FINGERPRINTING OF ROMAN MINTS USING LASER‐ABLATION MC–ICP–MS LEAD ISOTOPE ANALYSIS*

In this paper we present data to demonstrate the applicability of laser‐ablation MC–ICP–MS isotope analysis to archaeological artefacts, in this case Roman silver coins. The technique requires no chemical preparation, does minimal damage to the sample and yields external reproducibility that is better than conventional TIMS analysis; ²⁰⁷Pb/²⁰⁶Pb =±0.015% 2σ in comparison with ²⁰⁷Pb/²⁰⁶Pb =±0.04% 2σ, respectively. We show that Pb isotope compositions give isotope fingerprints to mints despite the likely reworking of the metal during coin production.     

LEAD ISOTOPE ANALYSIS OF ARCHAEOLOGICAL METALS BY MULTIPLE‐COLLECTOR INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY*

Lead isotope ratios in archaeological silver and copper were determined by MC–ICPMS using laser ablation and bulk dissolution without lead purification. Laser ablation results on high‐lead metals and bulk solution analyses on all samples agree within error of TIMS data, suggesting that problems from isobaric interferences and/or mass bias variations due to the presence of matrix elements are insignificant. Inaccurate laser ablation analyses on low‐lead copper reflect erroneous mass bias corrections from use of a non‐matrix matched standard. However, in most cases, silver and copper are analysable for lead isotopes by bulk dissolution or laser ablation MC–ICPMS with simplified sample preparation.     

LEAD ISOTOPE AND TRACE ELEMENT ANALYSIS IN THE STUDY OF OVER A HUNDRED SOUTH INDIAN METAL ICONS*

Technical investigations were made on 130 South Indian statuary images and a few miscellaneous artefacts mostly sampled from the Government Museum, Madras, India, and from the Victoria and Albert Museum and the British Museum, UK. Lead isotope investigations were attempted on 60 of these, and compositional analysis for 18 elements on 115, using inductively coupled plasma optical emission spectroscopy; thus, for 40 objects both lead isotope and trace element analysis was done. From the isotopic and elemental framework, insights are obtained into some art-historical problems of images and artefacts of the Pre-Pallava, Pallava, Chola (i.e., Vijayalaya Chola), Later Chola (i.e., Chalukya-Chola and Later Pandya), Vijayanagara (and Early Nayaka) and Later Nayaka (and Maratha) dynasties, spanning the Early Christian era to the nineteenth century, along with a few other regional styles. Inferences are also made regarding provenance of the lead and the early use of zinc and brass in the early historic period (c. fourth century BC—fourth century AD).     

IN‐SITU ELEMENTAL AND Sr ISOTOPE INVESTIGATION OF HUMAN TOOTH ENAMEL BY LASER ABLATION‐(MC)‐ICP‐MS: SUCCESSES AND PITFALLS*

Trace element and Sr isotope data were obtained by laser ablation‐ and solution mode‐(MC)‐ICP‐MS analysis for tooth enamel from remains excavated at the New Kingdom period Egyptian colonial and Nubian cemetery site of Tombos (Sudan). Elemental abundances determined by both methods of ICP‐MS analysis yielded comparable values; however, ⁸⁷Sr/⁸⁶Sr values obtained by laser ablation were higher compared to their solution mode counterparts. This discrepancy is related to the production of a molecular interference—Ca + P + O (overlaps ⁸⁷Sr); hence the higher ⁸⁷Sr/⁸⁶Sr values recorded during ablation analyses. Laser ablation studies of enamel may provide relatively precise ⁸⁷Sr/⁸⁶Sr values rather quickly but cannot be used for accurately deciphering historical population migrations.     

ON THE INFLUENCE OF DRYING AND FIRING OF CLAY ON THE FORMATION OF TRACE ELEMENT CONCENTRATION PROFILES WITHIN POTTERY*

On experimentally fired briquettes made of five chemically and mineralogically different clays, trace element concentration profiles from the centre to the surface of the briquettes have been measured by Neutron Activation in order to examine if drying and firing of the clays lead to a mobilization and subsequent migration of single components within a sherd. Mineralogical changes during firing have been determined by X‐ray diffraction. Generally, no such migration could be found. For two clays, arsenic was lost from the briquette during firing, forming non‐constant concentration profiles. If NaCl is present in the clay paste, sodium migrates towards the surface. Additionally, in the special case in which the presence of NaCl coincides with that of calcite, the heavier alkali elements evaporate, forming significant concentration profiles within the sherd.