The aqueous geochemistry of the rare-earth elements and yttrium

Stability constants for trivalent REE complexes containing fluoride, chloride, sulfate, carbonate or hydroxide ions have been predicted up to 350°C at saturated water vapor pressure using Helgeson's electrostatic approach, combined with the isocoulombic approach and available experimental thermodynamic data at low temperatures. In addition, the equilibrium boundary between divalent and trivalent REE ions was calculated at elevated temperatures...