Abstract
Stable iron isotope fractionation between aqueous Fe(II) and smectite
Mineralogical magazine, Vol.76(6), p.2556
Goldschmidt 2012
2012
Abstract
Redox transformations of Fe-bearing phyllosilicate minerals play an important role in Fe cycle in the subsurface environments. This experimental study determined the stable Fe isotopic exchange and fractionation factor between a (super 57) Fe-enriched aqueous Fe(II) and an isotopically "normal" smectite SWa-1 (iron oxide impurities stripped off by purification) using a three-isotope method. Leaching of solid with 0.5 M HCl for 0.5 hr, following separation with aqueous Fe(II) at different time points, yielded mostly Fe(II) in extract 1 and subsequent leaching with 0.5 M HCl for 24 hrs yielded mostly Fe(III) in extract 2. Isotopic exchange between different components was monitored by changes in their delta (super 57/56) Fe values. Isotopic exchange was limited between aqueous Fe(II) and bulk smectite. When excluding bulk smectite from the system, however, about 90% of exchange was achieved between aqueous Fe(II) and extract 1 (a weakly sorbed component) in the beginning of the experiments and leveled off with time, suggesting a steady-state condition was reached early on in the experiments between aqueous Fe and extract 1. Fraction of isotopic exchange (F) reached approximately 50% between aqueous Fe(II) and extract 2. The equilibrium fractionation factor between aqueous Fe(II) and extract 2 has been determined to be approximately -2.4ppm (below figure represents one of the duplicate experiments). Extract 2 could be an iron oxide phase as observed during electron transfer between aqueous Fe(II) and smectite and the mineralogy nature of extract 2 will be further identified using Mossbauer spectra. Nevertheless, the equilibrium Fe isotope fractionation between aqueous Fe(II) and smectite, driven by redox changes, has important implications for understanding redox processes in subsurface environments that is enriched in ferrous iron and clay minerals.
Details
- Title: Subtitle
- Stable iron isotope fractionation between aqueous Fe(II) and smectite
- Creators
- Lingling Wu - University of Wisconsin–MadisonBrian L BeardAnke NeumannMichelle M SchererEric E RodenClark M Johnson
- Resource Type
- Abstract
- Publication Details
- Mineralogical magazine, Vol.76(6), p.2556
- Conference
- Goldschmidt 2012
- Publisher
- Mineralogical Society
- ISSN
- 0026-461X
- eISSN
- 1471-8022
- Alternative title
- Goldschmidt 2012 abstract volume
- Language
- English
- Date published
- 2012
- Academic Unit
- Civil and Environmental Engineering
- Record Identifier
- 9984202134302771
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