干旱区生态环境知识资源中心(Arid): Petrology and Geochemistry of Some Ophiolitic Metaperidotites from the Eastern Desert of Egypt: Insights into Geodynamic Evolution and Metasomatic Processes

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	Petrology and Geochemistry of Some Ophiolitic Metaperidotites from the Eastern Desert of Egypt: Insights into Geodynamic Evolution and Metasomatic Processes
	Abdel-Karim Abdel Aal M; Azer Mokhles K; El-Shafei Shaimaa A
来源期刊	Acta Geologica Sinica
ISSN	1000-9515
出版年	2021
卷号	95 期号:4 页码:1139-1157
英文摘要	Ophiolitic peridotites exposed in the Eastern Desert (ED) of Egypt record multiple stages of evolution, including different degrees of partial melting and melt extraction, serpentinization, carbonatization and metamorphism. The present study deals with metaperidotites at two selected localities in the central and southern ED, namely Wadi El-Naba and Wadi Ghadir, respectively. They represent residual mantle sections of a Neoproterozoic dismembered ophiolite that tectonically emplaced over a volcano-sedimentary succession that represents island-arc assemblages. The studied metaperidotites are serpentinized, with the development of talc-carbonate and quartz-carbonate rocks, especially along shear and fault planes. Fresh relics of primary minerals (olivine, orthopyroxene and Cr-spinel) are preserved in a few samples of partiallyserpentinized peridotite. Most of the Cr-spinel crystals have fresh cores followed by outer zones of ferritchromite and Crmagnetite, which indicates that melt extraction from the mantle protolith took place under oxidizing conditions. The protoliths of the studied metaperidotites were dominated by harzburgites, which is supported by the abundance of mesh and bastite textures in addition to some evidence from mineral and whole-rock chemical compositions. The high Cr~# (0.62-0.69; Av. 0.66) and low TiO_2 (<0.3 wt%) contents of the fresh Cr-spinels, the higher Fo (89-92; Av. 91) and NiO (0.24-0.54 wt%, Av. 0.40) contents of the primary olivine relics, together with the high Mg~# (0.91-0.93; Av. 91) and low CaO, Al_2O_3 and TiO_2 of the orthopyroxene relics, are all comparable with depleted to highly depleted forearc harzburgite from a suprasubduction zone setting. The investigated peridotites have suffered subsequent phases of metasomatism, from oceanfloor hydrothermal alteration (serpentinization) to magmatic hydrothermal alteration. The enrichment of the studied samples in light rare earth elements (LREEs) relative to the heavy ones (HREEs) is attributed to most probably be due to the contamination of their mantle source with granitic source hydrothermal fluids after the obduction of the ophiolite assemblage onto the continental crust. The examined rocks represent mantle residue that experienced different degrees of partial melting (~10% to 25% for W. El-Naba rocks and ~5% to 23% for W. Ghadir rocks). Variable degrees of partial melting among the two investigated areas suggest mantle heterogeneity beneath the Arabian-Nubian Shield (ANS).
英文关键词	ophiolitic metaperidotites partial melting melt extraction geodynamic evolution Eastern Desert Egypt
类型	Article
语种	英语
收录类别	CSCD
WOS类目	Geology
CSCD记录号	CSCD:7032107
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/377393
作者单位	Abdel-Karim Abdel Aal M, Geology Department, Faculty of Science, Zagazig University, Zagazig, 44519, Egypt.; El-Shafei Shaimaa A, Geology Department, Faculty of Science, Zagazig University, Zagazig, 44519, Egypt.; Azer Mokhles K, Geological Sciences Department, National Research Centre, Cairo, 12622, Egypt.
推荐引用方式 GB/T 7714	Abdel-Karim Abdel Aal M,Azer Mokhles K,El-Shafei Shaimaa A. Petrology and Geochemistry of Some Ophiolitic Metaperidotites from the Eastern Desert of Egypt: Insights into Geodynamic Evolution and Metasomatic Processes[J],2021,95(4):1139-1157.
APA	Abdel-Karim Abdel Aal M,Azer Mokhles K,&El-Shafei Shaimaa A.(2021).Petrology and Geochemistry of Some Ophiolitic Metaperidotites from the Eastern Desert of Egypt: Insights into Geodynamic Evolution and Metasomatic Processes.Acta Geologica Sinica,95(4),1139-1157.
MLA	Abdel-Karim Abdel Aal M,et al."Petrology and Geochemistry of Some Ophiolitic Metaperidotites from the Eastern Desert of Egypt: Insights into Geodynamic Evolution and Metasomatic Processes".Acta Geologica Sinica 95.4(2021):1139-1157.