[EX] easyMelts version of tutorial: 'Quick start using MELTS'

[Paula]

This topic will show you how to work through one page of the (old) MELTS tutorial, using the current downloadable easyMelts software:

Testing MELTS installation using the sample input file - Try this first

The page is part of the 'Getting Started: Testing and Examples' section of the MELTS manual, written by Mark Ghiorso for the original graphical-user-interface (GUI) version. The idea of this topic is to show simularities and differences between the easyMelts GUI and the (Rhyolite-)MELTS GUI, and as a comparison with the alphaMELTS 2 and other versions of the same tutorial.

The software can be downloaded from the MAGMA Source GitList server. The links page summarizes the download options. Screen output will be added to this post later. There is very little difference between the interface on Windows, Mac, and Linux. Only note that if you want to start easyMelts by double-clicking on Mac, then you should click the easyMelts.command script that will open Terminal and then easyMelts (else you are likely to run into the where are my files? problem).

This example uses the starting conditions and bulk composition from an input file that has been modified from the Morb.melts file used in the original tutorial. The modifications simply bring it up to date with the latest GUI versions of MELTS and do not affect software results. Early versions of the MELTS software used a 'Mode: Fractionation' line in the input file to to select fractional crystallization, whereas in later versions this is replaced by 'Mode: Fractionate Solids'. Also some phases were suppressed in the original tutorial because the solid solution models were still being developed / tested. None of the phases are stable for the run conditions of the tutorial example, so suppressing these phases has no effect. However, the 'Suppress:  ' lines can cause read errors as the names of some phases have changed slightly since (see here).

If you have downloaded and installed alphaMELTS 2 then the modified Morb.melts file will be in the included 'tutorial' folder and you can copy it from there. Otherwise, copy the contents of the file from this reply and save it as 'Morb.melts'. Note that the version of Morb.melts available on the MAGMA Source server is the same except that it has Windows line endings but the morb.melts version linked on the Mac OS X download site differs slightly in Cr₂O₃ content and in the P-T conditions. Unlike the Rhyolite-MELTS GUI and alphaMELTS 2, easyMelts seems to tolerate incorrect line endings but if you are having trouble reading in a file then check the [FAQ] Fixing line ending issues with file-format.command post to see if that helps.

As mentioned above, you can start easyMelts on Windows or Mac by double-clicking easyMelts.exe or easyMelts.command. Double-clicking might work on some Linux systems (you may be asked if you want to open the file in a terminal, in which case select "yes") but on the Windows Subsystem for Linux you will have to open easyMelts from the command line. Navigate to where easyMelts is located, using 'cd path_to_easyMelts' (cd = 'change directory') then type './easyMelts'. For any of these methods easyMelts will always open in the path_to_easyMelts folder, and you will need to put Morb.melts in this folder to be able to open it. The melts.out and the .tbl output will be written to path_to_easyMelts or, on Windows to a subfolder called 'tables' (you don't get any choice about this location). If the phase assemblage differs between run 1 and run 2, melts.out and all the .tbl files for phases in run 2 will be overwritten but any other .tbl files from run 1 will still be hanging around.

There are a few ways to workaround this with easyMelts. One option is to move the files after each run (if you have alphaMELTS 2 installed you can do this easily by typing "run-alphamelts.command -x -p name_of_folder" which will make the folder and move the .tbl files to it). Alternatively, easyMelts can write out Excel files. These contain less information than in the full melts.out / .tbl files combination but may be enough for what you need. Finally you can put a copy of easyMelts in a folder that is in your Path (again if you have installed alphaMELTS 2 with default options then you will have a folder 'bin', 'Documents/bin', or 'Documents\bin' depending on your system that should already be in the Path). If you do that then open a terminal, navigate to where you want the input and output files to be and type 'easyMelts' (no './').

