Topic summary
CHUR model
Extracted from the Wikipedia article Samarium–neodymium dating.
The CHUR model
Through the analysis of isotopic compositions of neodymium, DePaolo and Wasserburg (1976) discovered that terrestrial igneous rocks at the time of their formation from melts closely followed the "chondritic uniform reservoir" or "chondritic unifractionated reservoir" (CHUR) line – the way the Nd:Nd ratio increased with time in chondrites. Chondritic meteorites are thought to represent the earliest (unsorted) material that formed in the Solar System before planets formed. They have relatively homogeneous trace-element signatures, and therefore their isotopic evolution can model the evolution of the whole Solar System and of the "bulk Earth". After plotting the ages and initial Nd/Nd ratios of terrestrial igneous rocks on a Nd evolution vs. time diagram, DePaolo and Wasserburg determined that Archean rocks had initial Nd isotope ratios very similar to that defined by the CHUR evolution line.