Cosmogenic 21Ne concentrations and exposure ages of summit bedrocks in the Grove Mountains, Antarctica

Various sources of 21 Ne and 22 Ne exist in surface rocks: cosmogenic, in situ nucleogenic from internal U and Th, trapped crustal nucleogenic and trapped atmospheric. This paper reports the first measurement, in China, of cosmogenic 21 Ne and 22 Ne in surface bedrocks. We developed a unique sample pre-treatment procedure that effectively removed inclusions inside quartz grains, and thus maximally reduced nucleogenic contributions of 21 Ne and 22 Ne. Step-heating experiments show that concentrations of cosmogenic 21 Ne and 22 Ne in summit bedrock samples R9202 and R9203 from Grove Mountains, Antarctica, are (3.83±0.87)×10 8 and (5.2280.51)×10 8 atoms/g, respectively. The corresponding minimum exposure ages are 2.2±0.5 and 3.0±0.3 Ma. This indicates that the ice sheet in East Antarctica was uncovered the crest of Mount Harding, a typical nunatak in Grove Mountains, since at least mid-Pliocene.