Neoproterozoic ophiolitic peridotites along the Allaqi-Heiani suture, South Eastern Desert, Egypt

Azer, Mokhles K.; Samuel, M.D.; Ali, Kamal A.; Gahlan, Hisham A.; Stern, Robert J.; Ren, Minghua; Moussa, Hilmy E.

doi:10.1007/s00710-012-0204-z

Cited by 52 publications

(12 citation statements)

References 68 publications

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“…Thus, although Zimmer et al (1995) inferred an open-ocean mid-ocean ridge tectonic setting for the Gerf ophiolites in the south Eastern Desert of Egypt, the past two decades have seen the development of a mounting consensus that all the ophiolitic rocks of Eastern Desert of Egypt formed in subduction-related settings (e.g., El Sayed et al 1999;Ahmed et al 2001;Farahat et al 2004;Azer and Khalil 2005;Azer and Stern 2007). At a finer level of detail, while the majority of recent studies of serpentinites throughout the Eastern Desert have assigned their origin to forearc settings (e.g., Azer and Stern 2007;Khalil and Azer 2007;Abd El-Rahman et al 2009;Azer et al 2013;Hamdy et al 2013;Khedr and Arai 2013;Khalil et al 2014;Gahlan et al 2015;Obeid et al 2016), a few ophiolitic outcrops continue to be assigned to backarc settings on the basis of the transitional geochemical character of their volcanic sequences, between those of island arcs and mid-ocean ridges (e.g., El Sayed et al 1999;Farahat et al 2004;Abd El-Rahman et al 2009;Basta et al 2011).…”

Section: Discussionmentioning

confidence: 99%

“…The whole-rock Mg# of massive serpentinite samples ranges between 0.91 and 0.92, higher than that of serpentinite-hosted magnesite samples (0.89-0.91), suggesting that there is depletion of Mg, addition of Fe, or both during carbonation. On the other hand, the serpentinites from the GMA area have, on the whole, a range of Mg# (0.89-0.92) con-sistent with the Mg# of modern oceanic peridotites (Mg# > 0:89; Bonatti and Michael 1989) and similar to that of other ophiolites in the Eastern Desert of Egypt (e.g., Azer et al 2013;Khalil et al 2014;Gahlan et al 2015;Obeid et al 2016). It is rare to be able to compare serpentinized peridotites to fresh peridotites to assess whether serpentinization itself, though obviously accompanied by mineral-scale redistribution of Mg and Fe, is accompanied by metasomatic alteration of whole-rock Mg#.…”

Section: Mineral Chemistrymentioning

confidence: 99%

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Multiple Stages of Carbonation and Element Redistribution during Formation of Ultramafic-Hosted Magnesite in Neoproterozoic Ophiolites of the Arabian-Nubian Shield, Egypt

Azer

Gahlan

Asimow

et al. 2019

The Journal of Geology

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We present a study of the serpentinized peridotites of the Ghadir-Mohagar-Ambaut area, Egypt. They represent the mantle section of a dismembered ophiolite, tectonically emplaced over a volcanosedimentary succession of island arc assemblages. The serpentinites are variably metamorphosed from greenschist to lower-amphibolite facies, metasomatized, and altered, including development of talc-carbonate and quartz-carbonate rocks, especially along shear zones and fault planes. Nevertheless, some samples contain relics of primary chromian spinel, olivine, and pyroxenes. Relict textures and whole-rock compositions (Mg# ½molar Mg=(Mg 1 Fe 21 ) p 0:92-0:93, with low Al 2 O 3 and CaO contents) both suggest harzburgite protoliths. The high Mg# and Ni contents of relict olivine and the high Cr# (molar Cr=(Cr 1 Al)) of fresh chromian spinel cores indicate that the protoliths experienced high degrees of partial melt extraction (∼34%-39%), well beyond the limit for exhaustion of clinopyroxene from the residue and consistent with formation in a forearc suprasubduction zone environment. The serpentinized ultramafic rocks in the study area are divided into massive serpentinite, serpentinitehosted magnesite masses, and magnesite-filled veins. The carbonation and formation of magnesite ores took place through two metasomatic stages; the first is represented by the magnesite masses and associated with deep-seated metasomatism and alteration during serpentinization, whereas the second, vein-forming stage postdates serpentinization and occurred during obduction of the ophiolite. The differences in chemical composition between massive serpentinite and serpentinitehosted magnesite masses suggest leaching of some elements and enrichment of others during carbonation; MgO, Cr, and Ni are depleted, whereas Fe 2 O 3 , CaO, MnO, Nb, Ba, Cu, Pb, Sr, and Zn are enriched in the serpentinite-hosted magnesite masses, relative to the host massive serpentinite.

