Conference Agenda

The Reykjanes Peninsula’s transition from an 815-year dormancy to active rifting provides a vital laboratory for eruption forecasting. By analyzing the shift from tectonic quiescence to high-intensity volcanism, this study deciphers mechanical signals like seismic swarms and crustal uplift that precede fissure formation. Understanding these strain patterns is essential for identifying the threshold where magmatic pressure overcomes rock strength to trigger dike intrusion.

The region’s magmatic evolution follows a chronological progression through three interconnected systems: the effusive Fagradalsfjall System (2021 to 2023), the high-intensity Sundhnúkur System (2023 to 2025), and the ongoing activity associated with the Svartsengi System. These events track a transition from primitive mantle-derived activity to the utilization of shallow crustal staging areas at depths of 4 to 5 km.

Geochemical analysis of Mg-rich olivine confirms a shared lineage from a mantle source 15 to 20 km deep. Despite this shared source, chemical signatures have become increasingly evolved, suggesting a maturing plumbing system with more efficient magma transport. Diffusion chronometry reveals that while the system is primed years in advance, final ascent now occurs within days. Integrating these petrological timestamps with GNSS and InSAR data creates a critical framework for forecasting future volcanic pulses.

Key References:

1. Gudnason, J., et al. (2024). Trace elements in olivine, JVGR.
2. Halldórsson, S. A., et al. (2022). Deep magmatic source, Nature.
3. Sigmundsson, F., et al. (2024). Svartsengi eruption, Sci. Rep.
4. Thorvaldsson, T. (2025). Volcanic early warning system, Stanford Earth Sci

This study provides new scientific insights into the Düdinghausen Geotrail in the German National Geopark GrenzWelten, advances the understanding of the region’s geological development, and facilitates the implementation of the Geotrail’s digital enhancement.

To establish a foundation for enhancing the content and educational value of selected stations along the trail, the former quarries Vitsenböhl and Borghagen, as well as the Kreuzberg viewpoint, were investigated in detail. Objectives include stratigraphic and petrographic classification of the exposed rock, structural analysis of the outcrops, characterisation of volcanic layers at Borghagen, and determination of the geomechanical properties of the siliceous limestones at Vitsenböhl, as well as the assessment of geomorphological and paleogeographic development of the Düdinghausen region.

The methodological approach integrates literature review, field surveys, discontinuity mapping, rock sampling, laboratory testing, and photogrammetry. Mineralogical and petrographic analyses were conducted using X-ray powder diffraction, thin sections, and standardised sample descriptions. Additionally, compressive and tensile strength tests were carried out, and fracture surface geometry was analysed using a 3D outcrop model.

Results indicate that the Borghagen outcrop can be partially assigned to a local calcareous sub-formation within the Kulm sequence. The volcanic layers were classified as acidic to intermediate in terms of magma composition and therefore show no connection to the neighbouring metavolcanic deposit near Welleringhausen. The siliceous limestones at Vitsenböhl exhibit brittle fracture behaviour and high to very high compressive and tensile strength. Structural features align with the regional tectonic framework, while geomorphological evidence indicates a multi-phase landscape evolution with pre-Pleistocene and Pleistocene influences.

We present the results of two Bachelor’s theses on diabase samples from the western Harz. One sample was collected at Sülteberg, SW of Langelsheim from a massy diabase, and the other one from the occurrence of pillow basalts at Wäschegrund, S of St. Andreasberg. Both occurrences are dominated by remnants of primary magmatic plagioclase and clinopyroxene (augite), and secondary chlorite. Magmatic textures range from intersertal to ophitic, (sub-)ophitic, and porphyric. The primary magmatic fabrics and minerals are strongly overprinted by secondary, low-temperature hydrothermal alteration processes that caused albitisation of plagioclase and chloritisation of mafic minerals. The observed mineral assemblages and replacement textures indicate extensive hydrothermal alteration and low-grade metamorphic overprinting of both occurrences.
Microfocus X-ray diffraction (μ-XRD, 50 μm) offers a method that does not require sample preparation and is completely non-destructive. Part of this study aims to determine how and to what extent μ-XRD can be used on glass-mounted polished thin sections. The main challenges in the μ-XRD procedure are setup configuration and addressing the problem of the glass background. After editing the 2D diffraction images, they were converted to powder diffractograms, which were used for analysis. Due to preferred orientation of crystallites, too few peaks are recorded, skewing the intensity relations of the powder diffractograms. This resulted in problems matching the correct phases. μ-XRD as a tool for petrographic analysis of thin sections is limited by the superimposed background from the glass slide, but can potentially reveal mineral phases in fine-grained rocks, where optical microscopy is difficult.

The International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty Organization under the Comprehensive Nuclear-Test-Ban Treaty is a global network of geophysical sensors composed of four monitoring technologies, including infrasound, designed to monitor and verify compliance with the CTBT through the detection of clandestine nuclear explosions. The Treaty was established by the United Nations (UN) in 1996 with the objective of prohibiting all nuclear tests in any environment. The IMS infrasound network is primarily intended to detect nuclear explosions and other events that generate atmospheric disturbances. In this context, it is important to note that infrasound technology is capable of recording inaudible acoustic waves generated at distances of up to 10,000 km due to their low attenuation. The objective of this study was to detect, locate, and characterize chemical explosions and detonations produced by mining companies in Brazil during their operations using the geophysical method of infrasound. The research aimed to achieve its goal by collecting records, from 2021 to 2025, acquired by the I09BR infrasound station located in Brasília, Brazil.

The Sandwich sealing system, as part of engineered barrier system to deposit radioactive waste, is composed of sealing segments (DS) made of bentonite and equipotential segment (ES) made of fine granular mineral material. While DS ensure the required sealing properties, the ES serves to homogenize the wetting of the DS, which needs to meet hydraulic requirement of permeability between 10^-11-10^-15m².

ES materials are composed of fine sand, silicates and carbonates. Mixtures with carbonates showed higher rising heights in column test experiments (Schuhmann et al. 2009). Either particle size distribution (PSD), surface properties of calcium carbonates or a combination of both could determine hydraulic properties of ES.

Surface wettability describes the ability of a liquid to spread on a solid surface, which can be quantified by measuring contact angle (CA). CA in turn determines the effect of capillary rise.

Thus, contact angles of different calcium/magnesium carbonates as calcites and dolomites were measured. Sessile drop method (SDM) with compressed tablets and Washburn method (WM) were utilized. In general, all the carbonates were hydrophilic with CA between 27° and 85°. Results varied as different preparations changed the geometry and surface properties of powders. CAs of one calcite sample with D50 of 7.7 μm were 30° ± 5° with n-Hexane, non-measurable with ethanol in WM, 34° in average in SDM.

In the same time, PSD and pore volume were measured to shed light on if there is relation between CA.

Volcanic eruption dynamics are largely driven by the degassing of volatile-bearing magma. Experimental studies are crucial for understanding these dynamic processes. To correlate experimental results with the mechanisms of explosive eruptions, the number of vesicles formed in a certain melt volume (Vesicle Number Density (VND)) is essential. Beyond that, crystal number density (CND) can play a significant role, as crystals may act as heterogeneous vesicle nucleation sites.

To determine the VND and CND in experimental products, ImageJ can be used to analyze intersected crystals and vesicles in 2D images and to create 3D VND and CND information with the program CSDCorrections. For the quantitative analysis of the crystals and vesicles, ImageJ requires an image in which each class (glass surface, crystals, and vesicles) is assigned a distinct color. One established method is to manually color the classes using an image editing program. However, this process is time-consuming.

Therefore, we tested Trainable Weka Segmentation as a potential alternative. This tool is widely used in fields like cell biology.

For our application, the method was used to analyze microscopic surface images of vesicles and crystals embedded in a glass matrix, obtained from vitreous samples of decompression experiments. Results from this method were compared with those of manual image processing.

Overall, the results derived from these different methods are consistent within the error range of half a log unit. The presented method simplifies and accelerates the determination of VNDs and CNDs, and significantly increases the analyzed sample area, enabling more robust data analysis.

Compositional concentration profiles across individual crystals or diffusion couples are largely determined by diffusion and growth processes. Both are particularly important during the formation of high-temperature rocks such as igneous and metamorphic rocks. Numerical simulations of compositional profiles in crystals are widely used in various fields such as geospeedometry or diffusion chronometry.

Here, we present our Finite Element (FE) package MovingBoundaryMinerals.jl (Stroh et al., 2025a) that can calculate the evolution of compositional profiles in diffusion couples with moving interfaces mirroring growth/resorption. We implemented various techniques including adaptive grid/timestep or regridding to deal with sharp compositional gradients/discontinuities near the interface, thereby resolving both, diffusion and growth, in a timely manner. Our code can be applied to various examples of single crystals or diffusion couples, integrating any combination of growth, diffusion, and temperature dependency. The software is generally applicable. Furthermore, we provide models for thermodynamically-constrained compositional profiles based on the Stefan interface condition. Results from our models can be used in petrology and geodynamic applications to provide tighter constraints concerning the pressure and temperature evolution of magmatic and metamorphic mineral assemblages (Stroh et al., 2025b).

Reference:

Stroh, A., Aellig, P., and Moulas, E.: AnStroh/MovingBoundaryMinerals.jl: v1.0.0, Zenodo [code], https://doi.org/10.5281/zenodo.17789035, 2025a.

Stroh, A., Aellig, P. S., and Moulas, E.: Numerical modelling of diffusion-limited mineral growth for geospeedometry applications, Geosci. Model Dev., 18, 10203–10220, https://doi.org/10.5194/gmd-18-10203-2025, 2025b.

The region around the abandoned Ngwenya iron ore mine in the Malolotja Nature Reserve of the BGB of northern Eswatini exposes multiply deformed strata of the Onverwacht (ca. 3.57-3.26 Ga), Fig Tree (ca. 3.26-3.23 Ga) and Moodies (ca. 3.224-3.215 Ga) groups, known for their excellent records of Archean geological history, in a scenic area of high topographic relief. Past publications concentrated on mineable ore, archaeology, and wildlife ecology. To add regional geological context to a planned science museum, we mapped this region, focusing on its detailed stratigraphic architecture, sedimentology, deformation style and tectonic history. Ultramafic volcanic and volcaniclastic strata interbedded with diverse cherts (Mendon Fm., uppermost Onverwacht Group) represent Archean ocean floor environments. They are conformably overlain by ferruginous fine-grained strata at the stratigraphic base of large, mostly lithic sandy submarine fans of the Mapepe Fm. (Fig Tree Group). These are, in turn, unconformably overlain by terrestrial-facies quartzose Moodies Group sandstones and conglomerates. The southeastern margin of the BGB, best exposed at Ngwenya, forms part of a ~140 km long suture zone with imbricated southeast-dipping ductile-brittle thrusts of several km horizontal and vertical displacements. The northwest-verging fold-and-thrust belt at Ngwenya, incorporating near-isoclinally folded Onverwacht strata, is dominated by the D1 Ngwenya Synclinorium. This fold-and-thrust belt was refolded about subvertical axes (D2) and deformed by subhorizontal syn- and post-Moodies shortening (D3), metamorphosed at lower greenschist grade (D4), and widely hydrothermally altered. The numerous instructive exposures of this region represent excellent locations for the reconstruction of Archean tectonic processes and sedimentary environments.

The Itsaq gneiss complex (IGC) and the associated Isua supracrustal belt (ISB) in Greenland represent a fundamental archive of Archean crustal evolution and preserve some of the oldest known rock sequences on Earth. While metamorphic P-T conditions are well constrained for the ISB¹, quantitative constraints on the tectono-metamorphic evolution of adjacent tonalite–trondhjemite–granodiorite (TTG) bodies and associated mafic enclaves remain elusive. Previous studies have suggested metamorphic conditions of approximately 650–675 °C and 0.40–0.60 GPa for such enclaves located in the 3.7 Ga TTG²; however, these thermobarometric estimates (Amp-Pl & GASP) appear inconsistent with observed textures and assemblages in investigated samples.

To better constrain the metamorphic record of the mafic enclaves, this study focuses on hornblendites within TTG host rocks from three distinct enclaves. Petrographic observations indicate mineral assemblages of hornblende–biotite–plagioclase–kspar–quartz–titanite–apatite–epidote, with accessory pyrite. Emphasis is placed on distinguishing between primary intrusive features and subsequent metamorphic overprints based on textural relationships. These observations suggest metamorphic conditions exceeding previously reported temperature estimates. Furthermore, in situ chemical analyses and geochronological dating of titanite are employed to constrain the timing of metamorphism and associated partial melting processes.

Special emphasis is placed on the characterization of melt-related microstructures and their integration with P-T–constraints. Mineral-chemical zoning in titanite and multiple generations of plagioclase and amphibolites are systematically investigated. This integrated approach aims to refine the metamorphic evolution of TTG-hosted enclaves and contribute to resolving the tectono-metamorphic history of the IGC and ISB.

¹Ramirez-Salazar et al., Tectonics, 40, (2021).

²Ramirez-Salazar et al., in review (2026).

Investigating fluvio-marine depositional environments from early geological times is important for understanding conditions that may have supported early life. This study reconstructs the deposition and evolution of such systems in the Palaeoarchean Moodies Group of the Stolzburg Syncline, Barberton Greenstone Belt, South Africa, using the ~490 m-long BASE-5B drill core. Sedimentological logging, facies analysis, and palaeocurrent measurements were used to identify 13 sedimentary facies grouped into five facies associations.

The lower part of the core (~490–294 m) shows an overall coarsening-upward trend and is dominated by unidirectionally cross-stratified sandstones with occasional conglomerates and early-diagenetic sulphate concretions. This succession is interpreted as a regressive, river-dominated fluvio-deltaic environment. The upper interval (~294–17 m) is fining upward and characterized by cross-stratified sandstones with mudstone drapes and bidirectional palaeocurrents. These features indicate a transgressive fluvio-estuarine system influenced by combined tidal and riverine processes, including a well-developed turbidity maximum zone.

The vertical stacking pattern records a transition from fluvio-deltaic to fluvio-estuarine conditions, reflecting an overall regressive-to-transgressive evolution driven by increased basin subsidence and/or reduced sediment supply. Two orders of transgressive-regressive cycles overprint this long-term trend and likely reflect relative sea-level fluctuations linked to changes in sediment supply.

These results refine the depositional model for the Moodies Group and provide new insight into Archean fluvio-marine dynamics and their response to external forcing.

