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Boron isotope systematics of tourmaline from granites and pegmatites; a synthesis

Shao-Yong Jiang and Martin R. Palmer
Boron isotope systematics of tourmaline from granites and pegmatites; a synthesis
European Journal of Mineralogy (December 1998) 10 (6): 1253-1265

Abstract

Tourmaline is abundant in many granites and pegmatites and is generally the most significant mineral sink for boron crystallising from a silicic melt. There is a wide variation in the delta (super 11) B values of tourmalines from granites, pegmatites, and associated hydrothermal veins (-29.9 per mil to +8.6 per mil). The boron isotopic compositions of granitic tourmalines are <0 per mil and can be as low as -30 per mil, but most of the data cluster between -15 per mil and 5 per mil. A similar delta (super 11) B distribution is seen in pegmatitic tourmalines, but tourmalines from granite-related veins at granite-country rock contacts or within adjacent country rocks show generally higher delta (super 11) B values with a maximum at -10 per mil to -5 per mil. The boron isotopic compositions of tourmaline from these settings are largely controlled by the composition of the magma source, magma degassing, contributions of boron from country rocks, and P-T conditions of tourmaline formation. The pre-melting history of boron mobilisation and its redistribution in granite source rocks may also have pronounced effects on boron concentrations and delta (super 11) B values of the magma. During magma degassing (super 11) B is preferentially partitioned into the vapour phase, leading to lower delta (super 11) B values in magmatic tourmalines relative to the exsolved hydrothermal fluids. Degassing also leads to a decrease in delta (super 11) B values from the early to late magmatic tourmalines.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 10
Serial Issue: 6
Title: Boron isotope systematics of tourmaline from granites and pegmatites; a synthesis
Affiliation: Max-Planck-Institut fuer Chemie, Mainz, Federal Republic of Germany
Pages: 1253-1265
Published: 199812
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 57
Accession Number: 1999-018597
Categories: Isotope geochemistryIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 199907
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