Testing MELTS - Simple Example

This example gives a simple procedure to test whether MELTS is installed correctly on your workstation. It also serves to show how to read in an existing input file and run a simple calculation.

 

• Start MELTS:
• The menu item on the far-left of the menu bar is the Commands menu. Position the mouse pointer over the Commands entry and with the left mouse button, click to pull-down the menu. The pointer should cha nge orientation and you should see this menu appear:
• Position the cursor over the open... menu entry and single click. A popup dialog box should appear.

  In the dialog file list, find the file morb.melts that you down-loaded along with the MELTS executable and double-click on the file name or highlight the file name and single click on the OK button. It may be necessary to change the default directory of the file list by modifying the file filter string (for hints on doing this see the complete description of the open... dialog).

  The contents of morb.melts are read into the program by the above action. Four things have been accomplished:

  • The bulk composition of the system has been defined. In this case the composition of a MORB has been entered into the liquid display panel.
  • An initial and final temperature and pressure have been entered and increments for modeling have been defined. In this case an estimate of the liquidus temperature (1200 C), an estimate of the solidus temperature (1000 C), and a temperature inc rement for reporting results (3 C) are input. The pressure is held constant at 500 bars by setting the initial and final pressure to this value. These items maybe set manually by invoking the T,P... entry of the I ntensive Variables menu.
  • Constraints have been specified (e.g. equilibrium or fractional crystallization). In this case the system evolves closed to mass transfer (i.e. in fractionation rather than equilibrium mode and with fixed total oxygen content). The reaction path is specified by changing values of T at constant P. This is the default method of modeling. Alternatives are defined through the Options menu.
  • The bulk ferric/ferrous ratio of the system has been entered or calculated. In this case the ferric/ferrous ratio of the MORB glass is used for the system. Indirectly, this sets the oxygen fugacity of the magma on the liquidus.

     

  In other examples the user is shown the sequence of steps to do each of these tasks manually.

• Next, go to the Commands menu and click on the menu item Find Liquidus. MELTS should iterate on the system temperature until the liquidus is located. Progress of the iteration is reported in the status display panel. The calculated liquidus temperature is assigned to the initial temperature of the system. The phase which first appears on the liquidus is indicated in the solids display panel. It's t he one with the near-zero chemical affinity.
• At this stage the initial conditions and reaction path constraints have been specified. The crystallization model is initiated by invoking the Exceute/Halt entry of the Commands menu.

  Modeling results are output to the display and to a number of disk files. For information on display elements (including graphs) consult the manual page.

  The model may be halted at any time by invoking the Execute/Halt entry of the Commands menu. The user may change bulk composition or model constraints and restart the calculation using the same menu entry.

  A manual page describes many common numerical problems that may occur when the program is running.

• The output files produced by this test example may be compared with files generated when runs are performed on a DEC Alpha Workstation running OSF/1 Version 3.0. Download and compare against files generated by MELTS running on your workstation:

  melts.out

  melts-liquid.tbl

   

• Exit the program by invoking the Exit entry of the Commands menu.

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