magmasource.caltech.edu

xMELTS will greatly expand the covered range of P-T conditions, when compared to MELTS and pMELTS. The original NSF award to Mark Ghiorso and co-workers lead to the development of the LEPR database and a provisional silicate liquid model. As part of an ARRA-funded collaboration, new volume models for garnet and spinel were calibrated at Caltech. We are continuing to work with Mark on extending and improving the thermodynamic solution models used with xMELTS. Eventually the updated solid solution models will be included in various xMELTS-based programs and tools.

The calculators on this site allow users to access the new volume and activity models, as and when they are published (or at least submitted for publication). The web tool is similar to the 'MELTS Supplemental Calculator' and successors. It allows users to input pressure, temperature, and mineral composition; a variety of formats are available. Thermodynamic data (currently just volume) and, if appropriate, ordering state are output and can be used for further calculations. Models available at present are:

• For more information on the intended scope of the xMELTS model, once it is finalized, see the 5th FAQ on Mark Ghiorso's MELTS homepage.
• For more information on the various phase property calculators available for solids and liquids in the MELTS and pMELTS models see the alphaMELTS links page.
• For more details about the Caltech - OFM Research calibration effort and the people involved, please see the alphaMELTS 'about us' page.

We ask that you please log in with your MELTS Software Users Forum account, if you have one. You can register here. Input and output will all be displayed in this window by default. This link to the Information Page will open in a new window so that you can switch between model details and / or input form for a given phase, without losing progress. Otherwise, use Ctrl-click or Shift-click to open the relevant Information link (under 'Calculators').

Once 'Submit' is clicked, scripts will validate the input and, if appropriate, calculate the ordering state and molar volume. Volume output will be at the top of the page. The input composition will be automatically converted to all possible input forms. 'Clear' deletes all text box entries but keeps radio button and checkbox selections unchanged. 'Reset' reloads the page, setting all options to their default value; if you are using the guest mode you will need to enter the captcha again. More specific instructions are given on the info page.

For queries about the manuscripts or volume model details, please contact the corresponding author Emily Hamecher (now at Cal State, Fullerton). This page and the volume calculator tools described above are maintained by Paula Antoshechkina (see below). Please address any questions, comments or bug reports to her. Each instance of the volume calculator can process one mineral composition / set of P-T conditions at a time. For bulk calculation of volumes for multiple data, please contact either of the authors mentioned here.