Abstract:
Ion beam analysis (IBA) techniques continue to have an important application in archaeology, and in particular, obsidian studies. Obsidian is a naturally occurring volcanic glass that was widely used in early prehistoric times in New Zealand, for cutting tools and weapons. There are numerous source deposits in the North Island that have distinctive elemental compositions. This thesis presents results from the application of the ion beam elemental analysis technique proton induced x-ray emission or PIXE, in analysing obsidian source samples, and development of a multipurpose database of their elemental concentrations. The database has the potential to make a powerful contribution in obsidian hydration dating by enabling archaeologists to provenance obsidian artefacts, and also assess the rate of hydration and chemical durability of individual obsidian samples. Glass corrosion is a complex process that involves the inter-diffusion of ionic species, to form a surface region depleted in alkali content and enhanced in hydrogen. Obsidian hydration dating uses a measurement of the thickness of this hydration layer to estimate the age of an obsidian artefact. This thesis describes research undertaken to develop an IBA technique using the 3.09MeV nuclear resonance reaction of 1H( 7Li, )8Be, to measure the thickness of obsidian hydration rims by detecting the actual hydrogen content. The feasibility of using the hydrogen depth profiling technique in obsidian hydration dating, is established by assessing its performance in analysing a selection of hydrated obsidian samples. The results indicate that the hydrogen profiling technique is capable of measuring hydration rims of small size and poor optical quality, with equal or better resolution than optical microscopy. A number of recommendations are made for the future development and use of the hydrogen depth profiling technique and the obsidian elemental composition database.