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Phase relationships in the system NaAlSiO_4-SiO_2-H_2O to 35 kilobars pressure

Boettcher, A. L. and Wyllie, P. J. (1969) Phase relationships in the system NaAlSiO_4-SiO_2-H_2O to 35 kilobars pressure. American Journal of Science, 267 (8). pp. 875-909. ISSN 0002-9599. doi:10.2475/ajs.267.8.875.

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Phase relationships in the system NaAlSiO_4-SiO_2-H_2O are first presented in P-T projections of the composition joins NaAlSi_3O_8 (albite)-SiO_2-H_2O, NaAlSi_3O_8-H_2O, NaAl_2Si_2O_6 (jadeite)-H_2O, and NaAlSi_2O_6-NaAlSiO_4 (nepheline)-H_2O. Crystalline phases encountered include albite, analcite, coesite, jadeite, nepheline, and quartz. Vapor-saturated melting curves for these compositions, including those for the melting of albite + quartz + vapor, albite + vapor, and albite + analcite + vapor, proceed with negative dP/dT slopes to invariant points at pressures between 10 and 13 kb where jadeite coexists with liquid. At higher pressures, the solidus curves for compositions on these joins extend with positive dP/dT slopes, and the quartz-bearing assemblages terminate at an invariant point marking the appearance of coesite. Albite-H_2O compositions melt incongruently at pressures greater than a singular point at 16 kb, and jadeite-H_2O compositions melt congruently above a singular point at 13 kb and form a stable thermal divide within this system. Together with the chemographic methods of Schreinemakers and experimental data for the system NaAlSiO_4-SiO_2, univariant and invariant equilibria for the ternary system are presented in P-T projection. The approximate solubility of H_2O in liquids of albite, nepheline, and jadeite composition at 15 kb is 27 (wt) percent, 36 percent and 22 percent, respectively. Nepheline-H_2O compositions are not binary at these pressures and break down to a jadeite-bearing assemblage at pressures above 10 kb and to jadeite + an unknown phase at higher pressures. Isobaric-polythermal diagrams, constructed on the basis of the melting relationships and solubility data, illustrate the primary fields for the crystalline phases and disclose that critical phenomena will intervene only for compositions rich in SiO_2.

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Alternate Title:Phase relationships in the system NaAlSiO4-SiO2-H2O to 35 kilobars pressure
Additional Information:© 1969 American Journal of Science. Contribution No. 68-15, College of Earth and Mineral Sciences, The Pennsylvania State University, University Park, Pennsylvania 16802. This work was supported at the University of Chicago by NSF Grant GP-4910 and at The Pennsylvania State University by NSF Grant GA-1364. We thank C. Wayne Burnham of the Pennsylvania State University for his critical review of the manuscript.
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Issue or Number:8
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Official Citation:A. L. Boettcher and P. J. Wyllie Phase relationships in the system NaAlSiO 4 -SiO 2 -H 2 O to 35 kilobars pressure Am J Sci October 1, 1969 267:875-909; doi:10.2475/ajs.267.8.875
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64021
Deposited By: Tony Diaz
Deposited On:27 Jan 2016 22:27
Last Modified:10 Nov 2021 23:24

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