Terrestrial gamma ray dose rates in andesitic terrains

Air absorbed dose rate data taken at 31 sites have been analyzed in order to understand the characteristics of dose rate levels in andesitic terrains. The dose rate increased with increasing K2O content of rock. The following three models were tested to interpret this trend, i.e., crystallization-differentiation of basaltic magma, mixing of basaltic and felsic magmas and partial melting of mantle materials. A semi-empirical formula expressing the dose rate as a function of K2O content was derived based on the above models. (author)