Lead isotopic and elemental analysis of copper alloy statuettes by double focusing sector field ICP mass spectrometry

Lead isotopic analysis may be of great interest for provenance determination of ancient bronze artefacts. Traditionally, thermal ionization mass spectrometry (TIMS) is used for this purpose, because of its superiority in terms of isotope ratio precision (RSD values typically <0.05%). However, TIMS analysis is quite time-consuming, especially since the analyte of interest has to be isolated from the matrix. Quadrupole-based ICP-MS can be used as an alternative, but its application range is limited because of the rather poor isotope ratio precision (RSD values typically 0.1–0.5%). Hence, in this study, double focusing sector field ICP mass spectrometry was examined for use in provenance studies. Twenty-six statuettes representing Roman Gods, most of them said to be found during dredging-operations in the rivers Scheldt and Durme around Hamme (Belgium), were selected for this study. The RSD values obtained for 204Pb/206Pb, 207Pb/206Pb and 208Pb/206Pb were 0.1–0.4%, 0.05–0.15% and 0.05–0.15%, respectively. Using simple bivariate plots, the lead used for the production of these statuettes was localized as originating from the British Islands or from the South of Europe (Cyprus, Greece and Italy). Also the elemental composition (Cu, Sn, Pb, Zn, Ni, Fe and Sb content) of the alloys was determined in order to date the statuettes approximately.