EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Experimental precipitation of cryogenic calcite and vaterite

Ozioma Carol Uwakwe1, Sylvia Riechelmann1, René Hoffmann1, Christoph Spötl2, Anne Jantschke3, and Adrian Immenhauser1
Ozioma Carol Uwakwe et al.
  • 1Institute of Geology, Mineralogy and Geophysics, Ruhr University Bochum, Germany (
  • 2Institute of Geology, Innsbruck University, Austria
  • 3Johannes-Gutenberg-Universität Mainz, Germany

Cryogenic cave carbonates (CCCs) are speleothems precipitated from freezing water bodies in caves. A series of scholarly papers have explored natural CCC precipitation kinetics, crystal habit, mineralogy, crystallography and geochemistry. However, cave depositional environments are complex multi-parameter systems, and the inherent difficulty of unravelling the physicochemical parameters of ancient speleothem formation also applies to CCCs. In order to test previous models and concepts, experiments were conducted by cooling calcium-rich bicarbonate water under controlled laboratory conditions. The experiments involved calcite precipitation at different durations (6 to 91 days) and temperatures (1, +0, -0.5, -0.7, -1 and -2 °C). The results show that subtle changes in temperature and calcite saturation index (SIcc) remarkably affect the CCC morphological variability and mineralogy. Rhombohedral calcite crystals precipitated both in experiments with and without ice. In contrast, spherulitic crystals (vaterite) precipitated from near-completely frozen waters with high calcite saturation indices. Experimental water monitoring revealed increased calcite precipitation followed by decreased water conductivity values. The formation of CCCs is accompanied by non-equilibrium reaction kinetics, which tends to enrich the isotopic composition of the parental water. Longer experimental durations lead to increasing CO2 degassing and 13C enrichment of the water. Data from the first experimental work dealing with cryogenic carbonate precipitation and isotope geochemistry, as documented here, shed light on the origin of these peculiar speleothems and provides constraints to interpret morphologies and isotopic compositions of ancient CCCs.


How to cite: Uwakwe, O. C., Riechelmann, S., Hoffmann, R., Spötl, C., Jantschke, A., and Immenhauser, A.: Experimental precipitation of cryogenic calcite and vaterite, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1178,, 2023.

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Supplementary material file