干旱区生态环境知识资源中心(Arid): Geochemistry of banded iron formations and their host rocks from the Central Eastern Desert of Egypt: A working genetic model and tectonic implications

Arid

DOI	10.1016/j.precamres.2019.02.011
	Geochemistry of banded iron formations and their host rocks from the Central Eastern Desert of Egypt: A working genetic model and tectonic implications
	El-Shazly, A. K.1; Khalil, K. I.2; Helba, H. A.2
通讯作者	El-Shazly, A. K.
来源期刊	PRECAMBRIAN RESEARCH
ISSN	0301-9268
EISSN	1872-7433
出版年	2019
卷号	325 页码:192-216
英文摘要	Banded iron formations (BIF) occur intercalated with Neoproterozoic volcanosedimentary units in 13 localities in the Egyptian Central Eastern Desert (CED). These units are characterized by magnetite and hematite-rich layers alternating with quartz-rich layers containing andradite-rich garnet, epidote, +/- calcite in the southern parts of CED, and chlorite +/- stilpnomelane, and calcite in the north. Localized hydrothermal alteration affected most deposits and is manifested by secondary Ca-bearing minerals. All BIFs and their host rocks were strongly deformed and metamorphosed under greenschist to epidote amphibolite facies conditions during the collisional stage of the Pan African orogeny. Geochemically, CED BIFs have higher Fe/Si compared to Algoma, Superior, or Rapitan BIF types. All BIFs have rare earth element - Y patterns similar to those of modern day oceanic water, with a few samples displaying a weak positive Eu anomaly. All BIFs have high SiO2/Al2O3 and Fe/Ti, and low Al/(Al + Fe + Mn), which suggest a hydrogenous origin with hydrothermal contributions and low detrital component. Geochemical trends, Y/Ho, and Pr/Yb values suggest deposition of Wadi El Dabbah BIF closest to land and Urn Nar and Wadi Kareim closest to hydrothermal vents. Host metavolcanic and metavolcaniclastic rocks show chemical signatures indicative of an immature oceanic arc setting with MORB affinities for the southern areas and back- or fore-arc basin affinities for the northern localities. These results lead to the conclusion that CED BIFs and their host rocks formed in small intra-arc basins and sloped or terraced silled basins in the back- and fore-arc areas surrounding an immature island arc. Restricted circulation of hydrothermal fluids in these basins concomitant with arc volcanism increased Fe+2 and Si in solution. During periods of arc quiescence, oxidation of Fe2+ led to deposition of Fe-oxyhydroxide. Diagenesis formed fine-grained magnetite, whereas subsequent hydrothermal alteration and metamorphism formed porphyroblastic magnetite and specularite.
英文关键词	Central Eastern Desert of Egypt Banded iron formation Thermobarometry Cathodoluminescence imaging U-Pb zircon ages Tectonic evolution
类型	Article
语种	英语
国家	USA ; Egypt
开放获取类型	Bronze
收录类别	SCI-E
WOS记录号	WOS:000463463800011
WOS关键词	RARE-EARTH-ELEMENTS ; VOLCANIC-ROCKS ; CRUSTAL EVOLUTION ; NEOPROTEROZOIC TECTONICS ; SETTING DISCRIMINATION ; LITHIUM BORATE ; CONSTRAINTS ; YTTRIUM ; ORIGIN ; MANTLE
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/2XILL650/218161
作者单位	1.Marshall Univ, Dept Geol, 1 John Marshall Dr, Huntington, WV 25755 USA; 2.Univ Alexandria, Fac Sci, Dept Geol, Alexandria, Egypt
推荐引用方式 GB/T 7714	El-Shazly, A. K.,Khalil, K. I.,Helba, H. A.. Geochemistry of banded iron formations and their host rocks from the Central Eastern Desert of Egypt: A working genetic model and tectonic implications[J],2019,325:192-216.
APA	El-Shazly, A. K.,Khalil, K. I.,&Helba, H. A..(2019).Geochemistry of banded iron formations and their host rocks from the Central Eastern Desert of Egypt: A working genetic model and tectonic implications.PRECAMBRIAN RESEARCH,325,192-216.
MLA	El-Shazly, A. K.,et al."Geochemistry of banded iron formations and their host rocks from the Central Eastern Desert of Egypt: A working genetic model and tectonic implications".PRECAMBRIAN RESEARCH 325(2019):192-216.