Pressure of vapor-saturation

The dissolved volatile content of a melt in equilibrium with a vapor can be used as a barometer because the sum of the partial pressures of all the vapor species must equal the total pressure (e.g., Anderson et al., 1989; Blundy & Cashman, 2009). This is the pressure of vapor saturation (Pv sat) barometer and is often applied to melt inclusions to calculate magma storage depths (e.g., Black and Andrews, 2020; Camejo-Harry et al., 2019, 2018; Colman et al., 2015; Wanless et al., 2015; Wieser et al., 2021) and sub-aqueous matrix glasses to calculate eruption depths (e.g., Belgrano et al., 2021; Coombs et al., 2006; Lund et al., 2018; Seaman et al., 2004).

VolFe calculates Pv sat, the melt speciation, and the vapor composition for a melt of given temperature and melt composition (including volatiles and fO2).

This calculation was outlined in detail Hughes et al. (2024) (schematic of the calculation shown in the figure below; Hughes et al., 2025).

_images/pvsatcalc.png

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

  • Example 1a: One analysis entered as a DataFrame using default options.

  • Example 1b: Multiple analyses in a csv file using default options.

  • Example 1c: Multiple analyses in a csv file using user-specified options.

  • Example 1d: Changing the identity of the volatile species “X”.

  • Example 1e: Including uncertainties on inputs into the calculation outputs.