Uranium in geologic fluids: Estimates of standard partial molal properties, oxidation potentials, and hydrolysis constants at high temperatures and pressures

Radionuclide Reaction Chemistry as a Function of Temperature at the Cheshire Site

“…Where rare earth elements appear to be good surrogates for the actinides, the appropriate ShockHelgeson fits may be used to estimate heat capacity data for actinide trivalent cations. With respect to higher valences, the coefficients suggested by Shock et al (1997a) give a calculated correlation for simple tetravalent cations that appears to be a better fit than the extension of the Criss-Cobble relationship defined for cations. However, this still leaves the outstanding problem of calculating heat capacities for pentavalent and hexavalent cations.…”

“…The approach of with revisions in subsequent publications Shock et al, 1997a;Shock et al, 1997b) gives improved fits for lower valence cations (1+, 2+ and 3+) and provides a fit for tetravalent cations. The equation is equivalent to Equation 3-5 with coefficients as described in Table 6.…”

“…Parameter values for calculating average heat capacities in cal/mol/K (Criss and Cobble, 1964b Table 6. Coefficients for Equation 3-5 for heat capacity estimates from entropy at 25 o C using the methods of , Shock et al (1997aShock et al ( , 1997b Table 7. Available thermodynamic data and calculated heat capacities for simple cations using the Shock-Helgeson family of coefficients shown in Table 4.…”

Integration of Concentration-Area Fractal Modeling and Spectral Angle Mapper for Ferric Iron Alteration Mapping and Uranium Exploration in the Xiemisitan Area, NW China

“…Hence, felsic magma usually has a high uranium content and crystallized felsic igneous rocks can host uranium mineralization [3]. The solubility of uranium depends on its valence (hexavalent uranium is more soluble in water-rich fluids than tetravalent uranium) [4,5], which is controlled mainly by the redox state of the geological environment [6]. The redox state of terrestrial igneous rocks is usually close to the fayalite-magnetite-quartz (FMQ) [7,8] buffer.…”

“…The redox state of terrestrial igneous rocks is usually close to the fayalite-magnetite-quartz (FMQ) [7,8] buffer. Under these conditions, uranium in magma is not oxidized from the tetravalent to the hexavalent state [6], thus preventing uranium from partitioning into a water-rich magmatic volatile phase that ultimately generates economic ore bodies [9][10][11]. Fortunately, oxidizing surface waters percolating along geological faults or fractures can mix with post-magmatic hydrothermal solutions, resulting in a more oxidizing fluid that is capable of leaching uranium from volcanic or sub-volcanic rocks.…”