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Impact of air, laser pulse width and fluence on U–Pb dating of zircons by LA-ICPMS†
Journal of Analytical Atomic Spectrometry ( IF 3.1 ) Pub Date : 2018-01-05 00:00:00 , DOI: 10.1039/c7ja00357a
Jay M. Thompson 1, 2, 3, 4 , Sebastien Meffre 1, 2, 3, 4 , Leonid Danyushevsky 1, 2, 3, 4
Affiliation  

The accuracy of zircon U–Pb dating by LA-ICPMS is limited by matrix effects related to differences in U–Pb fractionation between an unknown and the calibration standard. Zircon radiation dose has a strong influence on the ablation rate, which in turn affects the amount of U–Pb fractionation and subsequent age calculations. Presented in this study is a previously unrecognized source of uncertainty in LA-ICPMS U–Pb ages due to variations of atmospheric air absorbed onto the surfaces of samples. Laser properties such as fluence (J cm−2) will change the laser ablation rate, and therefore the degree of U–Pb fractionation, and this can change the amount of zircon matrix effect. To improve the accuracy of U–Pb dating by LA-ICPMS, a systematic error component related to radiation dose needs to be included, or alternatively a correction to U–Pb dates can be applied as a function of radiation dose relative to the primary calibration standard. This study proposes a method to calculate a correction factor for the zircon matrix effect by measurement of several zircon reference materials with varying radiation dosages.

中文翻译:

LA-ICPMS对锆石U–Pb定年的空气,激光脉冲宽度和注量的影响

通过LA-ICPMS进行锆石U–Pb定年的准确性受到与未知物和校准标准品之间U–Pb分级差异有关的基质效应的限制。锆石的辐射剂量对消融速率有很大影响,反过来又会影响U-Pb的分馏量和随后的年龄计算。由于大气吸收到样品表面的变化,本研究中提出的LA-ICPMS U-Pb年龄不确定性来源是以前无法识别的。能量密度(J cm -2)将改变激光烧蚀速率,从而改变U–Pb分级程度,这会改变锆石基质效应的量。为了提高通过LA-ICPMS进行U–Pb测年的准确性,需要包括与辐射剂量有关的系统误差分量,或者可以将U–Pb日期的校正作为辐射剂量的函数(相对于初始校准)进行应用标准。这项研究提出了一种通过测量几种具有不同辐射剂量的锆石参考材料来计算锆石基质效应的校正因子的方法。
更新日期:2018-01-05
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