Sulfur isotope fractionation derived from reaction-transport modeling in the Eastern Equatorial Pacific (ODP Leg 201, Site 1226)
Abstract
Recent theoretical models suggest that low cell-specific sulfate reduction rates (csSRR) in marine sediments should result in high S-isotope fractionation factors (1). Existing studies on marginal sediments show actual fractionation factors indeed approach the theoretical equilibrium fractionation of 70‰ (2,3,4). Here we apply a reaction transport model (REMAP) (5) to data from ODP Site 1226 in the abyssal plain of the Eastern Equatorial Pacific (same location as Leg 138, Site 846). Our results suggest volumetric sulfate reduction rates vary from 346 fmol/cm3/day at 3 mbsf to 0.4 fmol/cm3/day in deeper sediments. Using existing cell counts, this implies csSRR between 10-3 and 10-6 fmol/cell/day, orders of magnitudes lower than those observed in shallower marine settings (10-1 to 10-4 fmol/cell/day) (6). We show that the observed S-isotopes are best explained with a constant fractionation factor of 48‰, considerably smaller than the 70‰ predicted by theoretical models (1). We hypothesize that this is due to in-situ sulfide re-oxidation and disproportionation, promoted by high contents of sedimentary Fe(III) and Mn(IV) at Site 1226 (7). We will further explore this hypothesis in our poster.
Wing B.A. & Halevy I. Proc. Natl. Acad. Sci. USA 111, 18116-18125 (2014). Wortmann U.G. Geochem. Geophys. Geosyst. 7 (2006). Rudnicki M., Elderfield H. & Spiro B. Geochim. Cosmochim. Acta 65, 777-789 (2001). Tudge A.P. & Thode H.G. Canadian J. Res. 28, 567-578 (1950). Chernyavsky B.M. & Wortmann U.G. Geochem. Geophys. Geosyst. 8 (2007). Hoehler T.M. & Jørgensen B.B. Nature Rev. Microbiol. 11, 83-94 (2013). Gurvich E.G., Levitan M.A. & Kuzmina T.G. in Proc. of the Ocean Drilling Prog., Sci. Results, N. Pisias et al., Eds. (1995), vol. 138, pp. 769-778.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.B41A0390T
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCESDE: 0444 Evolutionary geobiology;
- BIOGEOSCIENCESDE: 0463 Microbe/mineral interactions;
- BIOGEOSCIENCESDE: 0473 Paleoclimatology and paleoceanography;
- BIOGEOSCIENCES