Geochemistry and tectonic evolution of the Neoproterozoic Wadi Ghadir ophiolite, Eastern Desert, Egypt

El‐Rahman, Yasser Abd; Polat, Ali; Dilek, Yıldırım; Fryer, Brian J.; El-Sharkawy, Mohamed; Sakran, Shawki

doi:10.1016/j.lithos.2008.12.014

Cited by 93 publications

(28 citation statements)

References 69 publications

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“…10) and Na do not correlate well with Zr suggesting the modification of their magmatic concentrations by post-magmatic alteration. These results are consistent with previous study on Wadi Ghadir ophiolitic metabasalt (Abd El-Rahman et al, 2009). Although the concentrations of LIL elements of the Wadi Ghadir basalts were modified by alteration and metamorphism, it can be inferred that the magmatic concentrations of these elements were enriched relative to N-MORB by analogy with the enrichment of these rocks in LREE.…”

Section: Element Mobility During Seafloor Hydrothermal Alterationsupporting

confidence: 92%

“…Consequently, the Wadi Ghadir ophiolitic metabasalts, with Zr/Nb ratios mostly between 23 and 30, are more akin to N-MORB. More recently, Abd El-Rahman et al (2009) reported even higher Zr/Nb ratios (37-50 for amygdaloidal pillowed basalt and 22-52 for ''D1'' dikes) and interpreted the LREE-enriched tholeiitic pillowed basalts and ''D1'' dikes of Wadi Ghadir ophiolite to be derived from fertile N-MORB source. The high Zr/Nb ratios, the low initial 87 Sr/ 86 Sr ratios and the high positive e Nd(t) values reported in the present study support that these rocks were derived from a depleted mantle source.…”

Section: Classification Geochemical Characteristics and Tectonic Setmentioning

confidence: 99%

“…These ophiolites are interpreted to be formed in back-arc (e.g. Basta et al, 1983;Berhe, 1990;El-Sayed et al, 1999;Takla et al, 2002;Abd El-Rahman et al, 2009), or fore-arc setting (Azer and Stern, 2007). Among the ANS ophiolites, the Gerf complex is the only Precambrian ophiolite with N-MORB chemistry, where the pillowed basalts and sheeted dikes originally formed in a major ocean basin (Zimmer et al, 1995).…”

Section: Introductionmentioning

confidence: 99%

“…The ophiolitic metavolcanics of Wadi Ghadir are interpreted to be developed at oceanic spreading centers (El-Bayoumi, 1980), in back-arc setting (Basta, 1983;Abd El-Rahman et al, 2009), or in continental back-arc basin (Farahat et al, 2004). El-Bayoumi (1980) suggested that Wadi Ghadir basalts are more differentiated than typical MORB and believed that they are plume basalts which originated from stratified and enriched low velocity zone at the initiation of spreading.…”

Section: Introductionmentioning

confidence: 99%

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Neoproterozoic contaminated MORB of Wadi Ghadir ophiolite, NE Africa: Geochemical and Nd and Sr isotopic constraints

Basta

Maurice

Bakhit

et al. 2011

Journal of African Earth Sciences

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Section: Element Mobility During Seafloor Hydrothermal Alterationsupporting

confidence: 92%

Section: Classification Geochemical Characteristics and Tectonic Setmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Neoproterozoic contaminated MORB of Wadi Ghadir ophiolite, NE Africa: Geochemical and Nd and Sr isotopic constraints

Basta

Maurice

Bakhit

et al. 2011

Journal of African Earth Sciences

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“…However, the tectonic setting and evolution of the ANS ophiolites are controversial topics of research, a variety of tectonomagmatic scenarios has been proposed, including: (i) back-arc basins (e.g. Bakor et al 1976;Kröner 1985;Pallister et al 1988;Ahmed et al 2001;Farahat et al 2004;Abd El-Rahman et al 2009a); (ii) mid-ocean ridges (MOR) (e.g. Zimmer et al 1995;Khalil 2007); or (iii) forearcs (e.g.…”

Section: Introductionmentioning

confidence: 99%

The Neoproterozoic Abu Dahr ophiolite, South Eastern Desert, Egypt: petrological characteristics and tectonomagmatic evolution

