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.

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.

We present a petrological⁠–geochemical investigation of peridotites of magmatic origin from the Ivrea⁠–Verbano Zone (Italian Alps), a large-scale section of lower continental crust. The main purpose is to provide new insights into the processes governing the evolution of primitive mantle magmas. We propose that studied peridotites were formed by reaction of a melt-poor olivine-rich crystal mush, or a pre-existing peridotite, with upward-migrating melts possessing a substantial crustal component.

Electron backscatter diffraction (EBSD) is a powerful tool to visualize and differentiate between foraminiferal test structures, by providing information on crystal orientation and crystal sizes. This can be used to trace diagenetic recrystallization, altering geochemical proxy signals. The sediment samples from a core from the equatorial Pacific used here, spanning the last 45 Myr, showed no evidence for foraminiferal recrystallization, highlighting the suitability as geochemical proxy archive.

The plagionite group is a family of complex sulfides (lead-antimony sulfosalts) encountered in various Pb-Cu-Zn ore deposits. Analysis of these crystal structures confirms a systematic Pb-versus-Sb substitution in two adjacent cation positions. Such a substitution varies according not only to the Pb / Sb ratio of each member but also, apparently, to the kinetics of crystallization. Re-examination of a Pb-free synthetic derivative permitted its redefinition as a Na-Sb sulfosalt.

Grain boundary diffusion is orders of magnitude faster compared to volume diffusion. We studied this fast transport process in a well-defined garnet grain boundary. State-of-the-art microscopy was used for quantification. A dedicated numerical diffusion model shows that iron diffusion requires the operation of two diffusion modes, one fast, one slow. We conclude that impurity bulk diffusion in garnet aggregates is always dominated by grain boundary diffusion.