### Abstract

We have experimentally determined the displacement of the equilibrium Grossular + 2 Kyanite + Quartz ⇄ 3 Anorthite (GASP) as a function of garnet composition in the systems Mg-Ca-Mn, Fe-Mg-Ca and Fe-Mg-Ca-Mn at 1000°C. The results were treated along with selected experimental and observational data available in the literature as well as binary parameters from other workers to obtain a set of mutually compatible binary mixing parameters of the quaternary (Fe,Mg,Ca,Mn)- aluminosilicate garnet solid solution. Attempts to determine equilibrium garnet composition in the GASP equilibrium in the Ca-Mg binary were unsuccessful due to the formation of pyroxene. Calculations of binary and ternary miscibility gaps show that the P,T,X combination required for unmixing of garnet solid solution is not realized by natural samples. The solution model was applied to account for compositional effects on Fe-Mg exchange between garnet and ortho- or clinopyroxene. Applications of the revised thermometric formulations to selected natural assemblages yield P-T conditions which are much less sensitive to compositional effects compared to the other available formulations, and are consistent with independent constraints. ΔV̄ and ΔV°: Partial molar volume change and end-member molar volume change of a reaction, respectively. W_{ij}^{G}, W_{ij}^{H}, and W_{ij}^{S}: Subregular free energy, enthalpic and entropie binary interaction parameter, respectively, between the components i and j. W^{G}(i-j), W^{H}(i-j), and W^{s}(i-j): Regular solution or simple mixture free energy, enthalpic and entropie interaction parameter, respectively, between the components i and j. ΔW_{1}: W(Mg-i) - W(Fe-i). X_{1}^{α}: Atomic fraction of the component i in the phase α in the site of mixing.

Original language | English (US) |
---|---|

Pages (from-to) | 137-151 |

Number of pages | 15 |

Journal | Contributions to Mineralogy and Petrology |

Volume | 126 |

Issue number | 1-2 |

State | Published - 1997 |

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### ASJC Scopus subject areas

- Geochemistry and Petrology
- Geophysics

### Cite this

*Contributions to Mineralogy and Petrology*,

*126*(1-2), 137-151.

**Thermodynamics of aluminosilicate garnet solid solution : New experimental data, an optimized model, and thermometric applications.** / Ganguly, Jibamitra; Cheng, Weiji; Tirone, Massimiliano.

Research output: Contribution to journal › Article

*Contributions to Mineralogy and Petrology*, vol. 126, no. 1-2, pp. 137-151.

}

TY - JOUR

T1 - Thermodynamics of aluminosilicate garnet solid solution

T2 - New experimental data, an optimized model, and thermometric applications

AU - Ganguly, Jibamitra

AU - Cheng, Weiji

AU - Tirone, Massimiliano

PY - 1997

Y1 - 1997

N2 - We have experimentally determined the displacement of the equilibrium Grossular + 2 Kyanite + Quartz ⇄ 3 Anorthite (GASP) as a function of garnet composition in the systems Mg-Ca-Mn, Fe-Mg-Ca and Fe-Mg-Ca-Mn at 1000°C. The results were treated along with selected experimental and observational data available in the literature as well as binary parameters from other workers to obtain a set of mutually compatible binary mixing parameters of the quaternary (Fe,Mg,Ca,Mn)- aluminosilicate garnet solid solution. Attempts to determine equilibrium garnet composition in the GASP equilibrium in the Ca-Mg binary were unsuccessful due to the formation of pyroxene. Calculations of binary and ternary miscibility gaps show that the P,T,X combination required for unmixing of garnet solid solution is not realized by natural samples. The solution model was applied to account for compositional effects on Fe-Mg exchange between garnet and ortho- or clinopyroxene. Applications of the revised thermometric formulations to selected natural assemblages yield P-T conditions which are much less sensitive to compositional effects compared to the other available formulations, and are consistent with independent constraints. ΔV̄ and ΔV°: Partial molar volume change and end-member molar volume change of a reaction, respectively. WijG, WijH, and WijS: Subregular free energy, enthalpic and entropie binary interaction parameter, respectively, between the components i and j. WG(i-j), WH(i-j), and Ws(i-j): Regular solution or simple mixture free energy, enthalpic and entropie interaction parameter, respectively, between the components i and j. ΔW1: W(Mg-i) - W(Fe-i). X1α: Atomic fraction of the component i in the phase α in the site of mixing.

AB - We have experimentally determined the displacement of the equilibrium Grossular + 2 Kyanite + Quartz ⇄ 3 Anorthite (GASP) as a function of garnet composition in the systems Mg-Ca-Mn, Fe-Mg-Ca and Fe-Mg-Ca-Mn at 1000°C. The results were treated along with selected experimental and observational data available in the literature as well as binary parameters from other workers to obtain a set of mutually compatible binary mixing parameters of the quaternary (Fe,Mg,Ca,Mn)- aluminosilicate garnet solid solution. Attempts to determine equilibrium garnet composition in the GASP equilibrium in the Ca-Mg binary were unsuccessful due to the formation of pyroxene. Calculations of binary and ternary miscibility gaps show that the P,T,X combination required for unmixing of garnet solid solution is not realized by natural samples. The solution model was applied to account for compositional effects on Fe-Mg exchange between garnet and ortho- or clinopyroxene. Applications of the revised thermometric formulations to selected natural assemblages yield P-T conditions which are much less sensitive to compositional effects compared to the other available formulations, and are consistent with independent constraints. ΔV̄ and ΔV°: Partial molar volume change and end-member molar volume change of a reaction, respectively. WijG, WijH, and WijS: Subregular free energy, enthalpic and entropie binary interaction parameter, respectively, between the components i and j. WG(i-j), WH(i-j), and Ws(i-j): Regular solution or simple mixture free energy, enthalpic and entropie interaction parameter, respectively, between the components i and j. ΔW1: W(Mg-i) - W(Fe-i). X1α: Atomic fraction of the component i in the phase α in the site of mixing.

UR - http://www.scopus.com/inward/record.url?scp=0030326807&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0030326807&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0030326807

VL - 126

SP - 137

EP - 151

JO - Contributions of Mineralogy and Petrology

JF - Contributions of Mineralogy and Petrology

SN - 0010-7999

IS - 1-2

ER -