Rapid U-Pb Geochronology by Laser Ablation Multi-Collector ICP-MS

Detrital zircon (DZ) U-Pb laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) has revolutionised the way geologists approach many Earth science questions. Although recent research has focused on rapid sample throughput, acquisition rates are limited to 100-300 analyses h(-1). We present a method to acquire zircon U-Pb dates at rates of 120, 300, 600 and 1200 analyses h(-1)(30, 12, 6 and 3 s per analysis) by multi-collector LA-ICP-MS. We demonstrate the efficacy of this method by analysing twelve zircon reference materials with dates from similar to 3465 to similar to 28 Ma. Mean offset from high-precision dates increases with faster rates from 0.9% to 1.1%; mean random 1suncertainty increases from 0.6% to 1.3%. We tested this new method on a sandstone sample previously characterised by large-nDZ geochronology. Quantitative comparison shows increased correspondence among age distributions comprising > 300 dates. This new method holds promise for DZ geochronology because (a) it requires no major changes to hardware, but rather modifications to software; (b) it yields robust age distributions well-suited for quantitative analysis and maximum depositional age calculations; (c) there is only a minor sacrifice of accuracy and measurement uncertainty; and (d) there is less burden to researchers in terms of time investment and analytical cost.

Automated summary

The study presents a method to acquire zircon U-Pb dates at significantly higher rates using multi-collector LA-ICP-MS. Results showed that the new method yielded robust age distributions suitable for quantitative analysis and maximum depositional age calculations. The study holds promise for DZ geochronology with minor sacrifices in accuracy and measurement uncertainty.