- General information
- Full model details and benchmark calculations
- Download THERMOCALC input files
- Information related to use with other software
Citation: 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.
|Phase||Also in sets||First published|
|silicate melt||this paper|
|aqueous fluid||this paper|
|Ibar1 plagioclase feldspar (Ca-rich)||metapelite, metabasite||Holland & Powell (2003) Contrib Mineral Petrol 145 492-501|
|Cbar1 plagioclase feldspar (Na-rich) and potassium feldspar||metapelite, metabasite||Holland & Powell (2003) Contrib Mineral Petrol 145 492-501|
|spinel, Cr-spinel and magnetite||this paper|
|clinopyroxene and pigeonite||this paper|
|cordierite||somewhat reparameterised from White et al (2014) J Metamorph Geol 32 261-286|
|biotite||somewhat reparameterised from White et al (2014) J Metamorph Geol 32 261-286|
|muscovite||metapelite, metabasite||White et al (2014) J Metamorph Geol 32 261-286|
|epidote||metapelite, metabasite||Holland & Powell (2011) J Metamorph Geol 29 333-383|
|hornblende||metabasite||Green et al (2016) J Metamorph Geol 34 845-892|
|ilmenite||metapelite, metabasite||White et al (2000) J Metamorph Geol 18 497-511|
Use for: partial melting equilibria involving basaltic through to granitic melt compositions, excluding equilibria involving very alkaline magmas, omphacitic or jadeitic pyroxene. Dry peridotite melting calculations are calibrated up to ~60 kbar; calculations in hydrated systems are limited to pressures below 20 kbar (or 30 kbar with caution) by the large uncertainties associated with dissolution of silicates in aqueous fluids.
The igneous set will form the basis for future developments to the HPx-eos. In principle they can be used to replace the metapelite and metabasite sets in many contexts – if you’ve done a comparison between the two, we’d be very interested to hear about it.
- (Orthopyroxene stability: although the HPx-eos for opx strictly spans a compositional space that is bounded by the diopside composition, users/implementers should keep the composition to XCaM2 < 0.5 to avoid the stability of a inappropriate high-Ca opx phase. — This problem should be solved in the new x-eos bundle from 13-07-2020.)
- For peridotite melting (and other contexts?), the calculated mode of orthopyroxene is often much too large, in some cases twice the expected volumetric proportion.
- Calculations with Perple_X indicate that small regions of multiple melt phase stability may occur near the solidus in peridotitic systems. If so, this is an unintended result, and we’d be glad to hear about it.
- 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 igneous-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, aqueous fluid, plagioclase feldspar (Ibar1; Ca-rich), plagioclase feldspar (Cbar1; Na-rich; also used for potassium feldspar), olivine, muscovite, biotite, garnet, epidote, cordierite, orthopyroxene, clinopyroxene (also pigeonite), spinel (also Cr-spinel, magnetite), hornblende, ilmenite (current 13-07-2020):
End-members from dataset version: 6.33 (Fri 23 Jun, 2017)
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 (current 13-07-2020):
Alternative Fig. 5 (RE46 basalt pseudosection) from the Holland et al (2018) paper. The published figure focuses on the 1 bar phase relations, and only extends these phase relations to higher pressure in an indicative sense, ignoring other phases that become stable at higher pressures. Due to feedback from users, Tim Holland has provided an alternative figure that shows the stable phase relations, neglecting a high-Ca opx that is stable at low pressure:
Download THERMOCALC input files
Download THERMOCALC input files/information for the igneous-set HPx-eos here (the current bundle is dated 13-07-2020):
- dataset 6.33 input file tc-ds633.txt (Fri 23 Jun, 2017)
- axfiles tc-ig47<system>.txt, formatted for THERMOCALC version 3.47, and tc-ig50<system>.txt, for version 3.50, in systems NCKFMASTOCr and NCKFMASHTOCr (these replace files in previous web distributions)
- 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.
Alternatively you can download the full web distribution that accompanied the paper (updated Apr 2019) on Tim Holland’s software pages. This includes the fo2melt program and more examples relating to calculations in the paper; however the axfiles included are compatible with THERMOCALC 3.47 only
Information related to use with other software
In Perple_X: HPx-eos that are unique to the igneous set are labelled “(HGP)”. Jeff Moyen’s spreadsheet gives more information.
Please contact us if you think there is other information we should include here.