Nanogeochronology of discordant zircon measured by atom probe microscopy of Pb-enriched dislocation loops.

ABSTRACT: Isotopic discordance is a common feature in zircon that can lead to an erroneous age determination, and it is attributed to the mobilization and escape of radiogenic Pb during its post-crystallization geological evolution. The degree of isotopic discordance measured at analytical scales of ~10 μm often differs among adjacent analysis locations, indicating heterogeneous distributions of Pb at shorter length scales. We use atom probe microscopy to establish the nature of these sites and the mechanisms by which they form. We show that the nanoscale distribution of Pb in a ~2.1 billion year old discordant zircon that was metamorphosed c. 150 million years ago is defined by two distinct Pb reservoirs. Despite overall Pb loss during peak metamorphic conditions, the atom probe data indicate that

SUBMITTER: Peterman EM 

PROVIDER: S-EPMC5010368 | biostudies-literature | 2016 Sep

REPOSITORIES: biostudies-literature