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Multiple sets of x-eos for magmatic systems have been published. As of December 2024, the sets recommended for use are:
- Weller et al, 2024 (W24) x-eos: for calculations in anhydrous subalkaline to alkaline magmatic systems.
- Green et al, 2025 (G25) x-eos, a correction to Holland et al (2018): for calculations in hydrous or anhydrous subalkaline systems.
We have removed the following sets of x-eos from this site, after discovering an algebraic error in the formulation of the melt x-eos:
- Tomlinson & Holland, 2021 (T21): Tomlinson, EL & Holland, TJB (2021). A thermodynamic model for the subsolidus evolution and melting of peridotite. Journal of Petrology 62 egab012. For calculations in peridotitic systems at ≤ 50 kbar. No replacement currently available.
- Holland et al, 2018 (H18): Holland, TJB, Green, ECR & Powell, R (2018). Melting of peridotites through to granites: a simple thermodynamic model in the system KNCFMASHTOCr. Journal of Petrology 59 881-900. For calculations in hydrous or anhydrous subalkaline systems. Replaced by Green et al, 2025.
See also: which x-eos for phases in each set?
Calculations in anhydrous subalkaline to alkaline systems
The W24 igneous set.
Citation: Weller, OM, Holland, TJB, Soderman, CR, Green, ECR, Powell, R, Beard, CD & Riel, N (2024). New Thermodynamic Models for Anhydrous Alkaline-Silicate Magmatic Systems. Journal of Petrology 65 egae098. For calculations in anhydrous subalkaline to alkaline magmatic systems.
As of December 2024, these x-eos can be used in MAGEMin (Riel et al, 2022), or in THERMOCALC version 3.51 and later. Download input files for THERMOCALC here:
For calculations in hydrous or anhydrous subalkaline systems
The G25 igneous set.
Citation: Green, ECR, Holland, TJB, Powell, R, Weller, OM, & Riel, N (2025). Corrigendum to: Melting of peridotites through to granites: a simple thermodynamic model in the system KNCFMASHTOCr, and, A thermodynamic model for the subsolidus evolution and melting of peridotite. Journal of Petrology, XXXXX
As of December 2024, these x-eos can be used in MAGEMin (Riel et al, 2022), or in THERMOCALC version 3.51 and later. Download input files for THERMOCALC here:
Which x-eos for which set?
The four sets of x-eos for magmatic systems listed above use various versions of x-eos for specific phases, some of which were published prior to H18. They also use different versions of the Holland & Powell (2011) internally-consistent dataset of end-member thermodynamic data. The following table summarizes the x-eos for individual phases and the dataset versions used in the four sets:
| Phases | G25 | W24 | T21* | H18* |
| silicate melt | liq_G25w | liq_W24d | liq_T21d | liq_H18w |
| aqueous fluid | fl_G25 | – | – | fl_H18 |
| olivine | ol_H18 | ol_H18 | ol_H18 | ol_H18 |
| garnet | g_W24 | g_W24 | g_T21 | g_H18 |
| spinel-group | spl_T21 | spl_T21 | spl_T21 | spl_H18 |
| feldspars | fsp_H22 | fsp_H22 | fsp_T21 | fsp_H03 |
| clinopyroxene | cpx_W24 | cpx_W24 | cpx_T21 | cpx_H18 |
| orthopyroxene | opx_W24 | opx_W24 | opx_T21 | opt_h18 |
| ilmenite/hematite | ilm_W24 | ilm_W24 | – | ilm_W00 |
| biotite | bi_G25 | – | – | bi_H18 |
| muscovite | mu_W14 | – | – | mu_W14 |
| clinoamphibole | amp_G16 | – | – | amp_G16 |
| epidote | ep_H11 | – | – | ep_H11 |
| cordierite | cd_G25 | – | – | cd_H18 |
| nepheline | – | nph_W24 | – | – |
| kalsilite | – | kals_W24 | – | – |
| leucite | – | lct_W24 | – | – |
| melilite | – | mel_W24 | – | – |
| Dataset version | 6.36 | 6.36 | 6.34 | 6.33 |
*should not be used due to algebraic mistake in melt x-eos.
The codes used in the x-eos names refer to the following studies, in addition to the four referenced above:
H22 – Holland, TJB, Green, ECR & Powell, R (2022). A thermodynamic model for feldspars in KAlSi3O8-NaAlSi3O8-CaAl2Si2O8 for mineral equilibrium calculations. Journal of Metamorphic Geology 40 587-600
G16 – The “metabasite” set. Green, ECR, White, RW, Diener, JFA, Powell, R, Holland, TJB &
Palin, RM (2016). Activity-composition relations for the calculation of partial melting equilibria in metabasic rocks. Journal of Metamorphic Geology 34 845-869
W14 – The “metapelite” set. New mineral activity-composition relations for thermodynamic calculations in metapelitic systems. Journal of Metamorphic Geology 32 261-286
H11 – Holland, TJB & Powell, R (2011). An improved and extended internally consistent thermodynamic dataset for phases of petrological interest, involving a new equation of state for solids. Journal of Metamorphic Geology 29 333-383
H03 – Holland, TJB & Powell, R (2003). Activity-composition relations for phases in petrological calculations: an asymmetric multicomponent formulation. Contributions to Mineralogy and Petrology 145 492-501
W00 – White, RW, Powell, R, Holland, TJB & Worley, B (2000). The effect of TiO2 and Fe2O3 on metapelitic assemblages at greenschist and amphibolite facies conditions: mineral equilibria calculations in the system K2O-FeO-MgO-Al2O3-SiO2-H2O-TiO2-Fe2O3. Journal of Metamorphic Geology 18 497-511
Contact us
Please contact us if you find problems with the Weller et al (2024) or Green et al (2025) x-eos, or if you think there is other information we should include on this page.
The HPx-eos and THERMOCALC 