HR: 0800h
AN: V51E-0839    [Abstracts]
TI: High-precision multiple-sulfur isotope analysis as a new tool to decouple isotope mixing and fractionation: application to subsurface sulfur cycles
AU: * Ono, S
EM: sono@mit.edu
AF: Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, United States
AB: Isotope mixing and fractionation are often two important processes that govern isotope ratios of geomaterials. Single isotope ratio analysis, however, is one-dimensional such that it constrains either isotope mixing or fractionation. Multiple-stable isotope ratios (e.g., ³²S/³³S/³⁴S/³⁶S) were thought to carry no additional information because they were thought to follow mass-dependent relationships such that isotope fractionation in ³³S/³²S, for example, is about a half of that of ³⁴S/³²S. Mass-dependent equilibrium isotope fractionation, in theory, follows a power law (e.g., ³³α = ³⁴α ^0.515) function, ultimately due to exponential function of the Boltzmann energy distribution. This power law function of mass-dependent isotope fractionation has important implication because it is expressed non-linearly in conventional delta-delta plots (e.g., δ³³S versus δ³⁴S). This contrasts to isotope mixing that is expressed as a linear function in delta-delta plots. This functional difference produces small but measurable variations in multiple-stable isotope systems, and can be used to decouple isotope mixing and fractionation. I will discuss application into natural systems, in particular, how high-precision multiple-sulfur isotope analysis is used to trace subsurface sulfur cycles, where both sulfur isotope mixing and fractionation is occurring. The same approach may be used to other multiple- stable isotope systems if required analytical precision can be achieved.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0424 Biosignatures and proxies
DE: 0450 Hydrothermal systems (1034, 3017, 3616, 4832, 8135, 8424)
DE: 0454 Isotopic composition and chemistry (1041, 4870)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting