Xenotime at the Nanoscale: U-Pb Geochronology and Optimisation of Analyses by Atom Probe Tomography

Research output: Contribution to journalJournal articleResearchpeer-review

  • Cilva Joseph
  • Denis Fougerouse
  • David W. Saxey
  • Verberne, Rick
  • Steven M. Reddy
  • William D. A. Rickard

Xenotime (YPO4) is an accessory phase common in low to high-temperature geological environments. Xenotime is an established geochronometer, though its small size, low modal abundance and textural complexity make it more difficult to analyse with traditional techniques but makes a prime candidate for nanoscale analysis. In this study, we develop an atom probe tomography (APT) protocol to determine the 206Pb/238U and 207Pb/206Pb ages of micro-scale xenotime crystals with analytical volumes four to six orders of magnitude smaller than typical geochronology techniques. A linear correlation between the 206Pb/238U fractionation and 238UO22+/238UO2+ was used to correct for the atom probe instrument parameters variability between specimens. For 207Pb/206Pb ages, we employed two methods of background correction owing to the 206Pb2+ thermal tail contribution to the 207Pb2+ counts: A constant background correction for the younger (~ 1000 Ma) Y1 reference material and a variable correction of background for Archaean age reference material xtc to correct for the thermal tail influence. This contribution also proposes strategies for optimisation of xenotime analysis using APT and permits us to explore the various geological problems in the nanoscale realm. This methodology potentially allows determining the age of small xenotime crystals in sedimentary rocks, low metamorphic grade settings and deformation microstructures.

Original languageEnglish
JournalGeostandards and Geoanalytical Research
Volume45
Issue number3
Pages (from-to)443-456
Number of pages14
ISSN1639-4488
DOIs
Publication statusPublished - 2021

    Research areas

  • Pb/U, Pb/Pb, APT, atom probe tomography, nanogeochronology, radiometric dating

ID: 275888078