Introduction to Pʜʀᴇᴇǫᴄ

This work was partly supported by NSF grant EAR-1926734, the endowment for the Haydn Murray Chair, and the Office of the Vice Provost for Research of Indiana University.

ᴘʜʀᴇᴇǫᴄ is a geochemical modeling software distributed by the U.S. Geological Survey and developed by David Parkhurst and Tony Appelo. It is written in the C and C++ programming languages and is designed to perform a wide variety of aqueous geochemical modeling calculations.

Here, the online version ᴘʜʀᴇᴇǫᴄ has new datasets diagenesis.dat and geothermal.dat, which have thermodynamic properties consistent with those in Zimmer et al. (2016) and allow ᴘʜʀᴇᴇǫᴄ calculations at elevated temperature and pressure.

  • diagenesis.dat is one type of ᴘʜʀᴇᴇǫᴄ dataset automatically generated by SupPhreeqc program. diagenesis.dat follows the framework of phreeqc.dat and includes (a) the analytic formula for the log K of aqueous species, minerals, and gases reactions covering the T-P range of 0.01-100 °C at 1 bar and 100-200 °C at PSAT; (b) molar volume parameters for solids and aqueous species for estimating the effect of pressure change on log K (suitable up to ~1000 bar and 200 °C (Appelo et al., 2014)); and (c) Peng-Robinson equation parameters, critical temperature, pressure, and acentric factor for calculating the gas fugacity (Parkhurst and Appelo, 2013). The Davies equation for aqueous species activity coefficients is used.
  • geothermal.dat is another type of ᴘʜʀᴇᴇǫᴄ dataset automatically generated by SupPhreeqc program, using B-dot equation parameters for computing activity coefficients of aqueous species. It follows the framework of llnl.dat. The T-P range of geothermal.dat is 0.01-100 °C at 1 bar and 100-300 °C at PSAT. geothermal.dat also has a library of BASIC language RATES blocks for about 100 minerals and log K for related PHASES. See more info on the tab BASIC Rate Scripts.


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