Rare earth elements in hydrothermal systems: Estimates of standard partial molal thermodynamic properties of aqueous complexes of the rare earth elements at high pressures and temperatures

Johnson R. Haas, Everett Shock, David C. Sassani

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455 Citations (Scopus)

Abstract

Standard partial molal thermodynamic properties including association constants for 246 inorganic aqueous rare earth element (REE) complexes with chloride, fluoride, hydroxide, carbonate, sulfate, bicarbonate, nitrate, and orthophosphate can be calculated at pressures from 1 to 5000 bars and temperatures from 0 to 1000°C, using experimental data from the literature and correlation algorithms. Predicted association constants for REE complexes are used to calculate the speciation of the REEs in simulated and natural fluid compositions over ranges of pH, temperature, and pressure. Our results demonstrate that in a generalized chloride-rich hydrothermal fluid, REE transport may be facilitated by formation of chloride, fluoride, and hydroxide complexes at acidic, neutral, and basic pH conditions, respectively. The HREEs (GdLu) are complexed more strongly by fluoride, and less strongly by chloride, than the LREEs (LaSm), whereas at basic pH conditions HREEs and LREEs strongly associate with hydroxide to an equivalent degree. Estimates of REE speciation in natural hydrothermal solutions that differ in composition and geologic setting demonstrate that different REE-complexes predominate in different environments. It follows that ad hoc assumptions about the identity of complexes which are responsible for REE mobility in a given geologic setting are not necessary.

Original languageEnglish (US)
Pages (from-to)4329-4350
Number of pages22
JournalGeochimica et Cosmochimica Acta
Volume59
Issue number21
DOIs
StatePublished - 1995
Externally publishedYes

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thermodynamic property
hydrothermal system
Rare earth elements
rare earth element
Thermodynamic properties
Chlorides
Fluorides
chloride
fluoride
hydroxide
Temperature
Association reactions
Fluids
element mobility
Carbonates
Bicarbonates
Chemical analysis
fluid composition
Nitrates
orthophosphate

ASJC Scopus subject areas

  • Geochemistry and Petrology

Cite this

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title = "Rare earth elements in hydrothermal systems: Estimates of standard partial molal thermodynamic properties of aqueous complexes of the rare earth elements at high pressures and temperatures",
abstract = "Standard partial molal thermodynamic properties including association constants for 246 inorganic aqueous rare earth element (REE) complexes with chloride, fluoride, hydroxide, carbonate, sulfate, bicarbonate, nitrate, and orthophosphate can be calculated at pressures from 1 to 5000 bars and temperatures from 0 to 1000°C, using experimental data from the literature and correlation algorithms. Predicted association constants for REE complexes are used to calculate the speciation of the REEs in simulated and natural fluid compositions over ranges of pH, temperature, and pressure. Our results demonstrate that in a generalized chloride-rich hydrothermal fluid, REE transport may be facilitated by formation of chloride, fluoride, and hydroxide complexes at acidic, neutral, and basic pH conditions, respectively. The HREEs (GdLu) are complexed more strongly by fluoride, and less strongly by chloride, than the LREEs (LaSm), whereas at basic pH conditions HREEs and LREEs strongly associate with hydroxide to an equivalent degree. Estimates of REE speciation in natural hydrothermal solutions that differ in composition and geologic setting demonstrate that different REE-complexes predominate in different environments. It follows that ad hoc assumptions about the identity of complexes which are responsible for REE mobility in a given geologic setting are not necessary.",
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T2 - Estimates of standard partial molal thermodynamic properties of aqueous complexes of the rare earth elements at high pressures and temperatures

AU - Haas, Johnson R.

AU - Shock, Everett

AU - Sassani, David C.

PY - 1995

Y1 - 1995

N2 - Standard partial molal thermodynamic properties including association constants for 246 inorganic aqueous rare earth element (REE) complexes with chloride, fluoride, hydroxide, carbonate, sulfate, bicarbonate, nitrate, and orthophosphate can be calculated at pressures from 1 to 5000 bars and temperatures from 0 to 1000°C, using experimental data from the literature and correlation algorithms. Predicted association constants for REE complexes are used to calculate the speciation of the REEs in simulated and natural fluid compositions over ranges of pH, temperature, and pressure. Our results demonstrate that in a generalized chloride-rich hydrothermal fluid, REE transport may be facilitated by formation of chloride, fluoride, and hydroxide complexes at acidic, neutral, and basic pH conditions, respectively. The HREEs (GdLu) are complexed more strongly by fluoride, and less strongly by chloride, than the LREEs (LaSm), whereas at basic pH conditions HREEs and LREEs strongly associate with hydroxide to an equivalent degree. Estimates of REE speciation in natural hydrothermal solutions that differ in composition and geologic setting demonstrate that different REE-complexes predominate in different environments. It follows that ad hoc assumptions about the identity of complexes which are responsible for REE mobility in a given geologic setting are not necessary.

AB - Standard partial molal thermodynamic properties including association constants for 246 inorganic aqueous rare earth element (REE) complexes with chloride, fluoride, hydroxide, carbonate, sulfate, bicarbonate, nitrate, and orthophosphate can be calculated at pressures from 1 to 5000 bars and temperatures from 0 to 1000°C, using experimental data from the literature and correlation algorithms. Predicted association constants for REE complexes are used to calculate the speciation of the REEs in simulated and natural fluid compositions over ranges of pH, temperature, and pressure. Our results demonstrate that in a generalized chloride-rich hydrothermal fluid, REE transport may be facilitated by formation of chloride, fluoride, and hydroxide complexes at acidic, neutral, and basic pH conditions, respectively. The HREEs (GdLu) are complexed more strongly by fluoride, and less strongly by chloride, than the LREEs (LaSm), whereas at basic pH conditions HREEs and LREEs strongly associate with hydroxide to an equivalent degree. Estimates of REE speciation in natural hydrothermal solutions that differ in composition and geologic setting demonstrate that different REE-complexes predominate in different environments. It follows that ad hoc assumptions about the identity of complexes which are responsible for REE mobility in a given geologic setting are not necessary.

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