Zircon modeling - thermodynamic databases

Description

Internally consistent datasets of equilibrium constants for minerals and aqueous species at 200 - 900 °C at 0.1 and 0.2 GPa. The databases were used to model zircon solubility in aqueous fluids and the replacement of metamict zircon by crystalline zircon using the software package "The Geochemist's Workbench" (Bethke, 2022) and the program "Phreeqc" (Parkhurst and Appelo, 2013). The *.dat files are in Phreeqc format. The *.tdat files are in GWB format. A manuscript will be submitted to "Geochemistry, Geophysics, Geosystems" in September 2024 that uses the databases and that includes the GWB scripts for the models. References Bethke, C. M. (2022). Geochemical and Biogeochemical Reaction Modeling (3rd ed.). Cambridge: Cambridge University Press. https://doi.org/DOI: 10.1017/9781108807005 Parkhurst, D. L., & Appelo, C. A. J. (2013). Description of input and examples for PHREEQC version 3—a computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations. US Geological Survey Techniques and Methods, Book, 6, 497.

Steps to reproduce

Internally consistent datasets of equilibrium constants for minerals and aqueous species at 200 - 900 °C at 0.1 and 0.2 GPa were constructed in this study by converting the SUPCRT database (Johnson et al., 1992) using SUPCRTBL (Zimmer et al., 2016) and SUPPHREEQC (Zhang et al., 2020). The PHREEQC-TYPE databases were converted for GWB using the program Tedit. We entered the coefficients for the H2O equation of state of Spycher and Reed (1988) into the *.tdat files. To compare the solubility of amorphous (metamict) zircon, we assumed that the standard state Gibbs free energy of formation of amorphous zircon ΔG°f is 40 kJ/mol higher than for crystalline zircon (Tromans, 2006) and added the new mineral phase Zircon_Am to the *.tdat files. References Johnson, J. W., Oelkers, E. H., & Helgeson, H. C. (1992). SUPCRT92; a software package for calculating the standard molal thermodynamic properties of minerals, gases, aqueous species, and reactions from 1 to 5000 bar and 0 to 1000 degrees C. Computers & Geosciences, 18(7), 899–947. Spycher, N. F., & Reed, M. H. (1988). Fugacity coefficients of H2, CO2, CH4, H2O and of H2O- CO2-CH4 mixtures: A virial equation treatment for moderate pressures and temperatures applicable to calculations of hydrothermal boiling. Geochimica et Cosmochimica Acta, 52(3), 739–749. https://doi.org/10.1016/0016-7037(88)90334-1 Tromans, D. (2006). Solubility of crystalline and metamict zircon: A thermodynamic analysis. Journal of Nuclear Materials, 357(1–3), 221–233. https://doi.org/http://dx.doi.org/10.1016/j.jnucmat.2006.06.012 Zhang, G. R., Lu, P., Zhang, Y. L., Tu, K., & Zhu, C. (2020). SUPPHREEQC: A program for generating customized PHREEQC thermodynamic datasets from SUPCRTBL and extending calculations to elevated pressures and temperatures. Computers & Geosciences, 143. https://doi.org/10.1016/j.cageo.2020.104560 Zimmer, K., Zhang, Y., Lu, P., Chen, Y., Zhang, G., Dalkilic, M., & Zhu, C. (2016). SUPCRTBL: A revised and extended thermodynamic dataset and software package of SUPCRT92. Computers & Geosciences, 90, Part A, 97–111. https://doi.org/http://dx.doi.org/10.1016/j.cageo.2016.02.013

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