9418560 Mattinson The objective of the proposed research is a significant refinement of the decay constants that are crucial to all U- Pb geochronology. The proposed research will have a geologic approach, which has two important advantages. First, errors in the present decay constants and in the thrid relevant constant, the isotopic composition of natural U, can be evaluated together, as a single source of error. Secondly, uncertainties in corrections for disequilibrium effects in the U decay chains (230-Th and 231-Pa) can also be evaluated. A wide range of U-Pb studies will benefit from the proposed work, especially calibration of the geologic timescale, and studies where comparisons or correlations are made with ages obtained by other high- precision geochronology methods, such as 40-Ar/39-Ar.
