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Science 2 June 2000:
Vol. 288. no. 5471, pp. 1629 - 1631
DOI: 10.1126/science.288.5471.1629
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Reports

Accretion of Primitive Planetesimals: Hf-W Isotopic Evidence from Enstatite Chondrites

Der-Chuen Lee, 12 Alex N. Halliday 2

Enstatite chondrites have often been considered to be closely related to the material from which Earth accreted. However, tungsten isotopic data reveal clear differences. Moreover, the silicate and metal fractions define distinct initial 182Hf/180Hf corresponding to a 13.8 ± 5.3 million year apparent age difference. Internal reequilibration does not provide a ready explanation for this result. Larger scale redistribution of tungsten is more likely, such as may have occurred during collisions between planetesimals.

1 Department of Geological Sciences, University of Michigan, Ann Arbor, MI 48109-1063, USA.
2 Institute for Isotope Geology and Mineral Resources, Department of Earth Sciences, ETH Zürich, CH-8092, Zürich, Switzerland.

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