphyroblasts with sigmoidal shape Rasse, 1974). (f) Al IV v. temperature for amphiboles after Blundy & Holland (1990). The open circle is the hornblende of the hornblende gneisses (the old ...
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... 2009 Blackwell Publishing Ltd in S 1 (Fig. 4h). Cordierite porphyroblasts have quartz, plagioclase, biotite, chlorite and ilmenite inclusions. Garnet and cordierite porphyroblasts are surrounded by a matrix of biotite, plagioclase, chlorite, quartz, ilmenite and rutile that define a continuous S 1 folia- tion. The plagioclase occurs as euhedral to anhedral elongate crystals ...
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... The post-peak conditions are difficult to determine. Some constraints however are provided by the late stage minerals chlorite, albite, actinolite and epidote. The presence of these phases implies that the hornblende gneisses re-equilibrated below the albite-in boundary and above the actinolite-out boundary (465-480 °C and <<5 kbar according to Fig. ...
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Citations
... The Wadi Feiran-Solaf metamorphic complex constitutes an elongated folded belt in southern Sinai, Egypt, that is about 40 km long and 5-11 km wide, trending NW-SE parallel to the orientation of the Najd fault system as shown in Fig. (1). It has evolved and was exhumed in close connection with the activity of this shear zone system [25,26]. Calcium silicate rocks were gathered from ore quarries in the Sinai Peninsula, and their most notable use is in building materials such as some forms of pottery, glass, and cement of all types. ...
... ): Location and geological map of investigated area[25,26] ...
... The shield is remarkably rich in dismembered ophiolitic rocks (particularly in the Eastern Desert), with ages ranging from ca. 890 to 690 Ma Stern et al., 2004). Metamorphic complexes of upper amphibolite facies were exhumed as tectonic windows formed either in extensional (Fritz et al., 1996) or transpressional settings (Abu-Alam and Stüwe, 2009;Meyer et al., 2014). Intermontane basins were formed in association with the exhumation of the metamorphic complexes (e.g., Meyer et al., 2014;Fritz et al., 2002). ...
... In the southern Sinai Peninsula, the Precambrian basement is built up of four metamorphic complexes (Fig. 2) (namely, Zaghra, Kid, Feiran-Solaf, and Taba) that are separated by voluminous unmetamorphosed granitoid rocks and several Ediacaran volcano-metasedimentary sequences (Eyal et al., 2010;Be'eri-Shlevin et al., 2011). The metamorphic complexes consist of ortho-and paragneisses and schists metamorphosed under conditions of greenschist to amphibolite facies (El-Shafei and Kusky, 2003;Abu El-Enen et al., 2004;Eliwa et al., 2008;Abu-Alam and Stüwe, 2009). ...
... Hornblende gabbros intrude into the orthogneisses and send offshoots and apophyses into them. These gneisses are the extention of the orthogneisses of Feiran Solaf Metamorphic Complex (Abu Anbar and Abd El-Wahed, 2004;Abu-Alam and Stüwe, 2009). Amphibolite (ortho-amphibolite) occurs as enclaves or bands alternating with orthogneisses. ...
Rodinia to Gondwana evolution record, South Sinai, Egypt: Geological and geochronological constraints
... Multimodal tectonic activity-related processes such as mantle melting and metasomatism, arc volcanism, hydrothermal solution migration, and metamorphic dewatering of crust are all involved in the subduction of Mozambican oceanic lithosphere beneath multiple oceanic arcs in a supra-subduction zone (SSZ) during the collision of West and East Gondwana Hamdy et al., 2011;Abu-Alam and Hamdy, 2014;Khedr and Arai, 2016;Gamaledlien et al., 2015Gamaledlien et al., , 2016Gamaledlien et al., , 2019a. During oblique island arc convergence (Abu-Alam and Stüwe, 2009;Meyer et al., 2014), deep-mantle ultramafics were exhumed in conjunction with NW-SE extension and thinning of the previously thickened crust . ...
