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| Titel |
Technical Note: A simple method for vaterite precipitation for isotopic studies: implications for bulk and clumped isotope analysis |
| VerfasserIn |
T. Kluge, C. M. John |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 11 ; Nr. 12, no. 11 (2015-06-03), S.3289-3299 |
| Datensatznummer |
250117962
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| Publikation (Nr.) |
 copernicus.org/bg-12-3289-2015.pdf |
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| Zusammenfassung |
Calcium carbonate (CaCO3) plays an important role in the natural
environment as a major constituent of the skeleton and supporting structure
of marine life and has high economic importance as an additive in food,
chemicals and medical products. Anhydrous CaCO3 occurs in the three
different polymorphs calcite, aragonite and vaterite, whereof calcite is the
most abundant and best characterized mineral. In contrast, little is known
about the rare polymorph vaterite, in particular with regard to the oxygen
isotope fractionation between H2O and the mineral.
Synthetic precipitation of vaterite in the laboratory typically involves
rapid processes and isotopic non-equilibrium, which excludes isotope studies
focused on the characterization of vaterite under equilibrium conditions. Here, we
used a new experimental approach that enables vaterite mineral formation from
an isotopically equilibrated solution. The solution consists of a
~0.007 mol L−1 CaCO3 solution that is saturated with NaCl
at room temperature (up to 6.4 mol L−1). Vaterite precipitated as
single phase or major phase (≥94%) in experiments performed
between 23 and 91 °C. Only at 80 °C was vaterite a minor
phase with a relative abundance of 27%. The high mineral yield per
experiment of up to 235 mg relative to the initially dissolved CaCO3
amount of on average 360 mg enables an investigation of the oxygen isotope
fractionation between the mineral and water, and the determination of clumped
isotope values in vaterite. |
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