|Title:||U‐Th‐Pb zircon geochronology by ID‐TIMS, SIMS, and laser ablation ICP‐MS: recipes, interpretations, and opportunities|
|Authors:||U. Schaltegger, A. K. Schmitt, M. S. A. Horstwood|
|Publication:||Chem. Geol., v. 402, p. 89‐110.|
|Publish Date:||May 2015|
The chronologic record encoded in accessory minerals, based on the radioactive decay of U and Th, is indispensable to extract quantitative process rates over timescales encompassing Earth’s evolution from the Hadean to the Holocene, and extending from terrestrial to extra‐terrestrial realms. We have essentially three different U‐Pb dating tools at hand, a high‐precision, whole‐grain bulk technique (isotope‐dilution thermal ionization mass spectrometry, ID‐TIMS), and two high‐spatial resolution but less precise in‐situ techniques (secondary ion mass spectrometry, SIMS, and laser ablation inductively‐coupled plasma mass spectrometry, LA‐ICP‐MS), all of which are predominantly applied to the mineral zircon. All three have reached a technological and methodological maturity in data quality and quantity, but interpretational differences, which are often common (albeit at different temporal and spatial scales) to all isotopic dating techniques, remain largely unresolved. The choice to use one of these techniques should be governed by the scientific question posed, such as (1) the duration of the geological process to be resolved; (2) the size and abundance of the material to be analyzed; (3) the complexity of the sample material and of the geological history to be resolved; and (4) the number of dates needed to address the question. Our compilation demonstrates that, ultimately, the highest confidence geochronological data will not only result from the optimal choice of appropriate analysis technique and the accurate treatment of analytical and interpretational complexities, but also require comprehensive sample characterization that employs the full gamut of textural (e.g., cathodoluminescence, charge contrast imaging, electron backscatter diffraction) and compositional (e.g., trace element, stable and radiogenic isotope) analysis.