New Heavy Isotope Studies in Archaeology

Kinetic theory relating to the separation of isotopes in nonequilibrium evaporation, originally developed in the 1920s, is discussed in the context of the possibility of anthropogenic lead isotope fractionation in ancient metallurgical processes. From a consideration of the chemistry of lead and lead compounds and the results of a small trial experiment, it is concluded that any isotopic fractionation of lead is unlikely to be archaeologically significant given current measurement precision. However, application of the same theory to the tin isotope system shows that substantial and measurable isotopic fractionation is likely to result from melting and remelting bronze. Furthermore, recent studies show that tin isotopes do not vary significantly in terrestrial ores. This raises the possibility that tin isotope ratios will be systematically altered by melting, casting, and recycling bronze. This paper discusses the principles of tin isotope fractionation in ancient metallurgy and the potential for tin isotope studies to yield quantitative data on prehistoric metal recycling.