The State Key Laboratory of Environmental Geochemistry;
Institute of Geochemistry;
Chinese Academy of Sciences;
Guiyang 550002;
China;
Laboratoire de Geochimie et Cosmochimie;
Institut de Physique du Globe de Paris;
Université Paris 7;
UMR 7579;
4 Place Jussieu;
75252 Paris Cedex 05;
France;