Neoproterozoic rocks around Bauchi comprise intermediate–felsic orthogneisses and migmatites, tectonically associated with rare paragneisses. Their ages, P–T evolution, and tectonic role remain poorly constrained, despite their significance for understanding the Pan-African Orogeny in northeastern Nigeria. Charnockitic orthogneisses contain orthopyroxene (ferrosilite, X_Mg 0.15–0.20), amphibole (ferro-tschermakite, X_Mg 0.15–0.30), ilmenite, and plagioclase (An_27–32), locally with inclusions of prograde biotite (X_Mg 0.14; Ti = 0.67 p.f.u.), indicating granulite facies peak conditions. Retrogression produced biotite (X_Mg 0.13; Ti = 0.57 p.f.u.), magnesio-hornblende (X_Mg 0.61–0.62), and titanite under amphibolite facies conditions. Paragneisses preserve prograde inclusions of plagioclase (An_28–31), biotite (X_Mg 0.60; Ti = 0.52 p.f.u.), and quartz within garnet. These were overprinted by a granulite facies assemblage of matrix plagioclase (An_32–33), biotite (X_Mg 0.61; Ti = 0.65 p.f.u.), fibrous sillimanite, and nearly unzoned garnet (Py_30–31Alm_62–63Sps_2.6–2.8Grs_4.2–4.6). Retrogression is marked by white mica formation. Hbl-Pl-thermobarometry yields 690–790 ± 50 °C and 4.3–5.6 ± 0.7 kbar for orthogneisses. Paragneisses record peak conditions of c. 900 °C and 10–11 kbar, followed by retrogression to 735–741 °C and 6.9–7.1 kbar (Grt-Bt geothermometry and Grt-Pl-alumosilicate-Qtz geobarometry). Phase equilibria modelling (MnNCKFMASHTO) supports peak conditions of c. 810 °C and 10 kbar, followed by decompression to 600–650 °C and c.7 kbar, defining a clockwise P–T path. This reflects burial to lower crustal depths followed by rapid exhumation to mid-crustal levels during the Pan-African orogeny, whereas orthogneisses record a lower-pressure granulite overprint in the middle crust. LA-ICP-MS U–Pb dating of zircon is ongoing.

Conodont bioapatite δ¹⁸O values have long been used for paleotemperature reconstructions under the assumption that phosphate precipitated in equilibrium with seawater or that conodont body- water was isotopically similar to ambient seawater. However, studies on modern sharks and marine mammals demonstrate that physiological processes can significantly modify the oxygen isotope compositions of both body-water and bioapatite [1]. Consequently, absolute temperature estimates derived from conodont bioapatite may be influenced by animal physiology.

Here, we present the first triple oxygen isotope (δ¹⁸O–δ¹⁷O) analyses of Triassic conodont and fish bioapatite spanning the Smithian–Spathian boundary (SSB) in Oman and the latest Spathian of Timor. Additionally, we constrain the isotopic composition of lamprey body-water relative to ambient water, considering lampreys as one of the closest extant physiological analogues for conodont animals.

Although our data confirm a +1.8‰ shift in δ¹⁸O across the SSB, Δ′¹⁷O values are elevated relative to those predicted for equilibrium with seawater, suggesting that absolute paleotemperature reconstructions may be noticeably biased. The elevated Δ′¹⁷O compared to modern sharks and marine mammals indicates a distinct physiology. Elevated Δ′¹⁷O values are also observed in lamprey body-water relative to ambient water further suggest physiological similarities between lampreys and conodont animals. The influence of different physiological factors on the oxygen isotope composition of conodont body-water and bioapatite is explored by quantitative body-water mass-balance modeling, incorporating all oxygen in- and outfluxes.

[1] Feng, D., et al., 2022. Isotopically anomalous metabolic oxygen in marine vertebrates as physiology and atmospheric proxy. Geochimica et Cosmochimica Acta, 328, pp.85-102

Since the discovery of substantial stable isotope fractionation in the global low-temperature element cycle of Ba [1], its isotopic composition is increasingly used in oceanography and biogeochemistry to understand productivity induced biogeochemical element cycling, the input/fate of weathering solutions through (subterranean) estuaries, benthic-pelagic coupling, and the formation of sedimentary geochemical signals [2,3]. This includes both, modern and paleo-systems.

We explored changes in dissolved Ba concentration and isotope fractionation reflected by vertical water column profiles at six stations taken on a transect between the Skagerrak and the Bothnian Bay in winter. Water depths, sampled with Niskin bottles, ranged between the surface down to 550 m, and include the euxinic Landsort Deep. Ba isotope data (d^137/134Ba), measured via MC-ICP-MS are compared to ICP-OES derived concentrations of SO₄, Si, P, and conservative elements. Ba concentrations measured with both methods agreed well. It was found that vertical and spatial differences are observed, with a coupled increase in Ba concentrations and d^137/134Ba values with decreasing salinity. Barite that formed in glacial clays from the reaction of downward diffusing SO₄ with Ba²⁺ desorbing from clay minerals shows isotope signatures similar to the dissolved inventory in the modern lower salinity range of the water column (Roeser et al., 2025). More knowledge about seasonality of riverine input and the role of salt water intrusion events is needed to fully understand the Ba isotope biogeochemistry of the Baltic Sea.

References:

[1]von Allmen K. et al. (2010) Chem.Geol.277

[2]Roeser P. et al. (2025) IAS-Spec.Publ.50

[3]Scholz F. et al. (2023) Front.Mar.Sci.10

Zirconium and Hf are strongly fractionated in modern seawater relative to their chondritic value due to preferential scavenging of Hf onto particle surfaces in low-temperature aqueous systems. Thus, Zr/Hf ratios are sensitive to water-mass age, circulation, and particle availability. The Zr-Hf-systematics in Precambrian oceans, however, remain poorly constrained but may provide a unique potential to trace ancient water mass evolution. Here, we compile published and new high-precision Zr-Hf data from Archean and Proterozoic banded iron and manganese formations (BIFs, MnFs) to evaluate the temporal evolution of seawater Zr/Hf and assess its applicability as a palaeoceanographic tracer.

Archean BIFs predominantly display near-chondritic Zr/Hf ratios, with only a few layers reaching values up to 75. Following the onset of the Great Oxidation Event, strongly super-chondritic ratios (>100) appear systematically within individual formations and are common at latest in the Neoproterozoic. The ~2.4 Ga Hotazel Formation exemplary shows the behaviour of Zr-Hf in ancient oceans: BIFs and MnF samples show a co-variation between Zr/Hf and Mn/Fe, where MnF samples exhibit Zr/Hf lower than the maximum Archaean value, suggesting preferential sorption of Hf onto Mn (oxyhydr)oxides. This process likely shifted seawater toward even more super-chondritic values, reflected in Zr/Hf > 75 in BIFs. This co-variation indicates a link between the particle-reactive cycling of Zr and Hf onto Mn (oxyhydr)oxides and the progressive oxygenation of marine environments.

The triple oxygen isotopic composition of animal body water (BW) is preserved in biominerals and principally records information from the hydrosphere, atmosphere and biosphere including animal physiology. We use this approach to study animal physiology of insects from the Atacama and Namib Desert (mainly Zygentoma and Coleoptera). We provide a framework to identify and quantify oxygen (H₂O, O₂, CO₂) fluxes into and out of insects. Our main goal being identification and quantification of the respective water sources.

Insect body water was extracted in the field without altering its primary isotopic composition using CaCl₂ [1]. Our results show a wide range of δ¹⁸O_BW and δ¹⁷O_BW reflecting the different water strategies. The famous fog basking beetles from Namibia mainly rely on condensed fog on their cuticular surface, exhibiting δ¹⁸O_BW of 2 ‰. Meanwhile less adapted darkling beetles with access to wet food but no access to fog exhibit a heavy δ¹⁸O_BW of 19 ‰. For Atacamus sp., a xerophilous silverfish relative from the Atacama, our measured light δ¹⁸O_BW of -5 ‰ indicates active water vapour uptake from undersaturated air. Combined with δ¹⁷O_BW ratios we model and quantify the proportion of all potential water source which includes a large portion of metabolic water produced from dry biomass and air O₂.

These results highlight the potential of triple oxygen isotope systematics to resolve the relative proportion of competing water flux pathways in Arthropoda, with broader implications for isotope-based studies in ecohydrology and paleoclimate reconstruction using biominerals.

[1] El-Shenawy et al., 2024. RCMS 38, e9646.

The evolution of ocean chemistry through deep time is tightly linked to crustal alteration, hydrothermal cycling, climate, and early habitability. Oxygen isotope ratios in chemical sediments, especially cherts, have long been used to reconstruct ancient seawater temperatures and seawater δ¹⁸O. However, the decrease in chert δ¹⁸O values with age remains controversial, with interpretations ranging from hot Archean oceans with near-modern seawater δ¹⁸O to cooler oceans with strongly ¹⁸O-depleted seawater.

Here we present new oxygen isotope data from well-preserved 3.4 Ga banded cherts of the Tomka Formation, Daitari Greenstone Belt, Singhbhum Craton, India. These samples display among the lowest δ¹⁸O values reported for Archean cherts, reaching +7.5‰. Interpreted using δ¹⁸O systematics alone, such values imply either very high seawater temperatures or highly ¹⁸O-depleted seawater, both difficult to reconcile with current thermodynamic and geodynamic constraints on early Earth seawater evolution.

Triple oxygen isotope (Δ’¹⁷O) analyses provide a way to resolve this ambiguity. Our Δ’¹⁷O data show that the cherts do not simply record equilibrium precipitation from seawater. Instead, they preserve a multifaceted oxygen isotope signature shaped by diagenetic evolution, changing pore-fluid oxygen isotope compositions, and temperature-dependent exchange with seawater-derived fluids. This complexity cannot be resolved from δ¹⁸O values alone, but requires all three stable oxygen isotopes. Our results demonstrate that low δ¹⁸O values in Archean cherts do not necessarily require extremely hot or strongly ¹⁸O-depleted oceans, highlighting triple oxygen isotopes as a robust framework for reconstructing Archean ocean chemistry.

Metal-silicate segregation is a fundamental process in planetary differentiation, controlling core formation, siderophile and chalcophile element partitioning, and the thermal evolution of terrestrial bodies. However, during the later stages of magma ocean crystallization, the ability of metallic liquids to migrate along complex polymineralic grain boundaries remains poorly understood. This is especially important for the Moon, where the small core size (~1-4wt.%) implies limited metallic melt during differentiation. If connectivity was poor in crystallising cumulates, residual Fe-Ni-S melt may have been trapped within the mantle, affecting element distribution and the completeness of core formation.

Assessing whether metallic melt can form interconnected pathways in such systems is therefore critical. Metallic melt mobility is commonly described using a single effective dihedral angle, assuming uniform wetting behaviour, yet natural interiors are polymineralic, raising the question of whether bulk parameters adequately reflect melt migration.

We investigate the topology and wetting behaviour of Fe-Ni-S melt in lunar-relevant polymineralic silicate matrices using multi-anvil experiments at 3-4 GPa. Melt distribution is characterised in three dimensions by X-ray microtomography, and interfacial properties are quantified through pair-specific apparent dihedral angle measurements.

Across all conditions, including metal fractions up to 16 wt.%, the metallic phase remains predominantly disseminated to weakly interconnected, with no evidence for a stable percolating network. Apparent dihedral angles are consistently high (median >90-100°), indicating globally non-wetting behaviour. Despite local variability between mineral pairs, results suggest inefficient melt drainage and partial metal trapping in the lunar mantle, consistent with the observed depletion of siderophile elements in lunar basalts.

Amphibole represents a highly important hydrous mineral phase in a variety of magmatic systems. Despite its crucial role in the differentiation of mafic and intermediate magmas (e.g. [1]) and despite frequent observations of chemically zoned amphibole crystals in volcanic rocks (e.g. [2]), the diffusion rates of most key elements in amphibole have remained surprisingly unexplored [3].

Here, we aim to investigate the diffusion rates and diffusion mechanisms of Li in amphibole by conducting diffusion couple experiments in rapid heat/rapid quench cold seal pressure vessels. For this we prepared crystal cubes (2x2x2 mm) from a cm-sized actinolite crystal which was previously characterized via femtosecond-laser ablation-sector field-ICP-MS (fs-LA-SF-ICP-MS). The diffusion couple consists of such a crystal cube in contact with an amphibole glass cube synthesized from powdered material of the same actinolite crystal and doped with ~100 µg/g Li. Diffusion experiments are run at temperatures between 600 °C and 900 °C and at a pressure of 100 MPa for time intervals sufficient to produce Li elemental and isotopic diffusion profiles in the crystal cubes. The profiles will be analyzed using fs-LA-SF-ICP-MS and fs-LA-multicollector-ICP-MS. The combined investigation of Li elemental and isotopic diffusion is highly suitable to explore the diffusion mechanisms of Li in amphibole, i.e. whether it occurs along interstitial- or lattice sites or both (cf. [4]).

References:

[1] Cawthorn & O'Hara (1976), AJS 276, 309-329.

[2] Rowe et al. (2008), JVGR 178, 593–607.

[3] Cherniak & Dimanov (2010), RevMinGeochem 72, 641-690.

[4] Richter et al. (2014), GCA 126, 352–370.

Nominally anhydrous minerals (NAMs) can incorporate ppm to wt% levels of H₂O in the form of H-related defects within their crystal lattice. Hydrogen incorporation affects mineral properties such as seismic velocities and electrical conductivity, contributing to geophysical anomalies in the Earth’s interior. High-pressure silica polymorphs, stishovite (rutile-type) and post-stishovite (CaCl₂-type), constitute ~25 vol% of subducted oceanic crust at lower-mantle conditions and exhibit the highest water storage capacity among lower-mantle NAMs. Although wt% levels of H₂O were reported in both Al-free and Al-bearing systems, accurate H₂O quantification remains challenging due to limited intercalibration between analytical methods.

Here, we synthesized a suite of H,Al-bearing stishovite and post-stishovite samples and characterized them using FTIR, nanoSIMS, X-ray diffraction, and solid-state NMR. Infrared molar absorption coefficients derived from absorption bands between ~2670 and ~3350 cm^-1 and nanoSIMS-derived H₂O concentrations are significantly lower than previously reported and show a moderate dependence on H and Al contents. The unit-cell volume correlates primarily with Al and appears insensitive to the Al/H ratio. Furthermore, we investigated the effect of Al+H incorporation on vibrational properties using Raman spectroscopy and FTIR at high pressures up to 45 GPa in diamond anvil cells. We find that, unlike in pure SiO₂, the Raman-active soft mode changes slope well into the stability field of post-stishovite. Concurrently, the intensities of the infrared-active O-H bands between 2900-3350 cm^-1 decrease, and a new broad band appears at lower wavenumbers. These findings suggest that the crystallographic phase transition and changes in H-bonding are decoupled and occur at different pressures.

Redox processes and volatile-element cycling in subduction and mid-crustal zones remain poorly understood. Elucidating redox reactions in rock-forming silicate minerals is essential for accurately modeling lithospheric electrical conductivity. Amphiboles (AB₂C₅T₈O₂₂W₂) are major constituents of subduction-zone lithologies. Raman studies have shown that Fe²⁺-bearing OH-dominant amphiboles undergo reversible temperature-induced oxidation and dehydrogenation, forming mobile polarons (delocalized e⁻ coupled with polar phonons) and H⁺, leading to polaronic conductivity and H⁺ diffusion (Della Ventura et al., 2018; Mihailova et al., 2022; Bernardini et al., 2025).

