Title: The Archean Mass-Independent Sulfur Isotope Record: Prospects and Limitations


Abstract: For about a decade, the existence of mass-anomalous isotopic compositions in Archean and early Paleoproterozoic sulfides and sulfates and their absence from younger rocks has been taken as the most robust geochemical evidence for a marked increase in atmospheric oxygen levels near the Archean-Paleoproterozoic boundary. However, most of what we know about the production of this anomalous isotopic signal remains phenomenological and a mechanistic understanding of the physical processes behind the fractionation is only marginally nearer today than it was ten years ago. Despite these challenges, and accepting that this isotopic signal was indeed produced in the atmosphere, it is possible to constrain aspects of the Archean biogeochemical sulfur cycle, as well as other properties of the ocean-atmosphere system and its interactions with the solid Earth. I will review the state of understanding of the processes responsible for production of anomalous sulfur fractionations and present modeling constraints on the ancient sulfur cycle.


http://www.its.caltech.edu/~ihal/