In-situ investigation of Hg-bearing sulfide and sulfate minerals structural stability and equation of state at high pressure and temperature

Recent studies propose Hg as a reliable geochemical proxy to trace large volcanic events linked to past mass extinctions in sedimentary and volcanic rocks, and isotopic analysis has revealed its deep mantle origin. Sulfide and sulfate minerals are considered the primary hosts for Hg. Understanding the stability and structure of Hg-bearing minerals, cinnabar and schuetteite, under P-T upper mantle conditions is crucial for modelling Hg migration from the Earth's interior. Previous HP-T experiments indicate that trigonal cinnabar crystal structure undergoes two polymorphic transformations (zinc blende and rock salt). Preliminary HP-T experiments performed on cinnabar at ID06 LVP did not reproduce the proposed phase diagrams. Regarding trigonal schuetteite, to date, no HP-HT studies exist. The study aims to perform in situ HP-T experiments on both mineral phases at ID06 LVP using a 2000T multi-anvil press coupled with angle dispersive XRD to constrain the P-T diagram and develop the EoS.