Concurrent Determination of U‐Pb Age and REE Mass Fractions of Zircon by High Mass Resolution SIMS

• Published in: Geostandards and geoanalytical research Vol. 44; no. 3; pp. 421 - 437
• Main Authors: Liu, Yu, Li, Qiu‐Li, Tang, Guo‐Qiang, Li, Xian‐Hua
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 01.09.2020
• Subjects: Analytical methods; concurrent determination; high spatial resolution; Lead; Mass; Rare earth elements; REE; Resolution; U‐Pb geochronology; Zircon
• ISSN: 1639-4488; 1751-908X
• DOI: 10.1111/ggr.12344

A combined geochronological and geochemical investigation for the same domain of zircon provides valuable information on timing and genesis, particularly in the case of multi‐growth metamorphic zircon. A high spatial resolution concurrent analytical method for zircon U‐Pb age and rare earth element content was successfully achieved in this study, using a multi‐collector secondary ion mass spectrometer (SIMS) at a ~ 8 μm diameter scale. Special instrument parameters were employed, including a high mass resolution of approximately 15000 applied to replace the previous energy filter method, and a dynamic multi‐collector mode used to reduce the measurement time to 18 min per analysis. Six zircon reference materials yielded precise and accurate 206Pb/238U ages, which are comparable to those obtained by the ordinary mono‐collector method, but with 2–3 times higher spatial resolution. All zircon grains measured in this study showed enriched heavy‐REE (HREE) contents consistent with previously reported values determined by LA and solution ICP‐MS methods. The light‐REE (LREE) mass fractions measured using both SIMS and LA‐ICP‐MS methods in this study, although with quite different volume, show consistent results within uncertainties. Key Points Concurrent determination of U-Pb age and REE mass fractions in zircon reference materials was achieved using multi-collector SIMS. 8-µm spot sizes were employed, and measurement time was approximately 18 min. Recommended values for REE in zircon M257 are provided.