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Title: The stability of sodalite in the system NaAlSiO sub 4 -NaCl

Abstract

The reaction sodalite = {beta}-nepheline + NaCl (s) was reversed in solid-medium apparatus and the reaction sodalite = carnegieite + NaCl (l) was reversed at 1 bar (1,649-1,652 K). The experimental reversals between 923 K and 973 K can be fit with a dP/dT of {minus}11 bar/K, suggesting that the excess entropy for sodalite is present only above 923 K. A phase diagram for the NaAlSiO{sub 4}-NaCl system that is consistent with the measured thermochemical data and the experiments between 973 and 1,650 K can be generated if the 61.7 J/mol{center dot}K entropy contribution is included in the S{sup 0}{sub 298} of sodalite. This entropy contribution must be removed below 973 K for the experiments to fit with calculations. Previously unreported thermodynamic data estimated in this study are {Delta}G{sup 0}{sub 298} for sodalite ({minus}12,697 kJ/mol) and carnegieite (NaAlSiO{sub 4}) ({minus}1,958 kJ/mol), S{sup 0}{sub 298} of carnegieite (129.6 J/mol{center dot}K) and compressibility of NaCl{sub liquid} (V{sup P}{sub 298} (cm{sup 3}) = 31.6{center dot}(1 - 24.7{center dot}10{sup {minus}3}{center dot}P + 800{center dot}10{sup {minus}6}{center dot}P{sup 2}))(T in K; P in kbar). Sodalite is a high-temperature, low-pressure phase, stable well above the solidus in sodic silica-undersaturated magmas enriched in NaCl, and its presence constrainsmore » NaCl activities in magmas. Estimates of minimum NaCl (l) activities in the Mont St-Hilaire sodalite syenites are 0.05 at 1,073 K and 0.13 at 1,273 K. Density calculations are consistent with the field observations that sodalite phenocrysts will float in a nepheline syenite liquid. This explains the enrichment of sodalite in the upper levels of the sodalite syenites at Mont St.Hilaire and elsewhere.« less

Authors:
 [1];  [2];  [3];  [4]
  1. (Carnegie Institution of Washington, DC (USA))
  2. (Northwestern Univ., Evanston, IL (USA))
  3. (S.U.N.Y., Stony Brook, NY (USA))
  4. (Univ. of Michigan, Ann Arbor (USA))
Publication Date:
OSTI Identifier:
7017995
Resource Type:
Journal Article
Resource Relation:
Journal Name: Geochimica et Cosmochimica Acta; (USA); Journal Volume: 53:8
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; IGNEOUS ROCKS; SILICATE MINERALS; METAMORPHIC ROCKS; PHASE STUDIES; STABILITY; THERMODYNAMIC ACTIVITY; CHEMICAL COMPOSITION; ENTROPY; GEOCHEMISTRY; INCLUSIONS; MAGMA; PHASE TRANSFORMATIONS; PRESSURE EFFECTS; REACTION KINETICS; ROCK-FLUID INTERACTIONS; SALINITY; SODIUM CHLORIDES; TEMPERATURE EFFECTS; ALKALI METAL COMPOUNDS; CHEMISTRY; CHLORIDES; CHLORINE COMPOUNDS; HALIDES; HALOGEN COMPOUNDS; KINETICS; MINERALS; PHYSICAL PROPERTIES; ROCKS; SODIUM COMPOUNDS; THERMODYNAMIC PROPERTIES; 580000* - Geosciences

