Recent  

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.

Garnet is a high-pressure mineral that may incorporate very small amounts of water in its structure (tens to hundreds of micrograms per gram H₂O). In this study, we show, based on analysis and modelling, that it can transport up to several hundred micrograms per gram of H₂O at depths over 80 km in a subduction zone. The analysis of garnet from the various rock types present in a subducted slab allowed us to estimate the contribution of garnet in the deep cycling of water in the earth.

We present the first determinations of the Fe oxidation state of tiny spinel inclusions (<40 µm) in olivine from a wehrlitic lapillus collected at Mt. Vulture (Italy) via in situ synchrotron Mössbauer spectroscopy. These data, along with the chemistry of olivine and (rare) orthopyroxene, allowed us to calculate the logf_O2 of the wehrlitic sample. This study opens the possibility to retrieve the redox state of mantle xenoliths using the Fe³⁺ / ∑Fe and chemistry of spinel inclusions in olivine.

We show that metamorphosed sedimentary rocks in the Western Alps have a detrital zircon signature that connects them to the Adrian plate along the Gondwana margin. We used zircon to learn that a jadeite-bearing orthogneiss intruded into these strata in the Ordovician (at ~460 Ma) and was metamorphosed at high pressure during early Alpine subduction of Adria beneath Europe at ~78 Ma. Our results are consistent with the complex subduction of Adria before full-on collision with the European plate.

Hochleitnerite is a new member of the paulkerrite group of minerals. Its crystal structure, chemical analyses and Raman spectroscopy are reported, and its crystallochemical properties are discussed in relation to other group members.

These results represent the first high-pressure and high-temperature degassing experiments simulating the injection of basaltic melt into a hydrous rhyolitic melt reservoir. Diffusion processes in the contact zone of the melts lead to a depletion of alkalis in the rhyolitic melt interface. The reduced alkali concentration significantly decreases the H₂O solubility of the rhyolitic melt and promotes enhanced H₂O vesicle formation and further degassing, which can trigger volcanic eruptions.

The La Picherais metagranite is a key example of undeformed high-pressure quartzofeldspathic rock from the Armorican Massif. Through petrological observations and thermodynamic modelling, this study determines that the metagranite was pressured above 1.7 GPa and the associated mafic lenses at ~ 2.1 GPa. This metagranite provides an opportunity to study the degree of transformation of quartzofeldspathic rocks at high pressure, which may have a significant impact on the dynamics of subduction.

In this study, unusual corundum- and spinel-bearing symplectites after muscovite were found in ultrahigh-pressure eclogites from the Dabie terrane, China. The results indicate that these symplectites formed by the low-pressure partial melting of muscovite during slab exhumation. We stress that the occurrence of corundum- and spinel-bearing symplectites after muscovite in eclogites provides important implications for fluid and melt actions in exhumed slabs.

This work shows that even under the low oxygen fugacities prevailing in the deep upper mantle and transition zone, around 410 km depth, the storage capacity in the nominally anhydrous mineral olivine and its high-pressure polymorph, wadsleyite, is still substantial, with up to 0.8–1 wt % at the iron-wüstite buffer and 1300–1400 °C for wadsleyite, even in the presence of carbon.

The past 40 years have been a golden age for eclogite studies, supported by an ever wider range of instrumentation and enhanced computational capabilities, linked with ongoing developments in the determination of the temperatures and pressures of metamorphism and the age of these rocks. These data have been used to investigate the spatiotemporal distribution of metamorphism and secular change but not without controversy in relation to the emergence of plate tectonics on Earth.

Quartz inclusions in garnet are used to constrain the metamorphic pressure–temperature history of multiple ~2.8 Ga metasedimentary rocks from Montana, USA. Inclusion studies along with mineral and whole rock chemistry suggests that the rocks of interest experienced a clockwise metamorphic P–T history that included isobaric heating to peak metamorphic temperatures once inclusions were entrapped. These findings place fundamental constraints on the P–T evolution of this important geologic setting.

When and how modern-style plate tectonics initiated is a matter of debate. Although the earliest unequivocal evidence for ultrahigh-pressure metamorphism is Neoproterozoic, similar processes have been proposed for Paleoproterozoic rocks of western Greenland. We intensely screened the area by studying detrital heavy minerals, garnet chemistry, and mineral inclusion assemblages in garnet. Our results raise considerable doubts on the existence of Paleoproterozoic ultrahigh-pressure rocks.

We have developed the thermodynamic theory of the properties of inclusions consisting of more than one phase, including inclusions containing solids plus a fluid. We present a software utility that enables for the first time the entrapment conditions of multiphase inclusions to be determined from the measurement of their internal pressure when that is measured in a laboratory.

The analysis by electron microprobe of platinum-group minerals, gold and cinnabar particles from heavy mineral concentrates of the Elbe showed a broad compositional variation of Os–Rus–Irs–(Pt) alloys as well as Pts–Fe alloys. The comparison with the literature showed that different sources account for the heavy mineral concentrate. This compositional variation of the alloys is also of interest for other placers of platinum-group minerals worldwide.

There are unresolved problems related to the nomenclature and identification of mineral species belonging to the triphylite group of minerals. They can be solved by discarding the traditional views on succession of mineral species during oxidation. In other words, it is necessary to separate the concepts of the origin of the mineral and the boundaries of the species.

The diversity of chemical patterns in multi-stage fluorite mineralization from two neighbouring deposits in the Black Forest is investigated. From over 70 samples, 7 fluorite groups and 3 hydrothermal events are identified after chemical and mathematical classification. The relative chronology and features suggest different mineralization histories and source aquifers for both deposits despite their proximity. Genetic differences are likely controlled by different behaviours of their host rocks.