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Characterization of zircon reference materials via high precision U-Pb LA-MC-ICP-MS

Abstract

Recent improvements in laser ablation and multicolector (MC)-ICP-MS technology offer higher sensitivity, robust stability, and larger dynamic ranges. Such advances are translated into improved accuracy and precision of U-Pb age determinations, reduced spot sizes for high spatial resolution and reliable corrections for any amount of common Pb (Pbc). Although a number of studies have focused on the high-spatial resolution of the LA-MC-ICP-MS method, comparatively fewer experiments have explored the precision and stability of multi-collector instruments for high-precision U-Pb geochronology. In this contribution, we describe the precision and accuracy of Pbc corrected, U-Pb ages obtained by LA-MC-ICP-MS, and discuss the homogeneity of two batches of zircon megacrysts (the Rio do Peixe (RP) and Blue Berry (BB)) as potential reference materials. The enhanced sensitivity and stability of the LA-MC-ICP-MS system allowed determination of apparent Pb/U and Pb/Pb ratios with uncertainties of 0.3 to 1 % (2s) for nearly all reference materials available. The measurements are done in automated mode, with a spatial resolution of 20 µm-wide spots. Short and long-term reproducibility of the 206Pb/238U, 207Pb/235U and 207Pb/206Pb ratios were assessed based on several reference materials including, GJ-1 (96 analyses), M125 (96 analyses), Temora (34 analyses), 91500 (29 analyses), FC-1 (17 analyses), BB (121 analyses) and Plešovice (133 analyses). The results show that accuracy and precision of the relevant ratios are often between 0.5 and 1.0% (RSD). U-Pb LA-MC-ICP-MS and TIMS dates of four new megacrystals of the BB zircons agreed within error at ca. 560 ± 1 Ma, and demonstrate that these constitute suitable reference materials for LA-ICP-MS analyses. U-Pb LA-MC-ICP-MS for the RP zircons revealed low concentrations of U and Pb and a scattering of ages from 580 to 600 Ma (mean of 593 ± 5 Ma). The RP zircons may only be suitable as quality control reference material.

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Supplementary files

Publication details

The article was received on 27 Apr 2017, accepted on 08 Aug 2017 and first published on 09 Aug 2017


Article type: Paper
DOI: 10.1039/C7JA00167C
Citation: J. Anal. At. Spectrom., 2017, Accepted Manuscript
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    Characterization of zircon reference materials via high precision U-Pb LA-MC-ICP-MS

    C. Lana, F. Farina, A. Gerdes, A. Alkmim, G. Gonçalves and A. C. Jardim, J. Anal. At. Spectrom., 2017, Accepted Manuscript , DOI: 10.1039/C7JA00167C

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