Petrolog

Software for modelling magma crystallisation and melt inclusions

Main features of Petrolog

Petrolog4 is software for modelling fractional and equilibrium crystallisation and reverse of fractional crystallisation at variable pressure, melt oxidation state and melt volatile contents, and for modelling post-entrapment re-equilibration of melt inclusions in olivine.

Modelling of crystallisation in Petrolog4 is based on the concept of pseudo-liquidus temperatures (Nathan, Vankirk, 1978; Nielsen, Dungan, 1983; Ariskin et al., 1986). The method relies on the ability of the mineral-melt equilibrium models to calculate liquidus temperature not only for the range of melt compositions where the minerals are stable, but also in the metastable regions of melt compositions for each phase (i.e., pseudo-liquidus temperatures).

The essence of the technique is to compare calculated pseudo-liquidus temperatures for a selected set of mineral species that may crystallize from a given melt composition. The mineral with the highest calculated temperature is considered the mineral on the liquidus of the given melt composition. This mineral is subtracted from melt, and then the process is repeated. Other minerals with calculated pseudo-liquidus temperatures that are lower than the liquidus temperature, are not on the liquidus of the melt.

Petrolog4 offers a model-independent algorithm, which can incorporate a potentially unlimited number of phase-melt equilibrium models for major and trace elements; and of models describing melt physical parameters, such as density and viscosity, solubility of fluid components in silicate melts, melt oxidation state and others.

- New feature in Petrolog4

• Modelling H2O-CO2 fluid - silicate melt equilibrium during magma
  evolution;

• Modelling H2O-CO2 fluid open and closed system degassing during
  magma evolution;

• Modelling sulphide melt - silicate melt immiscibility during magma
  evolution;

• Modelling redox equilibrium between Fe and S species in the
  silicate melt

• Modelling Fe oxidation state in the silicate melt as a function of
  melt composition, temperature and oxygen fugacity

• Modelling S oxidation state in silicate melt as a function of oxygen
  fugacity

• Modelling S solubility in silicate melts

• Modelling fluid solubility in silicate melt

• Modelling crystallisation of 5 silicate minerals (olivine, plagioclase, clinopyroxene, orthopyroxene, pigeonite)

• Modelling crystallisation of 3 oxide minerals (magnetite, spinel, ilmenite)

• Incorporating corrections for the effect of H2O content of the silicate melt and crystallisation pressure on the liquidus temperatures of silicate
  and oxide minerals

• Variable extent of fractionation of each phase during magma crystallisation

• Modelling trace-element distribution between melt and other phases in the magma

  We recommend reading the manual for the full list of features

- New models in Petrolog4