Magnesio-hornblende is of particular interest as a representative of the abundant ^TAl-containing Ca-amphiboles. Yet the influence of tetrahedrally coordinated Al on redox processes remains unexplored. Here we present the results from our study on charge-carrier activation and thermal stability in magnesio-ferri-hornblende by in situ high-temperature Raman spectroscopy. The sample composition was determined by wavelength-dispersive electron microprobe analysis:

^A(Na_0.12K_0.075)^B(Ca_1.816Na_0.098Mn_0.086)^C(Mg_3.396Fe³⁺_0.769Fe²⁺_0.550Al_0.217Mn2+_0.029Ti_0.025Zn_0.015)^T(Si_6.917Al_1.083)O₂₂^W((OH)_1.508F_0.416O_0.049Cl_0.026).

Experiments were performed in air and under vacuum (~10^-4 Pa) to simulate O_2-poor conditions. In both cases the sample was stable up to 1400 K. In air, temperature-induced phonon anomalies indicate Fe²⁺→Fe³⁺ oxidation, with the onset of e- delocalization at 1000 K coupled with reversible H⁺ delocalization at 1200 K. Under vacuum, these threshold temperatures are shifted by ~150-200 K towards higher values. Strong direction-dependent resonance Raman scattering was observed at 1150 K under vacuum and at 1050 K in air, revealing aligned polaron dipoles, a precondition for anisotropic polaronic conductivity. Indeed, direct-current electrical conductivity measurements with the electric field along and normal to the amphibole I-beams confirmed strong conductivity anisotropy.

Chondrules are among the oldest solid materials in the solar system and serve as key recorders of early solar nebula processes [1]. In particular, rare inversely zoned (IZ) chondrules provide valuable insights into atypical formation pathways that remain poorly understood. This study presents a combined chemical and structural investigation of IZ chondrules using energy-dispersive X-ray spectroscopy (EDX), light microscopy, backscattered electron imaging (BSE), and Raman spectroscopy. IZ chondrules are characterized by a pyroxene-dominated core surrounded by an olivine-rich rim [2]. The olivine exhibits elevated iron contents (Fa39–41), significantly higher than in most common chondrules. The core typically consists of radially arranged pyroxene. We propose that minor variations in the SiO₂ content of chondritic melts can drive the development of inverse zoning. During pyroxene crystallization at cooling rates of approximately 500-2500 K/h [3], the residual melt becomes progressively depleted in SiO₂. This shift in melt composition alters phase equilibria, promoting the crystallization of Fe-rich olivine and resulting in the formation of an olivine rim around a pyroxene core. These findings suggest that IZ chondrules formed under specific physicochemical conditions in the early solar system, reflecting localized variations in melt composition and crystallization pathways.

[1] Scott, A. E. (2003) Chondrites and their components, Treatise on geochemistry, 1, 711.

[2] Joseph, F., et al. (2025). Petrographic and geochemical analysis of inversely zoned chondrules. Meteoritics & Planetary Science, 60(8), 1785-1797.

[3] Libourel, G. and Portail, M. (2018) Chondrules as direct thermochemical sensors of solar protoplanetary disk gas, Science advances, 4(7), eaar3321.

This study addresses a fundamental challenge in environmental geochemistry: how to reliably map trace metal contamination in heterogeneous terrains where conventional sampling and laboratory analyses are spatially limited and economically restrictive. We develop a generalizable, spectroscopy-driven learning framework that integrates VIS–NIR–SWIR reflectance data (350–2500 nm) with multiple regression models (ANN, SVR, PLSR) to quantify how preprocessing governs predictive performance for trace metals. Using 110 soil samples and rigorous validation (10-fold cross-validation and independent testing, n = 25), we show that predictive performance is element-dependent, with highest reliability for cadmium (R²ₚ ≈ 0.92; RPD > 3), while lower accuracy for arsenic, chromium, and copper reflects variability in mineral–metal coupling strength. The key innovation lies in formalizing proxy-based environmental inference as a transferable modeling paradigm, where trace metals spectrally inactive are estimated through their associations with mineralogical carriers (e.g., iron oxides, clay minerals). This reframes soil spectroscopy from direct detection to relationship-driven prediction, explicitly accounting for context dependency and confounding effects. By coupling machine learning outputs with geostatistical interpolation (RMSE ≈ 0.82–1.07), the framework produces spatially continuous contamination fields that resolve localized hotspots consistent with geological structure, without assuming causality. Beyond this case study, the framework provides a scalable global template for screening-level environmental monitoring, enabling rapid prioritization of sampling, early identification of contamination risk zones, and cost-efficient deployment in data-limited regions. This establishes a methodological bridge between high-resolution laboratory geochemistry and large-scale environmental decision-making, with direct implications for sustainable land management and contamination risk assessment worldwide.

The increasing use of Raman spectroscopy in planetary science has established the technique as a key tool for the non-destructive characterization of lunar materials. Raman analyses enable rapid identification of mineral phases, volatiles, hydration signatures, and potential alteration products, making the method highly relevant for both laboratory investigations and future in-situ lunar exploration. However, the lack of a standardized and interoperable Raman spectral database for lunar materials remains a major limitation for data comparability, instrument calibration, and autonomous spectral interpretation during space missions.

This study presents the development of the MSM-MRD (Mineralogische-Staatssammlung-München-Mineral-Raman-Database), a comprehensive Raman spectroscopy database dedicated to lunar geology. The database integrates spectral datasets from lunar meteorites, lunar analog materials, and reference minerals acquired using both laboratory-grade and portable Raman systems. Each spectrum is linked to extensive metadata, including instrumental parameters, environmental conditions, and mineralogical context, ensuring reproducibility and cross-platform interoperability.

A major focus of the project lies in harmonizing measurements between high-resolution laboratory instruments and portable handheld Raman devices envisioned for robotic and crewed lunar missions. The database further provides a foundation for machine-learning-assisted spectral classification and adaptive calibration approaches capable of compensating for environmental effects such as temperature variations, regolith scattering, and reduced instrument stability under lunar surface conditions.

Beyond mission support, MSM-MRD aims to establish an open-access framework for planetary spectroscopy, fostering international collaboration in lunar science, instrument development, and planetary exploration. The project contributes to the advancement of autonomous analytical capabilities required for sustainable future operations on the Moon and beyond.

Well-established schemes for geochemical proficiency testing already exist, such as GeoPT, organized by the International Association of Geoanalysts (IAG) for laboratories that routinely analyse rocks. Recently, however, the need to include mineralogical composition in proficiency testing has been recognized, as mineralogy can significantly influence the choice of geochemical methods and their results. We are therefore developing a new mineralogical proficiency testing scheme (Min-PT) designed for laboratories that use quantitative XRD and automated mineralogy (AM) methods based on SEM or µ-XRF. The first round of Min-PT will be paired with the use of the same test material in the GeoPT programme so will uniquely provide the organisers with both classical bulk analysis and mineralogical compositions. For the initial rounds, five rock types were identified of which one material was characterized in detail to define suitable parameters such as particle size, complexity, and homogeneity. A narrow grain size fraction (38–150 µm) was produced by grinding and sieving, resulting in 20-30 kg of sample material. Although not representative of the original rock, this material is suitable for both GeoPT and MinPT proficiency testing schemes. All samples were characterized in detail, as for the example shown: an igneous rock from the Wurzen-Formation (Wurzen α-ignimbrite), where mineralogical, geochemical, grain size distribution investigation and other methods were applied. This material was also used to conduct homogeneity and splitting tests. It is intended to conduct several parallel GeoPT-MinPT rounds, also with complex rocks in later stages.

Pre-registration is now possible, please send your contact details to MinPT@hzdr.de

Laser Induced Breakdown Spectrometry (LIBS) is an analytical method that is used in various scientific fields including geology. Since sample preparation is not essential for LIBS, it also finds application under extreme conditions like on Mars and in the deep sea. However, major challenges of LIBS include matrix effects based on the sample and shot-to-shot variations during analyses. In this study, the classification of minerals from seafloor massive sulfide occurrences was investigated based on LIBS data from two different devices. These devices mainly differ in spectral range and resolution, and in laser spot size: 285­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­–960 nm with 21–70 pm resolution and 210–1000 nm with 47–222 pm resolution, respectively, and laser spot sizes of ~ 200 µm and ~ 75 µm, respectively. One device was employed to analyze relatively pure sulfide and silicate minerals. The other device was used to map sections of massive sulfides and mafic rocks. Linear and non-linear multivariate models were evaluated on the results of the analysis using cross validation and a separate sample set also containing monominerals, microcrystalline massive sulfide mineralization, and associated basaltic host rocks. This study demonstrates a stable processing workflow to create a databank that is optimal for classification purposes. In general, the non-linear models performed better compared to the linear models. The best results were obtained with k-Nearest Neighbors, Random Forest, and Artificial Neural Networks. This work was carried out ahead of underwater measurements under laboratory conditions.

A 70 cm long core section of UG2 Chromitite from the Karee mine from the Critictal Zone of the Bushveld complex was investigated in detail by µEDXRF scanning in 20µm steps. The results obtained show an extreme variety in mineral chemistry within this core. State of the art automated mineralogy based on µEDXRF approved by LA-ICP TOF-MS mapping and by EPMA single point analysis and chemical mapping elucidates the chemical complexity of chromite and silicates. Contrasting pattern of chromites are related to poikilitic hosts such as plagioclase, pyroxenes, phlogopite or dense chromitite schlieren differing in chemistry essentially in Cr#, Mg#, and Ti content, in grain size from host to host, but showing chemical gradients and grain coarsening from core to rim within poikilites at contacts to phlogopite zones. Poikilitic host were segmented automatically in the core sequence and chemistry of individual poikilites and hosted chromites were extracted showing distinct chemical variation within the core section on a larger scale. The results show that continuous µEDXRF scanning and subsequent automated mineralogy combined with automated textural analysis is an excellent tool to substantiate individual chemical signature of all phases within a thin section, and along a chromitite profile, and to unravel the complex textural and chemical patterns.

Density and viscosity govern the transport of silicate melts in Earth’s interior, yet both properties are rooted in short- and medium-range atomic structure. Element-specific X-ray Raman scattering (XRS) yields near-edge, XANES-like spectra through non-resonant inelastic scattering, with sensitivity to coordination in laser-heated diamond-anvil cells at high temperatures. As the principal network former in silicates, silicon dioxide (SiO₂) is therefore a natural benchmark for high-pressure–temperature melt physics [1,2]. We report in situ XRS at the Si L-edge and O K-edge in a laserheated diamond anvil cell, tracking the transformation of α-quartz into the high-pressure polymorphs coesite and stishovite. Along this transition path, edge-specific spectra resolve systematic changes in Si–O bonding, illustrating how XRS can fingerprint coordination in dense silica polymorphs. Experiments at ESRF beamline ID20 employed a power-stabilized 120 W CO₂ laser with parabolic-mirror focusing [3]. Stable heating for up to 8 h at 26 GPa and ∼2300 K, verified by pyrometry and in situ diffraction, demonstrates the long-term stability required for count-limited synchrotron measurements. These results establish a platform for XRS studies of silicate structure relevant to the deep Earth. We further outline planned experiments combining aerodynamic levitation, CO₂ laser heating, and a 1070 nm ytterbium laser to extend the approach to metallic and other optically challenging samples.

This work is supported by the BMFTR projects 05K22PE2, 05K22OF1, 05K25PE1 and 05K25OF1.

[1] Sanloup, C., et al. Nature 503.7474 (2013); [2] Murakami, M., Bass, J.D., Phys. Rev. Lett. 104.025504 (2010); [3] Spiekermann, G., et al. High Press. Res. 41.2 (2021)

Nitrogen possesses a complex phase diagram with more than 15 known solid phases [1] spanning both the molecular and non-molecular regimes. Studying its behavior under high pressure provides important insights into molecular bonding, structural stability, and possible routes toward novel high-energy-density materials. Additionally, nitrogen plays an important role in planetary science, as it is a major component of icy planets and moons.
In this study, we explore the pressure-dependent structural and electronic evolution of nitrogen using a combination of X-ray Raman scattering (XRS), X-ray diffraction (XRD), and optical Raman spectroscopy performed in diamond anvil cells. The measurements were carried out at the ID20 beamline of the European Synchrotron Radiation Facility (ESRF).
The investigated pressure range extends from ambient conditions up to 80 GPa and includes the liquid phase together with the molecular solid δ-, δ*-, ε-, and -phases. Significant pressure-induced changes are observed in the nitrogen K-edge XRS spectra, particularly in the π^*, σ^*, and continuum regions, reflecting modifications of the local electronic structure and intermolecular interactions.
To interpret the experimental results, we compare the spectra with calculations based on ab initio molecular dynamics simulations. The simulations reproduce the major spectral features and indicate restricted molecular rotational dynamics within the ε-phase. Complementary XRD and Raman spectroscopy measurements provide additional information on the structural evolution and phase stability throughout the investigated pressure regime.
This work was supported by the BMFTR projects 05K22PE2 and 05K22OF1.
[1] Turnbull et al., Nat. Commun. 9, 4717 (2018).

We present results obtained by X-ray micro-computed tomography, electron probe micro-analysis, and laser ablation inductively coupled plasma mass spectrometry mapping to elucidate prograde processes associated with the crystallization of a garnet population in a pelitic schist from the Kalak Nappe Complex (Scandinavian Caledonides, Arctic Norway). Systematic variations in the major component zoning of the analyzed grains support garnet growth during prograde metamorphism. Integration of major element chemistry and microstructural properties (grain shape, size, and distribution) suggests that growth rates were anisotropic and interface-controlled, with a positive correlation between grain size and relative growth rates. Similar concentration and spatial patterns for transition (Sc, Co, V, Ti) and rare earth elements (Gd to Lu) exist across differently sized grains, except at their cores. Numerical simulation of garnet crystallization suggests prograde growth over an interval of approximately 60°C and 1 kbar until 570 °C and 4.5 kbar. Whereas different length scales of major and trace element equilibration typically manifest in their decoupled distribution patterns within garnet grains, our dataset suggests the equilibration of major and trace elements in the intergranular medium during most of the garnet growth period. According to our results, trace element equilibration occurred at conditions as low as the garnet-zone grade and at least at the cm-scale, exceeding distances of heterogeneities observed in the rock, therefore, providing insights into the trace-element transport capacity of the rock’s intergranular medium. We suggest that this scenario is likely in rocks that underwent sufficiently slow heating rates (1°C/Myr) during prograde metamorphism.

