Precise thermal ionization mass spectrometric measurements of Nd-142/Nd-144 and Nd-143/Nd-144 isotopic ratios of Nd separated from geological standards by chromatographic methods

A chromatographic separation technique for Nd-142/(144) Nd and Nd-143/Nd-144 isotope ratio measurements is established and applied to the analyses of geological standards of basaltic compositions (BCR-2, BIR-1) using Isoprobe-T TIMS. The instrument was tested for reliability and reproducibility to measure Nd isotope composition using the synthetic standard JNdi-1. The techniques were also applied to a carbonatite lava sample, OL-6, Oldoinyo Lengai, to check the validity of method for carbonatite matrix. The isotope ratios of Nd-143/Nd-144 for synthetic Nd standard JNdi-1, geological standards BCR-2, BIR-1, and carbonatite lava sample OL-6 obtained by these methods are in good agreement with previously published data. The Nd-143/Nd-144 values for JNdi-1 and BCR-2 have an external precision of +/- 13 ppm and +/- 15 ppm (2 sigma), respectively. The JNdi-1 and BCR-2 data for Nd-142/Nd-144 has an external precision of +/- 12 ppm and +/- 8 ppm (2 sigma), respectively. The Nd-142/(144) Nd composition of the two geological standards BCR-2 and BIR-1 are indistinguishable from synthetic mono-element standard JNdi-1, and they all fall within the 12 ppm (2 sigma) envelope of external precision. The external reproducibility is sufficient to distinguish and resolve 20 ppm anomalies in Nd-142/(144) Nd values. Crown Copyright (C) 2010 Published by Elsevier By. All rights reserved.