Thermodynamics of selected hydrothermal minerals of As and Sb
Final Report Abstract
The project was based on the measurement of thermodynamic properties of selected natural and synthetic phases, assumed to control the aqueous solubility of these two elements in sulfur-poor or sulfur-free hydrothermal systems. These phases included chapmanite, heazlewoodite, skutterudite, tripuhyite, and schafarzikite. Calorimetric measurements (acid-solution calorimetry, high-temperature oxide-melt calorimetry, relaxation calorimetry) gave accurate and precise data for all studied phases. If needed, they were combined with previously published solubility measurements to yield internally consistent data sets. Significant effort was invested into measurements and extrapolation to higher temperatures so that the data are useful for geochemical modeling of hydrothermal processes (up to ~350 oC). This task was achieved by the application of the theoretical Kieffer model and thermodynamic calculations with the SUPCRTBL software. Models constructed (by PHREEQC or Geochemists Workbench) show phase relationships among the studied and related phases. The results document metastability of some of the studied phases (chapmanite) and stability of others limited to specific conditions (in terms of fO2, fS2, activity of aqueous metal species).
Publications
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Chapmanite [Fe2Sb(Si2O5)O3(OH)]: thermodynamic properties and formation in low-temperature environments. European Journal of Mineralogy, 33(4), 357-371.
Majzlan, Juraj; Kiefer, Stefan; Lilova, Kristina; Subramani, Tamilarasan; Navrotsky, Alexandra; Dachs, Edgar & Benisek, Artur
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Calorimetric study of skutterudite (CoAs2.92) and heazlewoodite (Ni3S2). American Mineralogist, 107(12), 2219-2225.
Majzlan, Juraj; Kiefer, Stefan; Lilova, Kristina; Subramani, Tamilarasan; Navrotsky, Alexandra; Tuhý, Marek; Vymazalová, Anna; Chareev, Dmitriy A.; Dachs, Edgar & Benisek, Artur
