The stability of sodalite in the system NaAlSiO4-NaCl
dc.contributor.author | Sharp, Z. D. | en_US |
dc.contributor.author | Helffrich, G. R. | en_US |
dc.contributor.author | Bohlen, Steven R. | en_US |
dc.contributor.author | Essene, Eric J. | en_US |
dc.date.accessioned | 2006-04-07T20:45:11Z | |
dc.date.available | 2006-04-07T20:45:11Z | |
dc.date.issued | 1989-08 | en_US |
dc.identifier.citation | Sharp, Z. D., Helffrich, G. R., Bohlen, S. R., Essene, E. J. (1989/08)."The stability of sodalite in the system NaAlSiO4-NaCl." Geochimica et Cosmochimica Acta 53(8): 1943-1954. <http://hdl.handle.net/2027.42/27840> | en_US |
dc.identifier.uri | http://www.sciencedirect.com/science/article/B6V66-489SJBT-65/2/860adf447b38588353cb0a9958e9861a | en_US |
dc.identifier.uri | https://hdl.handle.net/2027.42/27840 | |
dc.description.abstract | The reaction SODALITE = [beta]-nepheline + NaCl (s) was reversed in solid-medium apparatus (923 K, 7.6-8.0 kbar; 973 K, 7.4-7.6 kbar; 1073 K, 7.8-8.0 kbar; 1173 K, 8.4-8.6 kbar) and the reaction SODALITE = carnegieite + NaCl (l) was reversed at 1 bar (1649-1652 K). The calculated slope for the first reaction is -11 bar/K compared to the experimentally constrained slope above 973 K of +5 bar/K. This major discrepancy can be eliminated if the entropy of sodalite (Na8Al6Si6O24Cl2) is 61.7 J/mol [middle dot] K greater than the measured value of 848.1 +/- 4.0 J/mol [middle dot] K at 298.15 K. This entropy contribution is equal to that expected from 58% disorder of Al and Si on the tetrahedral sites, but could also be caused by a reversible phase change. The experimental reversals between 923 K and 973 K can be fit with a dP/dT of -11 bar/K, suggesting that the excess entropy for sodalite is present only above 923 K. A phase diagram for the NaAlSiO4-NaCl system that is consistent with the measured thermochemical data and the experiments between 973 and 1650 K can be generated if the 61.7 J/mol [middle dot] K entropy contribution is included in the S2980 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]G2980 for sodalite (-12697 kJ/mol) and carnegieite (NaAlSiO4) (-1958 kJ/mol), S2980 of carnegieite (129.6 J/mol [middle dot] K) and compressibility of NaClliquid (V298P (cm3) = 31.6 [middle dot] [1 - 24.7 [middle dot] 10-3 [middle dot] P + 800 [middle dot] 10-6 [middle dot] P2]) (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 1073 K and 0.13 at 1273 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. | en_US |
dc.format.extent | 1822308 bytes | |
dc.format.extent | 3118 bytes | |
dc.format.mimetype | application/pdf | |
dc.format.mimetype | text/plain | |
dc.language.iso | en_US | |
dc.publisher | Elsevier | en_US |
dc.title | The stability of sodalite in the system NaAlSiO4-NaCl | en_US |
dc.type | Article | en_US |
dc.rights.robots | IndexNoFollow | en_US |
dc.subject.hlbsecondlevel | Geology and Earth Sciences | en_US |
dc.subject.hlbsecondlevel | Chemistry | en_US |
dc.subject.hlbtoplevel | Science | en_US |
dc.description.peerreviewed | Peer Reviewed | en_US |
dc.contributor.affiliationum | Department of Geological Sciences, University of Michigan, Ann Arbor, MI 48109, U.S.A. | en_US |
dc.contributor.affiliationother | Geophysical Laboratory, Carnegie Institution of Washington, 2801 Upton Street, N.W., Washington, D.C. 20008, U.S.A. | en_US |
dc.contributor.affiliationother | Department of Geological Sciences, Northwestern University, Evanston, IL 60208, U.S.A. | en_US |
dc.contributor.affiliationother | Department of Earth and Space Sciences, S.U.N.Y, Stony Brook, NY 11794, U.S.A. | en_US |
dc.description.bitstreamurl | http://deepblue.lib.umich.edu/bitstream/2027.42/27840/1/0000249.pdf | en_US |
dc.identifier.doi | http://dx.doi.org/10.1016/0016-7037(89)90315-3 | en_US |
dc.identifier.source | Geochimica et Cosmochimica Acta | en_US |
dc.owningcollname | Interdisciplinary and Peer-Reviewed |
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