Lead isotope analyses on Late Republican sling bullets

Abstract

Forty-two lead objects (mainly sling bullets) from archaeological sites in Spain and Italy, dating into the late Roman Republican period, two ore samples from Portman (Cartagena region) and one further ore sample from a deposit on Ibiza were analysed for their lead isotope ratios by multicollector inductively coupled plasma mass spectrometry (MC ICP-MS). The objective of the present study was to answer questions, which cannot be solved by conventional archaeological methods alone but require further information on the materials composition. For this, MC ICP-MS as a modern and fast analytical method to obtain both chemical and isotopic information paired with very low material consumption is a helpful analytical tool to answer archaeological and technological considerations and questions like (a) on the origin of the raw metals used for the objects, (b) if individual production sites used more than one metal source and (c) if certain metal mining areas were preferred during particular periods in time. The results of this study, which were obtained by combining lead isotope analysis with common archaeological methods, clearly demonstrate that Late Republican sling bullets and some other lead objects of other usage from Menorca originate from ore minerals that were predominantly mined on the Iberian mainland. Mixing relationships also show that a number of them were manufactured from reprocessed material. This is also true for single Italian lead sling bullets. Additionally, some of the objects have lead isotope signatures interpreted as mixing relationships, which point towards a manufacturing from reprocessed material.