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DOI | 10.1016/j.gr.2017.09.001 |
Peridotite-chromitite complexes in the Eastern Desert of Egypt: Insight into Neoproterozoic sub-arc mantle processes | |
Khedr, Mohamed Zaki1; Arai, Shoji2 | |
通讯作者 | Khedr, Mohamed Zaki |
来源期刊 | GONDWANA RESEARCH
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ISSN | 1342-937X |
EISSN | 1878-0571 |
出版年 | 2017 |
卷号 | 52页码:59-79 |
英文摘要 | Neoproterozoic peridotite-chromitite complexes in the Central Eastern Desert of Egypt, being a part of the Arabian-Nubian Shield, are outcropped along the E-W trend from Wadi Sayfayn, Wadi Bardah, and Jabal Al-Faliq to Wadi Al-Barramiyah, from east to west. Their peridotites are completely serpentinized, and the abundance of bastite after orthopyroxene suggests harzburgite protoliths with subordinate dunites, confirmed by low contents of Al2O3, CaO and clinopyroxene (<3 vol%) in bulk peridotites. The primary olivine is F089.3-Fo92.6, and the residual clinopyroxene (Cpx) in serpentinites contains, on average, 1.1 wt% Al2O3, 0.7 wt% Cr2O3, and 0.2 wt% Na2O, similar in chemistry to that in Izu-Bonin-Marian forearc peridotites. The wide range of spinel Cr-number [Cr/(Cr + Al)], 0.41-0.80, with low TiO2 (0.03 wt%), MnO (0.3 wt%) and Y-Fe [(Fe3+/(Cr + Al + Fe3+) = 0.03 on average)] for the investigated harzburgites-dunites is similar to spinel compositions for arc-related peridotites. The partial melting degrees of Bardah and Sayfayn harzburgites range mainly from 20 to 25% and 25 to 30% melting, respectively; this is confirmed by whole-rock chemistry and Cpx HREE modelling (similar to 20% melting). The Barramiyah peridotite protoliths are refractory residues after a wide range of partial melting, 25-40%, where more hydrous fluids are available from the subducting slab. The Neoproterozoic mantle heterogeneity is possibly ascribed mainly to the wide variations of partial melting degrees in small-scale areas, slab-derived inputs and primordial mantle compositions. The Sayfayn chromitites were possibly crystallized from island-arc basaltic melts, followed by crystallization of Barramiyah chromitites from boninitic melt in the late stage of subduction. The residual Cpx with a spoon-shape REE pattern is rich in both LREE and fluid-mobile elements (e.g., Pb, B, Li, Ba, Sr), but poor in HFSE (e.g., Ta, Nb, Zr, Th), similar to Cpx in supra-subduction zone (SSZ) settings, where slab-fluid metasomatism is a prevalent agent. The studied chromitites and their host peridotites represent a fragment of sub-arc mantle, and originated in an arc-related setting. The systematic increase in the volume of chromitite pods with the increasing of their host-peridotite thickness from Northern to Southern Eastern Desert suggests that the thickness of wall rocks is one factor controlling the chromitite size. The factors controlling the size of Neoproterozoic chromitite pods are the thickness, beside the composition, of the host refractory peridotites, compositions and volumes of the supplied magmas, the amount of slab-derived fluids, and possibly the partial melting degree of the host peridotites. (C) 2017 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. |
英文关键词 | Podiform chromitite sizes Harzburgites Clinopyroxene Sub-arc mantle processes Neoproterozoic ophiolites |
类型 | Article |
语种 | 英语 |
国家 | Egypt ; Japan |
收录类别 | SCI-E |
WOS记录号 | WOS:000416498500005 |
WOS关键词 | TRACE-ELEMENT TRANSFER ; ARABIAN-NUBIAN SHIELD ; MELT-ROCK INTERACTION ; SLAB-DERIVED FLUIDS ; MARIANA FORE-ARC ; PODIFORM CHROMITITES ; OMAN OPHIOLITE ; ABYSSAL PERIDOTITES ; ULTRAMAFIC ROCKS ; HAPPO-ONE |
WOS类目 | Geosciences, Multidisciplinary |
WOS研究方向 | Geology |
资源类型 | 期刊论文 |
条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/199391 |
作者单位 | 1.Kafrelsheikh Univ, Dept Geol, Fac Sci, Kafrelsheikh 33516, Egypt; 2.Kanazawa Univ, Dept Earth Sci, Grad Sch Nat Sci & Technol, Kanazawa, Ishikawa 9201192, Japan |
推荐引用方式 GB/T 7714 | Khedr, Mohamed Zaki,Arai, Shoji. Peridotite-chromitite complexes in the Eastern Desert of Egypt: Insight into Neoproterozoic sub-arc mantle processes[J],2017,52:59-79. |
APA | Khedr, Mohamed Zaki,&Arai, Shoji.(2017).Peridotite-chromitite complexes in the Eastern Desert of Egypt: Insight into Neoproterozoic sub-arc mantle processes.GONDWANA RESEARCH,52,59-79. |
MLA | Khedr, Mohamed Zaki,et al."Peridotite-chromitite complexes in the Eastern Desert of Egypt: Insight into Neoproterozoic sub-arc mantle processes".GONDWANA RESEARCH 52(2017):59-79. |
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