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Degassing paths
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As magmas rise to the surface, volatiles dissolved in the melt exsolve into the vapor phase.
VolFe calculates the proportions of vapor and melt and their compositions and speciation during open- and closed-system, re- and degassing for various combinations of C, H, S, and noble gases as the volatile species.

This calculation is described in detail in `Hughes et al. (2025) <https://doi.org/10.30909/vol/imvc1781>`_ (schematic of the calculation shown in the figure below; `Hughes et al., 2025 <https://doi.org/10.30909/vol/imvc1781>`_). The isotopic fractionation calculation is described in the Supplementary Material of `Saper et al. (2025) <https://doi.org/10.1016/j.lithos.2025.108331>`_.

.. figure:: figures/degassingcalc.png

In these examples we will show you how to run this calculation for:

- :doc:`Example 2a <Examples/2a. degas_closed_bulk>`: Closed-system CHOS degassing where the melt composition is the bulk composition of the system (with and without sulfur saturation).

- :doc:`Example 2b <Examples/2b. degas_closed_gas>`: Closed-system CHOS degassing where there is melt and vapor at the start of degassing.

- :doc:`Example 2c <Examples/2c. degas_open>`: Open-system CHOS degassing.

- :doc:`Example 2d <Examples/2d. regas>`: Closed- and open-system CHOS regassing (i.e., increasing in pressure).

- :doc:`Example 2e <Examples/2e. degas_notCHOS>`: Closed-system degassing for different volatile systems (including noble gases).

- :doc:`Example 2f <Examples/2f. degas_closed_open_isotopes>`: Closed- and open-system CHOS degassing calculations including isotopes.