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| Titel |
Sr Incorporation and Calcium Isotopic Fractionation during Calcium Carbonate Precipitation |
| VerfasserIn |
A. Niedermayr, M. Dietzel, S. J. Köhler, F. Böhm, B. Kisakurek, A. Eisenhauer |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250028789
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| Zusammenfassung |
| Element substitution and calcium isotopic fractionation can provide information about the
mechanisms of CaCO3 precipitation, precipitation rates, temperatures and solution chemistry.
In the present study precipitation experiments for the formation of the CaCO3 polymorphs:
calcite, aragonite and vaterite were carried out. Calcium carbonates are formed at
various Mg/Ca ratios or in presence of polyaspartic acid at temperatures between 5
and 40Ë C at pH 8.3 by using an advanced CO2-diffusion technique (Tang et al.,
2008).
The results indicate elevated Sr distribution coefficients (DSr) during calcite and vaterite
formation at increasing precipitation rates, whereas DSr-values decrease only slightly with
increasing rate during the formation of aragonite. 44Ca/40Ca fractionation increases for
aragonite and calcite formation as precipitation rates increase. Preliminary results show
less calcium isotopic fractionation for vaterite compared to calcite and aragonite.
However, Î44-40CaCaCO3(s)-Ca(aq)-values for the three modifications indicate an
inverse correlation with DSr. Respective mechanisms and proposed models are
discussed.
Reference
Tang J., Köhler S.J., and Dietzel M. (2008) Sr2+/Ca2+ and 44Ca/40Ca fractionation
during inorganic calcite formation: I. Sr in corporation, Geochimica et Cosmochimica Acta,
72, 3718-3732. |
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