Carbonates reduce the melting point of the mantle, and carbonate melts produced in low-degree melting of a carbonated mantle are considered the precursor of CO₂-rich magmas. We established experimentally the melting relations of carbonates up to 9 GPa, showing that Mg-carbonates melt incongruently to periclase and carbonate melt. The trace element signature of carbonate melts parental to kimberlites is approached by melting of Mg-rich carbonates.

The equilibrium phase of A + HP clinoenstatite = forsterite + water was experimentally investigated at aH₂O = 1 in situ. In cold subducting slabs, it is of relevance to transport water to large depths, initiating the formation of dense hydrous magnesium silicate (DHMS). At normal gradients, the huge water amount from this reaction induces important processes within the overlying mantle wedge. We additionally discuss the relevance of this reaction for intermediate-depth earthquake formation.

Processes associated with open pores can change the physical properties of rocks and cause earthquakes. In borehole samples from the Alpine Fault zone, we show that many pores in these rocks were filled by weak materials that can slide easily. The amount of open spaces was thus reduced, and fluids circulating within them built up high pressures. Both weak materials and high pressures within pores reduce the rock strength; thus the state of pores here can trigger the next Alpine Fault earthquake.

Two new nanominerals: titanium monophosphide and titanium disilicide, formed at pressures of Earth’s upper mantle by the action of methane and hydrogen from the mantle on basaltic melts in the Luobusa ophiolite (Tibet). The minerals were characterized by 3D electron diffraction, which can solve the crystal structures of phases less than a micrometer in size. The results contribute to our understanding of deeply subducted crustal rocks and their exhumation back to the Earth's surface.

The structural response of the NH₄⁺ molecule to temperature and pressure changes is studied in ammonium phengite. The symmetry of the molecule is lowered by increasing P or decreasing T; the type and mechanism of this lowered symmetry is different in both cases. Devolatilisation (NH₄⁺ and OH loss) of ammonium phengite is studied as well. This study confirms the wide stability range of phengite and its volatiles and thus has important implications for N and H recycling into the deep Earth.