Knowledge Resource Center for Ecological Environment in Arid Area
DOI | 10.1016/j.lithos.2014.01.006 |
Banded iron formations of Urn Nar, Eastern Desert of Egypt: P-T-X conditions of metamorphism and tectonic implications | |
El-Shazly, A. K.1; Khalil, K. I.2 | |
通讯作者 | El-Shazly, A. K. |
来源期刊 | LITHOS
![]() |
ISSN | 0024-4937 |
EISSN | 1872-6143 |
出版年 | 2014 |
卷号 | 196页码:356-375 |
英文摘要 | Banded iron formations (BIF) in Um Nar, central eastern desert of Egypt, occur intercalated with schists of volcaniclastic and epiclastic origins within "ophiolitic-island arc rocks" of the Arabo-Nubian Shield. The BIF and its host rocks were affected by folding, thrusting, and regional metamorphism during the Pan-African Orogeny resulting in the development of north-verging overturned folds and E-W striking, S-dipping thrusts. Following the intrusion of granitoids, the entire sequence was refolded into south-plunging folds with NW-SE trending fold axes. Peak mineral assemblages of hornblende + plagioclase, and garnet + biotite + plagioclase + quartz in the host rocks, and andradite-rich garnet + epidote + hematite + magnetite + quartz in the BIF indicate metamorphism under epidote amphibolite facies conditions. Using the multiequilibrium approach of Thermocalc, and conventional thermobarometry, peak P-T conditions of metamorphism are estimated at 520 +/- 30 degrees C, 5 +/- 2 kbar. Fluids attending peak conditions in the oxide facies layers of the BIF were characterized by XCO2 similar to 0.03 and log fO(2) similar to -40. Textural and mineral chemical criteria suggest that, following peak conditions, the rocks underwent a stage of near-isobaric cooling or cooling and compression characteristic of a counter-clockwise P-T path. These results are consistent with a model in which the BIFs formed by hydrothermal activity from off-axis submarine vents in several pulses during a protracted event of oceanic crust generation in an inter-arc basin. Concomitant arc volcanism supplied the basin with pyroclastic material that imposed suboxic conditions on the basin leading to increased concentrations of soluble Fe2+. During periods of arc quiescence, Fe2+ was likely oxidized, leading to deposition of several layers of BIF. During the Pan-African Orogeny, the BIFs, tuffs, oceanic crust and lithospheric mantle were deformed and metamorphosed while being emplaced onto the continental margin. (C) 2014 Elsevier B.V. All rights reserved. |
英文关键词 | Banded iron formation Central Eastern Desert of Egypt Epidote amphibolite facies metamorphism Thermobarometry Fluid composition Tectonic evolution |
类型 | Article |
语种 | 英语 |
国家 | USA ; Egypt |
收录类别 | SCI-E |
WOS记录号 | WOS:000336347800023 |
WOS关键词 | ARABIAN-NUBIAN SHIELD ; CORE COMPLEX ; NEOPROTEROZOIC TECTONICS ; CRUSTAL EVOLUTION ; GEOCHEMISTRY ; CONSTRAINTS ; BIF ; GEOTHERMOMETRY ; ASSEMBLAGES ; SPREADSHEET |
WOS类目 | Geochemistry & Geophysics ; Mineralogy |
WOS研究方向 | Geochemistry & Geophysics ; Mineralogy |
资源类型 | 期刊论文 |
条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/183798 |
作者单位 | 1.Marshall Univ, Dept Geol, Huntington, WV 25755 USA; 2.Univ Alexandria, Fac Sci, Dept Geol, Moharram Bey, Egypt |
推荐引用方式 GB/T 7714 | El-Shazly, A. K.,Khalil, K. I.. Banded iron formations of Urn Nar, Eastern Desert of Egypt: P-T-X conditions of metamorphism and tectonic implications[J],2014,196:356-375. |
APA | El-Shazly, A. K.,&Khalil, K. I..(2014).Banded iron formations of Urn Nar, Eastern Desert of Egypt: P-T-X conditions of metamorphism and tectonic implications.LITHOS,196,356-375. |
MLA | El-Shazly, A. K.,et al."Banded iron formations of Urn Nar, Eastern Desert of Egypt: P-T-X conditions of metamorphism and tectonic implications".LITHOS 196(2014):356-375. |
条目包含的文件 | 条目无相关文件。 |
除非特别说明,本系统中所有内容都受版权保护,并保留所有权利。