A meta-analysis of geochronologically relevant half-lives: what’s the best decay constant?

2014-05-07T09:01:48Z (GMT) by Patrick Boehnke T. Mark Harrison
<div><p>Twenty-first century advances in both the analytical procedures and instrumentation used in geochronology promise age accuracy better than ±1‰, but realizing this potential requires knowledge of decay constants (<i>λ</i>) that exceed this level. Given the paucity of improved recent measurements of <i>λ</i>, the community has experimented with hybrid methodologies utilizing data largely generated during the 1970s. In this article, we perform a systematic review of laboratory decay constant determinations relevant to geochronology (i.e. <sup>87</sup>Rb, <sup>147</sup>Sm, <sup>176</sup>Lu, <sup>230</sup>Th, <sup>232</sup>Th, <sup>235</sup>U, and <sup>238</sup>U), focusing on methodological consistency. For radioisotopes for which multiple studies are available, results are combined through a random effects model to yield the best available values and associated uncertainties. Unfortunately, despite its vital role in modern geochronology, only one experimental determination of <sup>238</sup>U decay met our criteria for consideration, significantly limiting the ability to assess its reliability. Thus, utilizing <i>λ</i><sub>238</sub> as an anchor for establishing other decay constants (e.g. <sup>40</sup>K, <sup>176</sup>Lu, and spontaneous <sup>238</sup>U fission) places an unverified result at the core of geochronology. For geochronology to attain its greatest potential, more and better laboratory determinations of decay constants are required, along with a community methodology that permits us to continuously take advantage of new data.</p></div>