title: Chemical separation of Nd from geological samples for chronological studies using (146)Sm-(142)Nd and (147)Sm-(143)Nd systematics.
abstract: Sm-Nd dating, which involves long-lived (147)Sm-(143)Nd and short-lived (146)Sm-(142)Nd systematics, has been widely used in the field of geosciences. To obtain precise and accurate ages of geological samples, the determination of highly precise Nd isotope ratios with nearly complete removal of Ce and Sm is indispensable to avoid mass spectral interference. In this study, we developed a three-step column chemistry procedure for separating Nd from geological samples that includes cation exchange chromatography for separating major elements from rare earth elements (REEs), oxidative extraction chromatography using Ln Resin coupled with HNO3 + KBrO3 for separating tetravalent Ce from the remaining REEs, and final purification of Nd using Ln Resin. This method enables high recovery of Nd (>91%) with effective separation of Nd from Ce and Sm (Ce/Nd < 1.2 × 10(-5) and Sm/Nd < 5.2 × 10(-6)). In addition, we devised a new method for determining Sm/Nd ratios with the isotope dilution inductively coupled plasma mass spectrometry method using (145)Nd- and (149)Sm-enriched spikes coupled with a group separation of REEs using TRU Resin. Applying the techniques developed in this study, we determined the Sm-Nd whole-rock isochron age of basaltic eucrites, yielding 4577 - 88(+ 55) Ma and 4558 ± 300 Ma for (146)Sm-(142)Nd and (147)Sm-(143)Nd systematics, respectively.
authors: Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Ookayama, Tokyo 152-8551, Japan. Electronic address: kagami.s.ab@m.titech.ac.jp.
authors: Saya
authors: S
authors: Kagami
authors: Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Ookayama, Tokyo 152-8551, Japan.
authors: Tetsuya
authors: T
authors: Yokoyama
keywords: (145)Nd spike; Chemical separation; Isotope dilution ICP-MS; Oxidative extraction chromatography; Sm–Nd systematics; Whole-rock isochron