Molybdenum isotope mass fractionation in iron meteorites

An examination of the isotope fractionation of molybdenum in a range of iron meteorites has been carried out by thermal ionization mass spectrometry incorporating the double spike technique. Ten iron meteorites were dissolved in hydrochloric acid and double spiked with a 92Mo–98Mo mixture of enriched isotopes. An ion exchange-based chemical separation process was then used to remove any vestiges of zirconium and ruthenium from the samples, so as to eliminate any possibility of isobaric interferences, and to provide a final molybdenum extract suitable for mass spectrometric analysis. The molybdenum from each extracted meteorite was analysed under similar mass spectrometric conditions to a Laboratory Standard. The double spike technique enabled the magnitude of the isotope fractionation in the meteorites to be determined with high accuracy relative to the Laboratory Standard, whose absolute isotopic composition is known. The ten iron meteorites gave isotope fractionations in the range −0.5‰ to +1.2‰/mass unit with respect to the terrestrial standard, the isotopic composition of which is identical, within experimental uncertainty, to other terrestrial samples.

Graphical abstractAn examination of mass-dependent isotope fractionation of molybdenum in iron meteorites by double spike thermal ionization mass spectrometry found fractionations in the range −0.5‰ to +1.2‰/mass unit with respect to the terrestrial standard of known isotope composition.Figure optionsDownload full-size imageDownload as PowerPoint slide