Arid
DOI10.1016/j.jafrearsci.2010.10.008
Neoproterozoic contaminated MORB of Wadi Ghadir ophiolite, NE Africa: Geochemical and Nd and Sr isotopic constraints
Basta, Fawzy F.2; Maurice, Ayman E.1; Bakhit, Bottros R.1; Ali, Kamal A.3; Manton, William I.3
通讯作者Maurice, Ayman E.
来源期刊JOURNAL OF AFRICAN EARTH SCIENCES
ISSN1464-343X
EISSN1879-1956
出版年2011
卷号59期号:2-3页码:227-242
英文摘要

The ophiolitic metabasalts (pillowed and sheeted dikes) of Wadi Ghadir area, Eastern Desert, Egypt, were analyzed for their major, trace and rare earth elements, Nd and Sr isotopes and the chemistry of their plagioclase, amphibole and chlorite was also reported. Geochemically these rocks range from tholeiitic basalt to basaltic andesite. The generally low MgO, Cr and Ni and high Zr contents are consistent with derivation of these rocks from an evolved magma. The high TiO2 contents (mostly between 1.76% and 2.23%) classify Wadi Ghadir ophiolitic metabasalts as MORB ophiolite. The chondrite-normalized REE patterns of most samples display small LREE-enrichment with (La/Vb)(n) ranging from 1.44 to 2.56. The MORB-normalized spider diagram shows variable LILE abundances, which are either similar to or enriched relative to MORB, and most samples display small Nb depletion. The abundances of some LILE (Ba, Rb and K) as well as Na and Si were modified by post-magmatic seafloor hydrothermal alteration. Enrichment of the least mobile LILE (Th & U) indicates that Wadi Ghadir ophiolitic metabasalts are akin to C (contaminated)-MORB. These geochemical characteristics are similar to BABB modified by contamination.


Wadi Ghadir metabasalts have low initial Sr ratios (0.7010-0.7034) which are similar to those of MORB, while their epsilon(Nd(t)) values (+7.7-+4.5) are either more or less positive than the value of depleted mantle (DM). The more positive epsilon(Nd(r)) values indicate DM source for these basalts, while the less positive eNd(,) values reflect the involvement of slightly older component in Wadi Ghadir ophiolite. We suggest that the parent magma of metabasalts was contaminated by slightly older material, most probably oceanic-arc crustal rocks, which caused enrichment in LREE, and by analogy LILE, but did not significantly affect Nd isotopic systematics or modify Sr isotopes.


Such contaminated MORB character also revealed by other ophiolitic metavolcanics in the Central Eastern Desert, contrasting the N-MORB character of the Gerf ophiolite in the South Eastern Desert. Moreover, the present work suggests the increase of the degree of contamination of the ophiolitic metabasalts from south to north in the Central Eastern Desert. (C) 2010 Elsevier Ltd. All rights reserved.


英文关键词Contaminated MORB Geochemistry Sr and Nd isotopes Neoproterozoic Eastern Desert
类型Article
语种英语
国家Egypt ; USA
收录类别SCI-E
WOS记录号WOS:000287911200006
WOS关键词ISUA GREENSTONE-BELT ; EASTERN DESERT ; TECTONIC EVOLUTION ; MIDOCEAN RIDGE ; VOLCANIC-ROCKS ; WEST GREENLAND ; NUBIAN SHIELD ; OCEAN-FLOOR ; ICP-MS ; ZIRCON
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/2XILL650/168745
作者单位1.Beni Suef Univ, Fac Sci, Dept Geol, Bani Suwayf 62517, Egypt;
2.Cairo Univ, Fac Sci, Dept Geol, Giza 12613, Egypt;
3.Univ Texas Dallas, Dept Geosci, Richardson, TX 75080 USA
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Basta, Fawzy F.,Maurice, Ayman E.,Bakhit, Bottros R.,et al. Neoproterozoic contaminated MORB of Wadi Ghadir ophiolite, NE Africa: Geochemical and Nd and Sr isotopic constraints[J],2011,59(2-3):227-242.
APA Basta, Fawzy F.,Maurice, Ayman E.,Bakhit, Bottros R.,Ali, Kamal A.,&Manton, William I..(2011).Neoproterozoic contaminated MORB of Wadi Ghadir ophiolite, NE Africa: Geochemical and Nd and Sr isotopic constraints.JOURNAL OF AFRICAN EARTH SCIENCES,59(2-3),227-242.
MLA Basta, Fawzy F.,et al."Neoproterozoic contaminated MORB of Wadi Ghadir ophiolite, NE Africa: Geochemical and Nd and Sr isotopic constraints".JOURNAL OF AFRICAN EARTH SCIENCES 59.2-3(2011):227-242.
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