High-precision strontium isotope analysis of geological samples by thermal ionisation mass spectrometry

Tom Henshall (1) , David L Cook (1) , Marion Garҫon (1) , Maria Schönbächler (1)

1 Institute of Geochemistry and Petrology [ETH Zürich]

We present a method for the efficient separation of Sr from geological materials followed by high-precision measurement of Sr isotopes by thermal ionisation mass spectrometry (TIMS). These analyses focus on high-precision measurements of the low abundance isotope 84 Sr (0.56%), which is of high interest for cosmochemical applications. The robust dataset obtained through the analysis of a range of basalts and anorthosites sheds light on a number of issues regarding Sr isotopic analyses. Specifically, concerns that analytical artefacts may produce a spurious signal on 84 Sr have been investigated. The external reproducibility, based on replicate measurements of the basalt standard BCR-2, for ε 84 Sr is ± 0.36 (2SD), and is ± 0.51 (2SD) for repeated analyses of NIST SRM-987. In contrast with the static measurements of previous work (Moynier et al., 2012; Paton et al., 2013; Brennecka et al., 2013), our dynamic data reveal no 84 Sr variations in terrestrial rocks or standard material. The dataset indicates that, by the analytical procedure employed, 84 Sr variations in extra-terrestrial material larger than ~0.5ε are resolvable.

Domaines: Sciences de la Terre

Tom Henshall, David L Cook, Marion Garҫon, Maria Schönbächler. High-precision strontium isotope analysis of geological samples by thermal ionisation mass spectrometry. Chemical Geology, 2018, 482, pp.113-120. ⟨10.1016/j.chemgeo.2018.02.010⟩. ⟨hal-03708720⟩