Recent  

The chemical compositions of the synthetic minerals periclase and zincite in the MgO–ZnO binary system change smoothly and systematically with pressure when they exist together in equilibrium. We have studied these changes experimentally over a wide range of conditions and fitted the results to a thermodynamic model. The model may be used to predict the compositions of the coexisting phases accurately at high pressures and temperatures corresponding to the Earth’s crust and uppermost mantle.

Garnet often entraps small droplets of deep melts generated during mountain building processes. Using high-resolution techniques, we studied these droplets in order to provide hard numbers for the quantification of volatile budgets during crustal evolution, show how even melts formed at >1000°C contain water, and clarify how water behaves during metamorphism and melting at the microscale. Moreover, we provide the very first data on chlorine in natural melts from crustal reworking.

This article introduces a new nomenclature system for the cerite group minerals. This system was necessary to allow the nomenclature of new species of minerals that are currently being described.

Li is a critical element that is often enriched in pegmatites. To better understand the enrichment of Li in such systems, it is necessary to understand the underlying transport mechanisms. We performed experiments to investigate diffusion rates and exchange mechanisms of Li between a Li-rich and a Li-poor melt at high temperature and pressure. Our results indicate that fluxing elements do not increase the diffusivity of Li compared to a flux-free melt.

The present study is based on sample chemical and mineralogical analyses of oceanic sediment and rock that were collected in the Guaymas Basin during IODP Expedition 385. The contact aureoles are not only affected by maturation of organic matter and dehydration reaction, but mineralogical reactions concern all sediment components (silicates, sulfides, carbonates, organic matter) and can be the result of the combination of different stages of alteration during and after the sill emplacement.

The present study of mafic rocks from Jutulsessen, Gjelsvikfjella, extends the presence of high-pressure rocks in the Maud Belt in Dronning Maud Land, Antarctica. The physical conditions necessary for the development of these rocks were attained during continent–continent collision along the East African–Antarctic Orogen. The new data in this study largely confirm the geodynamic implication outlined by others for the region.

We study Icelandic silica sinter samples formed in hot-spring environments to evaluate the effect of both temperature and microstructure on the spectral properties of hydrothermal opal. We show that spectral changes can be related to different parameters such as fluid temperatures, hydrodynamics, microbial activity, and silica micro-textures, which are specific to their environment of formation within hot-spring geothermal contexts.

Despite many articles published about eruptions at Mt. Somma–Vesuvius (SV), the volatile contents of magmas associated with mafic (quasi-primitive) melts were not directly analyzed for many eruptions based on melt inclusions (MIs). We suggest that several high-Fo olivines formed at depths greater than those of the carbonate platform based on MI chemical composition. We also estimated that 347 to 686 t d^-1 of magmatic CO₂ exsolved from SV magmas during the last 3 centuries of volcanic activity.

The paper describes the formal establishment of the paulkerrite group of minerals and its nomenclature. It includes the application of a site-merging procedure, coupled with a site-total-charge analysis, to obtain unambiguous end-member formulae. Application of the procedure has resulted in the revision of the end-member formulae for several of the group members.

We present the description of new mineral – a Cd-dominant member of the tetrahedrite group, tetrahedrite-(Cd), from the Radětice deposit near Příbram, Czech Republic. All necessary data including crystal structure were successfully determined, and the mineral and its name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (number 2022-115).

The infrared spectrum of hydrous defects in corundum is routinely used in gemology, but the assignment of absorption bands to specific defects remains elusive. Here, we theoretically study selected defects and compare the results with available experimental data. The main results are the assignment of the 3161 cm⁻¹ series to OH groups associated with Fe²⁺ ions and the interpretation of bands below 2700 cm⁻¹ in corundum containing divalent cations in terms of overtones of OH bending modes.

Two examples of granites in the Variscan Iberian Massif were studied because they are associated with mafic rocks (appinites and vaugnerites), which raise the question of the role of mantle magma in the formation of granitic rocks. We conclude that appinites and vaugnerites derived from melting of different mantle sources, both previously modified by interaction with crustal materials. Subsequent differentiation of appinites and vaugnerites was influenced by contamination with coeval granites.

Minerals in a vein network from the Aravis limestone (Haute-Savoie, France) include carbonates, quartz, fluorite and phyllosilicates, crystallized at around 7 km depth and 190 °C. The mineralogy has been studied with emphasis on the chlorite types: chamosite (iron-rich), cookeite (lithium-rich) and sudoite. The presence of the three chlorite types sheds light on their phase diagrams, and observed cationic substitutions confirm the need for more systematic measurement of lithium in chlorite.

This study presents a new method designed to analyze micrometer-scale chemical and isotopic profiles in minerals, glasses, and other solids. The employed technique combines plasma mass spectrometers and a state-of-the-art femtosecond laser equipped with open-source software (LinuxCNC) that controls the movement of the laser beam. It allows for equably drilling into the sample surface, e.g., in order to measure chemically or isotopically zoned or heterogeneous materials at micrometer scales.

Regerite is the first new mineral species to be described from the Kreuzberg pegmatite, Pleystein, in the Oberpfalz, Bavaria. It has been characterised using electron microprobe analysis, Raman spectroscopy, optical measurements and a synchrotron-based single-crystal structure refinement. The structure type for regerite has not been previously reported.

We calibrate new models for the properties of solid and liquid FePt alloy. FePt alloy is used in experiments investigating the origin, differentiation, and evolution of planets to characterize oxygen fugacity. The new models facilitate use of FePt for more extreme conditions than has been possible previously. We also describe shortcomings in the present knowledge of FePt alloy properties and highlight strategies that could improve such knowledge.

This paper reports on metamorphic titanate + zircon pseudomorphs after igneous zirconolite based on the textural relationships in samples from a key locality of a Mesoproterozoic syenodiorite, in which the rock preserves different states of deformation and metamorphic recrystallisation. The metamorphic reaction to form titanite + zircon intergrowths required the zirconolite breakdown and the release of silica and calcium from the consumption of igneous pyroxene and feldspars.

Elba tourmaline crystals commonly display a sharp transition to dark colors at the analogous termination, but the mechanisms leading to the formation of such terminations are unclear. Here we propose a general genetic model in which, as a consequence of a pocket rupture event, chemical alteration of early formed Fe-/Mn-rich minerals in the enclosing pegmatite was responsible for the release of Fe and/or Mn in the geochemical system, allowing the formation of the late-stage dark terminations.

Since As is detrimental to the environment, the As content of ores should be reduced before it is released into the atmosphere through a smelting process. Thus, Raman spectra of typical As minerals were investigated, and these can be used in the industrial removal of As-rich ores prior to the ore beneficiation. An additional objective of our study was an investigation of the secondary products of enargite weathering. They play a decisive role in the release or retainment of As in the waste form.

We investigate rocks called eclogite, which are related to subduction and the collision of continents. Our samples show evidence of limited melting at high pressure corresponding to about 70 km depth, which may play an important role in the exhumation of these rocks and the differentiation of the crust. However, due to their composition and metamorphic evolution, melt production is limited, suggesting that similar rocks are unlikely to contribute strongly to subduction-related magmatism.

Batoniite is a new mineral species belonging to the Al₂O₃–SO₃–H₂O ternary system, first found in the Cetine di Cotorniano Mine (Tuscany, Italy). This hydrated Al sulfate shows a novel crystal structure, characterized by Al octamers, so far reported in only synthetic compounds.