Measurement of 26Al in Terrestrial Silicate Rock, Revisited

Cosmic-ray-induced 26Al in terrestrial silicate rock was remeasured by accelerator mass spectrometry (AMS) in order to confirm the value reported more than 30 years ago. The result of (5.2±1.0) ×106 26Al atoms/g SiO2 for the surface rock sample was consistent with the previous result determined by a low background γ-γ coincidence spectrometry system within experimental uncertainties. The lower amount of 26Al was found in the deeper part of the rock samples. From the result, the surface exposure age and the erosion rate at the sampling location were estimated to be 1.4×105 y and 3.7×10-4 cm/y, respectively.