Clean quartz matters for cosmogenic nuclide analyses: an exploration of the importance of sample purity using the CRONUS-N reference material

Corbett, L. B., Bierman, P. R., Brown, T. A., Caffee, M. W., Fink, D., Freeman, S. P.H.T. , Hidy, A. J., Rood, D. H., Wilcken, K. M. and Woodruff, T. E. (2022) Clean quartz matters for cosmogenic nuclide analyses: an exploration of the importance of sample purity using the CRONUS-N reference material. Quaternary Geochronology, 73, 101403. (doi: 10.1016/j.quageo.2022.101403)

Abstract

Reference materials are key for assessing inter-laboratory variability and measurement quality, and for placing analytical uncertainty bounds on sample analyses. Here, we investigate four years of data resulting from repeated processing of the CRONUS-N reference material for cosmogenic 10Be and 26Al analyses. At University of Vermont, we prepared a CRONUS-N aliquot with most of our sample batches from 2013 to 2017; these reference material samples were then distributed to four different accelerator mass spectrometry facilities, yielding 73 10Be analyses and 58 26Al analyses. We determine CRONUS-N 10Be concentrations of (2.26 ± 0.14) x 105 atoms g−1 (n = 73, mean, 1 SD) and 26Al concentrations of (1.00 ± 0.08) x 106 atoms g−1 (n = 58, mean, 1 SD). We find a reproducibility of 6.3% for 10Be and 7.7% for 26Al (relative standard deviations). We also document highly variable 27Al and Mg concentrations and a 10Be dispersion twice as large as the mean AMS analytic uncertainty. Analyses of the CRONUS-N material with and without density separation demonstrate that non-quartz minerals are present in the material and have a large impact on measured concentrations of 27Al, 10Be, and impurities; these non-quartz minerals represent only a very small portion of the total mass (0.6–0.8%) but have a disproportionally large effect on the resulting data. Our results highlight the importance of completely removing all non-quartz mineral phases from samples prior to Be/Al extraction for the determination of in situ cosmogenic 10Be and 26Al concentrations.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Wilcken, Mr Klaus and Rood, Dr Dylan and Freeman, Professor Stewart
• Authors: Corbett, L. B., Bierman, P. R., Brown, T. A., Caffee, M. W., Fink, D., Freeman, S. P.H.T., Hidy, A. J., Rood, D. H., Wilcken, K. M., and Woodruff, T. E.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Quaternary Geochronology
• Publisher: Elsevier
• ISSN: 1871-1014
• ISSN (Online): 1878-0350
• Published Online: 15 September 2022