Serpentinites play a pivotal role in carrying fluids and different elements into the Earth’s mantle. However, their role in exchanging silica (Si) between the marine environment and the mantle remains a matter of investigation. The Wadi Igla serpentinite (southern Eastern Desert of Egypt) formed at the expense of abyssal harzburgite by ∼15–22 % melting. It contains abundant Cr-spinel with sub-microscopic serpentine and chlorite-rich pores providing a base to explore Si cycling during serpentinization-carbonatization processes. The low-grade metamorphism of the harzburgite protolith started on the ocean floor, forming lizardite and chlorite (250–300 °C). Increasing the temperature (400–450 °C) caused the formation of brucite and antigorite. With the subduction in the fore-arc and the interaction with subducting sediments-related CO2-rich fluid, the Wadi Igla serpentinite underwent metasomatism, producing chlorite (300 °C), antigorite, tremolite, dolomite, and ferritchromite rims around Cr-spinel (Type 1), with brucite loss. In the upper greenschist-lower amphibolite facies (ca. 500 °C), CO2-rich hydrothermal fluids (with XCO2 of ∼0.55) penetrated a large volume of the protolith leading to full serpentinization together with abundant magnesite replacement. The resultant silica-rich fluids percolated in the Type 1 Cr-spinel from the outward to cores through microfractures and pores, producing Type 2 and Type 3 Cr-spinel with serpentine ± chlorite along cleavages, diminished Al-cores and growing outer ferritchromite zone and/or Cr-magnetite to magnetite zones. The suprachondritic NbN/LaN (up to 39.35) and NbN/BaN (up to 13.37) of whole rock implies for HFSEs metasomatism by subduction sediments input components, while slight enrichment in LREEs (LaN/YbN = 2.5–3) and FMEs (Li, Pb, Sr, and Ba) may have resulted from serpentinization-related hydrothermal alteration. The Wadi Igla serpentinite indicates silica cycled in a closed system, suggesting that the altered Neoproterozoic oceanic lithosphere may not have shared their main components with the surrounding environment whether to the ocean floor or the subduction zone.
... The Najd faults bordered the Meatiq and other gneissic domes in the Eastern Desert of Egypt were active between 615 and 585 Ma [23]. The sinistral strike-slip faults prevail across the Precambrian of Arabia and Egypt [24]. They formed due to a large zone of NW-SE trending crustal extension that was associated with the formation of the juvenile continental crustal in the northernmost part of Afro-Arabia [24]. ...
... The sinistral strike-slip faults prevail across the Precambrian of Arabia and Egypt [24]. They formed due to a large zone of NW-SE trending crustal extension that was associated with the formation of the juvenile continental crustal in the northernmost part of Afro-Arabia [24]. ...
... The NW trending sinistral strike-slip faults of the NFS of Arabia and Egypt were developed due to the escape tectonics associated with the collisional stage and were active during~630-560 Ma [24]. They permitted northward orogen-parallel extension because of the escaping of the ANS from the collision between East and West Gondwana. ...
The late Neoproterozoic gabbroic intrusion of the Wadi El-Faliq area in the central Eastern Desert of Egypt (north Arabian-Nubian Shield; henceforth, ANS) is a fresh, undeformed elliptical body elongated in a NW-SE trend following the main sinistral strike-slip faults of the Najd fault system. Mineralogical and geochemical evidence suggest that they were derived from hydrous tholeiitic mafic magmas with arc-like geochemical fingerprints resembling the post-collisional gab-broic intrusions in Saudi Arabia. Despite the arc-like signatures, their fresh and undeformed nature, together with the field relationships, indicates that the studied gabbroic intrusion postdates the main collisional phase, supporting its emplacement after subduction ceased and during the post-collisional stage. As a result, the arc-like signatures were possibly transmitted from the earlier ANS subduction episode. Indeed, the high (La/Sm) N , and negative-Nb and positive-Pb anomalies suggest contributions from subduction components. Lithospheric delamination was possibly facilitated by the Najd faults and shear zones formed during the post-orogenic crustal extension associated with the Pan-African orogenic collapse. The delamination process could have generated a rapid upwelling and melting of the asthenosphere mantle. The melt-rock reaction process likely played an important role in the genesis of the studied rocks through the interaction of the asthenosphere melts with lithosphere mantle rocks during ascent. The HREE fractionation suggests a probable mixing between melts from both spinel-and garnet-bearing peridotites. We suggest that the Wadi El-Faliq gabbroic intrusion was likely emplaced due to the stretching and thinning of the lithosphere during the extensional tectonism following the Pan-African orogeny.
