Extreme silicon isotope fractionation due to Si organic complexation: Implications for silica biomineralization

Franziska Maria Stamm*, Merlin Méheut, Thomas Zambardi, Jérôme Chmeleff, Jacques Schott, Eric H. Oelkers*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


A combination of theoretical predictions and isotopic equilibration experiments using the three-isotope method have been performed to assess Si isotope fractionation among minerals, and aqueous species in the presence of dissolved catechol. Aqueous Si in abiotic ambient temperature aqueous solutions is dominated by the IV-coordinated H4SiO04 species, but the presence of aqueous catechol provokes the formation of a VI-fold Si-catechol complex. Results show an equilibrium Si fractionation factor of ∼19 between the VI-fold coordinated Si-catechol complex and the IV-fold coordinated aqueous silicic acid, an amplitude never previously observed for silicon. The fractionation between V-fold Si-organo complexes (with diolate, glyconate or methyllactate groups) and silicic acid has also been estimated through theoretical predictions to be about −10. These extreme fractionations can be used to improve our ability to interpret the Si isotope compositions of natural solids, and in particular those associated with marine silica iomineralization processes (e.g. sponge spicules)
Original languageEnglish
Article number 116287
Number of pages12
JournalEarth and Planetary Science Letters
Publication statusPublished - 1 Jul 2020
Externally publishedYes


  • silicon
  • equilibrium isotope fractionation
  • organo-silicon complexes
  • first principle calculation
  • three-isotope method
  • Si coordination change


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