Surface effect of cosmogenic 7Be concentration on macroscopic basalt

The grain size effects associated with the adsorption of cosmogenic 7Be on basalt were studied experimentally by γ-ray spectroscopy. Samples of macroscopic basalt stones, with diameters between 0.5–50 mm, were used to find a power-law relationship between 7Be relative concentration and the diameter of the stones. It is shown that 7Be accumulates on the surface of the basalt, and that stones of smaller grain sizes show more 7Be relative adsorption than those of large ones. No evidence of the volume effect for the 7Be relative concentration was found over the diameter range of the samples.