... Because of the variable orientation of metamorphic complexes with respect to the Najd fault system, exhumation has been interpreted to have occurred in different tectonic regimes. Exhumation may have occurred in core complexes in a local extensional environment, but in an overall horizontal transpressive regime (Abu-Alam and Stüwe, 2009;Fritz et al., 2002;Loizenbauer et al., 2001). This reflects a regionally extensional regime that persisted throughout the Arabian-Nubian shield at the last stages of development (Greiling et al., 1994) or after collision ceased (Blasband et al., 2000). ...
... In Sinai, four metamorphic complexes (Feiran-Solaf, Kid, Sa'al-Zaghra, and Taba: Fig. 2B and Table 1) have been identified and interpreted as fragments of island arcs (Abu-Alam and Stüwe, 2009;Eyal et al., 2014;Hassan et al., 2021). These island arc sequences include meta-sedimentary rocks and mafic to felsic meta-volcanics intruded by granitoids, diorite, and gabbro (Hassan et al., 2021). ...
The Janub Metamorphic Complex (JMC) in southern Jordan provides new correlative data constraining the transition from compressional to extensional tectonics in the northern Arabian-Nubian Shield. This constraint comes from the identification of extensional mylonitic shear zones affecting both the JMC and some intruding granitoids. The JMC comprises metamorphosed andesitic-dacitic-rhyolitic flows and pyroclastics, meta-volcanogenic sediments, and hornfels. Volcanism ceased by 618 ± 5 Ma. The volcanosedimentary sequence formed in an intra-arc basin in a mature island arc and was then buried and regionally metamorphosed at lower greenschist facies conditions in the waning accretionary phase between 618 and 615 Ma. This is based on the age of crosscutting plutons of the Rumman Suite, which triggered local high-T/low-P metamorphism at ∼ 615 Ma. Rumman granitoids and JMC rocks were deformed by narrow gently-dipping mylonitic shear zones, interpreted as extensional, that ceased operating by 605 Ma, the age of crosscutting undeformed dikes and plutons of the Yutum Suite. At 596 Ma, a late granite intruded the JMC and thermally metamorphosed some of the meta-sediments. This granite was deformed in a Najd-related brittle shear zone at ∼ 590 Ma as recorded by 40Ar/39Ar geochronology. The JMC can be correlated with the higher-grade Abu-Barqa Metamorphic Complex (ABMC), despite tectonics relations being obscured by younger intrusive rocks. The main metamorphic phase in the ABMC occurred at a depth of 18 km at ∼ 620–615 Ma, followed by gradual uplift and high-T metamorphism at 615–610 Ma and exhumation to the surface at ∼605 Ma. Extensional shearing in the JMC and exhumation of the ABMC probably developed in a core-complex like setting triggered by orogenic collapse. Ductile shearing related to collapse ceased before 605 Ma. The 590 Ma brittle shear zone is the first dated Najd-related structure from the basement of Jordan. The central setting of our data allows correlation of metamorphic complexes in Sinai and Saudi Arabia and is consistent with the final assembly of Gondwana, initiation of orogenic collapse, and transition to extensional tectonics occurring at ∼ 620–610 Ma in the northern Arabian-Nubian Shield.
... The postcollisional magmatism in southern Sinai was formed as a result of tectonic escape after completion of collision between continental plates and/ or island arcs, with associated regional metamorphism during orogenesis (e.g., Stern 1994;Kusky and Matsah 2003;Abu-Alam and Stüwe 2009). This stage was represented by vast intrusions of granites and related volcanic rocks (Farahat et al. 2007El-Bialy 2010;Eyal et al. 2010;Be'eri-Shlevin et al. 2011;Johnson et al. 2011). ...
Postcollisional magmatism is widely distributed in southern Sinai, the extreme northern part of the Neoproterozoic Arabian-Nubian Shield. This article deals with mineral and whole-rock chemistry of postcollisional syenogranites and associated volcanic rocks from three localities in southern Sinai: Iqna Sharay'a, Rusis-Rutig, and Um Shuki-Abu Khusheib. The studied volcanic rocks have compositions between rhyolites and dacites with minor andesite. The whole-rock chemical compositions of the investigated rock types together with the biotite chemistry are consistent with high-K calc-alkaline and alkaline/peralkaline magma. The studied syenogranites and most volcanic rocks are more akin to anorogenic alkaline within-plate environments. Only a few samples of Um Shuki-Abu Khusheib volcanic rocks display some characteristics of orogenic arc-type environments. The high-K calc-alkaline to alkaline affinity and the relative enrichments in large ion lithophile elements (especially K, Rb, and Ba) and light rare earth elements together with a significant negative Eu anomaly imply that the studied granites and volcanic rocks were generated by partial melting of lower to middle crustal materials accompanied by the underplated mafic magma produced in the lithospheric mantle (convective diffusion). This convective diffusion describes a specific scenario of active chemical interaction between mafic and silicic magmas in order to explain formation of voluminous high-K calc-alkaline and alkaline/peralkaline magmatism in postcollisional tectonic environments. The enhanced temperatures of A-type silicic magmas of more than 10007C suggest that magma generation could occur even at the depth of the uppermost lithospheric mantle.
