Preliminary results of CoQtz-N: A quartz reference material for terrestrial in situ cosmogenic Be-10 and Al-26 measurements

Abstract

There is growing interest in geochronological applications of terrestrial in situ-produced cosmogenic nuclides, with the most commonly measured being 10Be and 26Al 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 26Al 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 Al 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.