Argon-based geochronology: advances, limitations and perspectives

Given that K constitutes about 3 wt.% of Earth's crust and is present in most rock-forming minerals, and that Ar diffusion in minerals is temperature-dependent, Ar-based geochronology (⁴⁰Ar/³⁹Ar and K-Ar dating) can date most rocks and also reveal their thermal history. This paper reviews recent advances and longstanding limitations in ⁴⁰Ar/³⁹Ar and K-Ar geochronology, and provides perspectives into future research on Ar-based geochronometers. Over the past two decades, multi-collector noble gas mass spectrometry has witnessed remarkable advancements in both sensitivity and resolution. Successive upgrades of mass spectrometer generations have significantly enhanced the precision of Ar isotope measurements, enabling a comprehensive revision and optimization of ⁴⁰Ar/³⁹Ar dating standard minerals. To achieve high-precision ⁴⁰Ar/³⁹Ar dating and minimize inter-laboratory discrepancies, researchers are focusing on refining the potassium decay constant, developing standardized mineral separation techniques, and harmonizing irradiation and data processing protocols. These efforts are pivotal for improving the analytical precision of low-K and young samples, thereby expanding the application frontiers of ⁴⁰Ar/³⁹Ar geochronology. For in  situ planetary dating, the K/Ar method currently remains the only feasible radiometric technique among radioactive isotope systems. Addressing challenges in simultaneous K and Ar measurements will facilitate streamlined acquisition of reliable datasets. Moreover, research is advancing toward a deeper understanding of Ar diffusion behavior in minerals-beyond temperature-dependent volume diffusion-to clarify its impact on ⁴⁰Ar/³⁹Ar data interpretation and geological significance. To further advance argon-based geochronology, the scientific community is committed to continuous exploration and resolution of methodological limitations inherent in these dating approaches.