Isotope imaging of ultra-traces by LA-fs HR-ICP-MS for U-series dating (U/Th) of archaeological biominerals: how far can we go?
Résumé
To overcome the problems associated with the traditional U-series dating protocol (large amount of sample required, possible contamination during preparation and consideration of sample contamination in the past), we present a new approach using isotope mapping of radioelements produced by femtosecond laser ablation coupled with high resolution mass spectrometry (LA-fs HR-ICP-MS). This protocol, developed and validated on different carbonate supports, has been applied to a series of archaeological biominerals (shells, teeth, calcitic crusts). A high resolution of a few micrometres has been achieved, as well as a significant improvement of the sensitivity. This allows to obtain U/Th ages with minimal sampling (< 1mg), even though only ultra-traces of uranium (sub-ppb) are present. The isotope mapping approach also allows a real study of the material, highlighting areas potentially contaminated with detrital thorium, but also areas that have experienced leaching. The potential of this method and its limitations are discussed.
Domaines
Chimie analytiqueOrigine | Fichiers éditeurs autorisés sur une archive ouverte |
---|