Project Details Recommendations for isotope data in geosciences

Project No.:
Start Date:
01 October 2006
End Date:
01 October 2013
Division Name:
Inorganic Chemistry Division
Division No.:


Update and harmonize recommendations on half-lives and isotopiccompositions.


The inter-Union project with the International Union of Geological Sciences (IUGS) strives to provide an authoritative recommendation based on a critical reevaluation of data on half-lives and decay schemes of long-lived radioactive nuclides used by the geological and planetary science communities. A specific goal of the project is to reconcile current inconsistencies between values used in geological and planetary sciences on the one hand, and those used in the nuclear physics and chemistry communities on the other.

The project will draw on complementary expertise present in IUGS and IUPAC. Previous work by IUGS (Working Group “Decay constants in geochronology”) and IUPAC (Commissions II.1 “Isotopic abundance” and V.7 “Radiochemistry and Nuclear Techniques”) will be included, harmonized, and updated. IUGS-IUPAC interaction will be tightened.

Initial work (2006-2008) focuses on 9 nuclides used in geochronology (40K, 87Rb, 138La, 147Sm, 176Lu, 187Re, 232Th, 235U, 238U). Half-lives, decay schemes, and measurement techniques will be critically evaluated, as well as isotopic compositions of parent and daughter elements. Uncertainty analyses need to be adequately reassessed following ISO/GUM procedures. Successive phases will both expand the number of nuclides and refine the isotopic abundances in view of an additional recommendation.


Mar 2007 – project announcement published in Chem. Int. Mar-Apr 2007, p. 17

Feb 2009 update – Geological and cosmochronological time is typically specified in orders of magnitude multiples of a year. Thus it becomes necessary to define a year in terms of the SI unit of time, the second, and accordingly the joint IUPAC-IUGS Task Group has defined the precise relationship between these units. (> provisional recommendation at ../provisional/abstract09/villa_300609.html)

April 2011 update – recommendations titled IUPAC-IUGS common definition and convention on the use of the year as a derived unit of time (IUPAC Recommendations 2011)’ published in Pure Appl. Chem. 2011, Vol. 83, No. 5, pp. 1159-1162; doi:10.1351/PAC-REC-09-01-22

October 2013 – an update report is published in Chem. Int. Sep-Oct 2013, p. 18

See Part II as this project 2012-036-2-200

project completed

Last update: 10 October 2013