In situ produced 10Be measurements at great depths:: implications for production rates by fast muons

In situ cosmogenic Be-10 values have been used to investigate a Brazilian quartz vein from the surface to a depth of 15 m. At depths greater than 1000 g/cm(2), deep enough for neutron-induced reactions to be insignificant, there is only a slight decrease in Be-10 concentration with increasing depth. Our results are consistent with deep production of Be-10 by a mechanism, presumably induced by fast muons, with an attenuation length of 5300 +/- 950 g/cm(2) and a contribution of 0.65 +/- 0.25% to the total surface production. Results are compared with values from the literature and implications of this re-evaluation are discussed. (C) 2003 Elsevier Science B.V. All rights reserved.