7. INTERLABORATORY COMPARISON OF ELECTRON PROBE MICROANALYSIS OF GLASS GEOCHEMISTRY1John B. Hunt,2 Peter D.
Clift,3 Christian Lacasse,4 Tracy
L. Vallier,5
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ABSTRACTTephrochronology commonly relies upon grain-discrete analysis of glass shards to reveal the subtle geochemical differences between tephras from past explosive volcanic eruptions. The use of electron probe microanalysis for this purpose is widely accepted by tephrochronologists. In addition, it is recognized widely that both precision and accuracy must be maximized, and that rigorous standardization procedures must be followed. In this paper, the performance of five electron microprobe centers used in the analysis of glass shards from Leg 152 tephras is compared, using a geochemically homogeneous obsidian secondary standard. The results reveal the compatibility of most of the participants, supporting the comparability of additional glass geochemistry presented within this volume. In recent years the application of distal tephrochronology to stratigraphical problems in the North Atlantic Quaternary record has become increasingly common. Geochemical standardization is vitally important at an early stage in the development of tephrochronological frameworks, and it is hoped that exercises such as that presented here will encourage the production of reliable tephra geochemical data, both on Ocean Drilling Program exercises and wider afield. |
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