Speciation of yttrium in fluorine-rich brines at hydrothermal and metamorphic conditions
Final Report Abstract
Rare earth elements are important geochemical tracers for geological processes. In hydrothermal and metamorphic environments, they are mainly transported by aqueous fluids. However, the capacity of a fluid to mobilize rare earth elements depends strongly on specific conditions of temperature, pressure and the chemical composition of the fluid, especially on the availability of suitable ligands such as fluoride and chloride. In this project we studied the speciation of yttrium in chloride- and fluoride-bearing aqueous fluids at subduction zone conditions using first-principles molecular dynamics simulations. Stable complexes under these condition do not have more than three chloride or fluoride ligands and mixed chloride-fluoride complexes are found to be rather unstable. Fluoride species become the dominant species already at low fluoride concentrations in the fluid, which suggests a very low fluoride activity to be present in subduction zones. This project has been part of a successful PhD thesis and the main results were published in a Special Issue of Solid Earth ”Exploring new frontiers in fluids processes in subduction zones”.
Publications
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(2018) Molecular modeling approaches to element speciation in aqueous fluids. EGU Galileo Conference, GC4-Subduction-13 Exploring new frontiers in fluids processes in subduction zones
Stefanski, J. and Jahn, S.
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(2020) Thermodynamic properties and structure of aqueous fluids in geological processes. Dissertation, Universität zu Köln
Stefanski, J.
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(2020) Yttrium speciation in subduction-zone fluids from ab initio molecular dynamics. Solid Earth, 11, 767-789
Stefanski, J. and Jahn, S.
