THE MINES THERMODYNAMIC DATABASE FOR MODELING CRUSTAL FLUID-ROCK SYSTEMS

A major problem for predicting fluid-rock equilibria in different geologic systems, is the selection of adequate activity models, equations of states and the thermodynamic data available for aqueous species, gases and minerals. For this purpose, the open access MINES thermodynamic database (http://tdb.mines.edu) has been launched for modeling complex crustal fluid-rock equilibria using the code package GEMS (http://gems.web.psi.ch). This database builds on the datasets commonly used for major rock forming minerals [1,2] and aqueous species from theoretical high P-T predictions [3,4]. Future versions will replace the theoretically predicted aqueous species with those derived from the more adequate experimental data, and also involve key multicomponent multisite mineral solid solution models. Recent implementations include experimental data for REE-bearing minerals [5,6], and other experimental data for aqueous REE-, Zr- and Al-bearing species, and much more.

The purpose of the MINES database embraces: i) testing and developing of internally consistent thermodynamic datasets relevant to ore forming processes and crustal metasomatism, ii) expanding our capabilities to model fluid – solid solutions equilibria, and iii) promoting and facilitating the use of GEMS [7,8] and its GUI. The philosophy of MINES is to focus on improving and testing a series of modeling projects that can be used to simulate specific chemical systems of real world geological examples. Using the MINES database, we will demonstrate the application of GEMS to simulate metasomatism and mobilization of REE in the Strange Lake REE-Zr-Nb mineral deposit, the mineralization in a Mississippi Valley Type (MVT) Pb-Zn-deposit, and the sequestration of CO₂ in Icelandic basaltic rock formations. The major goal of this research is to stimulate open-access critical evaluation of thermodynamic data among a network of researchers.

[1] Holland & Powell (1998) J. Metam. Geol. 16, 309-343. [2] Robie & Hemingway (1995) U.S. Geol. Survey Bull. 2131. [3] Johnson et al. (1992) Comput. Geosci. 7, 899-947. [4] Tanger & Helgeson (1988) Am. J. Sci. 288, 19-98. [5] Gysi et al. (2015) Chem. Geol. 401, 83-95. [6] Gysi & Williams-Jones (2015) Chem. Geol. 392, 87-101. [7] Kulik et al. (2013) Comput. Geosci. 17, 1-24. [8] Wagner et al. (2012) Can. Mineral. 50, 1173-1195.