Noble gases analysis by static mass spectrometry .Measurements and applications

Noble gases are extremely volatile elements found primarily in the Earth’s surface reservoirs, particularly in the atmosphere. Their elemental and/or isotopic compositions, which cannot be altered by chemical or biological reactions, thus depend on (i) their initial/inherited composition (in other words, the source), (ii) secondary contributions resulting from nuclear reactions (radioactivity, fission, spallation reactions), and/or (iii) mass-dependent fractionation linked to physical processes such as diffusion, evaporation, or condensation. Noble gas geochemistry is primarily used as a dating and tracing tool to shed light on geological processes that would otherwise be impossible to distinguish. It allows, for example, a thorough understanding of the physical processes during volcanic eruptions or the origin of certain fluids, rocks, or minerals. The isotopic composition of noble gases, when well characterized and quantified—whether in the atmosphere, the Earth’s crust, sediments, or the mantle—enables a thorough understanding of the evolution of a geological feature over time and highlights mixing phenomena between multiple reservoirs. Finally, they provide information on the origin and evolution of major volatile elements, such as water, carbon, and nitrogen, which are difficult to trace due to their involvement in chemical and biological reactions during geological processes. Determining when, and in what form(s), these volatile elements became available at the Earth’s surface is crucial for better understanding:

• changes in the atmosphere;

• the origin and fate of water on Earth;

• the creation of conditions conducive to the development of life.

However, before it can be fully utilized, this powerful search tool requires a thorough understanding of the entire analytical process, namely:

• the extraction of noble gases under ultra-high vacuum (UHV) to eliminate any atmospheric contamination [J 6 632] ;

• the purification and separation of noble gases from one another in UHV chambers specifically designed to meet the needs of research projects