Production rate of cosmogenic 21Ne in quartz estimated from 10Be, 26Al, and 21Ne concentrations in slowly eroding Antarctic bedrock surfaces

We estimated the production rate of 21Ne in quartz using a set of samples from slowly eroding sandstone surfaces in the Antarctic Dry Valleys. Geologic evidence as well as cosmogenic 10Be and 26Al concentrations indicate that i) these sites have experienced millions of years of surface exposure at low erosion rates, and ii) steady erosion has been sustained long enough that surface 10Be and 26Al concentrations have reached equilibrium with the erosion rate. Under these conditions, surface cosmogenic 21Ne concentrations should be a function only of the erosion rate and the 21Ne production rate. As the erosion rate can be determined from 10Be and 26Al concentrations, this allows an estimate of the 21Ne production rate. Estimating the reference 21Ne production rate on this basis, with the assumption that all 21Ne production is by neutron spallation, yields a poor fit to measured 21Ne concentrations and a systematic residual that is correlated with the erosion rate of the sample site. The same steady-erosion assumption with a production model that includes production by deeply penetrating muons yields a good fit both to our measurements and to similar, independent, measurements from an Antarctic bedrock core. Both data sets together yield a total reference 21Ne production rate of 18.3 ± 0.4 atoms g− 1 a− 1, of which 0.66 ± 0.10 atoms g− 1 a− 1 is due to muon interactions.