Molecular modelling of rare earth element complexation in subduction zone fluids

Unraveling rare earth element signatures in hydrothermal carbonate minerals using a source–sink system

“…The electrostatic attraction is thus proportional to the charge of ions and inversely proportional to the ionic radius squared. Both Coulomb's law and density functional theory (DFT) computations predict higher stability of complexes with the smaller HREE ions, both at ambient and at high pressures-high temperature conditions (e.g., van Sijl et al, 2009). These calculations also indicate that the strength of the lanthanide-ligand bond and its length vary with the geometry and coordination number of hydration sphere.…”

“…Seawater can be approximated as a H 2 O-NaCl mixture, with minor SO 4 , Mg, Ca, K and HCO 3 (Table 1; Turekian, 1968). Evaporation can easily increase the NaCl content from 3.5 to 25 wt.% before halite precipitates, even at ambient conditions.…”

“…1: seawater (Turekian, 1968); 2, 3: thermal waters (Land and Macpherson, 1992); 4: Modum Complex, Norway (Munz et al, 1995);5: Pyrenees (McCaig et al, 2000); 6: Salton Sea (Williams and McKibben, 1989); 7: Columbian emerald deposits 8;Black Smoker Fluid (James et al, 2014), 9;Capitan Pluton (Banks et al, 1994); 10: Mole Granite (Audétat et al, 2000;Rankin and Ramsey, 1992); 11: Cornwall granite (Bottrell and Yardley, 1988 rock types along their pathway, at varying pressure and temperatures. During fluid-rock interaction, dissolution of REEY-sourcing minerals is likely incongruent, and different minerals have different susceptibilities at the prevailing reaction conditions (Möller and Giese, 1997).…”

“…Nonetheless, strong REEY ligands such as CO 3 2 − and PO 4 3 − can dominate REEY speciation when these are abundant, for instance in seawater (e.g., Haas et al, 1995;Lee and Byrne, 1992). With increasing temperature, hydration becomes energetically less favorable, the coordination number of aquo-complexes decreases and shielding by aqueous ligands is consequently less effective (e.g., Haas et al, 1995;van Sijl et al, 2009). Complexation with anionic ligands then results in progressively higher REEY solubilities (e.g., Haas et al, 1995).…”

Titanium in subduction zone fluids: First insights from ab initio molecular metadynamics simulations

“…The optimisations are performed either in the gas-phase static limit or by implicitly treating the longrange effects of the bulk solvent using a so-called polarisable continuum model (PCM) (Cramer and Truhlar, 1991;Klamt and Schuurmann, 1993;Cossi et al, , 2002, which can be adjusted to simulate the effects of pressure and temperature (e.g. van Sijl et al, 2009). An explicit treatment of pressure and temperature is crucial for our understanding of titanium hydration in a subduction zone setting.…”