Isotopic interconnections in the earth system

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The broad objective of the proposed research program is to track 'electrons through time' using cutting-edge measurements of total sulfur and oxygen isotopes. Redox transformations, and the associated flow of electrons, link the co-evolution of the solid earth and its fluid envelope. The global biota mediate most of these transformations, enabling the redox trajectory of the earth surface environment to be interpreted as a record of biotic evolution. In the stable isotope laboratory of McGill University's Earth and Planetary Sciences department, we use laboratory experiments and studies of well-constrained modern environments to calibrate sulfur and oxygen isotopic tracers of paleoredox changes. Once calibrated, these tracers are then applied to well-characterized sample sets from the rock record. The focus of upcoming work, for example, will range from biogeochemical cycling in modern methane hydrates to piston-cylinder investigations on magmatic degassing. A common theme will be the extraction of sulfur and oxygen fractionation factors that characterize material cycling in these environments. Concurrent with laboratory investigations, field studies will span the full range of Earth history, from the recent products of volcanic eruptions to some of the oldest rocks of Earth (the Nuvvuagittuq greenstone belt). Successful completion of this work will provide a double benefit to the field of Earth System Science. First, the calibration of isotopic tracers for redox transformations will provide a