Effect of seawater contamination on modeled sulfur isotope fractionation during microbial sulfate reduction (ODP Leg 201, Site 1226)
Abstract
Studies of ODP Leg 201 Site 1226 using reaction-transport models (Wang et. al., 2008; Tsang & Wortmann, submitted) yield microbial sulfate reduction rates between 102 fmol/cm3/day in the near surface sediments to 10-1 fmol/cm3/day in deep sediments. The observed sulfate δ34S data is best explained if we use sulfate fractionation factors between 1.045 and 1.048. However, Site 1226 was also previously drilled by Leg 138 as Site 846. A comparison of the porewater data from Site 1226 and Site 846 reveals that seawater probably contaminated the porewater samples at Site 1226. We estimate that there is an average of 8% seawater in the porewater samples collected with advanced piston coring. This has only a minor influence on the modeled sulfate reduction rates, but increases the apparent fractionation factor to 1.058 to 1.060, which is more in line with theoretical predictions (Brunner & Bernasconi, 2005; Wing & Halevy, 2014) at around 1.07.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFM.B21A1951T
- Keywords:
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- 0424 Biosignatures and proxies;
- BIOGEOSCIENCES;
- 0454 Isotopic composition and chemistry;
- BIOGEOSCIENCES;
- 0465 Microbiology: ecology;
- physiology and genomics;
- BIOGEOSCIENCES;
- 1099 General or miscellaneous;
- GEOCHEMISTRY