Eliminating mass-fractionation effects on U-Pb isochron ages without double spiking

The utility of uranium-lead isochrons for dating rocks with a restricted ra nge in U/Pb is limited by any uncertainty in the mass fractionation of the analysis. Double spiking (TIMS) or thallium normalization (ICP-MS) remove m uch of this limitation, as does the method of Getty and DePaolo (1995) for very young rocks. Optimal use of the 3-D "Total Pb/U isochron," however, is extremely simple to apply, requires only single-spiked TIMS analyses, and essentially eliminates fractionation-related age imprecision for rocks of a ny age. Copyright (C) 2001 Elsevier Science Ltd.