In situ X-ray absorption spectroscopy measurement of vapour-brine fractionation of antimony at hydrothermal conditions

G. Pokrovski, J. Roux, J. Hazemann, A. Borisova, A. Gonchar, M. Lemeshko, Mineralogical Magazine 72 (2008) 667–681.

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Abstract
Despite the growing geological evidence that fluid boiling and vapour-liquid separation affect the distribution of metals in magmatic-hydrothermal systems significantly, there are few experimental data on the chemical status and partitioning of metals in the vapour and liquid phases. Here we report on an in situ measurement, using X-ray absorption fine structure (XAFS) spectroscopy, of antimony speciation and partitioning in the system Sb2O3-H2O-NaCl-HCl at 400°C and pressures 270–300 bar corresponding to the vapour-liquid equilibrium. Experiments were performed using a spectroscopic cell which allows simultaneous determination of the total concentration and atomic environment of the absorbing element (Sb) in each phase. Results show that quantitative vapour-brine separation of a supercritical aqueous salt fluid can be achieved by a controlled decompression and monitoring the X-ray absorbance of the fluid phase. Antimony concentrations in equilibrium with Sb2O3 (cubic, senarmontite) in the coexisting vapour and liquid phases and corresponding SbIII vapour-liquid partitioning coefficients are in agreement with recent data obtained using batch-reactor solubility techniques. The XAFS spectra analysis shows that hydroxy-chloride complexes, probably Sb(OH)2Cl0, are dominant both in the vapour and liquid phase in a salt-water system at acidic conditions. This first in situ XAFS study of element fractionation between coexisting volatile and dense phases opens new possibilities for systematic investigations of vapour-brine and fluid-melt immiscibility phenomena, avoiding many experimental artifacts common in less direct techniques.
Publishing Year
Date Published
2008-04-01
Journal Title
Mineralogical Magazine
Volume
72
Issue
2
Page
667 - 681
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Pokrovski G, Roux J, Hazemann J, Borisova A, Gonchar A, Lemeshko M. In situ X-ray absorption spectroscopy measurement of vapour-brine fractionation of antimony at hydrothermal conditions. Mineralogical Magazine. 2008;72(2):667-681. doi:10.1180/minmag.2008.072.2.667
Pokrovski, G., Roux, J., Hazemann, J., Borisova, A., Gonchar, A., & Lemeshko, M. (2008). In situ X-ray absorption spectroscopy measurement of vapour-brine fractionation of antimony at hydrothermal conditions. Mineralogical Magazine, 72(2), 667–681. https://doi.org/10.1180/minmag.2008.072.2.667
Pokrovski, Gleb, Jacques Roux, Jean Hazemann, Anastassia Borisova, Anastasia Gonchar, and Mikhail Lemeshko. “In Situ X-Ray Absorption Spectroscopy Measurement of Vapour-Brine Fractionation of Antimony at Hydrothermal Conditions.” Mineralogical Magazine 72, no. 2 (2008): 667–81. https://doi.org/10.1180/minmag.2008.072.2.667 .
G. Pokrovski, J. Roux, J. Hazemann, A. Borisova, A. Gonchar, and M. Lemeshko, “In situ X-ray absorption spectroscopy measurement of vapour-brine fractionation of antimony at hydrothermal conditions,” Mineralogical Magazine, vol. 72, no. 2, pp. 667–681, 2008.
Pokrovski G, Roux J, Hazemann J, Borisova A, Gonchar A, Lemeshko M. 2008. In situ X-ray absorption spectroscopy measurement of vapour-brine fractionation of antimony at hydrothermal conditions. Mineralogical Magazine. 72(2), 667–681.
Pokrovski, Gleb, et al. “In Situ X-Ray Absorption Spectroscopy Measurement of Vapour-Brine Fractionation of Antimony at Hydrothermal Conditions.” Mineralogical Magazine, vol. 72, no. 2, Mineralogical Society, 2008, pp. 667–81, doi:10.1180/minmag.2008.072.2.667 .

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