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DOI | 10.1016/j.chemer.2006.01.003 |
Chrome-spinels in serpentinites and talc carbonates of the El Ideid-El Sodmein District, central Eastern Desert, Egypt: their metamorphism and petrogenetic implications | |
Farahat, E. S. | |
通讯作者 | Farahat, E. S. |
来源期刊 | CHEMIE DER ERDE-GEOCHEMISTRY
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ISSN | 0009-2819 |
出版年 | 2008 |
卷号 | 68期号:2页码:193-205 |
英文摘要 | Serpentinites and talc-carbonate rocks of El Ideid-El Sodmein District (ISD), central Eastern Desert, Egypt, contain variably altered chrome-spinels. Back-scattered electron images and electron microprobe analyses of chrome-spinels and associated silicates are made to evaluate their textural and compositional variations with metamorphism. In most cases the chrome-spinel crystals are concentrically zoned with unaltered cores through transitional zone of ferritchromit to Cr-magnetite toward the rims. In talc-carbonate rocks chrome-spinels are extensively altered to Cr-magnetite. Compared to cores, the metamorphic rims are enriched in Cr# (0.83-1.0 vs. 0.58-0.63 for rims and cores, respectively) and impoverished in Mg# (0.05-0.29 vs. 0.57-0.63), due to Mg-Fe and Al(Cr)-Fe(3+) exchange with the surrounding silicates during regional metamorphism rather than serpentinization process. Textural and compositional features of the chrome-spinels suggest transitional greenschist-amphibolite up to lower amphibolite facies metamorphism (at similar to 500-600 degrees C,) which is isofacial with the country rocks. The common preservation of unaltered chrome-spinel cores in the serpentinites, contrary to talc-carbonate rocks, implies that full equilibration has not been attained due to small metamorphic fluid-rock ratio. Microprobe analyses profile across a concentrically zoned grain confirms the presence of two compositional (miscibility?) gaps; one between chrome-spinel core and ferritchromit zone; and another one between ferritchromit zone and Cr-magnetite outer rim. Chrome-spinel cores do not appear to have re-equilibrated completely with the metamorphic spinel rims and surrounding silicates, indicating relic magmatic composition not affected by metamorphism. Core compositions suggest an ophiolitic origin and derivation by high degrees of melting of reduced, depleted harzburgite to dunite mantle peridotites in an oceanic supra-subduction zone (marginal-basin) tectonic environment. (C) 2006 Elsevier GmbH. All rights reserved. |
英文关键词 | chrome-spinel alteration metamorphism neoproterozoic Pan-African ophiolities serpentinites Egypt |
类型 | Article |
语种 | 英语 |
国家 | Egypt |
收录类别 | SCI-E |
WOS记录号 | WOS:000258809600005 |
WOS关键词 | INTRUSIONS ; PERIDOTITE ; COMPLEX ; ORIGIN ; ROCKS |
WOS类目 | Geochemistry & Geophysics |
WOS研究方向 | Geochemistry & Geophysics |
资源类型 | 期刊论文 |
条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/156813 |
作者单位 | (1)Menia Univ, Fac Sci, Dept Geol, El Minia 61519, Egypt |
推荐引用方式 GB/T 7714 | Farahat, E. S.. Chrome-spinels in serpentinites and talc carbonates of the El Ideid-El Sodmein District, central Eastern Desert, Egypt: their metamorphism and petrogenetic implications[J],2008,68(2):193-205. |
APA | Farahat, E. S..(2008).Chrome-spinels in serpentinites and talc carbonates of the El Ideid-El Sodmein District, central Eastern Desert, Egypt: their metamorphism and petrogenetic implications.CHEMIE DER ERDE-GEOCHEMISTRY,68(2),193-205. |
MLA | Farahat, E. S.."Chrome-spinels in serpentinites and talc carbonates of the El Ideid-El Sodmein District, central Eastern Desert, Egypt: their metamorphism and petrogenetic implications".CHEMIE DER ERDE-GEOCHEMISTRY 68.2(2008):193-205. |
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