Improved fingerprinting of Melos obsidian using three complementary analytical techniques

The natural volcanic glass obsidian was one of the most appreciated materials of ancient man for cutting tools and has been found in many locations far away from any natural source. Reliable provenancing by means of its highly specific chemical composition, the “chemical fingerprint”, can provide information about economy, policy and the social system of ancient societies.
The application of three complementary analytical techniques enables both a maximum element spectrum and a comparison of the chemical compositions to provide the actual degree of the re-liability of the analytical results.
This approach reveals the most characteristic “chemical fingerprint“ and allow us to decide which least invasive analytical method should be chosen for the analysis of an archaeological artefact most likely stem from Melos by three different methods:

• Neutron Activation Analysis (NAA)
• Ion Beam Analysis (IBA) comprising of Proton Induced X-ray Emission (PIXE), Proton Induced Gamma-ray Emission (PIGE) and Rutherford Backscattering Spectrometry (RBS)
• Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS)

For this study, NAA, IBA and LA-ICP-MS measurements have been applied to the same sam-ples originating from the obsidian sources Agia Nychia and Demenegakion on the island of Melos (Greece). NAA investigations have been performed in the TRIGA Mark II 250 kW re-search reactor of the Atominstitut in Vienna. IBA studies have been carried out using the exter-nal 4 MeV proton beam of the 5 MV Tandem accelerator of the Ion Beam Centre of Helmholtz-Zentrum Dresden-Rossendorf. LA-ICP-MS measurements have been taken with the Thermo Element 2 ICP-MS coupled to an ArF gas Excimer laser system at the Aberystwyth University.
These investigations are part of a joint project to apply analytical techniques mentioned to check the self-consistency of the analytical results and to reveal the most characteristic “chemical fin-gerprint” of each available natural obsidian source in Europe. This knowledge should enable to decide which least invasive analytical method should be chosen for the analysis of a specific archaeological artefact on a case-by-case basis.