The origin of Zn isotope fractionation in sulfides

• Published in: Geochimica et Cosmochimica Acta
• Main Authors: Fujii, Toshiyuki, Moynier, Frédéric, Pons, Marie-Laure, Albarède, Francis
• Other Authors: Research Reactor Institute, Kyoto University Kyoto, Department of Earth and Planetary Sciences St Louis, Washington University in Saint Louis (WUSTL), McDonnell Center for Space Sciences, Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement Lyon (LGL-TPE), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), I-CARES, Washington University in Saint Louis
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2011
• Subjects: 1 ATM PRESSURE; AQUEOUS-SOLUTION; ZINC ISOTOPES; CARBONIC-ACID; BISULFIDE COMPLEXES; NMR-SPECTRA; NACL MEDIA; CHEMISTRY; RAMAN; IONIZATION; geo; envir; Carbonic acid
• Online Access: https://doi.org/10.1016/j.gca.2011.09.036; https://hal-insu.archives-ouvertes.fr/insu-00674540/file/j.gca.2011.09.036.pdf; https://hal-insu.archives-ouvertes.fr/insu-00674540

International audience Isotope fractionation of Zn between aqueous sulfide, chloride, and carbonate species (Zn(2+), Zn(HS)2, Zn(HS)(3)(-), Zn(HS)(4)(2-), ZnS(HS)(-), ZnCl(+), ZnCl(2), ZnHCO(3)(+), and ZnCO(3)) was investigated using ab initio methods. Only little fractionation is found between the sulfide species, whereas carbonates are up to 1 parts per thousand heavier than the parent solution. At pH > 3 and under atmospheric-like CO(2) pressures, isotope fractionation of Zn sulfides precipitated from sulfidic solutions is affected by aqueous sulfide species and the delta(66)Zn of sulfides reflect these in the parent solutions. Under high P(CO2) conditions, carbonate species become abundant. In high PCO(2) conditions of hydrothermal solutions, Zn precipitated as sulfides is isotopically nearly unfractionated with respect to a low-pH parent fluid. In contrast, negative delta(66)Zn down to at least -0.6 parts per thousand can be expected in sulfides precipitated from solutions with pH > 9. Zinc isotopes in sulfides and rocks therefore represent a potential indicator of mid to high pH in ancient hydrothermal fluids.