TY - JOUR
T1 - Extreme silicon isotope fractionation due to Si organic complexation: Implications for silica biomineralization
AU - Stamm, Franziska Maria
AU - Méheut, Merlin
AU - Zambardi, Thomas
AU - Chmeleff, Jérôme
AU - Schott, Jacques
AU - Oelkers, Eric H.
PY - 2020/7/1
Y1 - 2020/7/1
N2 - 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)
AB - 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)
KW - silicon
KW - equilibrium isotope fractionation
KW - organo-silicon complexes
KW - first principle calculation
KW - three-isotope method
KW - Si coordination change
U2 - 10.1016/j.epsl.2020.116287
DO - 10.1016/j.epsl.2020.116287
M3 - Article
SN - 0012-821X
VL - 541
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
M1 - 116287
ER -