Surface effect of cosmogenic Be-7 concentration on macroscopic basalt

The grain size effects associated with the adsorption of cosmogenic Be-7 on basalt were studied experimentally by gamma-ray spectroscopy. Samples of m acroscopic basalt stones, with diameters between 0.5-50 mm, were used to fi nd a power-law relationship between Be-7 relative concentration and the dia meter of the stones. It is shown that Be-7 accumulates on the surface of th e basalt, and that stones of smaller grain sizes show more Be-7 relative ad sorption than those of large ones. No evidence of the volume effect for the Be-7 relative concentration was found over the diameter range of the sampl es. (C) 1999 Elsevier Science Ltd. All rights reserved.