T238 Sulfates in the Solar System

Tuesday, 7 October 2008
8:00 AM - 12:00 PM

Microbial Sulfur Fractionation in Natural Springs - Implications for Archean Seawater Chemistry

Paper number: T238-2
Program: Technical Sessions
Time: 8:10 AM – 8:25 AM

Authors

Abstract

Net fractionations recorded in laboratory studies are not necessarily reflective of a microbial community under natural conditions. We examined the control of sulfate concentration on isotope fractionation by microbial communities in natural sulfur spring systems.

Our results show that Δδ34S is not significantly affected by temperature, however there is a strong log-linear relationship (r2=0.72) with [SO4]. Based on a Δδ34S =10‰ cutoff to define minimal fractionation, this equates to a sulfate value of 2340 μM. Our results based on natural systems thus show a significant divergence from previous laboratory based study, and suggest that concentrations of sulfate in the Archean ocean may have been an order of magnitude higher than previously thought.