|Title||An experimental investigation of the solubility and speciation of uranium in hydrothermal ore fluids|
|Download||Download (whole publication) |
|Licence||Please note the adoption of the Open Government Licence - Canada
supersedes any previous licences.|
|Author||Rempel, K U; Williams-Jones, A E; Fuller, K|
|Source||Targeted Geoscience Initiative 5: grant program final reports (2018-2020); by Targeted Geoscience Initiative Coordination Office; Geological Survey of Canada, Open File 8755, 2021 p. 281-288, https://doi.org/10.4095/328995 Open Access|
|Publisher||Natural Resources Canada|
|Related||This publication is contained in Targeted Geoscience
Initiative 5: grant program final reports (2018-2020) |
|Related||This publication is related to An experimental investigation
of the solubility and speciation of uranium in hydrothermal ore fluids|
|Subjects||economic geology; geochemistry; Science and Technology; Nature and Environment; mineral deposits; uranium; hydrothermal deposits; ore mineral genesis; mineralization; ore controls; modelling; uranium
geochemistry; solubilities; tectonic setting; hydrothermal systems; fluid dynamics; oxidation; precipitation; fluorides; chloride; alkalinity; acidity; oxides; hydroxides; Methodology|
|Illustrations||schematic diagrams; tables; plots|
|Program||Targeted Geoscience Initiative (TGI-5) Knowledge Management Coordination|
|Released||2021 10 27|
|Abstract||Experimental data on the solubility and speciation of uranium in hydrothermal solution is required to improve genetic models for the formation of ore deposits, yet very few data of this type have been
published. Of particular interest is the oxidation state of the uranium in solution, as conventional wisdom suggests that U is dissolved in the oxidized U(VI) state and precipitated as reduced U(IV) minerals, yet recent experiments have shown
ppm-level solubility for U(IV).|
This study investigated the mobility of reduced U(IV) and oxidized U(VI) in acidic (pH = 2), fluoride- bearing and alkaline (pH = 10), chloride-bearing solutions at 100-200°C and 1 to 15.8 bars (0.1-1.58 MPa).
Preliminary data for the mobility of U(IV) in pH 2 fluids with 0.01 m F- show concentrations of 1.76 to 3.92 ppm U at 200°C, indicating that, contrary to common belief, the reduced U(IV) can be transported in solution. We have also conducted
experiments on U(VI) solubility in pH 2 fluoride-bearing, and pH 10 chloride-bearing solutions. Uranium concentrations in the F- -bearing experiments ranged from 624 to 1570 ppm (avg. 825 ppm, n = 6) at 100°C, 670 to 1560 ppm (avg. 931 ppm, n = 4) at
150°C, and 3180 to 7550 ppm (avg. 5240, n = 9) at 200°C. In comparison, U concentrations in the Cl- -bearing runs range from 86.1 to 357 ppm (avg. 185 ppm, n = 15) at 200°C. Clearly, oxidized U(VI) is very readily mobilized in hydrothermal fluids.
However, the measured concentrations of U(VI) are independent of those of F- or Cl-, suggesting the formation of U oxide or hydroxide species rather than U chlorides or fluorides.
These experimental data will be verified and supplemented in future
experiments, which will be used to derive the stoichiometry and thermodynamic constants for the dominant uranium species in hydrothermal solutions. The data from this study will then be integrated into a comprehensive genetic model for uranium
|Summary||(Plain Language Summary, not published)|
The Targeted Geoscience Initiative (TGI) is a collaborative federal geoscience program that provides industry with the next generation of geoscience
knowledge and innovative techniques, which will result in more effective targeting of buried mineral deposits. This compendium is the result of the TGI Grant Recipients 2018-2020.