Radiometric Evidence for the Origin of Eugeosynclinal Materials

Abstract

Thorium and uranium contents of eugeosynclinal graywackes and associated volcanic rocks are similar and are in the range of 1-2 ppm thorium and 0.5-1 ppm uranium.  These values are much lower than average concentrations in the continental crust and apparently indicate derivation of orogenic material directly from the upper mantle without contribution for the craton.