An inter-laboratory comparison of cosmogenic He-3 and radiogenic He-4 in the CRONUS-P pyroxene standard

作者：Blard P H^*; Balco G; Burnard P G; Farley K A; Fenton C R; Friedrich R; Jull A J T; Niedermann S; Pik R; Schaefer J M; Scott E M; Shuster D L; Stuart F M; Stute M; Tibari B; Winckler G; Zimmermann L

来源：Quaternary Geochronology, 2015, 26: 11-19.

DOI：10.1016/j.quageo.2014.08.004

• Cosmogenic
• He-3
• Radiogenic
• He-4
• CRONUS-P
• Standard
• Calibration

This study reports an inter-laboratory comparison of the He-3 and He-4 concentrations measured in the pyroxene material CRONUS-P. This forms part of the CRONUS-Earth and CRONUS-EU programs, which also produced a series of natural reference materials for in situ produced Al-26, Be-10, C-14, Ne-21 and (CI)-C-36.
Six laboratories (GFZ Potsdam, Caltech Pasadena, CRPG Nancy, SUERC Glasgow, BGC Berkeley, Lamont New York) participated in this intercomparison experiment, analyzing between 5 and 22 aliquots each. Intra-laboratory results yield He-3 concentrations that are consistent with the reported analytical uncertainties, which suggests that He-3 is homogeneous within CRONUS-P. The inter-laboratory dataset (66 determinations from the 6 different labs) is characterized by a global weighted mean of (5.02 +/- 0.12) x 10(9) at g(-1) with an overdispersion of 5.6% (2 sigma). He-4 is characterized by a larger variability than He-3, and by an inter-lab global weighted mean of (3.60 +/- 0.18) x 10(13) at g(-1) (2 sigma) with an overdispersion of 10.4% (2 sigma).
There are, however, some systematic differences between the six laboratories. More precisely, 2 laboratories obtained mean He-3 concentrations that are about 6% higher than the clustered other 4 laboratories. This systematic bias is larger than the analytical uncertainty and not related to the CRONUS-P material (see Schaefer et al., 2015). Reasons for these inter-laboratory offsets are difficult to identify but are discussed below. To improve the precision of cosmogenic He-3 dating, we suggest that future studies presenting cosmogenic He-3 results also report the He-3 concentration measured in the CRONUS-P material in the lab(s) used in a given study.

• 出版日期2015-2