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Geochemistry and petrogenesis of post-collisional alkaline and peralkaline granites of the Arabian-Nubian Shield: a case study from the southern tip of Sinai Peninsula, Egypt

Khalil, A. E. S. and Obeid, M. A. and Azer, M. K. and Asimow, P. D. (2017) Geochemistry and petrogenesis of post-collisional alkaline and peralkaline granites of the Arabian-Nubian Shield: a case study from the southern tip of Sinai Peninsula, Egypt. International Geology Review, 60 (8). pp. 998-1018. ISSN 0020-6814. https://resolver.caltech.edu/CaltechAUTHORS:20180502-104518099

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Abstract

The southern Sinai Peninsula, underlain by the northernmost extension of the Arabian-Nubian Shield, exposes post-collisional calc-alkaline and alkaline granites that represent the youngest phase of late Neoproterozoic igneous activity. We report a petrographic, mineralogical and geochemical investigation of post-collisional plutons of alkaline and, in some cases, peralkaline granite. These granites intrude metamorphosed country rocks as well as syn- and post-collisional calc-alkaline granitoids. The alkaline and peralkaline granites of the southern tip of Sinai divide into three subgroups: syenogranite, alkali feldspar granite and riebeckite granite. The rocks of these subgroups essentially consist of alkali feldspar and quartz with variable amounts of plagioclase and mafic minerals. The syenogranite and alkali feldspar granite contain small amounts of calcic amphibole and biotite, often less than 3%, while the riebeckite granite is distinguished by sodic amphibole (5–10%). These plutons have geochemical signatures typical of post-collisional A-type granites and were most likely emplaced during a transition between orogenic and anorogenic settings. The parental mafic magma may be linked to lithospheric delamination and upwelling of asthenospheric mantle material. Differentiation of the underplated basaltic magma with contributions from the juvenile crust eventually yielded the post-collisional alkaline granites. Petrogenetic modelling of the studied granitic suite shows that pure fractional crystallization cannot quantitatively explain chemical variations with the observed suite, with both major oxides and several trace elements displaying trends opposite to those required by the equilibrium phase assemblage. Instead, we show that compositional variation from syenogranite through alkali feldspar granite to riebeckite granite is dominated by mixing between a low-SiO_2 liquid as primitive or more primitive than the lowest-SiO_2 syenogranite and an evolved, high-SiO_2 liquid that might be a high-degree partial melt of lower crust.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1080/00206814.2017.1364672DOIArticle
ORCID:
AuthorORCID
Asimow, P. D.0000-0001-6025-8925
Additional Information:© 2017 Taylor & Francis. Received 23 Feb 2017, Accepted 03 Aug 2017, Published online: 21 Aug 2017. Dr Azer has fellowship from the Cairo Initiative grant of the United States Agency for International Development to visit the Division of Geological & Planetary Sciences (GPS), California Institute of Technology, USA. PDA’s participation in the work is supported by the US National Science Foundation geoinformatics program under award EAR-1550934.
Funders:
Funding AgencyGrant Number
US Agency for International DevelopmentUNSPECIFIED
NSFEAR-1550934
Subject Keywords:Arabian-Nubian Shield, sinai, granites, post-collisional magmatism, anorogenic, riebeckite
Issue or Number:8
Record Number:CaltechAUTHORS:20180502-104518099
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20180502-104518099
Official Citation:A. E. S. Khalil, M. A. Obeid, M. K. Azer & P. D. Asimow (2017) Geochemistry and petrogenesis of post-collisional alkaline and peralkaline granites of the Arabian-Nubian Shield: a case study from the southern tip of Sinai Peninsula, Egypt, International Geology Review, 60:8, 998-1018, DOI: 10.1080/00206814.2017.1364672
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:86191
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:03 May 2018 21:15
Last Modified:03 Oct 2019 19:40

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