Isotopic composition (238U/235U) of some commonly used uranium reference materials

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1016/j.gca.2010.09.019. This is version 1 of this Preprint.

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Authors

Daniel Condon , Noah McLean , Stephen R Noble, Samuel Bowring

Abstract

We have determined 238U/235U ratios for a suite of commonly used natural (CRM 112a, SRM 950a, and HU-1) and synthetic (IRMM 184 and CRM U500) uranium reference materials by thermal ionisation mass-spectrometry (TIMS) using the IRMM 3636 233U–236U double spike to accurately correct for mass fractionation. Total uncertainty on the 238U/235U determinations is estimated to be <0.02% (2σ). These natural 238U/235U values are different from the widely used ‘consensus’ value (137.88), with each standard having lower 238U/235U values by up to 0.08%. The 238U/235U ratio determined for CRM U500 and IRMM 184 are within error of their certified values; however, the total uncertainty for CRM U500 is substantially reduced (from 0.1% to 0.02%). These reference materials are commonly used to assess mass-spectrometer performance and accuracy, calibrate isotope tracers employed in U, U–Th and U–Pb isotopic studies, and as a reference for terrestrial and meteoritic 238U/235U variations. These new 238U/235U values will thus provide greater accuracy and reduced uncertainty for a wide variety of isotopic determinations.

DOI

https://doi.org/10.31223/osf.io/fzkw5

Subjects

Chemistry, Cosmochemistry, Earth Sciences, Geochemistry, Inorganic Chemistry, Physical Sciences and Mathematics

Keywords

Geochronology, EARTHTIME

Dates

Published: 2017-11-05 14:43

License

Academic Free License (AFL) 3.0

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