F-OH exchange equilibria between mica-amphibole mineral pairs

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Authors:Westrich, H. R.
Author Affiliations:Primary:
Univ. Calif., Dep. Earth Space Sci., Los Angeles, CA 90024, United States
Volume Title:Contributions to Mineralogy and Petrology
Source:Contributions to Mineralogy and Petrology, 78(3), p.318-323. Publisher: Springer International, Heidelberg-New York, International. ISSN: 0010-7999
Publication Date:1981
Note:In English. 23 refs.; illus. incl. 6 anal., 6 tables
Summary:Fluoride-hydoxyl exchange equilibria between phlogopite-pargasite and phlogopite-tremolite mineral pairs were experimentally determined at 1173 K, 500 bar and 1073-1173 K, 500 bar, respectively. The distribution of F between phlogopite and pargasite was found to favour phlogopite slightly, 034DELTA ex (1173 K) = -1.71 kJ/anion, while in the case of phlogopite-tremolite, F was preferentially incorporated in the mica, 034DELTA ex (1703 K) = -5.67 kJ/anion and 034DELTA ex (1173 K) = -5.84 kJ/anion. These results have yielded new values of entropy and Gibbs energy of formation for fluortremolite, DELTA Sof = -2293.4 + or - 16.0 JK-1mol-1, and DELTA Gof = -11 779.3 + or - 25.0 kJ/mol, respectively. In addition, F-OH mineral-exchange equilibria support a recent molten oxide calorimetric value for the Gibbs energy of fluorphlogopite, DELTA Gof = -6014 + or - 7.0 kJ/mol, which is approximately 40 kJ/mol more exothermic than the tabulated value. [P.Br.]
Subjects:Amphibole group; Chain silicates; Clinoamphibole; Coexisting minerals; Fluorine; Geochemistry; Halogens; Ion exchange; Mica group; Pargasite; Phase equilibria; Phlogopite; Sheet silicates; Silicates; Thermodynamic properties; Tremolite; Mica-amphibole
Abstract Numbers:82M/2838
Record ID:1983021811
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom, Reference includes data from PASCAL, Institute de l'Information Scientifique et Technique
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