Petrology and geochemistry of Pan-African granitoids, Kab Amiri area, Egypt - implications for tectonomagmatic stages in the Nubian Shield evolution

Moghazi, A.M.

doi:10.1007/s007100200014

Cited by 71 publications

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“…The older granitoids are calc-alkaline I-type granitoids (syn-orogenic), varying in composition from quartz diorite to monzogranite, and were emplaced during active subduction processes between 800 and 614 Ma (Hussein et al 1982;Stern and Hedge 1985;Hassan and Hashad 1990;Stern 1994;Kröner et al 1994;Moghazi 1999Moghazi , 2002El-Bialy 2004;Moussa et al 2008). Younger granitoids are highly fractionated calc-alkaline I-type granites and rarely gran- Naqab (modified after Mushkin et al 2003) odiorites and were emplaced during the termination of compressive orogeny by suturing at plate boundaries between 610 and 550 Ma (Hashad 1980;Hussein et al 1982;Stern and Hedge 1985;Beyth et al 1994;El-Bialy 1999;Moghazi 1999Moghazi , 2002.…”

Section: Introductionmentioning

confidence: 98%

“…Younger granitoids are highly fractionated calc-alkaline I-type granites and rarely gran- Naqab (modified after Mushkin et al 2003) odiorites and were emplaced during the termination of compressive orogeny by suturing at plate boundaries between 610 and 550 Ma (Hashad 1980;Hussein et al 1982;Stern and Hedge 1985;Beyth et al 1994;El-Bialy 1999;Moghazi 1999Moghazi , 2002.…”

Section: Introductionmentioning

confidence: 98%

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Late Neoproterozoic alkaline magmatism in the Arabian–Nubian Shield: the postcollisional A-type granite of Sahara–Umm Adawi pluton, Sinai, Egypt

El-Bialy

Streck

2008

Arab J Geosci

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The Sahara-Umm Adawi pluton is a Late Neoproterozoic postcollisional A-type granitoid pluton in Sinai segment of the Arabian-Nubian Shield that was emplaced within voluminous calc-alkaline I-type granite host rocks during the waning stages of the Pan-African orogeny and termination of a tectonomagmatic compressive cycle. The western part of the pluton is downthrown by clysmic faults and buried beneath the Suez rift valley sedimentary fill, while the exposed part is dissected by later Tertiary basaltic dykes and crosscut along with its host rocks by a series of NNE-trending faults. This A-type granite pluton is made up wholly of hypersolvus alkali feldspar granite and is composed of perthite, quartz, alkali amphibole, plagioclase, Fe-rich red biotite, accessory zircon, apatite, and allanite. The pluton rocks are highly evolved ferroan, alkaline, and peralkaline to mildly peraluminous A-type granites, displaying the typical geochemical characteristics of A-type granites with high SiO and rare earth elements (REE) and low CaO, MgO, Ba, and Sr. Their trace and REE characteristics along with the use of various discrimination schemes revealed their correspondence to magmas derived from crustal sources that has gone through a continent-continent collision (postorogenic or postcollisional), with minor contribution from mantle source similar to ocean island basalt. The assumption of crustal source derivation and postcollisional setting is substantiated by highly evolved nature of this pluton and the absence of any syenitic or more primitive coeval mafic rocks in association with it. The slight mantle signature in the source material of these A-type granites is owed to the juvenile Pan-African Arabian-Nubian Shield (ANS) crust (I-type calc-alkaline) which was acted as a source by partial melting of its rocks and which itself of presumably large mantle source. The extremely high Rb/Sr ratios combined with the obvious Sr, Ba, P, Ti, and Eu depletions clearly indicate that these Atype granites were highly evolved and require advanced fractional crystallization in upper crustal conditions. Crystallization temperature values inferred average around 929°C which is in consistency with the presumably high temperatures of A-type magmas, whereas the estimated depth of emplacement ranges between 20 and 30 km (upper-middle crustal levels within the 40 km relatively thick ANS crust). The geochronologically preceding PanAfrican calc-alkaline I-type continental arc granitoids (the Egyptian old and younger granites) associated with these rocks are thought to be the crustal source of f this A-type granite pluton and others in the Arabian-Nubian Shield by partial melting caused by crustal thickening due to continental collision at termination of the compressive orogeny in the Arabian-Nubian Shield.

