The first author thanks Doodie James for help with analysis and Geoff Angel with XRD analysis. We also thank Klas Lackschewitz for making available electron microprobe data for comparisons. Prof. Keith Crook is thanked for his careful review of the paper. This research used samples and/or data provided by the Ocean Drilling Program (ODP). 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 Rapid Response Grant from the U.K. Natural Environmental Research Council to the first author. The second author thanks the Australian ODP Secretariat for a small postcruise grant.