AN INTEGRATED APPROACH TO DETRITAL ZIRCON ANALYSIS COUPLING U-PB GEOCHRONOLOGY WITH ZIRCON GRAIN SIZE, MORPHOLOGY, AND RADIATION DAMAGE

Uranium-lead (U-Pb) detrital zircon geochronology is frequently used to determine the provenance of sediments for tectonic, paleoclimate, and basin history models. Preferential sorting and fractionation of detrital particles during hydraulic transport have long been known to influence sedimentary deposits. However, their effects on detrital zircon transport remains poorly studied. Previous work has demonstrated that detrital zircon age spectra are biased depending upon the sedimentary environment from which a sample is collected. Moreover, self-irradiation over geologic timescales can damage zircon structural integrity in a way that reduces the likelihood of its preservation in sedimentary environments. Typical measures of dissimilarity between samples, such as Kolmogorov-Smirnov tests of U-Pb age distributions, do not account for these processes. Here, we present preliminary results of a new methodology we have developed, which integrates rapid U-Pb dating of large-n samples using LA-ICPMS with x-ray computed tomography and Raman spectroscopy, to fully quantify the age, size, morphology, and accumulated radiation damage of individual zircons in detrital samples. We present results from modern river sands collected in the Río Bermejo and the Río Paraná in northern Argentina, an overfilled retroarc foreland basin. Improvements in 3D image processing software allow for the quantification of zircon grain morphology data from x-ray computed tomography scans. Measurements of Raman spectra quantify crystal lattice damage, showing how alpha dosage relates to grain geometries and changes in age-population abundance during sedimentary transport. Using a large-n approach (n = 300-1,000) ensures that analyses better capture the ‘true’ distribution of all variables. This integrated methodology is expected to enable researchers to more comprehensively understand and account for physio-mechanical effects in detrital zircon studies, improving the accuracy of their geologic interpretations.