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.

The mineralogical and chemical heterogeneity of the mantle is poorly known because it is not able to be directly investigated. Melt–peridotite interaction processes play a fundamental role in controlling the mantle composition. The results of our reaction experiments help us to evaluate the role of temperature and melt composition in the modification of the mantle through the interaction with pyroxenite-derived melts with implications for the evolution of a veined mantle.

Dense hydrous magnesium silicates, like the 3.65 Å phase, are thought to cause deep earthquakes. We investigated the dehydration of the 3.65 Å phase at P and T. In both directions of the investigated simple reaction, additional metastable water-rich phases occur. The observed extreme reduction in grain size in the dehydration experiments might cause mechanical instabilities in the Earth’s mantle and, finally, induce earthquakes.

We examined the experimental deformation and phase transition of a bridgmanite analogue, NaCoF₃, using a resistive-heated diamond anvil cell and a synchrotron radiation source. We wanted to observe the behavior of NaCoF₃ under uniaxial compression and its plastic properties, as well as to determine if it is a suitable analogue for natural samples. We observe 100 and 001 compression textures and link those to the dominant deformation mechanism in the perovskite structure.

Carbonates play a key role in the chemistry and dynamics of our planet. The role of SrCO₃ in the deep mantle has received little attention due to its low abundance. However, knowing the high-pressure phase behaviour of natural carbonates across its full compositional range is essential to evaluate effects of chemical substitution in the system of deep-Earth carbonates. We performed powder and single-crystal X-ray diffraction up to 49 GPa and observed a phase transition in SrCO₃ at around 26 GPa.