Application of the 'double spike' technique to Pb-isotope geochronology

New Ph-isotope data are presented for three suites of carbonate-bearing sedimentary rocks from the Archaean and Proterozoic of Western Australia. The measured data are corrected for instrumental mass fractionation using both conventional and double-spike techniques, with the results contrasted on isochron diagrams. Compared with the data corrected using conventional methods, the double-spike-corrected data show a significant improvement in all cases: the isochrons produced are more tightly constrained, resulting in lower uncertainties in the age estimates obtained and marked improvements in MSWD values. While highlighting the enormous potential for the direct dating of carbonate sequences throughout the geological record, this study demonstrates the improvements possible using double-spike correction for mass fractionation-an issue pertinent to all aspects of Pb-isotope geochronology.