2015

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The Neoproterozoic Abu Dahr ophiolite, South Eastern Desert, Egypt, is one of the best preserved and least dismembered ophiolite successions in the Arabian-Nubian Shield. It contains a Penrose-type ophiolite sequence from mantle section below mafic crust upward to oceanic sedimentary cover overlying mafic volcanics, although the original magmatic (stratigraphic) contact between the mantle and crustal sections is disrupted by tectonism. The Abu Dahr ophiolite is metamorphosed under greenschist facies conditions, and low-temperature alteration is widespread. Petrography reveals that: (i) the mantle is homogenous, serpentinized, and dominated by harzburgite and less abundant dunite; (ii) the cumulate ultramafics are represented by wehrlite and pyroxenite; and (iii) the crustal section is represented by metagabbros, meta-anorthosites and metabasalts. The Abu Dahr serpentinized peridotites show high Mg# (0.92-0.93), with enrichment of Ni, Cr and Co, and depletion of Al 2 O 3 and CaO, and nearly flat and unfractionated REE chondrite-normalized pattern. Major and trace element characteristics of the Abu Dahr metagabbro and metabasalt (crustal section) indicate a tholeiitic to calc-alkaline affinity. Units of the crustal section have low-Nb and Zr concentrations, low Dy/Yb and relatively elevated La/Yb ratios, high U/Yb and Th/Yb ratios, and LREE enriched chondrite-normalized pattern. All of the Abu Dahr ophiolite units have trace-element signatures characterized by enrichment of LILE over HFSE. Rare and trace element patterns indicate a genetic link between the Abu Dahr mantle, cumulate ultramafics, and crust. Chromian spinel has survived metamorphism and is used as a petrogenetic indicator in the Abu Dahr serpentinized peridotites. The spinel is homogeneous with a limited composition, and shows high-Cr# (>0.6) combined with low-TiO 2 character (mostly <0.1 wt.%). The Abu Dahr ophiolite is interpreted as a fragment of depleted oceanic lithosphere that experienced high degrees of partial melting (up to 35 %) and originated in a fore-arc setting. Such interpretation contributes to the body of evidence suggesting that tectonomagmatic processes of the Neoproterozoic were largely similar to those of the Phanerozoic, implying little, or no significant, change in the geothermal regime of Earth since the Neoproterozoic.

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Mineralogy of a rare Ediacaran epidote‐bearing trondhjemitic complex from the Nubian Shield: Insights into P‐T conditions of magma emplacement

Abdel‐Rahman

Shwairi

2022

Geological Journal

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Igneous epidote occurring in tonalite–trondhjemite–granodiorite (TTG) rocks provides valuable insight into the physiochemical parameters of their magmatic system. Epidote has been identified within a newly discovered, rare, Ediacaran, high‐Al TTG‐suite at the Fannani Igneous Complex (FIC), Nubian Shield. The objective is to assess P–T conditions of magma emplacement using petrographic‐, mineral chemical data, and thermobarometry methods. The TTG‐suite is made up of ubiquitous oligoclase, variable contents of quartz, K‐feldspar, amphibole, biotite, epidote, accessory titanite, zircon, apatite and magnetite. Feldspars vary from An14 to An26 in plagioclase, with K‐feldspar having near‐end‐member compositions (Or91–Or95). Amphiboles are Al‐rich (AlT = 1.65–2.04 atoms per formula unit [apfu]), calcic (Ca = 1.83–1.93, apfu), with average Mg/(Fe + Mg) of 0.44, and are ferroedenite–edenite–ferropargasite. Biotites are moderately Fe‐rich (Fe/(Fe + Mg) = 0.50–0.58) characteristic of type ‘C’–biotite of calc–alkaline orogenic rocks. Epidote exhibits pistacite components [Ps = Fe3+/(Fe3++Al)] of Ps24–Ps33, typical of magmatic epidote. The average crystallization pressure of 5.41 kbar (calculated using the Al‐in‐Hb barometer) is consistent with the presence of magmatic epidote and reflects the mesozonal crustal levels of emplacement. The Hb–Plag–geothermometer produced an average crystallization temperature of 721°C. These values fall within experimentally‐determined P–T ranges of stability of magmatic epidote with fO2 buffered from nickel‐nickel‐oxide (NNO) to hematite (HM). The FIC rocks were developed from a wet, subsolvus, orogenic, Al‐rich magmatic system. Findings reported here could have implications for conditions of magma emplacement and mineralogical characterization of TTGs occurring within various continental masses.

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Geochemistry and tectonic evolution of the Neoproterozoic Wadi Ghadir ophiolite, Eastern Desert, Egypt

Cited by 93 publications

References 69 publications

Neoproterozoic contaminated MORB of Wadi Ghadir ophiolite, NE Africa: Geochemical and Nd and Sr isotopic constraints

Neoproterozoic contaminated MORB of Wadi Ghadir ophiolite, NE Africa: Geochemical and Nd and Sr isotopic constraints

The Neoproterozoic Abu Dahr ophiolite, South Eastern Desert, Egypt: petrological characteristics and tectonomagmatic evolution

Mineralogy of a rare Ediacaran epidote‐bearing trondhjemitic complex from the Nubian Shield: Insights into P‐T conditions of magma emplacement

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