Citation Formats

Sharp, Z.D., Helffrich, G.R., Bohlen, S.R., and Essene, E.J. The stability of sodalite in the system NaAlSiO sub 4 -NaCl. United States: N. p., 1989. Web. doi:10.1016/0016-7037(89)90315-3.
Sharp, Z.D., Helffrich, G.R., Bohlen, S.R., & Essene, E.J. The stability of sodalite in the system NaAlSiO sub 4 -NaCl. United States. doi:10.1016/0016-7037(89)90315-3.
Sharp, Z.D., Helffrich, G.R., Bohlen, S.R., and Essene, E.J. Tue . "The stability of sodalite in the system NaAlSiO sub 4 -NaCl". United States. doi:10.1016/0016-7037(89)90315-3.
@article{osti_7017995,
title = {The stability of sodalite in the system NaAlSiO sub 4 -NaCl},
author = {Sharp, Z.D. and Helffrich, G.R. and Bohlen, S.R. and Essene, E.J.},
abstractNote = {The reaction sodalite = {beta}-nepheline + NaCl (s) was reversed in solid-medium apparatus and the reaction sodalite = carnegieite + NaCl (l) was reversed at 1 bar (1,649-1,652 K). The experimental reversals between 923 K and 973 K can be fit with a dP/dT of {minus}11 bar/K, suggesting that the excess entropy for sodalite is present only above 923 K. A phase diagram for the NaAlSiO{sub 4}-NaCl system that is consistent with the measured thermochemical data and the experiments between 973 and 1,650 K can be generated if the 61.7 J/mol{center dot}K entropy contribution is included in the S{sup 0}{sub 298} of sodalite. This entropy contribution must be removed below 973 K for the experiments to fit with calculations. Previously unreported thermodynamic data estimated in this study are {Delta}G{sup 0}{sub 298} for sodalite ({minus}12,697 kJ/mol) and carnegieite (NaAlSiO{sub 4}) ({minus}1,958 kJ/mol), S{sup 0}{sub 298} of carnegieite (129.6 J/mol{center dot}K) and compressibility of NaCl{sub liquid} (V{sup P}{sub 298} (cm{sup 3}) = 31.6{center dot}(1 - 24.7{center dot}10{sup {minus}3}{center dot}P + 800{center dot}10{sup {minus}6}{center dot}P{sup 2}))(T in K; P in kbar). Sodalite is a high-temperature, low-pressure phase, stable well above the solidus in sodic silica-undersaturated magmas enriched in NaCl, and its presence constrains NaCl activities in magmas. Estimates of minimum NaCl (l) activities in the Mont St-Hilaire sodalite syenites are 0.05 at 1,073 K and 0.13 at 1,273 K. Density calculations are consistent with the field observations that sodalite phenocrysts will float in a nepheline syenite liquid. This explains the enrichment of sodalite in the upper levels of the sodalite syenites at Mont St.Hilaire and elsewhere.},
doi = {10.1016/0016-7037(89)90315-3},
journal = {Geochimica et Cosmochimica Acta; (USA)},
number = ,
volume = 53:8,
place = {United States},
year = {Tue Aug 01 00:00:00 EDT 1989},
month = {Tue Aug 01 00:00:00 EDT 1989}
}
  • A detailed study of the sodium aluminate-carnegieite system (Na{sub 2-x}Al{sub 2-x}Si{sub x}O{sub 4}, 0 {le} x {le} 1) at temperatures between 800 and 1300{degrees}C has revealed five previously unreported phases. All of the new phases can be described as modulated variants of an underlying {beta}-cristobalite parent structure. At x {approx} 0.05 the {gamma}-NaAlO{sub 2}-type structure (P4{sub 1}2{sub 1}2, a = 1/{radical}2a{sub p}, c = c{sub p}) (p = parent) is stabilized to room-temperature; at x {approx} 0.2-0.45 an orthorhombic (Pbca, a = {radical}2a{sub p}, b = 2b{sub p}, c = 1/{radical}2c{sub p}) KGaO{sub 2}-type structure is obtained, except at xmore » {approx} 0.35 where a new tetragonal (P4{sub 1}2{sub 1}2, a = {radical}2a{sub p}, c = c{sub p}) phase is observed; at x {approx} 0.5-0.6 a new cubic (P2{sub 1}3, a = 2a{sub p}) phase is obtained; at x {approx} 0.7-0.9 a new orthorhombic (Pc2{sub 1}b, a = {radical}2a{sub p}, b = 2b{sub p}, c = {radical}2c{sub p}) phase is obtained. XRD and electron diffraction data, refined unit cell dimensions, and the phase relationships at 1300{degrees}C are presented. The proposed space group symmetries are based on observed extinction conditions and constraints provided by a modulated structure description of the new phases. The materials are prepared by gel synthesis followed by solid state reaction in air.« less
