Enhancing tectonic and provenance information from detrital zircon studies: assessing terrane-scale sampling and grain-scale characterization

Determining detrital zircon U–Pb ages has become the method of choice for single- mineral-based provenance studies focused on the identification of potential source regions of siliciclastic sediments. Advances in microanalytical methods have significantly accelerated the acquisition rate of U–Pb ages, thus allowing for more statistically significant zircon age datasets to be acquired than previously. However, several studies have demonstrated limitations of relying solely on detrital zircon as a provenance proxy. To further assess the utility of this provenance indicator we measured U–Pb ages of detrital zircon derived from modern sediment collected from the French Broad River and its tributaries that drain portions of the Appalachian Orogen in southeastern USA. The results demonstrate that significant detrital zircon age variations occur along the length of the river. The age variations suggest that characterization of entire sedimentary formations by analysis of single samples may be misleading and that a multiple-sample approach is required. In addition, by incorporating high-magnification cathodoluminescence images with Th/U for each detrital grain, a more robust interpretation can be made regarding zircon source.