U pb dating of zircon by la icp ms
The uncertainty in age determination must be considered in order to interpret LA-ICPMS zircon U-Pb data rationally.
Simultaneous U–Pb and U–Th zircon dating using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was performed on the ~ 0.1 Ma Toya Tephra, Hokkaido, Japan.
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LA-ICPMS zircon U-Pb dating has been greatly advanced and widely applied in the past decade because it is a cheap and fast technique.
Results of three SIMS analyses on FS06 and WC09-2 are indistinguishable within error and give a best estimate of the crystallization age of 132.2 and 760.5 Ma (reproducibility is ∼1%, 2RSD), respectively.
Zircon U-Pb ages determined by LA-ICPMS in six laboratories vary from 128.3±1.0 to 135.0±0.9 Ma (2SE) for FS06 and from 742.9±3.1 to 777.8±4.7 Ma (2SE) for WC09-32, suggesting a reproducibility of ∼4% (2RSD).
LA-ICP-MS U-Pb dating of zircon is becoming an increasingly widespread geochronologic technique due to the availability of instrumentation, the relative ease of sample preparation, the short analytical time, and the reasonably precise and accurate age determinations.
CA-LA-ICP-MS age data are in good agreement with the CA-ID-TIMS dates and suggest advantages of using CA-LA-ICP-MS in order to define accurate ages.
In this report we present our method of U-Pb zircon analysis by LA-ICPMS including on our approach to assessing and assigning errors to our U-Pb and Pb-Pb analyses.
For this study we measured 7 zircon samples of known age (~1800 Ma to ~50 Ma), using a Thermo Finnigan Element2 magnetic sector ICP-MS coupled with a New Wave Research UP- 213 laser system, and using spot sizes of 30 or 40 ? Laser-induced time-dependent fractionation in both standards and samples was back-corrected to the beginning of the analysis using the intercept method.
All CA-treated zircon crystals show up to 50% less data scatter compared to the non-CA treated zircon grains and thus reduction of the calculated uncertainties is apparent.
The obtained wt average LA-ICP-MS U ages of the CA-treated zircon grains are up to 4–6% higher than those of the non-CA treated crystals, exceeding the analytical uncertainties of the LA-ICP-MS dating technique of 1–2%.