Garnet is a common rock-forming mineral, and is one of the principal sources of petrological information over a variety of geological settings. The recent development of in-situ Lu-Hf garnet dating via LA-ICP-MS/MS equipped with a reaction-cell and using NH₃ for resolving isobaric interference of Lu on Hf opened new opportunities for dating metamorphic, tectonic, and ore-forming processes. It side-steps the need for time-intensive chemical procedures and allows in-situ dating of garnets within petrographic context. We present the first results of successful Lu-Hf garnet dating obtained at the Ruhr-University Bochum, performed on metabasic and metasedimentary samples from Uruguay and NE Brazil, respectively. The analyses were conducted using an Agilent 8900 triple-quadrupole mass spectrometer connected to an ESI NWRimageGEO ArF excimer laser, and using GWA-1 and GWA-2 as primary and secondary reference garnets. The uncertainty of the obtained ages varies from sample to sample and can be as low as 2%. It is highly dependent on the number of analyses performed and on the presence or absence of Lu zoning in garnets. Thus, detailed petrographic and mineral-chemical characterization of the dated crystals vastly improves the chances of obtaining successful ages. Garnet-bearing amphibolites from Uruguay record both Paleoproterozoic and Neoproterozoic ages that agree with the main metamorphic events in the study area, and reflect the method’s potential for reconstructing polyphase tectonic histories. Garnets from metapelites in NE Brazil record a surprisingly long-lasting garnet crystallization history over tens of Myr in the Neoproterozoic, and might be sensitive to trace-element mobility induced by garnet break-down.

Carbonatites are rare, igneous rocks composed of more than 50% carbonate minerals. Despite their rarity, carbonatites play a disproportionately important role in economic geology (Yaxley et al., 2022). Geochemically, carbonatites are highly enriched in incompatible elements such as rare earth elements (REE), niobium (Nb), phosphorus (P), or fluorine (F). Nb has been mined at Catalao (Brazil) for decades and this deposit contains more than 40% of the world's Nb supply (e.g., Cordeiro et al. 2011). Whilst most of the previously mined ores have been completely altered, only recently the open pit mine at Boa Vista (Catalao II) has reached fresh carbonatite.

Here we present microanalytical results of unaltered carbonatite sample from the Boa Vista Mine, Catalao II (Brazil). The minerals of the samples were analysed by EPMA, conventional single spot LA-ICPMS analyses but we also produced laser ablation trace element maps using a Teledyne Iridia laser system coupled to a Thermo ICAP quadrupole ICP-MS. We use the following analytical procedures in our labs: (1) JEOL Hyperprobe: major element maps and BSE imaging. (2) Transfer of coordinates to the Laser Ablation-system, programming the trace element map. (2) HDIP software to identify crystals and for quantification. (3) A custom Python script that precisely aligns EPMA with LA-ICP-MS maps to generate fully quantitative major and trace element maps.

We will present the analytical results of the individual mineral phases, the element partitioning between the different mineral phases, and bulk ore metal distribution of the entire sample.

The novel, non-commercial software tool G.O.Joe (Altenberger et al. 2024) is designed to facilitate the calculation of trace element mass fractions in solid samples obtained by LA-ICP-MS analysis. It is written in the Dart programming language using the Flutter framework and operates entirely as a web-based application (i.e., no installation required). Since the data processing is performed on the user’s computer, there is no need to upload data to the G.O.Joe-server, maximizing data security. In addition to enabling the quick and efficient processing of large datasets, G.O.Joe includes various optional interference corrections methods.

G.O.Joe’s intuitive user interface simplifies the workflow during data evaluation, allowing for straightforward selections of peak- and background signals, importation of instrument settings, reference material compositions, and mass fractions of the internal standard to convert the measured raw signals into element mass fractions. The software´s key advantages include implemented corrections for isobaric interferences and abundance sensitivity.

The capabilities of G.O.Joe are demonstrated through the processing of two case studies, including trace element analyses of tungstates (e.g., scheelite) and silicates (e.g., garnet). In conclusion, G.O.Joe is a time-efficient, transparent and easy-to-use software tool that appeals to both experienced LA-ICP-MS users as well as newcomers to LA-ICP-MS data analysis. More details and the latest version of G.O.Joe are available at the following link: https://www.gojoe.software

References

Altenberger, F., Krause, J., Auer, T., Auer, A. Berndt, J (2024) G.O.Joe: A new non-commercial software tool for the processing of LA-ICP-MS trace element data, Geostandards and Geoanalytical Research., 49, 2, p. 281-294.

The radiogenic Hf isotopic composition (¹⁷⁶Hf/¹⁷⁷Hf) in zircon is a critical tracer in isotope geochemistry. However, the accuracy of in situ Hf isotope analysis is often compromised by isobaric interference from ¹⁷⁶Yb on ¹⁷⁶Hf, particularly in zircons with high Yb/Hf ratios (¹⁷⁶Yb/¹⁷⁷Hf > 0.03). The limited availability of reference materials (RMs) with elevated Yb/Hf ratios for instrument optimisation and quality control remains an important challenge. In this study, three potential zircon RMs with a range of Yb/Hf ratios (ML-2, US-2, and MADA) were characterised for in situ Hf isotope analysis. These materials are demonstrated to be homogeneous at the micrometre scale in Hf isotopic composition by laser ablation MC-ICP-MS, with ¹⁷⁶Yb/¹⁷⁷Hf values clustered at <0.01, 0.03–0.11, and 0.08–0.16, respectively. The results show that high-Yb zircons can exhibit substantial bias and increased scatter in measured ¹⁷⁶Hf/¹⁷⁷Hf during in situ analysis, whereas commonly used low-Yb RMs (e.g., PLE, Mud Tank, and Tanz) yield accurate and consistent results. Introducing N₂ into the central gas flow expands the axial ion beam distribution, thereby stabilising mass bias and enabling accurate ¹⁷⁶Hf/¹⁷⁷Hf determination even for high-Yb/Hf zircons. It is therefore strongly recommended that RMs with comparable or higher Yb/Hf ratios than the unknown samples be used for instrument optimisation and quality control during in situ Hf isotope analysis of high-Yb zircons, and that sufficient addition of N₂ be applied, as it has proven highly effective under such analytical conditions.

Mafic rocks often leave few options for obtaining their igneous formation age, especially when metamorphosed. In the absence of zircon, apatite is the only isotopically datable mineral in common metabasites that usually remains thermodynamically stable over the entire P-T path. Recent analytical advancements involving laser ablation inductively-coupled plasma tandem mass spectrometry (LA-ICP-MS/MS) enable in-situ Lu-Hf dating of apatite, which benefits from the higher closure temperature of Lu-Hf (675-750°C) compared to U-Pb in apatite (350-550°C), and low Lu-Hf mobility in fluids. The method relies on resolving the isobaric ¹⁷⁶Lu/¹⁷⁶Hf interference by utilizing an NH₃-He reaction gas. During metamorphism, apatite can undergo deformation and/or fluid-mediated recrystallization, which potentially compromises its ability to retain protolith age information, though this may sometimes enable dating recrystallization events. The preservation potential of relic igneous apatite and its Lu-Hf age information as a function of the intensity and modes of deformation and/or metamorphism remain poorly explored.

We aim to change this by applying in situ Lu-Hf dating to variably deformed metabasites from the Steinhügel metagabbro of the Münchberg Massif (N Bavaria, Germany). This ~0.5 km² metagabbro body displays well-preserved igneous textures in its center, while grading into progressively foliated garnet amphibolites towards its margins. Pilot Lu-Hf apatite data from undeformed central Steinhügel samples agree within uncertainty with a previously reported 496 ± 3 Ma (U-Pb zircon) intrusion date and predate 383-378 Ma (K-Ar Amphibole) amphibolite facies metamorphism (11 kbar, 600°C). Further Lu-Hf data will unravel how well this age information is preserved in increasingly deformed Steinhügel lithologies.

The rocks of the southern Hunsrück (SW Germany) consist predominantly of Devonian quartzites and slates which have been deformed in a fold-and-thrust-belt during the Variscan orogeny. The orogenic deformation led to NE-SW-striking folding and cleavage development under low-grade metamorphic conditions. In the southern area of the Hunsrück, a secondary cleavage has developed.

Along two N-S trending profiles near Idar-Oberstein, sampling and detailed structural mapping were carried out. The mapped area is characterized by mostly quartzite anticlines (Taunusquarzit and Zerf formation) surrounded by synclines composed of slates of the Hunsrückschiefer Group. Cleavage formed through a combination of mineral rotation or oriented growth and pressure solution-precipitation processes, and its intensity varies significantly among the clastic metasedimentary rocks.

Anisotropy of magnetic susceptibility (AMS) was used to characterize the rock fabric, revealing that magnetic fabrics are strongly controlled by mineralogy and lithology. Magnetic susceptibility values range from -3 to 540 x 10^-6 SI units and generally correlate well with the degree of anisotropy (1.03<P<1.25). Quartzites preserve weakly overprinted sedimentary fabrics, with magnetic foliation parallel to the bedding and magnetic lineations distributed within these planes. In contrast, clay-rich metapsammites and slates show magnetic foliations parallel to the cleavage and variable magnetic lineations, interpreted as intersection, crenulation or stretching lineation depending on strain intensity.

The enhanced melting of ice bodies and desiccation of lakes due to modern climate warming induces the unloading of Earth’s lithosphere at numerous locations worldwide. We use numerical modelling to gain insights on the effect unloading has on the earthquake cycle of faults in continental interiors. In a series of experiments with both normal and thrust faults, we vary the magnitude and width of the load, the duration of unloading, the length of the interseismic phase, the viscosity of the lower crust, and the strain rate to capture low-strain and tectonically active settings. In all experiments, the faults respond to unloading by increased coseismic slip. For unloading phases equal to or shorter than the interseismic phase, the largest amount of slip occurs toward the end of the unloading period. If the load is removed completely during the interseismic phase, enhanced coseismic slip may also occur up to thousands of years after unloading. Generally, the increase in coseismic slip is most pronounced for large and narrow loads, long recurrence intervals, low viscosities of the lower crust, and low strain rates. Our findings suggest that climate-induced unloading has the potential to increase earthquake magnitudes, to shorten earthquake recurrence intervals and to increase the seismic hazard especially in low-strain regions.

Strain localization along mantle–crust transition zones plays a major role in lithospheric weakening, mantle exhumation, and formation of oceanic core complexes, yet the role of reactive interfaces in detachment development remains poorly constrained. The Neyriz ophiolite of southern Iran, interpreted as Neo-Tethyan supra-subduction oceanic lithosphere, preserves well-exposed mantle–crust transition assemblages around asymmetric peridotite-cored domes.

Autobrecciated mafic units locally overlie foliated lherzolites, indicating mantle exposure prior to or during mafic magmatism. A persistent reactive interface occurs along the mafic–ultramafic boundary in several parts of the ophiolite. In arc-side domains, focused melt migration generated orthopyroxene–plagioclase-rich reaction zones associated with melt segregation, hydration, amphibolitization, grain-size reduction, and amphibole-rich mylonitic fabrics. More evolved domains contain dioritic segregations, layered gabbros, plagiogranites, and localized melting of adjacent metapelitic lithologies. In contrast, trench-side domains record lower thermal flux, where interaction between peridotites and carbonate-bearing lithologies mainly produced skarn and calc-silicate assemblages. Although deformation also occurred there, strain remained localized within skarn-bearing zones and did not evolve into melt-assisted detachments comparable to those in hotter arc-side domains.

Petrography, whole-rock geochemistry, and EBSD data indicate progressive coupling between melt migration, hydration, recrystallization, and deformation, leading to rheological weakening and transformation of reactive interfaces into strain-localized zones interpreted as detachments. The Neyriz transition system therefore provides a field-based analogue for asymmetric mantle–crust interface evolution during mantle exhumation and development of oceanic core complexes. These observations may also aid interpretation of oceanic drilling sections, where reactive mantle–crust interfaces may be misinterpreted as primary gabbroic crustal units.

Canyon wall failure at submarine canyons are observed worldwide and pose a great hazard to the population living in coastal areas as tsunami waves can form if the canyon wall failure is sufficiently large. Also, smaller canyon wall failures can have devastating consequences to e.g., submarine infrastructure. Canyon wall failures at submarine canyons are often retrogressive, forming characteristic terraces and cauliflower headwall patterns. Palliser Canyon in New Zealand’s Cook Strait is a prime example of retrogressive failure and is therefore exemplary for canyon systems offshore New Zealand’s coast and globally. Understanding the conditions under which initial failure and subsequent retrogressive propagation occurs may help assessing the associated risks. An important parameter controlling the stability of the canyon wall is the mechanical properties of the canyon sediments. Here, we study sediments from Palliser Canyon (Cook Strait, New Zealand) by conducting shear vane tests and triaxial experiments on samples from gravity cores. The cores were taken from retrogressive terraces during the MAWACAAP cruise (SO310) on the German research vessel SONNE in February/March 2025. The experiments give insights into the strength and state of consolidation of the sediments. We identify weak layers and trace those along the scars using Parasound data. The experimental results will inform numerical models to constrain the influence of mechanical properties on canyon wall instabilities and retrogressive failure at Palliser Canyon.

Subduction zones are the principal nexus of geochemical exchanges that link Earth’s surface and interior. However, the relative contributions of slab-derived fluids, melts, and sediments during mass transfer between the subducted slab and mantle wedge remain debated. Molybdenum (Mo) isotopes have emerged as a promising tracer of subduction inputs because Mo is both fluid-mobile and redox sensitive. Arc lavas globally tend to exhibit elevated δ^98/95Mo relative to the depleted MORB mantle (DMM; e.g., Pontow et al., 2025), with Mo isotope fractionation commonly attributed to mobilisation of heavy Mo isotopes by slab-derived fluids, whereas isotopically light Mo is retained in rutile within the slab. Alternatively, subducted sediments (e.g., black shales) are also postulated to be an important source of heavy Mo isotopes (e.g., Freymuth et al., 2015).

The Central American Volcanic Arc (CAVA) exhibits pronounced along-arc geochemical gradients (e.g., Ba/La, U/Th, Nd–Hf–Pb isotopes) from southeast to northwest, interpreted to reflect either increasing slab-fluid contributions or changes in sediment input. This makes CAVA an ideal setting to evaluate the controls on Mo isotope systematics in subduction zones.

Here, we present Mo isotope data for basalt to basaltic-andesite lavas from Guatemala to Nicaragua, alongside back-arc lavas in Honduras and subducting Cocos Plate ocean crust and sediments. We assess whether Mo isotope variations correlate with established geochemical gradients and evaluate how slab inputs vary along and across the arc. These results provide new constraints on the relative roles of fluids, melts, and sediments in controlling arc magma compositions.

