STAGE Precise and accurate determination of moderately volatile element abundances in Solar System materials

The objective of this Master 2 internship is to study the history of moderately volatile element delivery to planetary materials from the first solids (chondrules) to differentiated planets (e.g. Earth and Moon) by using high precision elemental measurements by isotope dilution. The student will have to develop protocols for precise determination of moderately volatile element concentrations in Solar System materials. While this project will largely focus on samples from meteorites (chondrites, martian meteorites…), Earth and the Moon, this work will develop key techniques for the study of important samples from future sample return missions from the Moon and possibly Mars. Trace element concentration data from geological samples are typically obtained by ICP-MS, ICP-AES or similar methods, with typical relative errors of ca. ±10%. The
isotope dilution method, offers improvements in the accuracy and precision of concentration measurements by more than an order of magnitude. In this approach, a known amount of an isotopically enriched tracer of the element of interest is added to the sample, and the elemental concentration is determined by the measurement of an isotope ratio rather than using absolute ion intensities. Ion sensitivities are vulnerable to a variety of negative effects, such as signal suppression due to the presence of matrix in the analyte solution and instrumental drift. Isotope ratios are relatively impervious to these effects, and the isotope dilution method thus provides greater accuracy and precision in concentration measurements. In particular it allows an improvement about 2 order of magnitude in precision that are necessary to test models of volatile element origin. Isotope dilution methods are also more robust to small amounts of blank, and permit accurate measurements to be made on relatively small amounts of sample. As a result, this method has become the standard for the characterisation of elemental concentrations in geological reference materials. However, despite the various advantages, the added complexity of the isotope dilution method has somewhat limited its adoption, and the majority of the trace element data for terrestrial and extraterrestrial data in the literature were obtained by less precise and accurate methods.