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

Condon, Daniel J.; McLean, Noah; Noble, Stephen R.; Bowring, Samuel A.. 2010 Isotopic composition (238U/235U) of some commonly used uranium reference materials. Geochimica et Cosmochimica Acta, 74 (24). 7127-7143.

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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.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: BGS Programmes 2010 > NERC Isotope Geoscience Laboratory
ISSN: 0016-7037
Additional Keywords: uranium isotopes, isotope fractionation, U-Pb geochronology, U-series geochronology, TIMS
NORA Subject Terms: Earth Sciences
Date made live: 13 Dec 2010 15:24 +0 (UTC)

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