URANIUM CONTENTS OF ZIRCONS IN GRANITE

Abstract

Zircon grains, isolated from the granite exposed at Kitashirakawa in the suburbs of Kyoto City, are separated under the binocular microscope into two main groups: the transparent grains and the cloudy ones covered with microfissures. Each zircon grain is fused into a NaF bead. The examination of the bead by fluorescent method reveals that the transparent group is much lower in uranium content than the other. The uranium behavior in the zircon grain is treated both petrologically and geologically.