Ancient armour provenance by LA-ICP-MS analysis of microscopic slag inclusions

Provenance studies of ancient armour based on trace elements in slag inclusions (SI) present analytical challenges due to the small size (<30 μm) of the particles. This paper presents an analytical protocol developed for this kind of SI using LA-ICP-MS. Two different LA-ICP-MS systems were tested: a double focusing inductively coupled plasma mass spectrometer coupled with a 193 nm nanosecond laser on the one hand, and a 257 nm femtosecond laser on the other hand. The protocol was used to analyse the composition of the SI in armour samples dating from the 13th to the late 16th centuries and assumed to have been made in different areas (northern Italy, southern Germany and eastern France). The goal was to both validate the methodology developed and address specific historical issues. The results allow us to distinguish different provenance groups. By comparing the SI chemical signatures with the macroscopic slag composition of different production areas, some archaeological pieces identified as armour plates were for the first time attributed to Lorraine (France). The results also present an opportunity to discuss the origin of Italian-style pieces. Among them, eight samples have a common chemical signature. This latter group constitutes the first set of chemical signatures for Italian armour, opening the door for further decisive studies.