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GEOLOGY

Demonstration of significant abiotic iron isotope fractionation in nature. Thomas D. Bullen, et al. Water Resources Division, U.S. Geological Survey, Menlo Park, California 94025, USA. Pages 699702. Iron is an abundant, bioreactive element and thus iron isotopes have the potential to be extremely useful for detecting microbial processes in the geologic record. Previous workers have suggested that iron isotopes on their own can be used as a biosignature, based on the assumption that only biologic processes are capable of fractionating these isotopes in nature. However, based on field and laboratory studies of the formation of the common iron mineral ferrihydrite, the authors present the first definitive evidence that abiotic processes are capable of fractionating iron isotopes in nature to the same extent as microbial processes. The authors also propose a plausible isotope fractionation mechanism, which promotes the preservation of an abiotic iron isotope fractionation signal in the geologic record.

How many Pacific hotspots are fed by deep-mantle plumes? Valrie Clouard, Jeune Equipe Terre-Ocan, Universit de la Polynsie Franaise, B.P. 6570, Faaa, French Polynesia, and Alain Bonneville, UMR Gosciences Marines, Institut de Physique du Globe, 4 place Jussieu, 75005 Paris, France. Pages 695698. The hotspot volcanism theory of the 1960s proposes that the linear intraplate volcanic chains that show an age progression in the direction of t
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Geological Society of America
20-Jul-2001