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Ephemeral carbonate melts in the upper mantle; carbonate-silicate immiscibility in microveins and inclusions within spinel peridotite xenoliths, La Gomera, Canary Islands

Maria-Luce Frezzotti, Jacques L. R. Touret and Else-Ragnhild Neuman
Ephemeral carbonate melts in the upper mantle; carbonate-silicate immiscibility in microveins and inclusions within spinel peridotite xenoliths, La Gomera, Canary Islands
European Journal of Mineralogy (October 2002) 14 (5): 891-904

Abstract

Carbonate droplets containing mafic silicate glass + or - CO (sub 2) occur within mineral inclusions and late microveins in spinel-bearing xenoliths (dunite, dunite-wehrlite and pyroxenite) from La Gomera. Primary carbonates are Mg-calcite (X (sub Ca) 0.89-0.93), dolomite (X (sub Ca) 0.46-0.54) with low Na (sub 2) O (< or = 0.1 wt.%) and variable MnO (0.2-8 wt.%). The mafic glass has high MgO (24-35 wt.%), FeO (1-18 wt.%) and SiO (sub 2) (40-55 wt%) with low Al (sub 2) O (sub 3) , TiO (sub 2) , CaO and alkalis and a high content (> 10 wt.%) of volatiles (i.e. H (sub 2) O). The composite carbonate droplets represent a quenched liquid, resulting from unmixing within the inclusions of a carbonate-rich melt into separate carbonate- and silicate-rich phases. If not protected within inclusions, these melts are ephemeral, unstable in the P-T field of spinel peridotites (10-18 kbar, 900-1000 degrees C). Mafic glass remnants in microveins represent a residual degassed hydrous mafic silicate fraction after decarbonation.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 14
Serial Issue: 5
Title: Ephemeral carbonate melts in the upper mantle; carbonate-silicate immiscibility in microveins and inclusions within spinel peridotite xenoliths, La Gomera, Canary Islands
Affiliation: Universita di Siena, Dipartimento Scienze della Terra, Siena, Italy
Pages: 891-904
Published: 200210
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 45
Accession Number: 2002-071651
Categories: General geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables
N27°45'00" - N29°30'00", W18°15'00" - W13°00'00"
Secondary Affiliation: Vrije Universiteit, NLD, NetherlandsUniversitetet i Oslo, NOR, Norway
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 200222
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