### Abstract

The univariant reaction governing the upper stability of heulandite (CaAl_{2}Si_{7}O_{18}·6H_{2}O), heulandite=laumontite+3 quartz+2H_{2}O (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 H_{2}O, defines an invariant point at which a third reaction, stilbite=heulandite+ H_{2}O, 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}= P_{total}.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 language | English |
---|---|

Pages (from-to) | 43-50 |

Number of pages | 8 |

Journal | Contributions to Mineralogy and Petrology |

Volume | 97 |

Issue number | 1 |

DOIs | |

Publication status | Published - Sep 1987 |

Externally published | Yes |

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### ASJC Scopus subject areas

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

### Cite this

*Contributions to Mineralogy and Petrology*,

*97*(1), 43-50. https://doi.org/10.1007/BF00375213

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

Research output: Contribution to journal › Article

*Contributions to Mineralogy and Petrology*, vol. 97, no. 1, pp. 43-50. https://doi.org/10.1007/BF00375213

}

TY - JOUR

T1 - An experimental investigation of heulandite-laumontite equilibrium at 1000 to 2000 bar Pfluid

AU - Cho, M.

AU - Maruyama, S.

AU - Liou, J. G.

PY - 1987/9

Y1 - 1987/9

N2 - 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.

AB - 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.

UR - http://www.scopus.com/inward/record.url?scp=0023497260&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0023497260&partnerID=8YFLogxK

U2 - 10.1007/BF00375213

DO - 10.1007/BF00375213

M3 - Article

AN - SCOPUS:0023497260

VL - 97

SP - 43

EP - 50

JO - Contributions of Mineralogy and Petrology

JF - Contributions of Mineralogy and Petrology

SN - 0010-7999

IS - 1

ER -