This research used samples and/or data provided by the Ocean Drilling Program (ODP). The ODP is sponsored by the U.S. National Science Foundation (NSF) and participating countries under management of Joint Oceanographic Institutions (JOI), Inc. Funding for this research was provided by the Centre National de la Recherche Scientifique (CNRS) with the French Program OCEANS and by the AFCRST PRA 99-02, which permits us to have helpful discussions with our Chinese colleagues. We wish to thank the two reviewers, Dr. Shu Gao and Dr. Karl Stattegger, for their constructive comments on the manuscript. We are also grateful to Olivier Dufaure and Rémy Pichon, who helped us to process XRD and major element analyses. This manuscript is dedicated to the memory of Dr. J. Bertaux, who died on 26 August 2002.