The elemental and isotopic composition of mantle-derived melts provide key insights into Earth’s physical and chemical state and evolution. However, in intracontinental settings, where melting primarily occurs near the lithosphere-asthenosphere boundary, it is often difficult to deconvolve signatures derived from the convecting mantle and those from the overlying lithosphere. In east Australia, Neogene volcanism is concentrated at the transition from thinner to thicker continental lithosphere. Volcanic fields coincide with elevated topography and slow asthenospheric shear-wave velocities, yet there is no evidence for a major plume or recent tectonic activity. Here, we present Sr-Nd-Hf-Pb isotope analyses of basanites and alkali basalts that record progressively increasing melt proportions from fertile lithologies closer to the step in lithospheric thickness. This trend is correlated with decreasing asthenospheric melt fractions. Fusible lithologies could either be derived from heterogeneities within the asthenosphere or from incorporation of refertilised continental lithosphere. In addition, some volcanic fields exhibit high Hf for given Nd isotope ratios, deviating from the global trend of oceanic basalts, and indicative of melting of previously depleted peridotite. Such melts can only be erupted if the same mantle region undergoes multiple melting episodes, strongly suggesting a role for ongoing, localised small-scale convection. Therefore, basalt isotope compositions confirm that intraplate volcanism across much of eastern Australia is induced by small-scale convective instabilities caused by the interplay of basal lithospheric topography and plate motion. Erupted lavas are mixtures of varying proportions of asthenospheric and lithospheric melts, but uniquely record melting of refertilised peridotite domains.

The Eastern Australian Potassic Suite (EAPS) is a ~700 km long, discontinuous Cenozoic volcanic chain forming the southern portion of the Cosgrove hotspot track. Compared with larger volume basaltic complexes along the eastern Australian seaboard, the EAPS occurs as low-volume, mafic, potassium-rich outcrops that erupted through lithosphere thicker than 120 km. Here, we re-evaluate these occurrences by combining whole-rock and mineral analyses to understand their petrology, mantle source enrichment, and melting processes. Whole-rock major, trace, and volatile element data show that EAPS chemistry varies between eruption centres, but that its potassium contents are exceptionally high compared with other mafic East Australian volcanism. Volatile element data show that EAPS lavas have nitrogen enrichments comparable to other lamproites and higher CO₂ contents, despite syn-eruption partial degassing. The trace element chemistry of the EAPS most closely resembles cratonic (anorogenic) lamproites, and trace element ratios indicate a highly enriched melt source that previously underwent silicate–carbonatite metasomatism. The most probable source for these lavas is a hydrous, phlogopite-bearing, olivine-poor assemblage originating in the garnet stability field (i.e. phlogopite-garnet pyroxenite). The high titanium and phosphorus concentrations suggest apatite and oxide minerals were also present in the metasomatised source. Our data record variations in mantle source mineralogy in an orogenic region adjacent to cratonic lithosphere. We suggest that prior incipient melts from the asthenosphere metasomatised the lithospheric source region, generating low-solidus domains that subsequently melted through conductive heating from underlying edge-driven convection and shear-driven upwelling.

Supra-subduction zone ophiolites like the Troodos Ophiolite are commonly interpreted as fragments of ancient fore-arc lithosphere and are therefore archives of subduction initiation and early mantle wedge evolution. However, their genetic link to modern fore-arc regions remains debated, partly because most studies have focused on volcanic sequences rather than the underlying mantle residues. The Troodos Ophiolite in Cyprus, a remnant of Late Cretaceous Tethyan oceanic lithosphere, provides an excellent opportunity to investigate this relationship from a mantle perspective.
Here, we combine petrographic observations, mineral major and trace element data, and first Hf-Nd isotope constraints from clinopyroxene separates of Troodos mantle peridotites. Major element compositions of olivine, spinel, clinopyroxene and orthopyroxene, together with trace element concentrations in residual pyroxenes, indicate variable degrees of mantle depletion. Spinel Cr# and pyroxene Al contents suggest melt extraction of approximately 10-19% in lherzolites, 16-20% in harzburgites and 18-20% in dunites. These estimates overlap with fore-arc and back-arc peridotites and are generally higher than typical abyssal peridotites. Light rare earth element enrichment in pyroxenes further points to pervasive melt-rock interaction.
Newly obtained Hf-Nd isotope data provide additional constraints on mantle source evolution, depletion and metasomatic overprinting. Together, the mineral chemical, trace element and isotope dataset suggests a complex history of high-degree melting, melt focusing and subduction-related melt-rock interaction.

The origin of placer gold in the Osa and Burica Peninsulas, Costa Rica, has been debated for decades. Two competing sources have been proposed: distal Miocene epithermal and porphyry systems of the Talamanca Cordillera (~75 km northeast) and local mineralisation within the Late Mesozoic - Early Paleogene basalts of the Osa Igneous Complex. This study integrates field mapping, petrography, whole-rock geochemistry, gold particle morphometry, EPMA, and LA-ICP-MS to resolve this longstanding debate.

Gold-bearing Osa Group conglomerates unconformably overlie hydrothermally altered basalts (prehnite-pumpellyite to greenschist facies) with accessory pyrite and chalcopyrite. Altered basalts contain anomalous Au (up to 178 ppb) and elevated As and Cu contents far exceeding MORB/OIB background values.

Morphometric analysis of gold particles yields a mean Cailleux Flattening Index of ~4, with a maximum of 9.5, indicating transport distances of ≤45km, ruling out a Talamanca source. EPMA data identify two gold populations. Type 1 particles are homogeneous electrum (Au 89-98 wt%, Ag 2-6 wt%), representing primary gold. Type 2 particles display Ag-depleted rims (Au 98-100 wt%, Ag 0.2-2 wt%), formed by supergene leaching. Sulphide and silicate inclusions in gold match those in Osa Igneous Complex basalts. LA-ICP-MS trace element analysis of gold cores reveals enrichment in chalcophile elements characteristic of mafic-hosted hydrothermal systems.

Collectively, our data support a local orogenic gold source within the Osa Igneous Complex, linked to metamorphic devolatilization during Paleocene-Eocene accretion of oceanic plateau basalts. This resolves a longstanding provenance debate and supports an orogenic model for gold mineralisation in southern Costa Rica.

The Palai-Islica deposit is a Miocene epithermal Au-Cu deposit located in the Almería Province, South-East Spain. It is hosted in calc-alkaline andesite, emplaced during the post-collisional extensional collapse of the Betic Cordillera and bound to the northwest by the Carboneras Fault Zone. The deposit was exploited for Pb and Cu during the 19th century; Drill core geochemistry records peak grades of 23 g/t Au, 110 g/t Ag and 8 wt% Cu in a high- and intermediate-sulfidation orebody. Previous work investigated the ore mineralogy, primary hydrothermal alteration zones and ore-forming fluids. However, a detailed understanding of the elemental mass balance in the magmatic-hydrothermal system is still missing. This study provides the first isocon-based mass balance and alteration zonation mapped from surface outcrops at Palai-Islica. The alteration zonation is characterised by a core zone of silicification, grading outward through a sericite-chlorite intermediate zone and a propylitic alteration in the distal zone, with pyrite being pervasive across all zones. Geochemistry shows a systematic depletion of Na, Mg and Ca and addition of K, Si and Fe towards the core zone. Hydrothermal replacement of plagioclase and mafic minerals by sericite causes Na, Mg and Ca loss and K-gain. Iron enrichment toward the core relates to multi-generational pyrite formation, while the Si-gain in the core zone reflects silicification by the mineralising fluids. Pyrite is the principal Au-hosting phase, linking Fe enrichment directly to Au mineralisation. The element mobility signatures quantified here provide exploration indicators within the Cabo de Gata volcanic belt and comparable epithermal systems.

Metamorphic devolatilization of metasedimentary and metavolcanic rocks at the greenschist-amphibolite facies transition is widely regarded as the principal source of fluids and metals for orogenic gold deposits. The devolatilization model describes how metamorphic reactions release water-rich fluids and associated volatiles (CO₂, S) that transport Au, Ag, and other metals. At temperatures > 600 °C, however, this model is challenged, because fluids can induce partial melting, thereby consuming the fluids and inhibiting hydrothermal deposit formation. Thermodynamic models suggest that serpentinized ultramafic rocks (e.g., komatiite) can generate Au‑bearing fluids up to the granulite facies, representing a potential source of fluids and metals for the formation of orogenic gold deposits.
We test whether ultramafic rocks produce Au‑rich fluids during prograde metamorphism. To this end, we investigate whole‑rock chemistry and mineralogy of 28 samples ranging from greenschist to granulite facies from Nunatak in SE Greenland and Tartoq, Isua, and Bjørneøen in SW Greenland. The production of metal-rich fluids upon metamorphic devolatilization is expected to be shown by a simultaneous decrease in the proportion of hydrated minerals (e.g. serpentine, talc, chlorite), volatile and metals content (e.g., Au, Cu, As, Sn, Te) in the samples at the greenschist - amphibolite and amphibolite - granulite facies transitions. Preliminary data show that the content of hydrated minerals decreases from greenschist (Tartoq) to amphibolite facies (Nunatak) in Greenland, suggesting production of metamorphic fluids that could contribute to orogenic Au deposits, such as the Storø gold deposit and the Tartoq gold prospect.

Porphyry-type ore deposits hold most of the global copper and molybdenum reserves. As these deposits are genetically linked to subduction zones, the possible sources of these metals can be narrowed to: The continental crust, the mantle wedge, or the subducting slab (further divided into the MORB part and the subducting oceanic sediment). Here, we study the partitioning of Cu, Mo, Zn and W between a synthetic subducting sediment and saline fluids at conditions corresponding to slab dehydration (600 – 700°C, 2.5 – 4.5 GPa) to determine whether these fluids can mobilize the metals and enrich them in primary magmas. For Cu and Zn, the bulk fluid/sediment partition coefficient (D^{fluid/sediment}) is lower than 1 for Cl-free runs. With saline fluids however, both elements immediately become mobile, reaching coefficients of up to 20 for Cu and up to 6 for Zn. Mo and W show minimal dependence on salinity and are highly mobile in aqueous fluids. Overall, our results show that Cl-bearing aqueous fluids are capable of mobilizing metals in the sediment and transporting them to the source of arc magmas. The contribution of sediments to the overall Cu enrichment is probably not particularly significant, since sediments are generally not enriched compared to other sources. However, since the subducting slab effectively provides a constant influx of metals, it may still be important to replenish the mantle wedge after repeated melt extraction. Molybdenum, however, is highly concentrated in some reduced sediments which may dominate the enrichment process.

Proterozoic massif-type anorthosites are relevant hosts for economic concentrations of Fe, Ti, V and P. The 916±11 Ma Hakefjorden Complex (SW Sweden) is an anorthosite-norite intrusion which formed through post-kinematic magmatism of the Sveconorwegian orogeny, broadly contemporaneous to the Tellnes ilmenite deposit. It comprises „ilmenite-rich leuconorite“ (IRL), enriched in ilmenite ± magnetite. Albeit not of economic interest, their distribution, texture and composition provide valuable insights into the crystallization sequence and petrogenesis of the IRLs.

Anorthosite occurs as individual megablocks within the norite, whereas Fe-Ti oxide enrichments form layers and vein-like structures. The Fe–Ti oxides of the IRLs are rounded and display cumulate textures with euhedral or poikilitic plagioclase and apatite, as well as poikilitic orthopyroxene and biotite. In IRLs and norites, Fe-Ti oxides exhibit complex subsolidus re-equilibration features, such as spinel crystallization at ilmenite-magnetite contacts, hematite exsolution within ilmenite and trellis-type lamellae in magnetite. In norite and anorthosite, Fe-Ti oxides are polygonal and partly skeletal. Pronounced alteration of ilmenite to rutile, hematite and titanite due to oxidation and/or hydrothermal fluids occurs in the anorthosite.

Micro-XRF element distributions maps were obtained to compare areas on thin-section scale to whole-rock XRF data, demonstrating a good agreement. Quantification of modal mineral compositions yields values of 34-62% for ilmenite in the IRLs. Overall, the crystallization sequence indicates that Fe and Ti became enriched in the magma following anorthosite formation. Subsequently, ilmenite-magnetite-plagioclase cumulates crystallized, while the residual melt formed the norite.

Carbonatites are major sources of rare‑earth elements (REE), niobium, and phosphorus, yet the timing, evolutionary history, and ore‑forming mechanisms, particularly of carbonatite complexes that have undergone metamorphic overprint, often remain poorly constrained. Metacarbonatite and meta‑fenite from the Jambil area, Pakistan, show conspicuous metamorphic replacement textures of primary magmatic minerals, which were investigated through detailed petrography, mineral chemistry, whole‑rock geochemistry, U‑Pb geochronology, and carbon-oxygen isotope analyses.

The protoliths of metacarbonatites are calcite carbonatites enriched in Nb, Zr, Ti, Ba, Th, and Sr, with high LREE/HREE ratios comparable to carbonatites worldwide. Their calcite δ¹³C and δ¹⁸O values suggest a mantle origin with minor low‑temperature alteration. Primary magmatic phases of carbonatite include calcite (Cal‑I), aegirine‑augite, albite, and accessory magnetite, ilmenite, apatite, monazite, and zircon, whereas late‑stage assemblages contain calcite (Cal‑II), biotite, and pyrochlore, the latter has intercalations of columbite and betafite. The potassic meta‑fenite, developed within the bordering paragneiss, hosts disseminated biotite–orthoclase veins with rutile and monazite; the latter of which has been replaced by an allanite-apatite corona. In‑situ U–Pb LA‑ICPMS dating reveals two distinct events: formation of magmatic monazite at ca. 477 Ma and its replacement by allanite‑apatite at ca. 21 Ma during the Himalayan orogeny.

These results demonstrate that the REE, Nb, and P enrichments are inherited from the primary carbonatite magma, while subsequent metamorphism mainly redistributes the elements and overprints the mineralogy, producing new REE-Nb-P carriers without net upgrading of the ore. The study also showcases the power of in‑situ dating techniques for unravelling the complex evolution of metacarbonatites.

Bangka and Belitung Islands are Indonesia’s principal tin-producing regions, hosting both placer and hard rock–hosted deposits. Despite extensive mining activity, geological knowledge on the architecture and origin of many deposits remains limited. This is particularly true for hard rock-hosted tin deposits, such as the Paku deposit on Bangka Island. Paku deposit is mined in an open-cast operation with approximately 12 kt of ore containing 0.03 wt% Sn produced in 2018. Because of the deep lateritic weathering, the mineralization is subdivided into two distinct zones: a shallower, intensively weathered oxide zone and a deeper sulfide zone. In a previous study of exploration drill cores from the sulfide zone, three paragenetic stages were identified: greisen-type Sn mineralization (stage 1), crosscut by veinlet and/or disseminated polymetallic sulfide assemblages (stage 2). Stages 1 and 2 are locally highly deformed and, finally, overprinted by supergene alteration was identified as stage 3.