Once you have started easyMelts you need to select the correct MELTS model. There is more explanation of the various MELTS versions in the MELTS decision tree. However, rhyolite-MELTS 1.0.2 should give identical results to the original MELTS model for the bulk composition used here. So, choose Init->Version->MELTS_v1.0.x. If you click on Set initial T & P and/or Set initial composition you will see that easyMelts comes with a initial conditions pre-loaded. These are actually the same as the other morb.melts so we will just need to change a couple of entries, rather than typing in everything from scratch.

First, click on Set initial T & P and change the pressure to 500.0 (bars) and click Save (note the tooltip warning that shows if you hover the mouse over the red '(?)'). Second, click on Set initial composition and change Cr2O3 from 0.043 to 0.03. Two buttons will appear. If you click the RedistFeOx one then the settings for the underlying MELTS algorithm should now the same as described in the 'Four things have been accomplished:' list in the original tutorial (although as the ferric/ferrous ratio is being taken from the MORB glass RedistFeOx will simply normalize the bulk composition). You can verify that the P-T conditions are set correctly in the panel to the right below Set options, and check the composition by clicking the Initial bulk composition dropdown.

Next click the Liquidus&RedistFeOx button and see that the Initial liquidus T and Current T are both set to 1220.31 (C). Then select Set run settings. The original tutorial used an "Increment Temperature: 3.00" and "Final Temperature: 1000.00" easyMelts doesn't use a Final Temperature (or Final Pressure) setting like this. Instead set Calc steps to 74 and Increment between steps to -3.00. Check the Solids box below Fractionate phases, and we are ready to click Equilibrate.

We can get to this point by reading in the Rhyolite-MELTS-style Morb.melts file instead. After selecting Init, go to Export/Load->Load .melts and select Morb.melts. There are two important things to note. Firstly, the pressure, temperature and bulk composition input boxes on the left are not updated, so if you select Save again you will be resetting the system to the other pressure and/or Cr2O3 content. Instead, verify that the P-T conditions are set correctly in the panel to the right below Set options, and check the composition by clicking the Initial bulk composition dropdown. Secondly easyMelts uses a signed Temperature increment like alphaMELTS 2. You will need to select Set run settings, add the Calc steps and correct the Increment between steps to -3.00.

Once completed, the calculation results will be displayed to the right. The Steps bar is a slider that you can drag to display the state at any step of the calculation, and the Liquid, Solid and fluid, and Fractionated solids and fluids are dropdowns with full information. You can also write out an Excel file with some of this information by selecting Export/Load->Export XLSX. If you switch to the Plot tab you will see two automatically generated interactive plots. You can select or deselect oxides on the Melt composition plot, and change the X-axis on the Phases in magma / Fractionated phases plot.

As mentioned previously, Rhyolite-MELTS GUI-style output files (melts.out and .tbl files) are written to the folder where easyMelts is running. On Windows, the .tbl files will be gather into a subfolder called 'tables'. As with the alphaMELTS 2 run there will be slight discrepancies between the newly generated melts.out file and the original output file. The most striking differences are the addition of Mn, Co and Ni to the olivine solid solution model, though none of these components are in the Morb.melts bulk composition, and splitting of the pyroxene phase into separate clinopyroxene and orthopyroxene phases (see here). The phase compositions are essentially the same though and differences in the phase masses are a few hundredths of a gram, at most.

If there are any problems or feedback about this post then please let me know.

Cheers!
Paula

[Paula]

If easyMelts crashes when you try to view the plots, then you probably forgot to select the Fractionate Solids checkbox. You should also update to the latest version of easyMelts (posted June 23rd, 2021) which fixes the bug that causes this crash when liquid is exhausted.

[jarettbd]

Excuse me, I am having trouble downloading the easyMelts software. Following the link provided in this post and on the alphaMelts links page leads me to a blank page with the URL https://magmasource.caltech.edu/gitlist/easyMelts.git.

I am wondering if there are some permissions I need in order to access the gitlist server, or if there is some other way to download the software, or if I am just missing something obvious.

Thanks!

[Paula]

Try again - it should be fine now. It just means I forgot to run a particular command after rebooting the server.