An experimental investigation of heulandite-laumontite equilibrium at 1000 to 2000 bar Pfluid

M. Cho, S. Maruyama, J. G. Liou

Research output: Contribution to journalArticle

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Abstract

The univariant reaction governing the upper stability of heulandite (CaAl2Si7O18·6H2O), heulandite=laumontite+3 quartz+2H2O (1), has been bracketed through reversal experiments at: 155±6° C, 1000 bar; 175±6° C, 1500 bar; and 180±8° C, 2000 bar. Reversals were established by determining the growth of one assemblage at the expense of the other, using both XRD and SEM studies. The standard molal entropy of heulandite is estimated to be 783.7±16 J mol-1 K-1 from the experimental brackets. Predicted standard molal Gibbs free energy and enthalpy of formation of heulandite are -9722.3±6.3 kJ mol-1 and -10524.3±9.6 kJ mol-1, respectively. The reaction (1), together with the reaction, stilbite=laumontite+3 quartz+3 H2O, defines an invariant point at which a third reaction, stilbite=heulandite+ H2O, meets. By combining the present experimental data with past work, this invariant point is located at approximately 600 bar and 140° C. Heulandite, which is stable between the stability fields of stilbite and laumontite, can occur only at pressures higher than that of the invariant point, for {Mathematical expression}= Ptotal.These results are consistent with natural parageneses in low-grade metamorphic rocks recrystallized in equilibrium with an aqueous phase in which {Mathematical expression} is very close to unity.

Original languageEnglish
Pages (from-to)43-50
Number of pages8
JournalContributions to Mineralogy and Petrology
Volume97
Issue number1
DOIs
Publication statusPublished - Sep 1987
Externally publishedYes

Fingerprint

heulandite
laumontite
Quartz
quartz
Metamorphic rocks
metamorphic rocks
Gibbs free energy
brackets
unity
Enthalpy
grade
Entropy
enthalpy
paragenesis
entropy
metamorphic rock
Scanning electron microscopy
scanning electron microscopy
X-ray diffraction
Experiments

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences(all)
  • Environmental Science(all)

Cite this

An experimental investigation of heulandite-laumontite equilibrium at 1000 to 2000 bar Pfluid. / Cho, M.; Maruyama, S.; Liou, J. G.

In: Contributions to Mineralogy and Petrology, Vol. 97, No. 1, 09.1987, p. 43-50.

Research output: Contribution to journalArticle

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