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

• Published in: Geostandards and geoanalytical research 2021-03, Vol.45 (1), p.37-57
• Main Authors: Sundell, Kurt E., Gehrels, George E., Pecha, Mark E.
• Format: Article
• Language: English
• Subjects: Ablation; Arizona LaserChron Center; detrital zircon; geochronology; Geochronometry; Geologists; Isotopes; laser ablation; Lasers; Lead; Mass spectrometry; Mass spectroscopy; Sandstone; Sedimentary rocks; Uncertainty; U‐Pb; Zircon
• ISSN: 1639-4488; 1751-908X
• DOI: 10.1111/ggr.12355

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 ~ 3465 to ~ 28 Ma. Mean offset from high‐precision dates increases with faster rates from 0.9% to 1.1%; mean random 1s uncertainty increases from 0.6% to 1.3%. We tested this new method on a sandstone sample previously characterised by large‐n DZ 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. Key Points We develop methods for multi‐collector LA‐ICP‐MS zircon U‐Pb geochronology at 120, 300, 600 and 1200 analyses h−1 (30, 12, 6 and 3 s per analysis). Results yield only a minor sacrifice of accuracy and precision. Age distributions show dramatically increased similarity with 300–600 analyses for complex detrital zircon samples.