[en] The problem of transverse zoning of island arches is considered. Reasons for U and Th content difference in separate volcanoes and volcanic zones, constituting one and the same province are analyzed. The published results of measuring U and Th content in volcanites of Kurilo-Kamchatskaya province, the Japanese Isles, the southern part of Kamchatka are used for comparison with the data on Zakarpatskaya depression. Mean values of radiogenous heat generation have been calculated for every volcanic zone. Two groups of volcanic structures have been singled out according to their radiogeneous properties. The radio-activity of magmatic formations in structures of both types increases in direct proportion to the basement structure complexity, which ref--lects the cyclic recurrence, duration and intensity of its development. Stated is the combining of U, Th and K summarized mean concentrations in rock structures of the first type and their abundance in basement rocks, with a corresponding silicic acidity