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

A chromatographic separation technique for 142Nd/144Nd and 143Nd/144Nd 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 143Nd/144Nd 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 143Nd/144Nd values for JNdi-1 and BCR-2 have an external precision of ±13 ppm and ±15 ppm (2σ), respectively. The JNdi-1 and BCR-2 data for 142Nd/144Nd has an external precision of ±12 ppm and ±8 ppm (2σ), respectively. The 142Nd/144Nd 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 (2σ) envelope of external precision. The external reproducibility is sufficient to distinguish and resolve 20 ppm anomalies in 142Nd/144Nd values.

Figure optionsDownload high-quality image (125 K)Download as PowerPoint slideResearch highlights▶ Chromatographic technique for separation of Nd from rock powders is established. ▶ The separated Nd was analyzed using TIMS for its isotopic composition. ▶ TIMS was tested for reliability using mono-element Nd reference standard. ▶ The 143Nd/144Nd values for standards had an external precision of ≤±15 ppm. ▶ The external reproducibility for 142Nd/144Nd is sufficient to resolve 20 ppm anomalies.