Carbonate and silicate intercomparison materials for cosmogenic 36Cl measurements

Mechernich, Silke; Dunai, Tibor J.; Binnie, Steven A.; Goral, Tomasz; Heinze, Stefan; Dewald, Alfred; Schimmelpfennig, Irene; Keddadouche, Karim; Aumaître, Georges; Bourlès, Didier; Marrero, Shasta; Wilcken, Klaus; Simon, Krista; Fink, David; Phillips, Fred M.; Caffee, Marc W.; Gregory, Laura C.; Phillips, Richard; Freeman, Stewart P.H.T.; Shanks, Richard; ... (2019). Carbonate and silicate intercomparison materials for cosmogenic 36Cl measurements. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 455, pp. 250-259. Elsevier 10.1016/j.nimb.2019.01.024

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Two natural mineral separates, labeled CoCal-N and CoFsp-N, have been prepared to serve as intercomparison material (ICM) for in situ-produced cosmogenic 36Cl and natural chlorine (Clnat) analysis. The sample CoCal-N is derived from calcite crystals in a Namibian lag deposit, while the sample CoFsp-N is derived from a single crystal of alkali-feldspar from a Namibian pegmatite. The sample preparation took place at the University of Cologne and a rotating splitter was used to obtain homogeneous splits of both ICMs. Forty-five measurements of CoCal-N (between 1 and 16 per facility) and forty-four measurements of CoFsp-N (between 2 and 20 per facility) have been undertaken by ten target preparation laboratories measured by seven different AMS facilities. The internal laboratory scatter of the 36Cl concentrations indicates no overdispersion for half of the laboratories and 3.9 to 7.3% (1σ) overdispersion for the others. We show that the CoCal-N and CoFsp-N splits are homogeneous regarding their 36Cl and Clnat concentrations. The grand average (average calculated from the average of each laboratory) yields initial consensus 36Cl concentrations of (3.74 ± 0.10) × 106 at 36Cl/g (CoCal-N) and (2.93 ± 0.07) × 106 at 36Cl/g (CoFsp-N) at 95% confidence intervals. The coefficient of variation is 5.1% and 4.2% for CoCal-N and CoFsp-N, respectively. The Clnat concentration corresponds to the lower and intermediate range of typical rock samples with (0.73 ± 0.18) µg/g in CoCal-N and (73.9 ± 6.8) µg/g in CoFsp-N. We discuss the most relevant points of the sample preparation and measurement and the chlorine concentration calculation to further approach inter-laboratory comparability. We propose to use continuous measurements of the ICMs to provide a valuable quality control for future determination of 36Cl and Clnat concentrations.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geological Sciences
08 Faculty of Science > Institute of Geological Sciences > Exogenous Geology

UniBE Contributor:

Akçar, Naki

Subjects:

500 Science > 550 Earth sciences & geology
500 Science > 530 Physics
500 Science > 540 Chemistry

ISSN:

0168-583X

Publisher:

Elsevier

Language:

English

Submitter:

Naki Akçar

Date Deposited:

25 Nov 2019 14:43

Last Modified:

25 Nov 2019 14:43

Publisher DOI:

10.1016/j.nimb.2019.01.024

BORIS DOI:

10.7892/boris.135182

URI:

https://boris.unibe.ch/id/eprint/135182

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