Isotope fractionation of Si in protonation/deprotonation reaction of silicic acid: A new pH proxy. (1st November 2015)

• Record Type: Journal Article
• Authors: Fujii, Toshiyuki; Pringle, Emily A.; Chaussidon, Marc; Moynier, Frédéric
• Is Part Of: Geochimica et cosmochimica acta. Volume 168(2015:Nov. 01)
• Page Start: 193
• Page End: 205
• Publication Date: 2015-11-01
• Subjects: Geochemistry -- Periodicals; Meteorites -- Periodicals; Géochimie -- Périodiques; Météorites -- Périodiques; Geochemie; Astrochemie; Electronic journals; 551.905
• DOI: 10.1016/j.gca.2015.07.003
• Languages: English
• ISSNs: 0016-7037

Abstract

Abstract: Isotopic fractionation of Si in protonation/deprotonation reactions of monomeric silicic acids was theoretically and experimentally studied. The reduced partition function ratio for Si (as 1000 ln β ) complexes was theoretically estimated by ab initio methods. Three permil of isotope fractionation was estimated to be possible for the 28 Si- 30 Si isotope pair. This prediction was experimentally demonstrated by multi-collector inductively coupled plasma mass spectrometer measurements of Si-bearing aqueous solutions, for which equilibrated Si(OH)4 and SiO(OH)3 − were separated using an anionic exchange column. The results create a new possibility for the application of Si isotopes as proxies for paleo-pH in the 9 < pH < 12 range.