U-Pb zircon in situ dating with LA-MC-ICP-MS using a mixed detector configuration

Anais da Academia Brasileira de Ciências

Farid Chemale Jr²  Koji Kawashita¹  Ivo A. Dussin¹  Janaína N. Ávila¹  Dayvisson Justino¹  Anelise Bertotti¹ 

[1] ,Universidade de Brasília Instituto de Geociências Brasília DF ,Brasil

关键词: MC-ICP-MS;    SHRIMP;    Faraday cups;    Multi-ion Counting System;    U-Pb in situ zircon dating;    MC-ICP-MS;    SHRIMP;    Copos Faraday;    Sistema de Contagem de Multiplicadores de ions;    Datação in situ de U-Pb em zircão;   

DOI  :  10.1590/S0001-37652012005000032

来源: SciELO

【 摘 要 】

The LA-MC-ICP-MS method applied to U-Pb in situ dating is still rapidly evolving due to improvements in both lasers and ICP-MS. To test the validity and reproducibility of the method, 5 different zircon samples, including the standard Temora-2, ranging in age between 2.2 Ga and 246 Ma, were dated using both LA-MC-ICP-MS and SHRIMP. The selected zircons were dated by SHRIMP and, after gentle polishing, the laser spot was driven to the same site or on the same zircon phase with a 213 nm laser microprobe coupled to a multi-collector mixed system. The data were collected with a routine spot size of 25 μm and, in some cases, of 15 and 40 μm. A careful cross-calibration using a diluted U-Th-Pb solution to calculate the Faraday reading to counting rate conversion factors and the highly suitable GJ-1 standard zircon for external calibrations were of paramount importance for obtaining reliable results. All age results were concordant within the experimental errors. The assigned age errors using the LA-MC-ICP-MS technique were, in most cases, higher than those obtained by SHRIMP, but if we are not faced with a high resolution stratigraphy, the laser technique has certain advantages.

【 授权许可】

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