Åsgruvanite-(Ce) is a new rare Earth element (REE) mineral from Åsgruvan in Västmanland, Sweden, linked to Bastnäs-type mineralisation. The chemical formula ideally includes cerium, aluminium, silicon, arsenic, carbonate groups, chlorine, and fluorine. The mineral forms small, grey-green, lustrous grains with distinct cleavage and high density and is associated with carbonates and REE minerals like gadolinite and an allanite-like mineral. It has a unique layered crystal structure.

Western Norwegian “diamond facies” eclogite contains tiny mineral inclusions of quartz and amphibole lamellae that are not stable in the diamond field. Low trace amounts of water in the lamellae-bearing host minerals suggest that the inclusion microstructure was not formed by fluid infiltration but by dehydration during early exhumation of these rocks. Some samples with higher water content argue that a late fluid overprint was spatially restricted and erased evidence of extreme metamorphism.

We examined the influence of Al₂O₃ and H₂O on the position of the coesite–stishovite transition by means of in situ X‑ray diffraction measurements with the large-volume press at the synchrotron PETRA III in Hamburg. The position of the transition was found to be shifted almost in parallel by about 1.5 GPa to lower pressures compared to results for the pure SiO₂ system by Ono et al. (2017). Stishovite of this study containing Al and H is only partially quenchable but transforms back to coesite.

We studied primary granitic and halogen-rich melt inclusions trapped in mantle rocks in the Bohemian Massif (Germany) in order to retrieve important information about the nature of the melt and the source rock. The melt was produced by the partial melting of metasediments during the deepest stages of subduction and interacted with the mantle. This work is an excellent example of transfer of crustal material, volatiles in particular, in the mantle during the subduction of the continental crust.

We examined the reaction phase A plus high-P clinoenstatite to forsterite plus water (Reaction 1) by means of in situ X-ray diffraction measurements with the large volume press at the synchrotron PETRA III, Hamburg. Contrary to other studies, in which all experiments on Reaction (1) were performed at a water activity of 1, the reversed experiments presented in this study were performed at reduced water activity with mole fractions of about X_H2O = X_CO2 = 0.5.