Crystal-chemistry of xenon in antigorite, main carrier of volatile elements to the mantle

The aim of this proposal is to understand how xenon (Xe), a key tracer of terrestrial and atmosphere formation, is recycled at depth through subduction processes. Xenon isotopes in mantle fluids indeed show that atmospheric Xe is recycled at depth via subduction, with a larger contribution to the mantle Xe budget than in the case of Ar, and potentially essentially carried in phyllosilicates due to their cage and layered structures along with water and other major volatile elements. However, there are very few data available to document this hypothesis in the case of Xe, and no crystallographic data at all. We therefore plan to elucidate Xe retention mechanism(s) in antigorite, the high pressure (P) form of serpentine and main carrier of water back into the mantle. For this, we need to collect high quality powder diffraction data in situ within antigorite stability field, and beyond in temperature (T) to probe Xe behavior upon antigorite breakdown and water release.