Uranium–lead system in fragments of a single zircon grain

Abstract

Since the demonstration that U–Pb analyses of zircon fractions1 (from a few grains up to several thousand grains or fragments of grains2) or single zircon grains3,4 yield reliable radiometric age data, this method has been widely applied to igneous, metamorphic and sedimentary rocks. The present investigation of U–Pb systems for a suite of distinct fragments of a single zircon grain from a 1,093±2118-Myr old syenite of the Pikes Peak batholith (Colorado, USA) demonstrates that uranium is heterogeneously distributed in this zircon crystal. Most parts of the grain suffered various degrees of lead loss, the others show a closed-system behaviour. We show that degrees of lead loss are not correlated with uranium concentrations of the fragments.