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Project Progress

In Year 1 and 2, most of our focus was on methods development and initial applications, with iron and molybdenum isotopes getting the bulk of attention. The most relevant finding to biomarker studies was our demonstration that iron isotopes can be fractionated by chemical processes in the absence of biology. This was demonstrated using ion exchange chromatography. Our interpretation of the data is that fractionation occurs during equilibration between dissolved iron complexes in solution, which suggests that some of the natural variations in iron isotopic composition may be due to non-biological chemistry. This interpretation also provides insight into the mechanism(s) of biological iron isotope fractionation. This work was presented in 1999 at the V. M. Goldschmidt Conference, GSA and AGU, and published in Science in April, 2000.

We intend to follow up on these findings in Year 3 by conducting non-biological experiments using systems more relevant to nature than those used to date, and by exploring natural systems where biological influence is unlikely.

We also observed natural variations in the isotopic composition of Mo, which suggest a possible application for paleoredox studies. This will be a major area of emphasis in Year 3 in collaboration with the Harvard Team. Two manuscripts on Mo isotopes are in preparation.