Abstract
Several suites of volcanic rock samples from Japan are investigated by non-destructive gamma-ray spectrometry. Each suite consists of a variety of rock types from a single volcano. The individual volcanoes show a variation in both Th and U series specific activities which parallels the change in K content. Strong coherence between Th and U series activities is also present. A detailed examination of three types of plot, Th series vs. U series, Th series vs. K and U series vs. K, reveals that each volcano has a characteristic pattern. It appears that gamma-ray spectrometric data can be used to distinguish between products from different families of magma.
