Photoactivation analysis studies at the Madison Accelerator Laboratory to investigate the copper origin of artifacts excavated in the vicinity of the "lost" Roanoke colony

In this presentation we will be discussing our summer research project related to the irradiation at MAL of copper artifacts from James River Institute for Archaeology. The goal of this investigation was driven by a key question about the provenance of the copper, that is, whether it was of European or Native Indian origin. Out of the 8 artifacts that we investigated, a band excavated from the Elizabeth Gardens, a site located within Fort Raleigh National Historic Site, was of particular interest to the team of archaeologists from James River Institute. Based on their previous work, there were qualitative differences in the chemical compositions of European and Native copper artifacts. For example, some elements like Zinc or Tin were present only in the composition of European copper.

Qualitative Photoactivation Analysis (PAA) was applied to determine the chemical composition of the irradiated artifacts by the MAL’s linac. The γ-rays following the β-decays of these activated artifacts via (γ,n) or (n,γ) reactions were subsequently detected with a 45% relative efficiency High Purity Germanium detector. The γ-ray emission energy peaks were recorded by the Genie 2000 data acquisition software and analyzed with a dedicated γ-ray spectroscopy data analysis tool.

Our findings regarding the copper origin of the Elizabethan Garden band, based on qualitative PAA only, may be significant. The site where the band was found contains only Native American artifacts and therefore a European origin would be evidence of contact between Raleigh’s colonists and the Roanoke Indians.