Magmatic-hydrothermal mineralization at the Paku deposit overprints a metasedimentary host rock succession that has not been studied in much detail. This study, therefore, investigates host rock characteristics using drill core samples. Preliminary results indicate that the host rock succession comprises of metasandstone and metasiltstone as well as carbonaceous and pyritic shale that has experienced low-grade regional metamorphism. Locally, deformation is very intense with cataclastic and mylonitic structures abundant. Magmatic-hydrothermal mineralization is associated with intense deformation. Further work, including detailed geochemical analyses, is conducted to better understand the relationship between deformation and hydrothermal mineralization and to constrain ore-forming processes at the Paku deposit.

Mica schists of Bockau-Aue, Western Erzgebirge, host local tin (Sn) mineralization that predates the post-orogenic granites, but is younger than the deposition age of the protoliths ^[1], implying that Sn addition is not related to granite intrusions or to detrital input from the sediments. The protoliths of the schists are correspondents of voluminous, highly weathered (low Na, Ca, Sr) Early Ordovician shales. These shales have Sn contents up to 13 ppm ^[2], much lower than their metamorphic equivalent schists (50-250 ppm), implying that Sn was added during metamorphism. Cassiterite (SnO₂), the primary Sn mineral in the schists, occur in the prograde mineral assemblages as disseminations in biotite-rich bands and along margins of metamorphic quartz segregates, and locally as inclusions in Sn-rich biotite. A second, younger generation of cassiterite occur as inclusions within chloritized biotite, associated with retrogression of biotite.

Comparison of the chemical compositions of the Sn-rich schists with their protoliths ^[2] demonstrates that Sn addition during prograde metamorphism was parallelled by major additions of Si, Fe (and Li) and loss of K, Rb and Ba. The presence of cassiterite inclusions in prograde minerals of these greenschist facies schist demonstrates that Sn mobility may occur at relatively low temperatures. During retrogression of the schists, B and Si were added, whereas Sn was redistributed on the local scale.

[1] Romer, R.L., et al., 2022. Geology, 50(12), 1361–1365.

[2] Romer, R.L. and Hahne, K., 2010. Gondwana Research, 17(2-3), 236–253.

Carbonatites represent one of the major global sources of light rare earth elements (LREEs). During late-stage evolution primary carbonatitic melts are modified by hydrothermal processes, forming highly complex brine-melt systems. The structure and REE speciation in these high temperature melts remain poorly understood at the atomistic level due to the complexity of in situ experimental approaches. We investigate REE speciation in a model H₂O–Na₂CO₃–NaCl-REE brine-melt at 1000K with 4.55 wt% H₂O using ab initio molecular dynamics (AIMD) combined with well-tempered metadynamics to access the underlying free energy landscape. Enhanced sampling allows us to resolve coordination dynamics and ligand exchange processes beyond the timescale of AIMD. Our simulations show that REE complexes are dominantly stabilized by carbonate ligands (CO₃^2-), while chloride plays a secondary role in the first coordination shell. The results suggest a strong stabilization of REE-carbonate complexes under magmatic brine-melt conditions and provide molecular-scale insight into processes that may control REE mobility and fractionation during the evolution of carbonatitic systems.

Understanding the formation of Sn and Li deposits, where cassiterite (SnO₂) and Li-bearing micas are key ore minerals, is essential for developing robust ore-forming models that support efficient exploration. This study examines Sn and Li isotope systematics in granitic and greisen systems to constrain mineral crystallization conditions. Two contrasting settings are investigated: the melt-dominated rare-metal granite system of Argemela (Portugal) and the fluid-dominated greisen system of Sadisdorf (eastern Erzgebirge, Germany).

Tin isotope variations in cassiterite reveal two main processes controlling Sn mobility: Rayleigh fractionation as the dominant first-order process and a late-stage, local oxidation producing secondary signatures at the grain scale. A clear distinction between magmatic and hydrothermal cassiterites is observed: hydrothermal cassiterite from Sadisdorf commonly exhibits elevated W concentrations and negative δ^124/117Sn_3161a values in distal veins, whereas Argemela cassiterite is enriched in Nb and Ta, with early magmatic cassiterite displaying positive δ^124/117Sn_3161a values.

Complementary in situ analyses of Li-bearing micas were conducted using UV fs-LA-MC-ICP-MS to characterize Li isotope ratios at the grain scale. As a fluid-mobile element, Li isotopes may provide valuable insights into the transport medium and the evolution of the ore-forming conditions. Preliminary results indicate that micas from Sadisdorf display higher isotope ratios (δ^7/6Li_Lsvec = +1.2 to +6.59 ±0.21‰), consistent with preferential transport of ⁷Li in the fluid, while Argemela samples show lower signatures (δ^7/6Li_Lsvec = -1.44 ±0.22‰ to +0.51 ±0.18‰), in line with the interpretation that evolved residual melts preferentially retain lower δ^7/6Li values, when compared to the Li isotopic signature of fluids.

Pyrite is the most abundant sulfide on Earth and can be a major host for critical metals in magmatic-hydrothermal ore deposits. Despite pyrite’s ubiquitous nature, the fundamental partitioning behaviour of trace elements between ore-forming fluids and precipitating pyrite remains mostly unknown hampering its use as a quantitative fluid proxy. Here, we present siderite batch replacement experiments synthesizing hydrothermal pyrite from fluids with known trace element contents (1 ppm) at high water-rock ratios (~6000), weakly acidic (pH = 5), water-saturation pressure (5 – 40 bar), and ranging from 150 to 250 °C approximating ore-forming conditions of natural Carlin-type systems.

All experimental runs show near full replacement of siderite by pyrite (~90 %) and only minor marcasite (~10 %) by coupled dissolution and precipitation processes. High-resolution (~3 µm), quantitative trace element mapping by LA-ICP-MS reveals systematic zonation patterns with high trace element contents focused on the first replacement front in direct contact with the initial fluid. Using the initial fluid composition and the first ~30 µm of the newly formed pyrite we define the maximum pyrite-fluid partitioning coefficients (D pyrite/fluid) for Cd, Zn, Ni, Pb, Co, Cu, Tl, Se, As, Sb, Au and Ag. Systematic changes of pyrite trace element contents with temperature suggest a potential use as a geothermometer as known from other sulfides such as sphalerite. These temperature-sensitive findings and partitioning coefficients are key for using pyrite composition as a proxy for magmatic-hydrothermal fluids and provide the foundation for future quantitative modelling approaches to understand various natural pyrite-forming environments.

The mineralogy of Pb-Zn-Ag-rich epithermal vein infills in the Freiberg District is exceptionally well documented, quite in contrast to associated wall rock alteration. A detailed investigation was carried out in order to document the styles and age of wall rock alteration proximal to the epithermal veins. Host rocks considered in this study included medium- to coarse-grained Variscan augen gneisses (locally referred to as “grey gneiss”) and weakly metamorphosed mafic volcanic / subvolcanic rocks of presumed Devonian age from the northern part of the district. Both host rocks are cross-cut by narrow veins infilled by the typical galena-sphalerite-quartz-dominated mineral assemblage. Macroscopically visible wall rock alteration around the narrow veins is very variable in extent. Alteration halos are 0-20 cm wide in augen gneiss, but were found to exceed 1 m in width in a diabase intrusion. The alteration halo is always zoned and alteration products are similar, irrespective of the actual host rock. In close vicinity to the vein selvage intense sericitization and silicification is associated with finely disseminated sulphides. With increasing distance from the vein selvage, alteration intensity decreases and chloritization becomes prominent. This reflects the typical zoning of wall rock alteration associated with epithermal vein systems elsewhere. Ar-Ar dating of sericite and U-Pb EMPA dating of monazite define an age range of 308-295 Ma for hydrothermal mineralization. This is in excellent agreement with U-Pb zircon ages recently published for rhyolitic dykes in the Freiberg District, suggesting a genetic link between this felsic magmatism and magmatic-hydrothermal mineralization.

Rising global lithium (Li) demand has drawn much attention to areas where increased heat flow coincides with Li-enriched host rock, such as fractionated granite bodies. Lithium extraction from geothermal wells depends on the enrichment and stability of mica minerals - the dominant Li host. Post-Caledonian granites in the Grampian Highlands (NE Scotland) have been a target for early detailed field studies in the 1980s and 1990s, but mineral chemistry data remain sparse. We present findings from field investigations of seven large post-tectonic Caledonian granite plutons, focusing on the role of mica groups in Li enrichment and mobilization during magmatic and hydrothermal processes. Biotite is ubiquitously present across all sampled granite bodies, whereas primary muscovite is restricted to plutons that underwent a higher degree of fractional crystallization. Secondary muscovite is also prevalent, indicative of later-stage hydrothermal muscovitization involving reaction of aqueous fluids with biotite. Both biotite and primary muscovite host substantial Li concentrations of up to 0.5 wt%, correlating with elevated F, Rb, Cs, Sn, W, Nb and Ta. The most significant enrichment is observed in zinnwaldite(-like) micas, which are commonly zoned and petrographically distinct. Lithium contents of up to 1 wt% are observed in zinnwaldite cores, dropping by approximately half towards rims, suggesting a primarily magmatic Li budget, subsequently modified by hydrothermal leaching. Intense hydrothermal alteration is further evidenced by widespread K-feldspar sericitization. Micro-scale analysis shows heterogeneous Li distribution within biotite grains undergoing chloritization. This intra-grain variation, together with pervasive sericitization and chloritization, constitute direct evidence of hydrothermal Li mobilization.

The northern contact zone between the Ramberg Granite and hornfelsed slate is exposed in the vicinity of the Hagental adit (Gernrode, Northern Harz), on the first level of the former fluorite mine Hohe Warte. Such contact zones are recognised for their economic mineral potential, particularly with regard to elements such as lithium or tin.

At the margin of the Ramberg Granite, a medium-grained, equigranular granite composed of quartz, plagioclase, alkali feldspar, biotite, and muscovite is observed. Irregularly distributed patches of pegmatite, dominated by quartz and plagioclase, occur at the contact with the host rock or as apophyses within the granite. Tourmaline, white mica, and cassiterite have been identified in particular within the pegmatitic zones. Zoned fluorite has been observed by cathodoluminescence as accessory phase in the granite, where it is present in veinlets and as inclusion in feldspars. Whole-rock geochemical data of granite samples show a negative correlation of alkali content with increasing SiO₂, reaching up to c. 80 wt. % SiO₂, which is similar to a greisen-type alteration. Archive data describe this contact zone as a quartz-mica-rich marginal granite-type.

Further investigations will focus on the question if the fluorite observed in the granite is associated with the mined fluorite veins or with incipient greisenisation of the granite. Additionally, we will determine whether lithium is incorporated into mica and/or tourmaline. Understanding these processes enhances our understanding of the genesis of greisen and their potential as sources of critical elements.

Tracking down the formation of granite-related Sn-W deposits and critical metal (Li, Ta-Nb) deposits in pegmatites, a knowledge gap becomes apparent in characterizing the magmatic-hydrothermal transition in the evolution of these systems. Significant fractionation of stable boron isotopes is expected between melt and fluid when boron coordination differs between the phases (i.e. trigonal or tetrahedral). The isotopic signature of the resulting fluid may be preserved in tourmaline, a borosilicate mineral widespread in aforementioned deposits. Its potential to record magmatic-hydrothermal transitions and fingerprint the magmatic origin of ore-forming fluids motivates this study. The aim is to constrain boron isotopic fractionation between granitic melts and fluids, enabling to constrain the source of boron and the potential contribution of external fluids to the formation of the deposit. To simulate magmatic-hydrothermal conditions in the lab, previously synthesized peraluminous rhyolitic glasses (600 µg/g B; 4.2 wt% H₂O, Spallanzani et al. (2022)) were equilibrated with boron-free water in autoclaves at temperatures of 700 and 750 °C, each at 1.0 and 1.5 kbar for two weeks. Electron Probe Microanalysis and Raman spectroscopy for H₂O-content reveal chemical homogeneity. Runs at 1 kbar showed onset of alkali feldspar crystallization within the chemically homogeneous quenched melt. Secondary ion mass spectrometry of the glass and multi-collector inductively coupled plasma-mass spectrometry of the quenched fluid will be used to determine the boron isotopic compositions of the two phases. These results will provide new insights into the fluid-melt fractionation of boron isotopes and fluid-melt interactions in ore-forming systems.

Spallanzani et al. (2022) https://doi.org/10.1007/s00410-022-01937-2

Abundant pyroxenitic veins in ijolite rocks of the Iivaara alkaline complex attest to the role of metasomatic alteration of these rocks. Veins showing textural evidence of reactive replacement of host nepheline mainly by aegirine-augite are interpreted to reflect carbonatite metasomatism. Apatite that has formed at the vein margins is expected to be the best host for the fluids associated with such decarbonation reactions. Apatite cores host heterogeneous assemblages of fluid inclusions that are highly variable with respect to size, shape and composition. Multi-component inclusions (liquid, vapour, solids) dominantly have low vapour proportions (v < 15%). Homogenization temperatures cluster around a median of 320 °C (>400 – 264 °C). Frequent observation of sylvite, halite, and nahcolite attests to high K, Na, Cl and carbonate in the inclusions. Raman spectroscopy confirms H₂O, H₂S and CO₃^2- in the fluid, H₂O and CH₄ in the vapour, as well as K-feldspar and carbonates among the solids. Sharp initial LA-ICP-MS signals indicate presence not only of Na, K and Cl but also of S, Br, Li, Rb and B in the fluid. Significant amounts of Fe and Mn are bound to an opaque, thermally unstable Raman inactive solid phase interpreted as poorly crystalline Fe-Mn(hydr)oxide. Inclusions also contain solid phases hosting Zr, Nb and Ti as well as Cu, Zn, Pb and Ba. Results show that this fluid was a highly saline alkali-rich carbo-hydrothermal fluid with substantial transport capacity for Al, Si, HFSE and transition metals.

To understand the formation of HFSE (high-field-strength element) deposits in alkaline magmatic rocks, it is crucial to resolve mineralogical changes and element enrichment at the miaskitic/agpaitic transition in such systems. This is shown for the Fohberg phonolite (Kaiserstuhl, SW Germany), an evolved magmatite with high Na₂O (~10 wt.%) and elevated HFSE concentrations, e.g. REE, Zr and Nb. It is dominantly miaskitic, i.e. HFSE are bound in common minerals such as apatite and titanite, but in spatially restricted zones HFSE are incorporated into distinct Na-HFSE-silicates, which is characteristic for agpaitic rocks.

