Terrestrial gamma ray dose rates in dacitic and rhyolitic terrains

Air absorbed dose rate data taken at 36 sites have been analyzed in order to understand lithologic characteristics of dose rate levels measured on soils in dacitic and rhyolitic 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 mafic or felsic magma, partial melting of mafic or felsic material, and mixing of mafic and felsic magmas. Semi-empirical formulas expressing the dose rate as a function of K2O content were derived based on the above models. (author)