![]() Condon, D.J., Schoene, B., and Bowring, S.A. Isotopic Composition ( 238U/ 235U) of some commonly used Uranium reference materials. Geochimica et Cosmochimica Acta, v. Condon, D.J., McLean, N., and Noble, S.R.The results of the U-Pb calibration experiment can be found in this pair of papers: A comprehensive calibration exercise was carried out on the EARTHTIME tracers, addressing many prior assumptions (e.g., 238U/ 235U = 137.88?) allowing for a calibration that can be traced back to SI units. Calibration of the EARTHTIME U-Pb tracers provided an opportunity to assess and improve the accuracy of the U-Pb system. See ET353 and ET2355 Tracer information page for details of how to acquire them.Ģ. Subsequent inter-laboratory agreement exercise indicate a significant reduction in bias (see below). ![]() This was carried out in 2005 and the tracer is now being used in XX U-Pb ID-TIMS laboratories worldwide. ![]() The issue of inter-laboratory bias was identified as a priority issue at the EARTHTIME I and EARTHTIME II workshops, at what level of uncertainty could we compare U-Pb ID-TIMS dates from different laboratories?Īn initial U-Pb ID-TIMS inter-laboratory agreement exercise in 2004/5 demonstrated that bias existed between laboratories at a level that exceeded estimated calibration uncertainties, raising many questions about the calibration of the U-Pb ID system in each laboratory.Īt the EARTHTIME II workshop it had been agreed that an effective way to effectively eliminate inter-laboratory bias related to the calibration of mixed U-Pb tracers used in each laboratory would be to mix and distribute a large quantity of U-Pb tracer that all labs engaged with ‘high-accuracy’ U-Pb geochronology for all to use. ![]()
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