  • The dissolution kinetics of five glasses along the NaAlSiO 4-NaBSiO 4 join were used to evaluate how the structural variations associated with boron-aluminum substitution affect the rate of dissolution. The composition of each glass varied inversely in mol% of Al 2O 3 (5 to 25 mol%) and B 2O 3 (20 to 0 mol%) with Na 2O (25 mol%) and SiO 2 (50 mol%) making up the remaining amount, in every case Na/(Al+B) = 1.0. Single-pass flow-through experiments (SPFT) were conducted under dilute conditions as a function of solution pH (from 7.0 to 12.0) and temperature (from 23° to 90°C).more » Analysis by 27Al and 29Si MAS-NMR suggests Al (~98% [4]Al) and Si atoms (~100% [4]Si) occupy a tetrahedral coordination whereas, B atoms occupy both tetrahedral ([4]B) and trigonal ( [3]B) coordination. The distribution of [3]B fractionated between [3]B(ring) and [3]B(non-ring) moieties, with the [3]B(ring)/ [3]B(non-ring) ratio increases with the B/Al ratio. The MAS-NMR results also indicated an increase in the fraction of [4]B with an increase in the B/Al ratio. But despite the changes in the B/Al ratio and B coordination, the 29Si spectra maintain a chemical shift between -88 to -84 ppm for each glass. Unlike the 29Si spectra, the 27Al resonances shift to more positive values with an increase in the B/Al ratio which suggests mixing between the [4]Al and [3]B sites, assuming avoidance between tetrahedral trivalent cations ( [4]Al-O- [4]B avoidance). Raman spectroscopy was use to augment the results collected from MAS-NMR and demonstrated that NeB4 (glass sample with the highest B content) was glass-glass phase separated (e.g., heterogeneous glass). Results from SPFT experiments suggest a forward rate of reaction and pH power law coefficients,η, that are independent of B/Al under these neutral to alkaline test conditions for all homogeneous glasses. The temperature dependence shows an order of magnitude increase in the dissolution rate with a 67°C increase in temperature and suggests dissolution is controlled by a surface-mediated reaction, evident by the activation energy, E a, being between 44±8 and 48±7 kJ/mol. Forward dissolution rates, based on Na and Si release, for homogeneous glasses are independent of the B/Al ratio, whereas dissolution rates based on Al and B release are not. Dissolution rates based on B release increase with an increase in the fraction of [3]B(ring). Finally in accord with previous studies, the data discussed in this manuscript suggest rupture of the Al-O and Si-O bond as the rate-limiting step controlling the dissolution of these glasses.« less
  • Cited by 1
  • Nepheline shows first order, congruent dissolution rates, followed by a lowering of the rates due to precipitation of new phases from solution, initially aluminum hydroxides, and later, as the activity of silica in solution increases, amorphous aluminosilicates. The reaction rates obey the law: R/sub imeas/ = R/sub idiss/ - ..sigma../sub j/ R/sub iprec/ where R/sub imeas/ is the measured rate of input of ion i into solution during dissolution of nepheline, R/sub idiss/ is the true rate of nepheline dissolution, and ..sigma../sub j/ R/sub iprec/ is the rate of removal of ion i from solution, either by precipitation or adsorption,more » summed over all the precipitated phases, j, that incorporate the ion, i. This law predicts that the concentration of ion, i, in solution should increase asymptotically to a steady state value, determined by the ratio of the rate of input of i into solution by nepheline dissolution and the rate of its removal from solution by precipitation or adsorption. At low pH, rates of dissolution (R/sub idiss) obey the law: R/sub idiss/ = k/sub +/(a/sub H+/)/sup 1.0/, while at high pH, the rate law is R/sub idiss/ = k/sub +/(a/sub H+/)/sup -0.2/. Nepheline dissolution rates (R/sub idiss) exhibit a minimum in the pH range 5-7. Initial rates of consumption of protons indicate that in the acid pH region, a positively charged complex is formed on the nepheline surface by adsorption of protrons. It is postulated that it is the rate of breakdown of the surface complex so formed which determines the rate of dissolution of nepheline. Activation energies for the dissolution of nepheline are in the range 53-77 kJ/mole. Addition of 3 m NaCl to the aqueous solution at pH 5 and 60/sup 0/C lowers the dissolution rate by an order of magnitude. The most stable conditions (i.e. conditions under which a mineral is least reactive) for nepheline are in the pH range 5 less than or equal to pH less than or equal to 7, and in highly saline aqueous solutions.« less