1. ETH Zürich, Institute of Geochemistry and Petrology, Clausiusstrasse 25, CH-8092 Zürich, Switzerland
2. CEA, DAM, Ile-de-France, 91297 Arpajon Cedex, France
3. Laboratoire de Géologie de Lyon, ENS Lyon and UCBL, UMR 5276, CNRS, 69364 Lyon Cedex, France