1. Department of Archaeology, University of NottinghamUniversity Park Nottingham NG7 2RD UK
2. The University of Nottingham Ningbo China No. 199, Taikang East Road Ningbo 315100 China
3. NERC Isotope Geosciences LaboratoryBritish Geological Survey, Keyworth Nottingham NG12 5GG UK
4. Inorganic GeochemistryBritish Geological Survey, Keyworth Nottingham NG12 5GG UK
5. Xi'an archaeological institute of cultural relics protection No. 68, Youyi West Road Xi'an 710068 China