Geology Club Seminar

Locating the sources of far travelled geological material has important applications in many aspects of Earth science, and compositional analyses of geological and archaeological material has become a vital tool in provenance and correlation studies. The development of laser ablation (LA) ICP-MS over the last 25 years as a trace element micro-analytical method has been particularly important in studies of volcanic ash deposits (tephrochronology) and in archaeological studies, and examples of both will be described in this presentation.

The accurate characterisation of juvenile material (notably glass shards) in tephra deposits from widely separated sites provides an important chronology in Quaternary studies, allowing  proxy records of climate change to be correlated, and giving information on eruption frequency, magnitude and, if source volcanoes can be identified, hazard. LA-ICP-MS has greatly enhanced the reliability with which tephra deposits can be recognised and correlated, but required careful development for the analysis of tiny shards of glass often only 10-20 μm across. Data from distal tephra records is now starting to give insights into magmatic processes (e.g. the presence of 5 compositionally distinct magma batches contributing to Youngest Toba Tuff eruption), which have hitherto remained hidden within bulk analyses of proximal material.

In archaeology, the accurate provenancing of artefacts provides information on movement of material by ancient peoples, trade-routes, etc. Here, LA-ICP-MS offers effectively non-destructive analysis of archaeological materials, ideal for the analysis of scarce or precious samples. A successful application of LA-ICP-MS microanalysis to the source of some of the Stonehenge "bluestones" will also be described.