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A limited role for metasomatized subarc mantle in the generation of boron isotope signatures of arc volcanic rocks

Lubomira Tomanikova, Ivan P. Savov, Jason Harvey, Jan C. M. De Hoog, Tatiana G. Churikova, Boris Gordeychik and Gene M. Yogodzinski
A limited role for metasomatized subarc mantle in the generation of boron isotope signatures of arc volcanic rocks
Geology (Boulder) (April 2019) Pre-Issue Publication

Abstract

Metasomatized subarc mantle is often regarded as one of the mantle reservoirs enriched in fluid-mobile elements (FMEs; e.g., B, Li, Cs, As, Sb, Ba, Rb, Pb), which, when subject to wet melting, will contribute to the characteristic FME-rich signature of arc volcanic rocks. Evidence of wet melts in the subarc mantle wedge is recorded in metasomatic amphibole-, phlogopite-, and pyroxene-bearing veins in ultramafic xenoliths recovered from arc volcanoes. Our new B and delta (super 11) B study of such veins in mantle xenoliths from Avachinsky and Shiveluch volcanoes, Kamchatka arc, indicates that slab-derived FMEs, including B and its characteristically high delta (super 11) B, are delivered directly to a melt that experiences limited interaction with the surrounding mantle before eruption. The exceptionally low B contents (from 0.2 to 3.1 mu g g (super -1) ) and low delta (super 11) B (from -16.6 ppm to +0.9 ppm) of mantle xenolith vein minerals are, instead, products of fluids and melts released from the isotopically light subducted and dehydrated altered oceanic crust and, to a lesser extent, from isotopically heavy serpentinite. Therefore, melting of amphibole- and phlogopite-bearing veins in a metasomatized mantle wedge cannot alone produce the characteristic FME geochemistry of arc volcanic rocks, which require a comparatively large, isotopically heavy and B-rich serpentinite-derived fluid component in their source.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: Pre-Issue Publication
Title: A limited role for metasomatized subarc mantle in the generation of boron isotope signatures of arc volcanic rocks
Affiliation: University of Leeds, School of Earth and Environment, Leeds, United Kingdom
Published: 20190415
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 54
Accession Number: 2019-038004
Categories: Isotope geochemistryIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. geol. sketch map
N51°00'00" - N60°00'00", E155°00'00" - E168°00'00"
Secondary Affiliation: University of Edinburgh, GBR, United KingdomRussian Academy of Sciences, Far East Division, Institute of Volcanology and Seismology, RUS, Russian FederationUniversitaet Goettingen, DEU, GermanyUniversity of South Carolina, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 2019
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