Textural observations, HFSE enrichment, and the mineralogical evolution during the crystallization sequence of the phonolitic magma can be summarized as follows: 1) Early-formed aggregates of andradite and augite are accompanied by HFSE-rich apatite, titanite, and HFSE-poor götzenite (type I). 2) Götzenite (type II) in interstitial spaces between felsic matrix components (sanidine, feldspathoids) is significantly enriched in REE, Nb, and charge-balancing Na. 3) Elongated cavities contain mm- to cm-sized, HFSE-rich götzenite (type III), wöhlerite, and mm-sized, pink eudialyte. 4) Straight fissures in the rock are lined with similar götzenite, wöhlerite, and eudialyte. Aegirine-augite is a common associate. Remaining cavities are filled with Na-zeolites. These mineralized fissures resemble 5) common zeolite fissures cutting through the phonolite in large number. We interpret this textural sequence from 1) to 5) as temporal succession of fractional crystallization from a miaskitic towards an increasingly HFSE- and fluid-enriched agpaitic magma composition with a final, consecutive zeolite-dominated and HFSE-free hydrothermal event at the onset of brittle mechanical deformation.

Low-grade metasedimentary units in Saxo-Thuringia (Germany) have recently become a focus of interest, as they provide key constraints on the region’s metamorphic evolution. To further refine the timing and potential trigger mechanisms, this study applies electron probe microanalysis (EPMA) Th–U–Pb monazite dating combined with monazite textural analysis to Lower Palaeozoic units from the North Saxon Anticline, Elbe Zone, Berga Antiform, and Schwarzburg Antiform. The data reveal a polyphase thermal history, variably recorded across Saxo-Thuringia, reflecting spatially and temporally distinct thermal events with different driving mechanisms. Early metamorphic overprint is documented in the North Saxon Anticline, Elbe Zone, and Berga Antiform during the Late Cambrian to Early Ordovician (ca. 510–478 Ma), broadly consistent with rifting processes related to the opening of the Rheic Ocean. Enigmatic Middle to Late Ordovician monazite ages (ca. 460 Ma) are also confirmed in this study. Although their precise origin remains unresolved, their widespread occurrence provides further evidence for a supra-regional thermal event during this interval. A Late Devonian–Carboniferous metamorphic age (ca. 355 Ma) from the eastern Berga Antiform records early Variscan tectonic activity. In contrast, the youngest monazite ages (ca. 302 Ma) from the northwestern Schwarzburg Antiform reflect monazite growth associated with contemporaneous volcanic activity in the adjacent Thuringian Forest Basin. The approach presented here demonstrates that the timing of metamorphic overprint can be successfully constrained even in low-grade metasedimentary rocks, confirming recent applications in Saxo-Thuringia and further supporting its applicability for resolving complex metamorphic histories in low-grade metamorphic rocks.

The paleogeographic position of the Alpine terrane with respect to (peri-)Gondwana during the Paleozoic is still a matter of debate. In this study we use a multi-proxy approach to analyze the provenance of siliciclastic sedimentary rocks from the Carnic Alps and the Northern Greywacke Zone, which include detrital U-Pb zircon dating, petrography and bulk geochemistry. The biostratigraphically well constrained deposits from the Carnic Alps have been used as a reference profile, and these results were compared to samples from the monotonous sediment record of the Northern Greywacke Zone. The stratigraphic interval ranges from the Middle Ordovician to the Silurian.

The petrographical and geochemical data indicate a high compositional maturity, which is supported by ZTR-dominated heavy mineral spectra. The results of U-Pb zircon dating show signatures typical for sedimentary rocks from the margin of Northern Gondwana and can be assigned to the East African-Arabian province. Most of the zircons show Pan-African ages, but presence of Meso- to Palaeoproterozoic and few Archean ages point to contributions from central Gondwana. Cambro-Ordovician zircon ages are linked to local volcanism at the northern margin of Gondwana. A stratigraphic trend both in the Carnic Alps and the Greywacke Zone is characterized by an increase of zircons with Tonian ages (900-700 Ma) and a decrease of zircons with Pan-African ages (700-550 Ma).

We interpret the shift in detrital zircon ages by enhanced sediment input from the center of Gondwana mainland and reduced input by detritus from Cadomian crust of Northern Gondwana.

High-temperature low-pressure (HT-LP) metamorphism is typical for late stages of the Variscan orogeny in Central Europe. In the Saxo-Thuringian part of the Bohemian Massif, HT-LP metamorphism can be observed in narrow shear zones in the roof of the Saxon Granulite Massif and in the Elbe Zone. Whereas the HT overprint in the schist cover of the granulites is well known, the HT shear zone in the Elbe Zone was described just recently. Here, we discuss the temporal and spatial relationship between both areas.

The Saxon Granulite Complex was formed under HP-UHT metamorphic conditions at 340 Ma. Its rapid isothermal exhumation into the upper crust finally resulted in a prograde thermal overprint of the low-grade metamorphic schist envelope (~330 Ma). The HT shear zones in the roof granulite and in the schist envelope display a uniform shear sense top to the SE.

Late Variscan tectonics of the Elbe Zone are characterized by pervasive NW-SE directed strike-slip culminating in the juxtaposition of the Erzgebirge with the Lausitz. The intervening low-grade metamorphic rocks of the Elbtalschiefergebirge were partially affected by HT-LP metamorphism and accompanied by the synkinematic intrusion of the Meissen Massif (333 Ma).

We argue that both HT shear zone suites are caused by advective heat transfer of the exhuming granulites. NW-directed flat-lying shearing in the roof is accompanied by steeply inclined transfer zones at the lateral edge. Thus, the formation of the Elbe Zone, the intrusion of the Meissen Massif and the exhumation of the Saxon Granulite Massif are genetically linked.

Changes in eruption intensity are common during volcanic events although the causes of such changes remain enigmatic. The 2021 Tajogaite eruption on La Palma waned several times during its 85-day eruptive duration, repeatedly reawakening with renewed vigour, which led to intense frustration for the population and civil protection authorities. Here we show, using mineral barometry, lava geochemistry, earthquake location data, and volcanotectonic modelling that the Tajogaite eruption was fed by a double magma reservoir system with the two major storage regions located at ca. 8 - 12 and 20 - 25 km depth and that the interaction between these two reservoirs was primarily responsible for alternations in eruption intensity. The eruption was initially fed by the upper reservoir, but magma supply from the deeper reservoir became increasingly more significant as the eruption progressed. We propose that intensity fluctuations were related to (1) changes in the geometry (length and aperture) of the volcanic fissure, and (2) changes in the pressure gradient between reservoirs, which drove and controlled the rate of magma transfer from the lower to the upper reservoir. Eruptive intensity fluctuations are therefore expected in cases of multi-reservoir plumbing systems and ought to be considered in volcanic hazard mitigation.

Spinel is an important petrogenetic indicator in magmatic-, metamorphic- and extraterrestrial- rocks. We have carried out an experimental study to determine the rates of Cr-Al interdiffusion in Mg-bearing spinels. Synthetic, gem quality single crystals of MgAl₂O₄ were cut into cubes (~1mm on the side), polished on one surface, and coated with a ~250 nm thin-film of MgCr₂O₄ using pulsed laser deposition (PLD). These couples were annealed at 850 to 1200 °C at a controlled oxygen fugacity of log(fO₂[bar])=-14 for different durations. Concentration gradients were determined using a novel approach of using BSE imaging on FIB-lamellae of cross sections from the diffusion couples. This procedure yields a spatial resolution of 17 nm for concentration profiles of lengths up to 3 μm.

The results yielded Cr-Al interdiffusion rates that are slower than those for Fe-Mg [1] by 2-3.5 log units, and showed a minor effect of fO₂ (when compared to studies at atmospheric fO₂ [2]). Counter-intuitively, diffusion rates in Fe-bearing spinels [3,4] appear to be slower than those measured in this work. Our experimental results provide an additional tool for geospeedometry involving spinels where Fe-Mg profiles may have been completely reset (e.g. slowly cooled plutonic or mantle rocks), and provides a basis to evaluate the closure behavior of geothermometers and tectonic indicators based on Cr-Al exchange.

[1] Liermann & Ganguly (2002), GCA 66, p.2903

[2] Stubican & Oesenbach (1984) AICeramics 10, p.406

[3] Posner et al., (2016), GCA 176, p.29

[4] Suzuki et al., (2008), PCM 35, p.433

Xenopumice is light-coloured, vesiculated, pumice-like, felsic rock that occurs in mafic volcanic rocks. The origin of xenopumice is disputed and it has been suggested that the material represents juvenile silicic magma fragments, remelted magmatic material or xenoliths from pre-existing rocks. Here we investigate xenopumice from the Garusar volcano, a Quaternary monogenetic cinder cone in the Syunik region of South Armenia, with the aim to determine its origin and better understand the deep magmatic processes prior to its eruption.

White xenopumice fragments are typically 3-15 cm in diameter. They are predominantly rhyolitic in composition (SiO₂ = 68-75 wt.%), whereas the host scoria are basaltic trachyandesites. The xenopumice has lower REE contents and distinct Sr and Nd isotopic compositions compared to the host scoria. Mineralogically, xenopumice is dominated by quartz and feldspars with accessory biotite, amphibole and Fe-oxides. Glass is abundant and varies in colour and composition from brown and trachytic towards colourless and rhyolitic.

The microstructure of the xenopumice is unlike juvenile material but suggests broken-up, broadly granitic components. The geochemical data are inconsistent with an origin by pure fractional crystallisation. Instead, a mixing process of rhyolitic and mafic melts is favoured. The gradual transition in glass composition and colour indicates frozen-in mixing of partial melts from xenolithic granitoids with juvenile mafic melts. This process of melt-rock interaction is relevant for influencing magma composition and the eruptive behaviour of volcanoes.

Diffusion-driven Li isotope fractionation has gained wide interest for tracing rapid geological processes, such as kinetic isotope effects during fluid exsolution from melts during magma ascent [1]. However, it remains unclear how the diffusion-driven isotope fractionation factor β changes with melt water content. Here, we investigate Li isotope fractionation in hydrous silicate melts using experiments originally produced by Troch et al. [2]. These diffusion-couple experiments used rhyodacitic, high-silica rhyolitic, and peralkaline rhyolitic glasses with different initial Li concentrations. The experiments were performed at 720-1100 °C, 100-700 MPa, and 1-8 wt.% H₂O for 5-25 min. Here, we measured Li isotope profiles parallel to the direction of diffusion and used these data to determine the β factor. Analytical and experimental uncertainties were propagated using a Monte Carlo approach, in which run duration, log₁₀D, plateau compositions, interface position, and isotope data were randomly selected (n = 1000) within their respective uncertainty ranges. The model yields preliminary β values ranging between 0.15 and 0.24, with typical uncertainties of ±0.01-0.03, consistent with the commonly reported β value of ~0.2 for Li isotope diffusion in silicic melts [3]. While previously determined Li diffusivities increase with increasing temperature and melt H₂O content [1], the here determined β factors remain similar in experiments containing 1-4 wt.% H₂O, but decrease to 0.15-0.16 ± 0.02 at 8 wt.% H₂O. This suggests that high H₂O contents make Li diffusion faster, but may reduce the difference between ⁶Li and ⁷Li diffusion rates. These results improve the application of Li isotope diffusion as a geochronometer for processes in volatile-rich silicic magmas.

The Pulvermaar, located in the western Eifel volcanic field, produced tephra deposits that contain rounded plutonic nodules. The nodule cores are coarse-grained with local melt veins between the crystals. The key minerals are olivine, clinopyroxene, biotite and amphibole, but their modal abundance varies considerably from pyroxenite to hornblendite. These nodules likely originate from a disrupted mush zone, thus providing insights into the formation and processes of magma mush systems.

The olivines have multiple growth stages, starting with Ca-poor and Ni-rich cores (Fo_core = 0.89, X_Ca = 0.002). These are overgrown by progressively Mg-poorer zones incorporating more Ca (Fo_rim = 0.84, X_Ca = 0.02). Conditions of growth are constrained using thermodynamic models (MELTS). Diffusion models of the chemical gradients between these growth zones indicate slow magma accumulation over days and weeks, and a fast-paced extraction of the nodules from the magma mush, which occurs on the order of hours to a day. A wide distribution of timescales and petrographic textures indicate that multiple magma intrusions formed the mush zone.

The Chaîne des Puys (French Massif Central) is among the youngest intraplate volcanic chains in Europe. It consists of ca. 80 monogenetic volcanoes distributed along an 80 km long, N-S trending chain that is only 3-4 km wide. Volcanic activity began with an early low-volume basalt-only phase around ca. 90 ka, which continued over the following 85 ka, accompanied by increasing eruptive intensity and compositional variation. Throughout this period, basaltic and basanitic melts were produced in the mantle [Boivin et al. 2017], from which they ascended through the entire, overlying crust. With time, however, small shallow crustal magma chambers developed, resulting in the formation of more evolved magmas. A final eruption period starting at 15 ka produced a range of compositions from undifferentiated basaltic/basanitic to highly differentiated trachytic magmas [Boivin et al. 2017].

This study examines geochemical and radiogenic isotope systematics of basaltic/basanitic and trachybasaltic magmas – SiO₂ between 45 and 49 wt.% and MgO from 8 to 4 wt.% – as the continuous production of primitive magmas for nearly 90 ka offers a unique possibility to study the evolution of the mantle source below the Chaîne des Puys. Furthermore, comparison of trachytic magmas from the youngest eruption phase with SiO₂ >60 wt% and MgO <1.3 wt% with contemporaneous basalts were investigated to quantify the influence of crustal assimilation during magma ascent. Finally, with an understanding of the degree of assimilation, geochemical changes caused by differentiation can be singled out and tight to specific mineral phases causing these.

The partitioning of CaO between olivine and silicate melt shows a systematic dependence on the melt H₂O concentration and can, therefore, be used as a geohygrometer [1]. However, Gavrilenko et al. (2025) showed that the current hygrometer calibration underestimates melt H₂O contents for melts in equilibrium with primitive olivine (Fo-content > ~85 mol%) [2]. In order to refine the Calcium-in-Olivine hygrometer, we performed hydrous high-pressure experiments at 200 MPa using an internally heated pressure vessel and anhydrous 1 atm experiments using a gas mixing furnace. The experiments were conducted with different melt H₂O contents (anhydrous to ~6 wt%) using several starting compositions (basalt, nephelinite, basanite, boninite, lherzolite) to cover a wide compositional range. Our approach aims at synthesizing olivine crystals in equilibrium with a hydrous silicate melt that are sufficiently large for LA-ICP-MS analysis. Experimental charges were slowly cooled from super-liquidus conditions into the olivine stability field with 0.1 °C/min to promote crystal growth while minimizing nucleation. The CaO contents of experimentally produced olivine are analyzed via LA-ICP-MS to avoid analytical uncertainties related to secondary fluorescence during microprobe measurements. Glass H₂O contents are quantified using Raman spectroscopy. Preliminary results support the finding that the current hygrometer calibration underestimates melt H₂O contents. Further experiments and analyses are in progress to resolve compositional effects and, ultimately, to provide an improved calibration of the hygrometer.

