Iron isotopes biogenic fractionations

Iron is thought to have been an important part of the biogeochemistry of the early Earth. However, fractionations within the iron-isotope system tend to be smaller than those observed for the lighter elements and are frequently only a few parts per mil. This means that it can be difficult to uniquely identify biogenic iron-isotope signatures in the geological record because abiotic fractionation is of comparable magnitude (Fig. 6.2). 

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