... The postcollisional magmatism in southern Sinai was formed as a result of tectonic escape after completion of collision between continental plates and/ or island arcs, with associated regional metamorphism during orogenesis (e.g., Stern 1994;Kusky and Matsah 2003;Abu-Alam and Stüwe 2009). This stage was represented by vast intrusions of granites and related volcanic rocks (Farahat et al. 2007El-Bialy 2010;Eyal et al. 2010;Be'eri-Shlevin et al. 2011;Johnson et al. 2011). ...
... Plagioclase in the boninitic diabase is classified as albite, due to the effects of low-grade albitisation, whereas in the gabbro and the tholeiitic diabase it appears as albite, labradorite and andesine. Magmatic amphibole is present within the gabbro and to a smaller extent in the tholeiitic diabase as interstitial crystals and blebs, displaying lower silica and higher Ti, Al and Na contents compared to secondary amphiboles, such as tremolite and actinolite (Maeda et al., 2002;Koutsovitis and Magganas, 2016;Abu-Alam and Stüwe, 2009;Ridolfi et al., 2010). Based on the textural characteristics and the chemistry of amphiboles in the gabbros and tholeiitic diabasic rocks of our study, we consider that blebs and granular hornblende were crystallised during the main magmatic stage from a hydrous silicate melt, whereas fibrous amphibole (actinolite) formed at the expense of magmatic hornblende and clinopyroxene during the metasomatic stage. ...
In the Veria-Naousa ophiolitic complex (north Greece), rodingite appears mainly in the form of cross cutting dykes within serpentinised peridotites. It is distinguished into three types, based upon the provenance of its protoliths, textural characteristics, mineralogical assemblages and geochemical affinities. Type I rodigites were derived from boninitic diabasic protoliths and their mineralogical assemblage include garnet + clinopyroxene + chlorite. Type II rodingites were formed at the expense of gabbroic precursors, comprising clinopyroxene + garnet + vesuvianite ± quartz, whereas Type III rodingites replaced diabasic tholeiitic protoliths comprising of garnets + vesuvianite + clinopyroxene + chlorite. Rodingitisation resulted in desilification, decrease of alkalies, Al, Fe, Mg and increase in Ca contents. In Type I rodingites the MREE (middle rare earth elements) and HREE (heavy rare earth elements) were slightly reduced. Type II rodingites experienced LREE (light rare earth elements) depletions, whereas MREE and HREE remained fairly stable. Restricted mobility of REE in Type III rodingites is assigned to shallow-level rodingitisation under decreasing pH.
Rodingitisation occured in two distinct stages at fore-arc settings. The first stage occured under mildly oxidising conditions and enhanced CO2/H2O ratios. This stage affected the protoliths of all rodingite types. The second rodingitisation stage occured under more oxidising conditions and lower CO2/H2O ratios, which corresponds to the exhumation stage of the serpentinite-rodingite formations. Types II and III rodingites were subjected to further rodingitisation under the increasing influence of slab-derived hydrous phases at shallower depths, leading to the formation of late-stage andradite and vesuvianite. All stages of rodingitisation are estimated to have occurred under relatively moderate temperatures and pressure (~300 to 450 °C; ~2–6 kbar respectively).
