Correlation and characterisation of individual glass shards from tephra deposits using trace element laser ablation ICP-MS analyses: current status and future potential†
Article first published online: 23 APR 2007
Copyright © 2007 John Wiley & Sons, Ltd.
Journal of Quaternary Science
Volume 22, Issue 7, pages 721–736, October 2007
How to Cite
Pearce, N. J. G., Denton, J. S., Perkins, W. T., Westgate, J. A. and Alloway, B. V. (2007), Correlation and characterisation of individual glass shards from tephra deposits using trace element laser ablation ICP-MS analyses: current status and future potential. J. Quaternary Sci., 22: 721–736. doi: 10.1002/jqs.1092
Pearce, N. J. G., Denton, J. S., Perkins, W. T., Westgate, J. A. and Alloway, B. V. 2007. Correlation and characterisation of individual glass shards from tephra deposits using trace element laser ablation ICP-MS analyses: current status and future potential. J. Quaternary Sci., Vol. 22 pp. 721–736. ISSN 0267–8179.
- Issue published online: 18 SEP 2007
- Article first published online: 23 APR 2007
- Manuscript Accepted: 3 OCT 2006
- Manuscript Revised: 21 SEP 2006
- Manuscript Received: 26 JAN 2006
- NSERC Canada
- Royal Society of New Zealand Marsden Fund. Grant Number: UoA 609
- volcanic glass;
- glass shards;
- trace element analysis;
- laser ablation;
Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is a high spatial resolution analytical method which has been applied to the analysis of silicic tephras. With current instrumentation, around 30 trace elements can be determined from single glass shards as small as ∼ 40 µm, separated from tephra deposits. As a result of element fractionation during the ablation process using a 266 nm laser, a relatively complex calibration strategy is required. Nonetheless, such a strategy gives analyses which are accurate (typically within ±5%) and have an analytical precision which varies from ∼ ±2% at 100 ppm, to ∼ ±15% at 1 ppm. Detection limits for elements used in correlation and discrimination studies are well below 1 ppm. Examples of the application of trace element analysis by LA-ICP-MS in tephra studies are presented from the USA, New Zealand and the Mediterranean.
Improvements in instrumental sensitivity in recent years have the potential to lower detection limits and improve analytical precision, thus allowing the analysis of smaller glass shards from more distal tephras. Laser systems operating at shorter wavelengths (e.g. 193 nm) are now more widely available, and produce a much more controllable ablation in glasses than 266 nm lasers. Crater sizes of <10 µm are easily achieved, and at 193 nm many of the elemental fractionation issues which mar longer wavelengths are overcome. By coupling a short wavelength laser to a modern ICP-MS it should be possible to determine the trace element composition of glass shards as small as 20 µm and, providing sample preparation issues can be overcome, the determination of the more abundant trace elements in glass shards as small as 10 µm is within instrumental capabilities. This will make it possible to chemically fingerprint tephra deposits which are far from their sources, and will greatly extend the range over which geochemical correlation of tephras can be undertaken. Copyright © 2007 John Wiley & Sons, Ltd.