HR: 13:40h
AN: PP33D-01 INVITED     [Abstracts]
TI: Evaluating Fe and Zn Isotopes as Tracers in the Marine System
AU: * Boyle, E A
EM: eaboyle@mit.edu
AF: Earth, Atm., Planet. Sci., Massachusetts Institute of Technology, E34-258 77 Mass. Ave., Cambridge, MA 02139 United States
AU: Bergquist, B A
EM: bbergqui@umich.edu
AF: Department of Geology, University of Michigan, University of Michigan, Ann Arbor, MI 48109 United States
AU: John, S
EM: sjohn@mit.edu
AF: Earth, Atm., Planet. Sci., Massachusetts Institute of Technology, E34-258 77 Mass. Ave., Cambridge, MA 02139 United States
AB: Early work on Fe and Zn isotopes showed that these isotope systems show significant fractionations under earth-surface conditions and that earth-surface samples are significantly fractionated from one another. Because both of these elements are essential to marine life, they may limit the growth of marine organisms in certain circumstances (Fe has been demonstrated to be limiting in parts of the modern ocean; Zn has not yet been shown limiting in the modern ocean, but may have been limiting under different environmental conditions). Hence we need tools to understand their chemistry in the ocean and to evaluate past changes they have undergone. By (very rough) analogy to the carbon and nitrogen isotope system, it seems that the stable isotopes of these elements might be useful in understanding the present and past chemistry of these elements in the ocean. Information is scarce on these isotope systems in the marine environment; most published work concerns samples from sedimentary rocks, ferromanganese nodules, sediment traps, and laboratory experiments. There is no published information on these isotope systems in marine plankton or ocean waters, mainly because these elements occur at very low levels in the ocean and marine samples are difficult to process without contamination. Armed with experience in oceanic trace element sampling and analysis, we have undertaken Fe and Zn isotope analyses of samples of plankton tows and seawater from the marine environment in the North Atlantic and North Pacific Oceans, as well as samples from laboratory cultures and a few other types of marine materials. These samples show significant Fe and Zn isotope fractionations. Although we do not yet have enough information to confidently describe the mechanisms driving these fractionations, this data provide support for the hope that these isotope systems may prove useful in evaluating the marine environmental chemistry of these elements.
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 0489 Trace element cycling (4875)
DE: 4870 Stable isotopes (0454, 1041)
DE: 4875 Trace elements (0489)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005