1. Department of Earth Sciences, University of Manchester, Oxford Road, Manchester M13 9PL, UK ()
2. Department of Geological Sciences, University of Michigan, Ann Arbor, MI 48109-1063, USA
3. Institute for Isotope Geology and Mineral Resources, Department of Earth Sciences, ETH Zurich, 8092-Zurich, Switzerland
4. Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Boad Branch Road NW, Washington, DC 20015, USA