Isotope systematics and chemical composition of tin ingots from Mochlos (Crete) and other Late Bronze Age sites in the eastern Mediterranean Sea: An ultimate key to tin provenance?

Daniel Berger,Ehud Galili,Gerhard Brügmann,Jeffrey S Soles,Alessandra R Giumlia-Mair,Ernst Pernicka,Nicole Lockhoff,Andrea Zerboni

doi:10.1371/journal.pone.0218326

Abstract

The origin of the tin used for the production of bronze in the Eurasian Bronze Age is still one of the mysteries in prehistoric archaeology. In the past, numerous studies were carried out on archaeological bronze and tin objects with the aim of determining the sources of tin, but all failed to find suitable fingerprints. In this paper we investigate a set of 27 tin ingots from well-known sites in the eastern Mediterranean Sea (Mochlos, Uluburun, Hishuley Carmel, Kfar Samir south, Haifa) that had been the subject of previous archaeological and archaeometallurgical research. By using a combined approach of tin and lead isotopes together with trace elements it is possible to narrow down the potential sources of tin for the first time. The strongly radiogenic composition of lead in the tin ingots from Israel allows the calculation of a geological model age of the parental tin ores of 291 ± 17 Ma. This theoretical formation age excludes Anatolian, central Asian and Egyptian tin deposits as tin sources since they formed either much earlier or later. On the other hand, European tin deposits of the Variscan orogeny agree well with this time span so that an origin from European deposits is suggested. With the help of the tin isotope composition and the trace elements of the objects it is further possible to exclude many tin resources from the European continent and, considering the current state of knowledge and the available data, to conclude that Cornish tin mines are the most likely suppliers for the 13th–12th centuries tin ingots from Israel. Even though a different provenance seems to be suggested for the tin from Mochlos and Uluburun by the actual data, these findings are of great importance for the archaeological interpretation of the trade routes and the circulation of tin during the Late Bronze Age. They demonstrate that the trade networks between the eastern Mediterranean and some place in the east that are assumed for the first half of the 2nd millennium BCE (as indicated by textual evidence from Kültepe/Kaneš and Mari) did not exist in the same way towards the last quarter of the millennium.

Highlights

Tin objects are extremely rare in the archaeological record, and only very few are known from prehistoric contexts
The archaeometallurgical examination of 27 Late Bronze Age (LBA) tin ingots (1530–c. 1300 BCE) from five sites in the eastern Mediterranean area enables the localisation of the potential suppliers of the tin ores by means of chemical and isotopic analyses for the first time
The lead isotope composition of the tin is the most important fingerprint in this regard. It clearly identifies European deposits as tin sources for the Israeli ingots because the Pb-Pb model age of the tin of about 290 million years (Ma) links the Variscan orogenic belt to the parental tin ores used for the production of the tin ingots

Summary

Introduction

Tin objects are extremely rare in the archaeological record, and only very few are known from prehistoric contexts (for artefacts in the eastern Mediterranean and the Near East dating from before 1000 BCE see Fig 1; summary of Eurasian finds in [1]). Deterioration may be enhanced at low temperatures, less than 13 ̊C, when the crystal structure of tin changes, turning the white metal to a grey powder This so-called tin pest is often stated in archaeological literature [5,6,7,8], but since its occurrence has not yet been confirmed on prehistoric artefacts its contribution to the problem is certainly small.

Methods

Results

Conclusion