EGU21-10140
https://doi.org/10.5194/egusphere-egu21-10140
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

The ikaite to calcite transformation: A key to understanding the palaeoclimatic significance of glendonites?

Martin Vickers1, Madeleine Vickers2, Rosalind Rickaby3, Han Wu4, Stefano Bernasconi5, Clemens Ullmann6, Gerhard Bohrmann7, Robert Spielhagen8, Nicolas Thibault2, and Christoph Korte2
Martin Vickers et al.
  • 1UCL, Chemistry, London, United Kingdom of Great Britain – England, Scotland, Wales (martin.vickers@ucl.ac.uk)
  • 2IGN, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen, Denmark
  • 3Department of Earth Sciences, University of Oxford, Parks Road, Oxford OX1 3PR, U.K.
  • 4Department of Chemical Engineering, UCL, Torrington Place, London WC1E 7JE, U.K.
  • 5ETH Zurich, Geologisches Institut, Sonneggstrasse 5, 8092 Zürich, Switzerland
  • 6Cambourne School of Mines, University of Exeter
  • 7MARUM, Center for Marine Environmental Sciences and Faculty of Geosciences, University of Bremen
  • 8GEOMAR, Helmholtz Centre for Ocean Research Kiel, Wischhofstraße 1-3, 24148 Kiel, Germany

Keywords: Ikaite; Glendonite; Palaeoclimate; Powder X-Ray Diffraction; Clumped isotope thermometry

Marine sedimentary ikaite is the parent mineral to glendonites, stellate pseudomorphs found throughout the geological record. Glendonites are a controversy in palaeoclimatic studies as there is an ongoing debate as to whether their presence in sedimentary successions may be used as cold-climate indicators. Glendonites are typically found associated with glacial sediments, and for a long time ikaite was believed to only nucleate and grow at temperatures < 7 °C. However, with the successful laboratory synthesis of ikaite at higher temperatures, the climatic significance of glendonites was brought into question. This study uses a combination of physical and inorganic chemistry techniques to demonstrate the variable stability of natural marine sedimentary ikaites over short (minutes to hours) and longer (weeks to months) timescales, both between ikaite samples, and in a given ikaite. We examine the nucleation of calcite from the destabilized ikaite, observing that this process is much more complex than previous studies suggest. We demonstrate that over much longer (e.g. months or more) timescales, natural marine sedimentary ikaites are not stable above 5 °C, and thus glendonite presence in sedimentary successions may be considered cold climate indicators.

How to cite: Vickers, M., Vickers, M., Rickaby, R., Wu, H., Bernasconi, S., Ullmann, C., Bohrmann, G., Spielhagen, R., Thibault, N., and Korte, C.: The ikaite to calcite transformation: A key to understanding the palaeoclimatic significance of glendonites?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10140, https://doi.org/10.5194/egusphere-egu21-10140, 2021.

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