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Oxygen isotope fractionation between grossular-spessartine garnet and water; an experimental investigation

Uwe Lichtenstein and Stephan Hoernes
Oxygen isotope fractionation between grossular-spessartine garnet and water; an experimental investigation
European Journal of Mineralogy (April 1992) 4 (2): 239-249

Abstract

Oxygen isotope fractionations have been determined between hydrothermally crystallized oxide mixtures of spessartine composition and water at 500-750 degrees C and 2-12 kbar. Direct exchange calibration of the fractionation factor (alpha) for natural spessartine- and grossular-rich garnets was performed only at 750 degrees C and 16 kbar because the garnet-H (sub 2) O exchange reaction takes place extremely slowly. At 750 degrees C both garnets gave identical fractionation factors, indicating that substitutions of the octahedrally coordinated divalent cation have a negligible influence on the O-isotope fractionation. SEM studies showed that in the direct-exchange experiments the garnet-H (sub 2) O exchange occurs largely by solution- precipitation mass- transfer mechanism. The spessartine-H (sub 2) O fractionation fits the equation: 1000 ln alpha (sub Sp-H) (sub 2) (sub O) = 1.27 (+- 0.25) x 10 (super 6) /T (super 2) - 3.65 (+- 0.31) where T is in Kelvin, in the range 500 +- 750 degrees C. Combining these results with earlier reported quartz-H (sub 2) O fractionation gives the quartz- garnet equation: 1000 ln alpha Q-Gt = 2.83 x 10 (super 6) /T (super 2) .


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 4
Serial Issue: 2
Title: Oxygen isotope fractionation between grossular-spessartine garnet and water; an experimental investigation
Affiliation: Max-Planck-Institut fuer Chemie, Mainz, Federal Republic of Germany
Pages: 239-249
Published: 199204
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 33
Accession Number: 1995-056224
Categories: Mineralogy of silicatesIsotope geochemistry
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: 3 tables
Secondary Affiliation: Mineralogisches Institut, DEU, Federal Republic of Germany
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 199520
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