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| Titel |
Precipitation of smithsonite under controlled pCO2 between 25 and 60˚ C - Fractionation of oxygen isotopes |
| VerfasserIn |
Anja Füger, Vasileios Mavromatis, Albrecht Leis, Martin Dietzel |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250129164
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| Publikation (Nr.) |
 EGU/EGU2016-9237.pdf |
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| Zusammenfassung |
| Owing to the large fractionation (i.e. Δ18Osolid−diss. ∼30) between carbonate
minerals and aqueous fluids with respect to their 18O/16O composition, the oxygen
isotope composition of carbonates has been a fundamental tool for the estimation
of mineral formation temperature by the geoscience community. Indeed the last
6 decades, a wide number of experimental studies investigated the temperature
relation of Δ18Osolid−diss. between divalent metal carbonates and aqueous fluids.
To date however no experimental data exist for the temperature dependence of
Δ18Osolid−diss. between smithsonite (ZnCO3) and fluid. This lack of data likely
stems from a kinetic barrier effect, that of the dehydration of aqueous Zn2+ and the
formation of hydrozincite (Zn5(CO3)2(OH)6). Smithsonite is a secondary zinc mineral
that is one of the components of zinc ore bodies. It is formed through oxidation of
primary zinc ores by the reaction with a carbonate source or by precipitation of zinc
salt solutions with a CO2-saturated and bicarbonate-rich solution. In this study we
hydrothermally synthesized smithsonite at the temperature range between 25 and 60 ˚ C
and report the temperature dependence of oxygen isotope distribution between
smithsonite and aqueous fluid. In order to avoid the formation of hydrozincite our
experiments were conducted in titanium batch reactors using Teflon-inlets where the CO2
pressure was adjusted to 10 bars. The low pH conditions provoked by the elevated
pCO2 applied, lead to the dissolution of hydrozincite, which is initially formed by
mixing of Na2HCO3 (0.1 M) and Zn(NO3)2.4 H2O (0.02 M) solutions, to yield -
under the prevailing conditions - the thermodynamically stable mineral smithsonite. |
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