Interpreting and reporting 40Ar/39Ar geochronologic data

TLDR

The 40Ar/39Ar dating method is a versatile geochronometer capable of dating K‑bearing materials from Earth’s formation to the historical era, but inferring a meaningful age from measured dates depends on the geological context and underlying assumptions. The study aims to highlight collateral information requirements and reinforce reporting recommendations for 40Ar/39Ar data to ensure their utility, reproducibility, and FAIR compliance. The authors propose a framework that specifies collateral information—such as single‑crystal fusion, incremental heating, and microsampled in‑situ analyses—and reinforces reporting guidelines to make 40Ar/39Ar datasets FAIR. Modern noble‑gas mass spectrometry yields 40Ar/39Ar dates with ~0.1% uncertainty, yet analyses of smaller subsamples reveal age dispersion in many materials, and the authors provide examples that guide presentation and interpretation to enhance interdisciplinary use, reproducibility, and longevity.

Abstract

Abstract The 40Ar/39Ar dating method is among the most versatile of geochronometers, having the potential to date a broad variety of K-bearing materials spanning from the time of Earth’s formation into the historical realm. Measurements using modern noble-gas mass spectrometers are now producing 40Ar/39Ar dates with analytical uncertainties of ∼0.1%, thereby providing precise time constraints for a wide range of geologic and extraterrestrial processes. Analyses of increasingly smaller subsamples have revealed age dispersion in many materials, including some minerals used as neutron fluence monitors. Accordingly, interpretive strategies are evolving to address observed dispersion in dates from a single sample. Moreover, inferring a geologically meaningful “age” from a measured “date” or set of dates is dependent on the geological problem being addressed and the salient assumptions associated with each set of data. We highlight requirements for collateral information that will better constrain the interpretation of 40Ar/39Ar data sets, including those associated with single-crystal fusion analyses, incremental heating experiments, and in situ analyses of microsampled domains. To ensure the utility and viability of published results, we emphasize previous recommendations for reporting 40Ar/39Ar data and the related essential metadata, with the amendment that data conform to evolving standards of being findable, accessible, interoperable, and reusable (FAIR) by both humans and computers. Our examples provide guidance for the presentation and interpretation of 40Ar/39Ar dates to maximize their interdisciplinary usage, reproducibility, and longevity.