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Oligo-Miocene A-type granites and granophyres from Yemen; isotopic and trace-element constraints bearing on their genesis

Simone Tommasini, Giampiero Poli, Piero Manetti and Sandro Conticelli
Oligo-Miocene A-type granites and granophyres from Yemen; isotopic and trace-element constraints bearing on their genesis
European Journal of Mineralogy (August 1994) 6 (4): 571-590

Abstract

New major and trace element data together with REE analyses and Sr isotopic data are presented for 27 specimens of Oligo-Miocene A-type granites and granophyres from the Yemen, emplaced during the early stages of lithospheric break-up and thinning prior to the onset of rifting and sea-floor spreading of the Red Sea. The Yemen granites and granophyres have high alkali (7-11 wt.%), HFS element and Zn contents along, with low Sr and Ba; they are characterized by high FeO (sub tot) /MgO and Ga/Al ratios and (super 87) Sr/ (super 86) Sr (sub i) values of 0.704 to 0.721. The Y/Nb, Yb/Ta and Ce/Nb values are similar to those of the Yemen Trap series basalts and cluster towards the OIB field. These trace element ratios argue against an origin by crustal anatexis processes and provide evidence for a genetic link with coeval basalts of the Yemen Trap series. Two groups of high-silica magmas are recognized, characterized by Nb/Y values of approximately 1 (low Nb/Y granites) and approximately 2 (high Nb/Y granites). The overall geochemical characteristics of these granites and granophyres, and their Sr isotope composition, support an origin by a two-stage assimilation and fractional crystallization process, starting from two types of the Yemen Trap series basalts with slightly different within-plate signatures. Each of the two AFC stages could have occurred in distinct magma reservoirs in the lower and upper crust.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 6
Serial Issue: 4
Title: Oligo-Miocene A-type granites and granophyres from Yemen; isotopic and trace-element constraints bearing on their genesis
Affiliation: Universita degli Studi di Firenze, Dipartimento di Scienze della Terra, Florence, Italy
Pages: 571-590
Published: 199408
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 59
Accession Number: 1995-001814
Categories: Isotope geochemistryIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables
N12°30'00" - N18°30'00", E42°30'00" - E53°00'00"
Secondary Affiliation: Universita degli Studi di Perugia, ITA, Italy
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 199501
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