Maximising data and precision from detrital zircon U-Pb analysis by LA-ICPMS: The use of core-rim ages and the single-analysis concordia age

U-Pb detrital zircon geochronology is a powerful and well-established tool in provenance studies. Modern analytical techniques (particularly LA-ICPMS) increasingly facilitate the rapid acquisition of large datasets. While improvements in data handling approaches have been explored in detail (e.g., m...

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Bibliographic Details
Published in:Sedimentary geology 2018-11, Vol.375, p.5-13
Main Authors: Zimmermann, Sebastian, Mark, Chris, Chew, David, Voice, Peter J.
Format: Article
Language:English
Subjects:
Discordance filters
LA-ICPMS
Single-grain concordia ages
U/Pb detrital zircon dating
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Summary:U-Pb detrital zircon geochronology is a powerful and well-established tool in provenance studies. Modern analytical techniques (particularly LA-ICPMS) increasingly facilitate the rapid acquisition of large datasets. While improvements in data handling approaches have been explored in detail (e.g., more robust propagation of analytical uncertainties and inter-laboratory age reproducibility studies), there currently are no commonly established protocols for target spot location on polyphase detrital zircon grains: should the analyst ablate the zircon core, rim, or both? Here, we present two regional U-Pb detrital zircon datasets, one from the Banda Arc in Eastern Indonesia and one from the European Alps pro-foreland basin. We demonstrate that preferential ablation solely of cores or rim overgrowths results in a failure to detect age peaks, and also that generation of single-grain core-rim age pairs can permit additional characterisation of the source rock. Thus, both cores and rims should be analysed where possible, to maximise the data obtained from detrital zircon. In addition, we advocate the use of the single-analysis concordia age in visualizing and presenting U-Pb data, which is currently under-utilised in detrital provenance studies. We utilise a large (ca. 49,500 analyses) detrital zircon dataset to demonstrate that the single-analysis concordia age maximises precision throughout geological time (which removes the need to present ages derived from different isotopic ratios across an arbitrary age threshold), and obviates the necessity to separately assess discordance.
ISSN:0037-0738
DOI:10.1016/j.sedgeo.2017.12.020