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Section: Discussionmentioning

confidence: 99%

Section: Mineral Chemistrymentioning

confidence: 99%

Multiple Stages of Carbonation and Element Redistribution during Formation of Ultramafic-Hosted Magnesite in Neoproterozoic Ophiolites of the Arabian-Nubian Shield, Egypt

Azer

Gahlan

Asimow

et al. 2019

The Journal of Geology

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“…El Sayed et al 1999;Farahat et al 2004;Abd El-Rahman et al 2009;Basta et al 2011). A fore-arc setting has rarely been considered for the ophiolites (Azer and Stern 2007;Khalil and Azer 2007;Abd El-Rahman et al 2009;Hamdy et al 2013;Khedr and Arai 2013;Azer et al 2013).…”

Section: Tectonic Setting and Petrogenesismentioning

confidence: 99%

“…The ultramafic rocks of the ANS ophiolites are essentially represented by harzburgites and dunites (e.g. Farahat et al 2011;Azer et al 2013). On the other hand, the ultramafic rocks of layered mafic-ultramafic intrusions show a wide variation in rock types, including wehrlite, dunite, lherzolite and pyroxenites with minor harzburgite.…”

Section: Correlations With Other Late Neoproterozoic Ultramafic Rocksmentioning

confidence: 99%

Petrological studies of neoproterozoic serpentinized ultramafics of the nubian shield: spinel compositions as evidence of the tectonic evolution of egyptian ophiolites

Azer¹

2014

Acta Geologica Polonica

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The mafic-ultramafic rocks of the Gabal El-Degheimi area, Central Eastern Desert of Egypt, are parts of an ophiolitic section. The ophiolitic rocks are dismembered and tectonically enclosed within, or thrust over, island arc assemblages. Serpentinites, altered slices of the upper mantle, represent a distinctive lithology of the dismembered ophiolites. Some portions of the serpentinized rocks contain fresh relicts of primary minerals such as chromian spinel and olivine. The abundance of bastite and mesh textures suggests harzburgite and dunite protoliths, respectively, for these serpentinites. Some fresh cores of chromian spinel are rimmed by ferritchromite and Cr-magnetite. The development of alteration rims around chromian spinel cores indicates their formation during prograde alteration and under oxidizing conditions during lower amphibolite facies metamorphism. Fresh chromian spinels are characterized by high contents of Cr2O3 (48.92-56.74 wt. %), Al2O3 (10.29-20.08wt. %), FeO (16.24-28.46 wt. %) and MgO (4.89-14.02 wt. %), and very low TiO2 contents (<0.16 wt. %). The analyzed fresh chromian spinels have high Cr# (0.62-0.79) characteristic of spinels in mantle peridotite that has undergone some degree of partial melting. The data presented here suggest that the mantle peridotites of the Gabal El-Degheimi area are similar to forearc peridotites of suprasubduction zone environments.

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“…(9) Lenz et al (2013) present the first major and trace compositions, as well as Sm and Pb isotopic signatures form the Cerro Bori orthogneisses in the Dom Feliciano Belt. Ophiolitic rocks of the Arabian-Nubian Shield are studied by (10) Khedr and Arai (2013) and (11) Azer et al (2013).…”

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confidence: 99%

Gondwana collision

et al. 2013

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Neoproterozoic ophiolitic peridotites along the Allaqi-Heiani suture, South Eastern Desert, Egypt

Cited by 52 publications

References 68 publications

Multiple Stages of Carbonation and Element Redistribution during Formation of Ultramafic-Hosted Magnesite in Neoproterozoic Ophiolites of the Arabian-Nubian Shield, Egypt

Multiple Stages of Carbonation and Element Redistribution during Formation of Ultramafic-Hosted Magnesite in Neoproterozoic Ophiolites of the Arabian-Nubian Shield, Egypt

Petrological studies of neoproterozoic serpentinized ultramafics of the nubian shield: spinel compositions as evidence of the tectonic evolution of egyptian ophiolites

Gondwana collision

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