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The last subduction-related volcanism in the northern tip of the Arabian-Nubian Shield: A Neoproterozoic arc preceding the terminal collision of East and West Gondwana

Maurice, Ayman E. and Bakhit, Bottros R. and Basta, Fawzy F. and Asimow, Paul D. and Wälle, Markus and Azer, Mokhles K. and El-Sobky, Atef F. (2018) The last subduction-related volcanism in the northern tip of the Arabian-Nubian Shield: A Neoproterozoic arc preceding the terminal collision of East and West Gondwana. Precambrian Research, 310 . pp. 256-277. ISSN 0301-9268. http://resolver.caltech.edu/CaltechAUTHORS:20180327-090036434

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Abstract

The medium- to high-K calc-alkaline subduction-related Dokhan volcanic rocks of the Wadi Hamad area record two flare-up events during the history of a Neoproterozoic continental island arc, an early pulse dominated by andesite and a later pulse dominated by dacite. The trace element abundances and (La/Yb)_n ratios of the basalts, andesites and dacites all overlap, contrary to the expectations of a single fractional crystallization trend, suggesting the need for three distinct parental magmas for the three groups. The parental magmas of the basalts and andesites were generated by variable degrees of partial melting of subduction-metasomatized mantle, whereas that of the dacites requires mixing of mantle and crustal melts. The andesites and dacites both evolved mostly through fractionation of clinopyroxene and plagioclase, accompanied by apatite and Fe-Ti oxides in the more evolved dacitic rocks. Oscillatory and reverse zoning in clinopyroxene and plagioclase indicates that magma replenishment and mixing played a role in the genesis of the basalts and andesites. Depth-sensitive geochemical parameters show that the earlier andesites evolved at deeper levels in the arc crust compared with the later dacites, but not so deep as to stabilize garnet as a fractionating phase. Estimated values of the arc crust thickness indicate that the crust thickened from ∼35 km to ∼50 km from the time of basalt eruption to the time of andesite eruption, probably implying a high rate of crustal growth. The estimated arc crust thickness during the later subduction flare-up is slightly less than that of the earlier one despite ongoing magmatic addition, implying that arc crust delamination began before the production of the later dacites. The subduction-related geochemical characteristics of the Dokhan volcanic rocks suggest that the terminal collision between East and West Gondwana in the tip of the Nubian Shield occurred at ∼600 Ma.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.precamres.2018.03.009DOIArticle
https://www.sciencedirect.com/science/article/pii/S0301926817306022PublisherArticle
ORCID:
AuthorORCID
Asimow, Paul D.0000-0001-6025-8925
Additional Information:© 2018 Elsevier B.V. Received 29 October 2017, Revised 6 March 2018, Accepted 14 March 2018, Available online 15 March 2018. The authors wish to thank Prof. Dr. Christoph Heinrich, ETH-Zürich, Switzerland, for laboratory facilities. Prof. Dr. Peter Ulmer, Dr. Eric Reusser and Lydia Zehnder are deeply acknowledged for the help in the geochemical and microprobe analyses conducted at ETH-Zürich. Comments by Prof. Moshe Eyal, Prof. Bernard Bonin and anonymous reviewers improved the present version of the manuscript. Dr. Kamal Ali (associate editor) and Prof. Guochun Zhao (editor) are acknowledged for editorial handling.
Subject Keywords:Continental island arcs; Arc Magma Genesis; Gondwana Assembly; Arabian-Nubian Shield; Eastern Desert
Record Number:CaltechAUTHORS:20180327-090036434
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20180327-090036434
Official Citation:Ayman E. Maurice, Bottros R. Bakhit, Fawzy F. Basta, Paul D. Asimow, Markus Wälle, Mokhles K. Azer, Atef F. El-Sobky, The last subduction-related volcanism in the northern tip of the Arabian-Nubian Shield: A Neoproterozoic arc preceding the terminal collision of East and West Gondwana, Precambrian Research, Volume 310, 2018, Pages 256-277, ISSN 0301-9268, https://doi.org/10.1016/j.precamres.2018.03.009. (http://www.sciencedirect.com/science/article/pii/S0301926817306022)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:85448
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:27 Mar 2018 18:49
Last Modified:27 Mar 2018 18:49

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