Assessment of USGS BCR-2 as a Reference Material for Silicate Rock U-Pa Disequilibrium Measurements |
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| Authors: | Julie Prytulak Tim Elliott Dirk L Hoffmann Christopher D Coath |
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| Institution: | Bristol Isotope Group, Department of Earth Sciences, University of Bristol, Queen's Road, BS8 1RJ, Bristol, UK;Bristol Isotope Group, School of Geographical Sciences, University of Bristol, University Road, BS8 1SS, Bristol, UK |
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| Abstract: | The accuracy of 231Pa-235U measurements can be readily assessed using a secular equilibrium reference material (RM), but a secular equilibrium RM is also required to calibrate the 233Pa spike used in 231Pa determinations. The only silicate RM commonly accepted to be in secular equilibrium is Table Mountain Latite (TML) and so an additional reference is required. Our measurements on the widely available USGS BCR-2 (Basalt Columbia River) rock powder yielded (231Pa/235U) = 0.997 ± 0.013 2s (n = 10), indicating its value as a secondary reference to test the fidelity of U-Pa determinations. Such a reference material additionally provides a useful check on data reduction, which our literature survey highlights can lead to discrepancies of up to 53% between reported (231Pa/235U) activity ratios and corresponding U and Pa concentration data. |
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| Keywords: | BCR-2 protactinium U-series secular equilibrium activity ratios |
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