U‐Pb Zircon Geochronology with an Integrated LA‐ICP‐MS Microanalytical Workstation: Achievements in Precision and Accuracy

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 238 U (< 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) 206 Pb/ 238 U 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.