There are three ways I study volatile elements under mantle pressure and temperature conditions.  through the study of diamonds,  experimental petrology, and  using the Deep Earth Water Model (this page).
The Deep Earth Water Model is a platform which enables geochemists to study aqueous geochemistry under extreme conditions, from their laptops. This work is novel and exciting and really began in 2014 (Sverjensky et al. 2014). However, it has already forged a global community with researchers from across the world (see website).
To advance a vision of how fluids have linked the deep Earth and the near surface environment through deep time.
Integration of predictive theoretical models with experimental data, field studies, and remote observation of the deep Earth to investigate the nature, migration, and reactivity of deep fluids in Earth.