Volatiles (H, He, Ar) in olivine grain boundaries

Abstract:

The volatiles are key tracers of the evolution of the terrestrial mantle-atmosphere system: a realistic description of their abundance and isotopic heterogeneities in the Earth’s mantle is required to properly understand the mantle-atmosphere interactions. In order to be able to interpret measured volatiles heterogeneities, notably H, He and Ar, we need constraints on the fundamental behaviour of volatiles in the mantle (where are they stored, how do they partition during melting or metasomatism and how might they be transported). At present, these parameters are poorly constrained since it is technically challenging to perform experiments with volatiles at high temperature and high pressure, but also because volatiles behaviour in silicate minerals is complex and can be related to numerous possible different host sites and incorporation mechanisms. Here, we synthetize the results of high temperature – high pressure experiments, which aim to constrain hydrogen and noble gas behaviour in crystalline solids versus mono-mineralic aggregates, including grain boundaries, that mimic mantle compositions and conditions. These experiments provide basics for further thermodynamic modeling.