HR: 15:00h
AN: H33E-04    [Abstracts]
TI: A Global Perspective on Nd-Hf Isotope Systematics in the Ocean From Marine Sediments and Ferromanganese Precipitates Around Antarctica
AU: van de Flierdt, T
EM: tina@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory and Department of Earth and Environmental Sciences, Columbia University, 61 Route 9W, Palisades, NY 10964, United States
AU: Goldstein, S L
EM: steveg@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory and Department of Earth and Environmental Sciences, Columbia University, 61 Route 9W, Palisades, NY 10964, United States
AU: * Hemming, S R
EM: sidney@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory and Department of Earth and Environmental Sciences, Columbia University, 61 Route 9W, Palisades, NY 10964, United States
AU: Roy, M
EM: roy.martin@uqam.ca
AF: Département des Sciences de la Terre et de l'Atomosphère, Université du Québec à Montréal, C.P. 8888, Succ. Centre-Ville, Montréal, QC H3C 3P8, Canada
AU: Frank, M
EM: mfrank@ifm-geomar.de
AF: IfM-GEOMAR, Leibniz Institute for Marine Sciences, Wischhofstrasse 1-3, Kiel, 24148, Germany
AU: Halliday, A N
EM: Alex.Halliday@earth.ox.ac.uk
AF: University of Oxford, Department of Earth Sciences, Parks Road, Oxford, OX 3PR, United Kingdom
AB: Neodymium-hafnium systematics of proximal terrigenous sediments around Antarctica are of major interest as they contain the power to address topics as diverse as crustal evolution, sedimentary processes, and the reconstruction of ocean circulation patterns. Here we present data on glacio-marine core-top sediments from around the perimeter of Antarctica. The results range from ε _Hf = -30.1 to ε _Hf = +0.8, reflecting the large range of basement ages and lithologies around the Antarctic continent. When plotted against Nd isotope results on the same sediments the data are collinear with the global silicate Earth array ("terrestrial array"). Hafnium and Nd isotopic compositions of Circum-Antarctic ferromanganese precipitates lie on the global "seawater array". The offset between these two arrays provides evidence for the sources and mechanisms by which these elements are added to ocean water. Lutetium-Hf and Sm-Nd evolution and mixing calculations provide compelling evidence that while hydrothermal contributions of Hf to the ocean may play a role, continental contributions are absolutely required to explain the variations in Hf isotope ratios in seawater. Furthermore, it can be shown that incongruent weathering of continental sources is alone sufficient, without any hydrothermal contributions, to create the observed offset of the Nd-Hf isotope array in seawater.
DE: 1040 Radiogenic isotope geochemistry
DE: 4825 Geochemistry
DE: 4924 Geochemical tracers
DE: 9310 Antarctica (4207)
SC: Hydrology [H]
MN: 2007 Joint Assembly