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Dating Micrometre‐Thin Rims Using a LA ‐ ICP ‐ MS Depth Profiling Technique on Zircon from an Archaean Metasediment: Comparison with the SIMS Depth Profiling Method
Author(s) -
Kelly Colter J.,
McFarlane Christopher R.M.,
Schneider David A.,
Jackson Simon E.
Publication year - 2014
Publication title -
geostandards and geoanalytical research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.037
H-Index - 73
eISSN - 1751-908X
pISSN - 1639-4488
DOI - 10.1111/j.1751-908x.2014.00314.x
Subject(s) - zircon , mineralogy , analytical chemistry (journal) , geology , chemistry , geochemistry , chromatography
Laser ablation‐inductively coupled plasma‐mass spectrometry ( LA ‐ ICP ‐ MS ) was examined as a tool for measuring isotopic variation as a function of ablation depth in unpolished zircon from an Archaean metasediment specimen. This technique was able to identify micrometre‐thin (> 3 μm) isotopically distinct mineral domains characterised by ca . 100 Myr younger 207 Pb/ 206 Pb ages associated with 2 s age uncertainties as low ~ 0.2%, as well as elevated U content relative to grain interiors (up to an order of magnitude). Our calculated drilling rate suggests that each laser pulse excavated depths of ~ 0.06 μm. Ages resolved through the LA ‐ ICP ‐ MS methods overlap the 2 s uncertainties of 207 Pb/ 206 Pb ages measured using SIMS depth profiling on the same zircon population. The rims were further evinced by the detection of relative enrichment (> 3 orders of magnitude) in REE in the outermost micrometres of the same zircon, measured using a different and independent LA ‐ ICP ‐ MS depth profiling technique. We propose a LA ‐ ICP ‐ MS U–Pb technique capable of quickly identifying and quantifying rims, which are indication of late, yet geologically significant, fluid events that are otherwise undefined.