Geochemical changes during Egyptian copper smelting? An experimental approach to the Ayn Soukhna process and broader implications for archaeometallurgy

摘要

This paper presents the results of comprehensive geochemical analysis of experimental copper smelting products. An iterative, long-term experimental programme has been incorporated in the ongoing excavation of Middle Kingdom metallurgy remains at Ayn Soukhna (Egypt) in order to better understand the copper production chain at the site. The integration of archaeometry into this research methodology has enabled a detailed understanding of the geochemical changes which may occur during copper smelting in furnaces of this type. These include significant elemental fractionation, as well as important shifts in lead isotope ratios between ores and end products (slag and copper). This research presents an interpretative framework not only for understanding production waste from Ayn Soukhna itself, but more broadly the provenance and technology of copper alloys circulating in ancient Egypt. The significant shifts in lead isotope ratios observed for an experimental low-lead copper smelting system are highly relevant here, given the similar composition of many Sinai and Eastern Desert ores exploited throughout Pharaonic history. However, the implications of this research may be extrapolated beyond Egypt to low-lead copper provenance research across the ancient world and thus provide an important new methodological perspective for archaeometallurgy more generally. Furthermore, limitations to using iron in copper artefacts as a guide for their production technology are pointed out. Similar iron contents are observed for woodand charcoal-based smelting systems, inviting a reappraisal of fuel use at ancient metal production contexts in Egypt and elsewhere. A research approach integrating excavation, experimentation and analysis is essential when confronting the complexity of production chains underlying Egyptian copper artefacts. While daunting, this generates more nuanced interpretative frameworks for studying copper provenance and technology.