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 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.

Cenozoic tectonostratigraphic evolution and architecture of the Central Andes in northern Chile based on the Aquine region, Western Cordillera (19°-19º30’ S).

“…The analytical work was undertaken by using a "Resonetics Resolution M50" 193 nm laser "Excimer of ArF" connected to a "Thermo Xii Series Quadrupole Mass Spectrometer" following analytical procedures and technical details after Solari et al (2010). Selected zircon minerals were mounted in epoxy and polished.…”

“…Analyzed spots were 23 micrometers, using an analytical protocol modified from Solari et al (2010), Geostandards Geoanalyt Res.…”

Geología y estratigrafía del pozo profundo San Lorenzo Tezonco y de sus alrededores, sur de la Cuenca de México

“…De la muestra XO-1204 se analizaron en total 20 cristales de circón; mientras que de la muestra XO-1205 se analizaron en total 18 cristales y por último, de la muestra XO-1210 se analizaron 26 cristales (Tabla 3). Los cristales de circón se montaron en portaobjetos de vidrio y se pulieron para ser analizados por espectrómetro de masas con acoplamiento inductivo con ablación láser (LA-ICP-MS, por sus siglas en inglés) siguiendo la metodología descrita en Solari et al (2010) para geocronología por U-Pb. Estos análisis se llevaron a cabo en el Laboratorio de Estudios Isotópicos del Centro de Geociencias, UNAM, Juriquilla, Querétaro, México.…”

<i>In situ</i> U-Pb Zircon Micro-Geochronology of MCT Zone Rocks in the Lesser Himalaya Using LA–MC–ICPMS Technique

“…The signal reaches 95% of peak intensity in ~1 sec after the laser is fired (Figure 1). Similarly, the washout time is also reduced to <2 sec to recede to <5% of peak value as against 7-12 sec in case of HelEx-I design 23 or other two-volume 24 or single, smallvolume sample cell designs 25 . Such fast signal response and washout time in HelEx-II can reduce between sample washout times, thereby significantly improving sample throughput.…”