... These blocks originally formed by deposition of volcano-sedimentary formations in an oceanic or marginal marine environment between dispersed continental fragments (Nance et al. 1986;Murphy and Nance 2003). Influence of the pre-Neoproterozoic continental crust or Rodinia-related events within the ANS was deduced based on geological observations (Agar 1985;Fowler and Hassen 2008;Abu-Alam and Stüwe 2009;Hassan et al. 2014;Fowler et al. 2015Fowler et al. , 2018, age dating information (Calvez et al. 1983;Be'eri-Shlevin et al. 2009;Ali et al. 2009Ali et al. , 2010Ali et al. , 2012Eyal et al. 2014;Abd El-Rahman et al. 2019) and Pb, Nd and Sr isotopic signatures (Baubron et al. 1976;Stacey et al. 1980;Fleck and Hadley 1982;Stacey and Stoeser 1983;Stacey and Hedge 1984;Stacey and Agar 1985;Windley et al. 1996). The pre-Neoproterozoic continental crust is sometimes referred to as "contaminated shield" that shows continental 207 Pb/ 206 Pb isotopic signatures (Type III Pb; Stoeser and Stacey 1988), low or commonly negative initial eNd values and old TDM ages . ...
The majority of geological investigations that deal with the Arabian-Nubian Shield are concerned with the processes of ocean closure, subduction, orogenesis and crustal growth, in relation to the assembly of Gondwanaland in the late Neoproterozoic. Other valuable published works deal with the earlier development of the Arabian-Nubian Shield in the light of the configuration of Rodinia (assembly and rifting) and the Mozambique Ocean. Progress in modern geochronological and structural data from the Arabian-Nubian Shield reveals that some of the Arabian-Nubian Shield rocks were derived from older crustal material and were affected by tectonic events of the early ensimatic stage of the Mesoproterozoic Rodinia breakup. The studies of Arabian-Nubian Shield ophiolites and related mélange rock units, representing remnants or fragments of earliest simatic (mafic-ultramafic) lithosphere, provide essential constraints on the oceanic realm predating the accretionary and collisional stages of the Arabian-Nubian Shield (~780–600 Ma). Understanding the complete tectonic evolution of the Arabian-Nubian Shield requires providing special attention to the structural, petrological, geochemical and geochronological characteristics of its early primitive stage during the Rodinia breakup.
... The required heat for crustal rock anatexis can be assigned by the contribution of intraplating mantle-derived; volatile-rich melt (Azer and Farahat, 2011;Azer et al., 2020). Moreover, the northern parts of the ANS were subjected to oblique compressional force, which led to the activity of Najd Fault System (Abu-Alam and Stüwe, 2009). This force can push the lower crust toward the asthenosphere produce shear heating which may accelerate the partial melting process (Stüwe and Barr, 1998). ...
The Egyptian older and younger granitic rocks emplaced during pre‐ and post‐collision stages, respectively, of Neoproterozoic Pan‐African Orogeny, are widely distributed in the southern Sinai Peninsula, constituting 70% of the basement outcrops. The Wadi El‐Akhder southwestern Sinai, is a mountainous terrain exposing two granitoid suites, namely the Wadi El‐Akhder Older Granites (AOG) and the Homra Younger Granites (HYG). The AOG (granodiorites with subordinate tonalite compositions) have geochemical characteristics of medium‐K calc‐alkaline, metaluminous to mildly peraluminous granitoids formed in an island‐arc environment, which are conformable with well‐known Egyptian older granitoids rocks, whereas the HYG display calc‐alkaline to slightly alkaline nature, peraluminous syeno‐, monzogranites and alkali feldspar granites matching well those of the Egyptian younger granites. With respect to the AOG granitoids, the HYG granites contain lower Al2O3, FeO∗, MgO, MnO, CaO, TiO2, Sr, Ba, and V, but higher Na2O, K2O, Nb, Zr, Th, and Rb. The AOG are generally characterized by enrichment in LILE and LREE and depletion in HFSE relative to N‐MORB values (e.g., negative Nb and Ta anomalies). The geochemical features of the AOG follow assimilation‐fractional crystallization (AFC) trends indicative of extensive crustal contamination of magma derived from a mantle source. The chemical characteristics of the AOG are remarkably similar to those of subduction‐related granitoids from the Arabian‐Nubian Shield (ANS). The compositional variations from monzogranites through syenogranites to alkali feldspar granite within HYG could not be explained by fractional crystallization solely. Correlating the whole‐rock composition of the HYG to melts generated by experimental dehydration melting of meta‐sedimentary and magmatic rocks reveals that they appear to be derived by extended melting of psammitic and pelitic metasediments, which is similar to the most of younger granitic suites in the ANS.
