Chronological discrimination of silver coins based on inter-elemental ratios using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS)

摘要

This paper details the application of a statistical method for the chronological discrimination of silver coins using counts per second trace elemental, inter-elemental ratios. The statistical method described is based on a method that has been applied to similar archaeological materials to determine their provenance. The method makes use of the inter-element association patterns of multi-element analytical data determined using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The majority of the 266 coins analysed for this study have already been successfully identified by their mint markings. The data from LA-ICP-MS analyses, together with what is known about the coins through visual identification, were used to discriminate the reigning sovereign, and in the case of Mexico, the year of minting, of individual coins within the elemental fingerprint of different mints. Subsequently, unidentified coins can be placed in the confusion matrix, and their trace element information used to identify their year of minting when compared with other, identified coins from the same mint. The interpretational statistical technique linear discriminant analysis (LDA) was used to explore an identification of year of minting of coins that have previously not been identified by other means based on a statistical comparison against a database of compositional analysis of silver coins of known year of minting.