TY - JOUR

T1 - Phase relations and compositional dependence of H2O solubility in quartz-feldspar melts

AU - Pichavant, Michel

AU - Holtz, François

AU - McMillan, Paul F.

N1 - Funding Information: This study was supportedb y the European Economic Community (Action de Stimulation ST2"0252), Procope (91162), German Science Foundation (SFB 173) and by the CNRS program Ultimatech. Pascal Richer, Don Dingwell and Yan Bottingaa regratefully acknowledgefdo r the invitationt o presentth is study at the Le Hohwald Workshop.T hanksto J.M. Brny, M. Henry and B. Mottet for discussions, to C. Constant for drafting the figures and to C. Le Coq for preparationof the tables and referencesR. eviewedb y W.L. Brown and H. Keppler. Copyright: Copyright 2014 Elsevier B.V., All rights reserved.

PY - 1992/4/15

Y1 - 1992/4/15

N2 - Liquidus phase relations are presented for the systems Qz-Ab and Qz-Or at 2 and 5 kbar under both H2O1bsaturated and H2O1bundersaturated conditions. The data allow to specify the effects on phase equilibria of: (1) varying the water content of the melt under isobaric conditions; and (2) varying pressure under H2O1bsaturated conditions. The effects are different from each other and they depend on the system investigated. Increasing the water content of the melt at 2 kbar lowers liquidus and eutectic temperatures more in the Qz-Ab than in the Qz-Or system, while eutectic compositions remain unchanged. In contrast, the effect of increasing P(=PH2O) from 2 to 5 kbar is mainly to shift the eutectic composition in the Qz-Ab system towards more albite-rich compositions, whereas no compositional change is observed for the Qz-Or eutectic. The contrast between the two systems when isobarically varying the water content of the melt can be attributed to higher water solubilities in Na-than in K-bearing melt compositions. Liquidus phase relations with varying P(=PH2O) reflect the combination of the effects of pressure and water content of the melt. The compositional range of water contents in the melt used in this study implies that molecular H2O is the water species involved in the observed changes in phase relations. Current models and recent spectroscopic data for water solubility mechanisms in aluminosilicate glasses and melts are critically examined. The variation in water solubility between aluminosilicate melts is due to the differential incorporation of molecular H2O.

AB - Liquidus phase relations are presented for the systems Qz-Ab and Qz-Or at 2 and 5 kbar under both H2O1bsaturated and H2O1bundersaturated conditions. The data allow to specify the effects on phase equilibria of: (1) varying the water content of the melt under isobaric conditions; and (2) varying pressure under H2O1bsaturated conditions. The effects are different from each other and they depend on the system investigated. Increasing the water content of the melt at 2 kbar lowers liquidus and eutectic temperatures more in the Qz-Ab than in the Qz-Or system, while eutectic compositions remain unchanged. In contrast, the effect of increasing P(=PH2O) from 2 to 5 kbar is mainly to shift the eutectic composition in the Qz-Ab system towards more albite-rich compositions, whereas no compositional change is observed for the Qz-Or eutectic. The contrast between the two systems when isobarically varying the water content of the melt can be attributed to higher water solubilities in Na-than in K-bearing melt compositions. Liquidus phase relations with varying P(=PH2O) reflect the combination of the effects of pressure and water content of the melt. The compositional range of water contents in the melt used in this study implies that molecular H2O is the water species involved in the observed changes in phase relations. Current models and recent spectroscopic data for water solubility mechanisms in aluminosilicate glasses and melts are critically examined. The variation in water solubility between aluminosilicate melts is due to the differential incorporation of molecular H2O.

UR - http://www.scopus.com/inward/record.url?scp=0026459491&partnerID=8YFLogxK

U2 - 10.1016/0009-2541(92)90061-9

DO - 10.1016/0009-2541(92)90061-9

M3 - Article

AN - SCOPUS:0026459491

VL - 96

SP - 303

EP - 319

JO - Chemical Geology

JF - Chemical Geology

SN - 0009-2541

IS - 3-4

ER -