1. Univ Lyon, ENSL, Univ Lyon 1, CNRS, LGL-TPE, F-69007 Lyon, France
2. GenESI, INRA, Rouillé, France
3. Center for Earth Evolution and Dynamics, University of Oslo, N-0315 Oslo, Norway
4. Bristol Isotope Group, School of Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK