Browsing by Author "Heinze, S"

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    Carbonate and silicate intercomparison materials for cosmogenic 36Cl measurements
    (Elsevier, 2019-09-15) Mechernich, S; Dunai, TJ; Binnie, SA; Goral, T; Heinze, S; Dewald, A; Schimmelpfennig, I; Keddadouche, K; Aumaître, G; Bourlès, D; Marrero, S; Wilcken, KM; Simon, KJ; Fink, D; Phillips, FM; Caffee, M; Gregory, LC; Phillips, R; Freeman, SPHT; Shanks, R; Sarikaya, MA; Pavetich, S; Rugel, G; Merchel, S; Akçar, N; Yesilyurt, S; Ivy-Ochs, S; Vockenhuber, C
    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. © 2019 Elsevier B.V.
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    Preliminary results of CoQtz-N: a quartz reference material for terrestrial in-situ cosmogenic 10Be and 26A1 measurements
    (Elsevier, 2019-10-01) Binnie, SA; Dewald, A; Heinze, S; Voronina, E; Hein, AS; Wittmann, H; von Blanckenburg, F; Hetzel, R; Christl, M; Schaller, M; Léanni, L; ASTER Team; Hippe, K; Vockenhuber, C; Ivy-Ochs, S; Maden, C; Fülöp, RH; Fink, D; Wilcken, KM; Fujioka, T; Fabel, D; Freeman, SPHT; Xu, S; Fifield, LK; Akçar, N; Spiegel, C; Dunai, TJ
    There is growing interest in geochronological applications of terrestrial in situ-produced cosmogenic nuclides, with the most commonly measured being 10Be and 26A1 in quartz. To extract and then separate these radionuclides from quartz and prepare them in the oxide form suitable for accelerator mass spectrometry (AMS) requires extensive and careful laboratory processing. Here we discuss the suitability of a crushed, sieved and etched, sub-aerially exposed vein quartz specimen (CoQtz-N) to act as a reference material for chemical laboratory preparation and AMS measurements. Splits of CoQtz-N were distributed to eleven target preparation laboratories. The CoQtz-N 10Be targets were then measured at seven different AMS facilities and five of the preparation laboratories had their 26A1 targets measured at four different AMS facilities. We show that CoQtz-N splits are sufficiently homogeneous with regard to nuclide concentrations, that it has been cleaned of any atmospheric derived (i.e. meteoric) 10Be and that it has low concentrations of the major elements that can interfere with Be and A1 extraction chemistry and AMS measurements. We derive preliminary concentrations for 10Be and 26Al in CoQtz-N as 2.53 ± 0.09 × 106 at/g and 15.6 ± 1.6 × 106 at/g, respectively, at the 95% confidence limit. © 2019 Elsevier B.V.