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

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.