U-Pb Zircon Geochronology with an Integrated LA-ICP-MS Microanalytical Workstation: Achievements in Precision and Accuracy |
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Authors: | Luigi A. Solari ,Arturo Gó mez-Tuena ,Juan Pablo Bernal ,Ofelia Pé rez-Arvizu , Martin Tanner |
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Affiliation: | Universidad Nacional Autónoma de México, Centro de Geociencias, Campus Juriquilla, 76001 Querétaro, QRO, Mexico;Universidad Nacional Autónoma de México, Instituto de Geología, Ciudad Universitaria, 04510 México DF, Mexico |
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Abstract: | Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is a microanalytical tool especially suitable for providing fast and precise U-Pb geochronological results on zircon grains. A new 193 nm excimer laser adapted to a micromachining workstation, equipped with a newly designed two-volume ablation cell and coupled with a quadrupole ICP-MS, is presented here. The system was tuned routinely to achieve sensitivities in the range of 3000 cps/μg g−1 for 238U (< 2% RSD), with a 34 μm spot size, at 5 Hz and ∼ 8 J cm−2, while ablating the NIST SRM 612 glass reference material. The system was capable of providing fast (< 1.5 minutes each analysis) and precise (generally < 1.5% 1s errors) 206Pb/238U zircon ages. The ages of widely used reference material zircons (Plesovice, 337 Ma; Temora, 416 Ma; R33, 418 Ma; Sri Lanka, 564 Ma; 91500, 1065 Ma) could be precisely matched, with an accuracy on isotopic ratios that ranged from ∼ 2 to ∼ 6%, depending on the homogeneity of the natural reference materials. |
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Keywords: | geochronology U-Pb laser ablation excimer mass spectrometry |
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