New Thorium Isotope Ratio Measurements in Silicate Reference Materials: A‐THO,AGV‐2, BCR‐2, BE‐N,BHVO‐2 and BIR‐1 |
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| Authors: | Marion Carpentier Abdelmouhcine Gannoun Christian Pin Olgeir Sigmarsson |
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| Institution: | 1. Laboratoire Magmas et Volcans, OPGC, CNRS UMR 6524, Clermont‐Ferrand Cedex, France;2. Norvolc, Institute of Earth Sciences, University of Iceland, Reykjavik, Iceland |
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| Abstract: | A two‐step Th isolation protocol, involving micro‐columns of TRU‐Spec extraction chromatography material and AG1 resin, was evaluated. The MC‐ICP‐MS procedure included 232Th tailing characterisation and correction, and calibrator bracketing using an in‐house standard solution (ThS1) to correct for instrumental mass bias and Faraday cup to secondary electron multiplier relative gain. Repeated analyses of reference solutions (UCSC Th ‘A’, WUN, OU Th ‘U’, IRMM‐36) were consistent with published data. Six reference materials (A‐THO, BCR‐2, AGV‐2, BHVO‐2, BE‐N and BIR‐1) were processed. The average 230Th/232Th values obtained for these samples are in excellent agreement with published data. In addition, we report the first 230Th/232Th values for BE‐N and BIR‐1. The intermediate precisions for rock samples ranged from ± 0.24 to ± 0.49% (2 RSD) and were similar to those achieved for synthetic solutions, thereby supporting the overall validity of the chemical separation, data acquisition and reduction procedures. Counting statistics on the 230Th isotope was the most significant source of uncertainty. The intermediate precision of the mean 230Th/232Th for the Th‐depleted BIR‐1 (5.64 × 10?6 ± 0.27%, 2 RSD) is in the range of the analyses of other reference materials analysed in this study. |
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| Keywords: | thorium isotopes reference materials TRU‐Spec extraction chromatography calibrator bracketing MC‐ICP‐MS Isotopes du thorium maté riaux de ré fé rence chromatographie d'extraction TRU‐Spec encadrement par standard MC‐ICP‐MS |
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