Isotopic imaging using fsLA single-collector ICP-SFMS for direct U/Th dating of small archaeological carbonates

Martin, L. , Galy, A., Barbotin, G., Claverie, F., Pons-Branchu, E., Tribolo, C., Mercier, N. and Pécheyran, C. (2022) Isotopic imaging using fsLA single-collector ICP-SFMS for direct U/Th dating of small archaeological carbonates. Analytical Chemistry, 94(7), pp. 3046-3055. (doi: 10.1021/acs.analchem.1c02241) (PMID:35061344)

Abstract

We present a new methodology for the U/Th dating of carbonate materials using femtosecond laser ablation single-collector inductively coupled plasma sector field mass spectrometry (fsLA single-collector ICP-SFMS), isotopic mappings, and image processing. This approach allows working on samples at very low U levels (ng·g–1). One of the major advantages of this imaging method is that it allows us to exploit deteriorated samples that could not be analyzed by conventional bulk U/Th dating methods, thanks to the identification of contaminated or leached areas at the scale of a few tens of microns and the subsequent correction for detrital 230Th incorporation. Only a few milligrams of material are required for measurement, which allows us to work on small samples such as shell fragments. The parameters of the fsLA single-collector ICP-SFMS coupling have been carefully optimized to ensure very high sensitivity detection and ultralow background while preserving good plasma robustness and a spatial resolution of 30 × 50 μm2. The accuracy was evaluated from low-level U speleothems previously dated by a conventional U/Th dating technique involving digestion, resin purification, double spike, and detection by multicollector inductively coupled plasma mass spectrometry (MC-ICPMS). U/Th ages of two archaeological samples with U at low ng·g–1 levels, a giant terrestrial snail shell and a burned ostrich eggshell, were determined. The measured U/Th ages are consistent with the expected ages determined by luminescence dating methods.

• Item Type: Articles
• Keywords: U-series, dating, ablation, inorganic carbon compounds, isotopes, lasers, plasma.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Martin, Dr Loic
• Authors: Martin, L., Galy, A., Barbotin, G., Claverie, F., Pons-Branchu, E., Tribolo, C., Mercier, N., and Pécheyran, C.
• Subjects: C Auxiliary Sciences of History > CC Archaeology; Q Science > QD Chemistry
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Analytical Chemistry
• Publisher: American Chemical Society
• ISSN: 0003-2700
• ISSN (Online): 1520-6882
• Published Online: 21 January 2022
• Copyright Holders: Copyright © 2022 American Chemical Society
• First Published: First published in Analytical Chemistry 94(7):3046-3055
• Publisher Policy: Reproduced in accordance with the publisher copyright policy