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Future trends of in-situ beta decay dating

The field of mass spectrometry has seen an impressive boost with the commercialization of an older idea of sandwiching a reaction cell between two mass filters, a configuration dubbed MS/MS. This allows controlled reactions between ions within an ICP-MS instrument and reaction gases, with the aim of reducing or even eliminating isobaric interferences. Rather established now is the example of eliminating 87Rb+ on m/z of 87 by reacting the desired 87Sr+ with gases such as N2O or SF6 to 87Sr16O+ or 87Sr19F+, leaving the Rb-ion behind. This allows Rb-Sr dating from transient signals, in particular when coupled to a laser ablation system, currently the most commonly utilized “in-situ beta decay dating” tool.

Within the field of in-situ Rb-Sr dating, particular attention is given to develop primary reference material for the scientific community. Here I will demonstrate that more emphasis should be spent on better characterizing suitable reference material (e.g., with the help of isotope dilution TIMS and MC-ICP-MS) rather than trying to “matrix-match” every possible target material. Furthermore, I am calling for a paradigm shift when dealing with Rb-Sr data from the classical isochron approach towards single spot dating, allowing e.g. detrital and age zonation studies.

Besides Rb-Sr dating, with the same technique it has been demonstrated that other exciting beta decay schemes are accessible to in-situ dating, specifically K-Ca, Re-Os and Lu-Hf. Progress was and will be possible by systematically studying ion-molecule reactions from a wide spectrum of reactive gases and gas mixes, such as CH4 and H2+SF6.


Thomas Zack1
1University of Gothenburg, Sweden
GeoMinKöln 2022