HPx-eos: metabasite set

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• General information
• Full model details and benchmark calculations
• Download THERMOCALC input files
• Information related to use with other software

General information

Citation: 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.

Phases:

Phase	Also in sets	First published
silicate melt		this paper
hornblende, actinolite and glaucophane	igneous	this paper
augitic clinopyroxene		this paper
jadeite-omphacite-diopside clinopyroxene		this paper
plagioclase and potassium feldspar (ternary)	metapelite, igneous	Holland et al (2021) J Metam Geol DOI 10.1111/jmg.12639
low albite with solid solution towards anorthite		Holland et al (2021) J Metam Geol DOI 10.1111/jmg.12639
garnet	metapelite	White et al (2014) J Metamorph Geol 32 261-286
biotite	metapelite	White et al (2014) J Metamorph Geol 32 261-286
orthopyroxene	metapelite	White et al (2014) J Metamorph Geol 32 261-286
olivine		Holland & Powell (2011) J Metamorph Geol 29 333-383
muscovite	metapelite, igneous	this paper
chlorite	metapelite	White et al (2014) J Metamorph Geol 32 261-286
epidote	metapelite, igneous	Holland & Powell (2011) J Metamorph Geol 29 333-383
ilmenite and hematite	metapelite	White et al (2000) J Metamorph Geol 18 497-511
spinel magnetite	metapelite	White et al (2002) J Metamorph Geol 20 41-55

Use for: equilibria in typical metabasite bulk compositions at < 20 kbar (or cautiously at < 30 kbar).

Known issues/warnings:

• Subsolidus equilibria! Calculated stable phase relations in the blueschist and greenschist facies are very sensitive to some poorly known parameters, chiefly (I think) the standard enthalpies of formation of the amphibole end-members, which appear in three amphibole phases. To see the problem, compare calculations using ds62 and ds63. Although these two datasets are not meaningfully different in a statistical sense (ds63 was created in order to add some new end-members related to (?)peridotite equilibria), the stable assemblages look petrologically sensible with ds62, but not with ds63.
• Note that there are two different cpx x-eos in this set, augitic clinopyroxene and jadeite-omphacite-diopside clinopyroxene. They should never be used together! There are notes on this included with the file downloads below.
• Clinopyroxene appears to be too stable in amphibolites.
• The clinoamphibole x-eos sometimes takes too much tetrahedral Al, resulting in < 6 Si p.f.u. on a 24-oxygen basis.
• Are you aware of any other problems? Please let us know!

Full model details and benchmark calculations

Here we provide human-readable details of the metabasite-set HPx-eos, along with benchmark calculations to allow implementations to be tested. Contact us if anything remains unclear.

Download full HPx-eos details for phases: silicate melt, clinoamphibole, clinopyroxene (with tschermaks substitution; no M2-site order-disorder), clinopyroxene (no tschermaks substitution; full omphacitic order-disorder), orthopyroxene, garnet, olivine, feldspars, spinel/magnetite, ilmenite/hematite, epidote, biotite, muscovite, chlorite (current 30-01-2022):

End-members from dataset version: 6.2 (Mon 6 Feb, 2012)

Benchmarks, generated with THERMOCALC 3.50. These files don’t necessarily represent key (or necessarily most stable) equilibria; they are just to check implementation of the x-eos. Contact us if you need specific additional calculations for comparison and are unable to produce these yourself. Download here:

Download THERMOCALC input files

If you’re new to THERMOCALC, please begin by reading the THERMOCALC section of the website, and download the files below as directed in the Get started guide.

Download THERMOCALC input files/information for the metabasite-set HPx-eos here (the current bundle is dated 30-01-2022):

• Dataset 6.2 input file tc-ds62.txt (Mon 6 Feb, 2012).
• Axfiles tc-mb47NCKFMASHTO.txt, formatted for THERMOCALC version 3.47, and tc-mb50NCKFMASHTO.txt, for version 3.50. These files replace tc-6axNCKFMASHTOm40.txt and 6axNCKFMASHTOm45.txt from the original web distribution, correcting a typo in the model for Ibar1 plagioclase in 6axNCKFMASHTOm45.txt.
• Full descriptions of the x-eos, including definitions of mixing sites, end-members and compositional variables.
• Samecoding information and a selection of starting guesses for compositional/order variables that might be suitable as a starting point for a calculation.

Information related to use with other software

In Perple_X: HPx-eos that were first published in the metabasite set are labelled “(G)”. The many x-eos that are shared by the metabasite and metapelite sets, and were first published in the metapelite set, are labelled “(W)”. Jeff Moyen’s spreadsheet gives more information.

Please contact us if you think there is other information we should include here.