干旱区生态环境知识资源中心(Arid): The common origin and alteration history of the hypabyssal and volcanic phases of the Wadi Tarr albitite complex, southern Sinai, Egypt

Arid

DOI	10.1016/j.lithos.2018.12.015
	The common origin and alteration history of the hypabyssal and volcanic phases of the Wadi Tarr albitite complex, southern Sinai, Egypt
	Azer, Mokhles K.1; Gahian, Hisham A.2,3; Asimow, Paul D.4; Al-Kahtany, Khaled M.5
通讯作者	Azer, Mokhles K.
来源期刊	LITHOS
ISSN	0024-4937
EISSN	1872-6143
出版年	2019
卷号	324 页码:821-841
英文摘要	New data and interpretations are presented for the igneous albitites of the Wadi Tarr area, southern Sinai, Egypt The albitite masses are isolated in outcrop from any granitic intrusions and have intrusive contacts against the country rocks without any structural control. They have marginal zones of brecdas with jigsaw-fit angular clasts suggesting explosive, in-situ formation. The albitites are of two types: the western, medium-grained, hypabyssal albitite and the eastern, fine-grained porphyritic albitite. The field relations suggest emplacement at different levels in a magmatic cupola: the hypabyssal texture and steeply dipping slope of the upper contact of the western albitite imply deeper emplacement whereas the gently dipping contacts and porphyritic texture of the eastern albitite masses indicate that they define the probable location of the cupola apex. Both types of albitites consist of albite (92-97%) with minor amounts of quartz, K-feldspar and biotite. The accessory minerals include Fe-oxides, augite, sulphides, zircon, rutile, xenotime, titanite, allanite and monazite. The whole-rock compositions of the hypabyssal and porphyritic albitites are closely related, but the porphyritic type has lower abundances of Sr, Ba, Y, Nb, Th and Zr. We show that the hypabyssal and porphyritic albitites have a common petrogenetic origin, most likely as late-stage cumulates from a fractionating, strongly alkaline A-type magma, consistent with the compositions of the mafic minerals.The source magma was probably a tephritic liquid; we use MELTS models to show that only a sufficiently alkaline magma follows a differentiation path that both avoids quartz saturation and encounters the alkali feldspar solvus, reaching a residual liquid in equilibrium with highly sodic feldspar. Although the MELTS results show a chemically consistent means of forming igneous albitite, they are incomplete in that physical segregation mechanisms are still required to isolate the albite from mafic minerals and or a low-temperature aqueous alteration stage is needed to leach K from the feldspar. Alteration surrounding the Wadi Tarr albitites is extensive and dominated by alkali metasomatism similar to fenitization. Alteration in the marginal breccia zone of the albitite is dominated by precipitation of amphibole and carbonate in veins and in the breccia matrix, whereas the volcanic country rocks show replacement of feldspars by sericite, carbonate and epidote as well as vein carbonate. The altered volcanic country rocks show lower concentrations of Fe2O3, Sr, Cu, Pb, Ba and Ce, accompanied by higher concentrations of Na2O and MgO compared to unaltered equivalent samples. (C) 2018 Elsevier B.V. All rights reserved.
英文关键词	Albitite Fenitization Sodic amphibole Cupola Intrusive carbonate Sinai Arabian-Nubian Shield
类型	Article
语种	英语
国家	Egypt ; Saudi Arabia ; USA
开放获取类型	Green Accepted
收录类别	SCI-E
WOS记录号	WOS:000457819800053
WOS关键词	ARABIAN-NUBIAN SHIELD ; KATHERINA RING COMPLEX ; A-TYPE GRANITES ; CALC-ALKALINE ; CLINOPYROXENE COMPOSITION ; SEDIMENTARY SUCCESSIONS ; EASTERN DESERT ; CORE COMPLEX ; EVOLUTION ; PENINSULA
WOS类目	Geochemistry & Geophysics ; Mineralogy
WOS研究方向	Geochemistry & Geophysics ; Mineralogy
来源机构	King Saud University
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/217511
作者单位	1.Natl Res Ctr, Geol Sci Dept, Cairo, Egypt; 2.King Saud Univ, Dept Geol & Geophys, Riyadh 11451, Saudi Arabia; 3.Assiut Univ, Geol Dept, Assiut 71516, Egypt; 4.CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA; 5.King Saud Univ, Coll Sci, Seism Studies Ctr, Riyadh, Saudi Arabia
推荐引用方式 GB/T 7714	Azer, Mokhles K.,Gahian, Hisham A.,Asimow, Paul D.,et al. The common origin and alteration history of the hypabyssal and volcanic phases of the Wadi Tarr albitite complex, southern Sinai, Egypt[J]. King Saud University,2019,324:821-841.
APA	Azer, Mokhles K.,Gahian, Hisham A.,Asimow, Paul D.,&Al-Kahtany, Khaled M..(2019).The common origin and alteration history of the hypabyssal and volcanic phases of the Wadi Tarr albitite complex, southern Sinai, Egypt.LITHOS,324,821-841.
MLA	Azer, Mokhles K.,et al."The common origin and alteration history of the hypabyssal and volcanic phases of the Wadi Tarr albitite complex, southern Sinai, Egypt".LITHOS 324(2019):821-841.