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An experimental and thermodynamic study of cymrite and celsian stability in the system BaO-Al (sub 2) O (sub 3) -SiO (sub 2) -H (sub 2) O

Colin M. Graham, Jalees A. K. Tareen, Paul F. McMillan and Barrie M. Lowe
An experimental and thermodynamic study of cymrite and celsian stability in the system BaO-Al (sub 2) O (sub 3) -SiO (sub 2) -H (sub 2) O
European Journal of Mineralogy (April 1992) 4 (2): 251-269

Abstract

The stabilities and growth kinetics of celsian and cymrite have been investigated in the system BaO-Al (sub 2) O (sub 3) -SiO (sub 2) - H (sub 2) O at <= 10 kbar and <= 800 degrees C; a broad area of P-T space has been identified at low P and T in which cymrite grows rapidly and metastably in runs of short duration, being replaced by celsian in longer runs. The equilibrium cymrite reversible double half arrows celsian + H (sub 2) O has been tightly bracketed at approx 9.7 kbar, 800 degrees ; 9.0 kbar, 710 degrees C; 8.0 kbar, 580 degrees C; results at lower P and T confirm that cymrite is only stable at high P, providing a valuable metamorphic geothermometer. Cymrite is not stable in low P-T sedimentary and hydrothermal environments and documented natural occurrences in these environments must be considered to have resulted from metastable growth and persistence in the celsian stability field. The molecular H (sub 2) O contents of cymrites vary systematically with PH (sub 2) O and T of synthesis, increasing with increasing P and decreasing T to a maximum of 1 H (sub 2) O per formula unit. The incorporation of H (sub 2) O yields an enthalpy change of approx 59 kJ/mol and an entropy change of approx 133 J/K/mol; isopleths have been calculated for the equilibrium water content of cymrite as a function of PH (sub 2) O and T.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 4
Serial Issue: 2
Title: An experimental and thermodynamic study of cymrite and celsian stability in the system BaO-Al (sub 2) O (sub 3) -SiO (sub 2) -H (sub 2) O
Affiliation: University of Edinburgh, Department of Geology and Geophysics, Edinburgh, United Kingdom
Pages: 251-269
Published: 199204
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 40
Accession Number: 1995-056225
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: 5 tables
Secondary Affiliation: University of Mysore, IND, IndiaArizona State University, USA, United States
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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