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| Titel |
Solubility of Aragonite in Aqueous Fluids at High Pressure and High Temperature |
| VerfasserIn |
Sébastien Facq, Isabelle Daniel, Sylvain Petitgirard, Hervé Cardon, Dimitri Sverjensky |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250095281
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| Publikation (Nr.) |
 EGU/EGU2014-10730.pdf |
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| Zusammenfassung |
| Deep crustal and mantle aqueous fluids play a crucial role in geologic processes occurring in
the Earth’s interior, especially at high PT conditions. Dissolved carbon appears to be
a major element constituting these aqueous fluids, occurring under the form of
molecular species (CO2, CO, CH4), ionic species such as carbonate or bicarbonate
ions or some more complex organic compounds [1]. However, the nature and the
content of the chemical species constituting these C-bearing aqueous fluids may
strongly be affected by the environmental geologic conditions such as the pressure and
the temperature range. If fluid speciation and solubility of carbonate minerals are
well characterized at HT and relatively low pressure, less is evident at pressure
above 2 GPa where experimental challenges make trickier speciation and solubility
measurements.
Thanks to recent advances in theoretical aqueous geochemistry [1–3], combined
experimental and theoretical efforts allow now the investigation of speciation and solubility
of carbonate minerals with pure water at higher PT conditions than previously feasible [4].
However, direct measurements of solubility of carbonate minerals at HP–HT conditions are
still needed to help to the development of quantitative models of carbon transport
by aqueous fluids in subduction zones and validate existing aqueous speciation
model.
In this study, we present recent X–ray fluorescence measurements and thermodynamic
model of solubility of carbonate in aqueous fluids at pressure up to 5 GPa. The amount of
dissolved aragonite in the fluid has been measured from the intensity of the Ca K–lines at the
ESRF–ID27 using an externally-heated membrane-type diamond anvil cell and an
incident monochromatic focused X–Ray beam at 20 keV. The combination of the
XRF data on dissolution of CaCO3mineral combined to previous speciation results
permits now to calculate the solubility KS of aragonite a pressure in excess of 2
GPa.
[1] Manning, C. E. et al., Review in Mineralogy & Geochemistry, 75, 109 (2013).
[2] Sverjensky, D. A et al., Geochimica et Cosmochimica Acta (2014, in press).
[3] Pan et al., Proceedings of the National Academy of Sciences, 110, 6646
(2013)
[4] Facq et al, Geochimica et Cosmochimica Acta (2014, submitted). |
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