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 98%

Late Neoproterozoic alkaline magmatism in the Arabian–Nubian Shield: the postcollisional A-type granite of Sahara–Umm Adawi pluton, Sinai, Egypt

El-Bialy

Streck

2008

Arab J Geosci

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“…Following the previous tectonic schemes for the Pan-African crustal evolution (e.g., Stern 1994;Moghazi 2002;Farahat et al 2007), the studied older granitoids correspond to granites of collision stage. Field aspects and geochemical attributes indicate their I-type nature in the sense of White and Chappell (1977).…”

Section: Petrogenesis Of the Older Granitoidsmentioning

confidence: 99%

“…7 and 8). So, these rocks can be regarded as belonging to the volcanic arc collision stage of the Eastern Desert of Egypt formed between 665 and 614 Ma (Moghazi 2002).…”

Section: Geochemistrymentioning

confidence: 99%

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Late Proterozoic older granitoids from the North Eastern desert of Egypt: petrogenesis and geodynamic implications

Mahallawi

Ahmed

2010

Arab J Geosci

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Major, trace, and REE data for three localities of calc-alkaline older granitoid rocks exposed in the north Eastern Desert of Egypt are presented. These rocks were selected to cover wide compositional spectrum of the Egyptian older granitoid varieties. They are petrographically represented by granodiorite, tonalite, quartz-diorite, and quartz-monzodiorite. The rocks are comparable with the peraluminous, unfractionated calc-alkaline suites and fall within the volcanic arc and I-type granite fields. So, they can be regarded as belonging to the volcanic arc collision stage (665-614 Ma).

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Neoproterozoic calc‐alkaline peraluminous granitoids of the Deleihimmi pluton, Central Eastern Desert, Egypt: implications for transition from late‐ to post‐collisional tectonomagmatic evolution in the northern Arabian–Nubian Shield

et al. 2011

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The widely distributed late-collisional calc-alkaline granitoids in the northern Arabian-Nubian Shield (ANS) have a geodynamic interest as they represent significant addition of material into the ANS juvenile crust in a short time interval . The Deleihimmi granitoids in the Egyptian Central Eastern Desert are, therefore, particularly interesting since they form a multiphase pluton composed largely of latecollisional biotite granitoids enclosing granodiorite microgranular enclaves and intruded by leuco-and muscovite granites. Geochemically, different granitoid phases share some features and distinctly vary in others. They display slightly peraluminous (ASI ¼ 1-1.16), non-alkaline (calc-alkaline and highly fractionated calc-alkaline), I-type affinities. Both biotite granitoids and leucogranites show similar rare earth element (REE) patterns [(La/Lu) N ¼ 3.04-2.92 and 1.9-1.14; Eu/Eu Ã ¼ 0.26-0.19 and 0.11-0.08, respectively) and related most likely by closed system crystal fractionation of a common parent. On the other hand, the late phase muscovite granites have distinctive geochemical features typical of rare-metal granites. They are remarkably depleted in Sr and Ba (4-35 and 13-18 ppm, respectively), and enriched in Rb (381-473 ppm) and many rare metals. Moreover, their REE patterns show a tetrad effect (TE 1,3 ¼ 1.13 and 1.29) and pronounced negative Eu anomalies (Eu/Eu Ã ¼ 0.07 and 0.08), implying extensive open system fractionation via fluid-rock interaction during the magmatic stage. Origin of the calc-alkaline granitoids by high degree of partial melting of mafic lower crust with subsequent crystal fractionation is advocated. The broad distribution of late-collisional calc-alkaline granitoids in the northern ANS is related most likely to large areal and intensive lithospheric delamination subsequent to slab break-off and crustal/mantle thickening. Such delamination caused both crustal uplift and partial melting of the remaining mantle lithosphere in response to asthenospheric uprise. The melts produced underplate the lower crust to promote its melting. The presence of microgranular enclaves, resulting from mingling of mantle-derived mafic magma with felsic crustalderived liquid, favours this process. The derivation of the late-phase rare-metal granites by open system fractionation via fluid interaction is almost related to the onset of extension above the rising asthenosphere that results in mantle degassing during the switch to post-collisional stage. Consequently, the switch from late-to post-collisional stage of crustal evolution in the northern ANS could be potentially significant not only geodynamically but also economically.

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Petrology and geochemistry of Pan-African granitoids, Kab Amiri area, Egypt - implications for tectonomagmatic stages in the Nubian Shield evolution

Cited by 71 publications

References 0 publications

Late Neoproterozoic alkaline magmatism in the Arabian–Nubian Shield: the postcollisional A-type granite of Sahara–Umm Adawi pluton, Sinai, Egypt

Late Neoproterozoic alkaline magmatism in the Arabian–Nubian Shield: the postcollisional A-type granite of Sahara–Umm Adawi pluton, Sinai, Egypt

Late Proterozoic older granitoids from the North Eastern desert of Egypt: petrogenesis and geodynamic implications

Neoproterozoic calc‐alkaline peraluminous granitoids of the Deleihimmi pluton, Central Eastern Desert, Egypt: implications for transition from late‐ to post‐collisional tectonomagmatic evolution in the northern Arabian–Nubian Shield

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