The relation between radioactivity and discordance in zircons

The use of U-Th-Pb isotope systems in zircons has been practiced for a number of years, since Tilton and Patterson first made it possible to work with microquantities of these elements with considerable precision and accuracy. I have been interested in the geochemistry of the U-Pb and Th-Pb systems, and as one phase of this interest I have been looking at the behavior of zircons in rock systems.