[1] Gavrilenko et al. (2016) J. Petrol. 57(9)

[2] Gavrilenko et al. (2025) Contrib. Mineral. Petrol. 180(54)

Despite recent scientific progresses, there is still a crucial need to improve our knowledge of the influence of physical and chemical parameters on magmatic phase equilibria and, therefore, our general understanding of igneous systems. For example, existing petrological tools to reconstruct magmatic processes, such as thermobarometry or thermodynamic models, are frequently of only limited validity due to significant uncertainties, model interdependence, or deficient calibrations complicating the application of these tools to natural rocks.

The prediction of phase equilibria is particularly complex for calc-alkaline magmatic systems, because water contents and oxygen fugacity can vary significantly. This contribution is an attempt to fill this gap by providing new experimental data exploring systematically the effects of temperature, pressure, magma composition, H₂O, and fO₂ on phase equilibria in calc-alkaline basaltic systems. Experiments were run in internally heated pressure vessels (IHPV) at 200 and 400 MPa and varying bulk H₂O contents (0-9 wt.%) with fO₂ conditions buffered between NNO+1 and NNO+2.3.

Combining our new experimental data with high-quality experimental datasets from literature, we established systematic changes in phase assemblages (i.e. mineral stability fields) and the impact of crystallisation parameters on silicate mineral chemistry. Employing our dataset, we formulated empirical and semi-thermodynamic mineral saturation models for plagioclase and clinopyroxene predicting the saturation of these phases as a function of bulk system composition, pressure, temperature, H₂O, and fO₂. Furthermore, we use our new dataset to recalibrate pre-existing silicate mineral-melt equilibrium models (e.g. plagioclase-melt) and extend them to arc magmatic systems.

The Late Neoproterozoic Jaswantpura Granites of NW India intruded along reactivated crustal structures, marking the transition from stretched to stabilized continental crust in a back-arc setting. Granite emplacement can be traced for 65 km and define a ca. 10 km wide belt, the Jaswantpura Granite Belt (JGB). The biotite ± hornblende A-type within-in plate granites are metaluminous to weakly peraluminous with Neoproterozoic (750-770 Ma) Malani Igneous Suite affinities and are compatible with partial melting of intermediate to mafic lower crust. Major-element systematics indicate fractional crystallization of plagioclase, apatite, titanite, and Fe-oxides. REE patterns show LREE enrichment and pronounced negative Eu anomalies. Multi-element plots display enrichments in Rb-Th-U-Pb and depletions in Ba-Sr-Nb-Ta-Zr-Hf, consistent with derivation from an intracrustal source. The granites are crosscut by evolved mafic dolerite dykes that show positive Pb and negative Nb-Ta anomalies relative to E-MORB implying mantle sources modified by subduction-derived fluids or crustal assimilation.

A key result is a systematic east-west geochemical gradient across the narrow JGB. Neodymium isotope ratios range from -1.34 to +2.64, increasing westward together with LILE, Nb, Pb, and Nb/Ta. We interpret this as an indicator for rapid melt transport from a deep crustal source without significant mixing between melts derived from two different adjacent crustal blocks. Field relationships and geochemical signatures together indicate a post-collisional extensional regime during late-Tonian slab-roll back and associated reactivation of heterogeneities in the crustal architecture of the continental margin.

The Pennsylvanian Saubach–Schneckenstein granite porphyries intruded the western contact zone of the Eibenstock granite massif, yet the magmatic origin of ore‑bearing porphyry systems in the western Erzgebirge/Vogtland region remains poorly understood. The Saubach outcrop provides key evidence, hosting centimeter‑scale quartz crystals interpreted to record prolonged growth from magmatic to hydrothermal conditions. Cathodoluminescence and µ‑XRF imaging are used to characterize internal quartz textures, and Ti and Ge trace‑element variations measured by LA‑ICP‑MS across these domains are employed to reconstruct the petrogenetic evolution of the magma.
The Saubach porphyry shows quartz–sericite alteration with tourmaline and topaz. Cassiterite is the primary ore mineral, accompanied by minor arsenopyrite, as well as supergene pharmakosiderite, symplesite, and scarce covellite. Ge/Ti ratios in primary quartz indicate a biotite‑granite–derived magma (Ge/Ti = 0.014–0.094, with Ti concentrations of 14.72–64.41 ppm and Ge concentrations of 0.88–1.39 ppm). A small subset of analyses also suggests the influence of a drier magma, characterized by Ge/Ti ratios of 0.005–0.007 (Ti = 104.87–133.26 ppm; Ge = 0.55–0.96 ppm). Ti‑in‑quartz thermobarometry indicates quartz crystallization near the wet‑granite solidus at 641–697 °C, whereas analyses interpreted as reflecting a drier magma yield correspondingly higher temperatures of 751–783 °C. While the latter are typical for the Late Paleozoic Central European Extensional Province and reflect the characteristically dry, superheated silicic magmas of that setting, crustal contamination and the long-lived nature of magmatic systems appear to have been key in producing volatile‑rich magmas that ultimately formed the hypogene Sn‑rich mineralization.

During the Cenozoic, continental rift-related magmatism has represented the dominant type of igneous activity in Central Europe, being responsible for forceful volcanic eruptions. Moreover, magmatic activity is still ongoing as demonstrated by active degassing activity and earthquake swarms recorded in the Eifel Volcanic Field or the Eger Rift (ER). Consequently, both represent ideal study sites to establish CO₂ and H₂O fluxes for active volcanic systems.

In this study, natural samples obtained at the ICDP drilling project EGER are used to establish magmatic storage and generation conditions of the nephelinites of the Bažina maar, centred in the Cheb basin (Czech Republic), representative of the mafic magmas produced during ER´s latest magmatic activity. Petrographic studies are combined with new experimentally determined phase relationships. In detail, natural olivine and Cr-spinel composition as well as chemical zonation profiles are used to constrain magma storage conditions and ascent timescales. Experiments were performed in an internally heated pressure vessel at 400 MPa, temperatures ranging from 1250 °C to 1000 °C, and varying xH₂O [H₂O/(H₂O + CO₂)] of the coexisting fluid.

Natural olivine crystals show distinct zoning patterns in forsterite contents (Fo) transitioning from Fo₈₅ in the core to Fo₇₅ at the rim. This zoning is used to deduce ascent rates. Our preliminary data shows that olivine and spinel are stable below 1200 °C. Experimental results show that Fo contents of olivine decrease with decreasing xH₂O and approach natural olivine compositions at rather dry and CO₂-rich conditions, implying that magmatism at Bažina maar is strongly CO₂ driven.

Clinopyroxenes (cpx) are rock-forming minerals in both igneous and metamorphic systems. Fe–Mg diffusion profiles in cpx have been used as geospeedometers to reconstruct thermal histories in metamorphic contexts or to determine timescales of magmatic processes. However, the reliability of such applications strongly depends on the accurate experimental calibration of the diffusion coefficients and their dependence on intensive thermodynamic parameters (e.g., P, T, and fO₂), crystallographic orientation, and chemical composition of cpx.

We performed a new set of experiments to study the effect of composition and anisotropy on Fe–Mg diffusion in cpx. We used thin-film diffusion couples and, in addition, synthetic or natural cpx powders as diffusion reservoirs. With the different types of diffusion couples (cryst. oriented single crystals Di₉₀Hd₁₀ and diffusion reservoirs composed of Di_xHd_1-x, with x between 50–80), a variety of experiments in the T range 1100 – 1300 °C were performed in a gas-mixing furnace to create diffusion profiles that could be spatially resolved with a Dual-Beam Scanning Electron Microscope (FIB-SEM) using Backscattered Electron Imaging or Energy-Dispersive X-ray Spectroscopy (EDX) at low acceleration voltages down to 5 kV, or Electron Probe Microanalysis (EPMA) in some cases for long-duration experiments.

Only at 1300 °C were we able to obtain a measurable diffusion profile, which suggests that Fe–Mg diffusion in cpx may be substantially slower than previously reported, in which case timescales obtained so far would be underestimated.

Natural silicate glasses preserve valuable information on magmatic redox conditions and the evolution of mantle-derived melts, which can be accessed through the oxidation state of iron in the glass. In particular, determination of Fe²⁺/∑Fe enables reconstruction of oxygen fugacity (fO₂) which exerts a fundamental control on magma differentiation and mineral stability.
We present new Fe²⁺/∑Fe data for tholeiitic glasses recovered during IODP Expedition 324 from Shatsky Rise, a large oceanic plateau in the northwest Pacific. Investigated samples span two contrasting volcanic domains: a high-flux, plume related shield magmatism at Tamu Massif (U1347) and a less voluminous volcanism at Ori Massif (U1350), reflecting a shift from vigorous plume-head magmatism to waning plume-ridge interaction.

Measurements were conducted by electron probe microanalysis using the flank method, exploiting shifts in Fe Lα and Lβ emission spectra to quantify Fe²⁺ in natural glasses. Fe²⁺/∑Fe ratios for selected samples were independently determined with colorimetric wet chemistry (Schuessler et al., 2008), and both methods show good agreement.

Preliminary results show Fe²⁺/∑Fe values of 0.76-0.83 for Tamu Massif glasses and 0.81-0.86 for primitive Ori Massif glasses. Using the Borisov et al. (2018) model, these ratios correspond on average, to fO₂ conditions of ca. FMQ +1 for Tamu glasses and FMQ + 0.6 for Ori glasses. These results support a potential tendency for plume-related magmas to evolve towards more reducing conditions with decreasing plume influence.

Borisov, A. et al. (2018) Contributions to Mineralogy and Petrology 173.

Schuessler, J. A. et al. (2008) American Mineralogist 93, 1493-1504.

Thermal conduction is a key mechanism of heat transport in solid materials and plays an important role in both technological applications and the thermal evolution of the Earth. In insulating minerals, heat is mainly carried by atomic vibrations, and the phonon contribution to thermal conductivity depends strongly on temperature, pressure and chemical composition. In this study, molecular-scale computer simulations are used to predict the thermal conductivity of insulating oxides and silicates over a wide range of conditions, from ambient conditions to pressures and temperatures relevant to the Earth’s lower mantle and core-mantle boundary (CMB). Crystalline MgO periclase and MgSiO3 phases, including bridgmanite and post-perovskite, constitute a simplified model system for the Earth’s lower mantle. Thermal conductivity is calculated using non-equilibrium molecular dynamics (NEMD) simulations, where a temperature gradient is imposed and the resulting heat flux is analyzed. Different interatomic interaction models, including classical empirical potentials and machine-learning force fields, are compared to assess how the predicted thermal conductivity depends on the description of atomic interactions. The influence of simulation cell size, finite-size extrapolation, pressure and temperature is examined to evaluate the reliability of the simulations under geophysically relevant conditions. This work contributes to a broader effort to develop a consistent molecular-scale model of heat transport in lower mantle minerals and across the core-mantle boundary.

Empirical electronic polarizabilities α of I­­⁻, Br­­⁻, S²­­⁻, Se²­­⁻, and Ag⁺ were determined at λ = 589.3 nm to predict refractive indices of compounds containing these species. Polarizabilities of the ions were obtained from the total electronic polarizabilities of compounds as derived from their mean refractive indices by subtracting the contributions of the other constituent ions. The anion polarizability parameters α°_ and N_o (in the equation α_ = α°_ · 10^{−N_o / V_an1.2} see Shannon & Fischer, 2016) were determined by least-squares methods from compounds with known refractive indices.

Cation polarizability is influenced by the coordination number (CN) according to α(CN) =(a₁ + a₂ CN e^-a₃CN)^-1. The polarizability of Ag⁺ was previously determined by Shannon and Fischer (2016). Expanding their dataset by iodides and bromides allowed the α(Ag⁺) values to be recalculated. Notably, 94% of compounds show <6% deviation between observed and calculated mean refractive indices using the new polarizabilities.

Using electronic polarizabilities of the ions calculated here enable the prediction of refractive indices of iodides, bromides, sulfides, and selenides (see also Nezamabadi et al., 2025).

Nezamabadi, S., Fuzon, P, A., Kraus. F., Fischer. R. X. (2025): Eur. J. Mineral, 37, 889– 907

Shannon, R.D., Fischer, R.X. (2016): Am. Mineral, 101, 2288-2300

Fischer et al. (2026) reported on twinned götzenite from the Fohberg phonolite. In X-ray diffraction experiments a large C-centered unit cell was found, with a = 37.346(2) Å, b = 7.3299(3) Å, c = 5.7259(2) Å, β = 96.866(2)°. During the process of structure analysis, the mineral was identified as triclinic götzenite (a = 9.6191(3) Å, b = 5.7342(2) Å, c = 7.3386(2) Å, α = 89.986(1)°, β = 101.040(1)°, γ = 100.485(1)°), twinned about 2[001], with operation ‑a‑1/2c, -b, c, hereby mimicking the larger C-centered unit cell.

Applying two different approaches, 1) using the orientation matrices for the götzenite cell and its twin-partner to reconstruct reciprocal space in the 3D software Blender, and 2) consulting the software Geminography (Nespolo & Ferraris, 2006), the twinning was confirmed. Geminography found reticular pseudo-merohedry with twin-index 2, with a vertical plane (-104) and obliquity 0.06°.

Testing potential alternative twinning by mirror, Geminography suggested twinning by the pair of twin elements (100); [411] with obliquity 1.95° and an I-centered twin-lattice, which after suitable transformations resulted in exactly the same twin-lattice as for the 2[001] twin. These results are compared with the 3D-reconstruction of the twins in reciprocal space, discussing the findings from both approaches.

Fischer RX, Birkenstock J, Biskup G, Fischer LA, Klügel A, Nezamabadi S, and Spürgin S., 2026. Eur. J. Min. 38(1):75–101. doi:10.5194/ejm-38-75-2026.

Nespolo M, Ferraris G, 2006. Acta Cryst. A 62(5):336–349. doi:10.1107/S0108767306023774.

Ternary chloride salts such as MgCl₂–KCl–NaCl are promising candidates for use as heat transfer fluids (HTF) and thermal energy storage (TES) media in next-generation concentrating solar power (CSP) plants. However, MgCl₂ has hygroscopic properties and therefore easily absorbs moisture, resulting in the formation of magnesium hydrochloride (MgOHCl). During its decomposition, corrosive HCl gas is produced, and the salt composition is irreversibly altered. Thus, salt purification is of key importance for safe and long-term use of the salts and the structural components of CSP plants

This study examines the structural changes of the salt with and without the addition of pure magnesium during a thermal purification process. After each temperature stage, characterisation is performed using X-ray diffraction (XRD), with subsequent pattern refinement for phase analysis and structural characteristics.

First results show differences in the phase development and structural changes of both approaches. The aim is to investigate the potential use of economical purification methods and their impact on structural properties of chloride salts in terms of their usage as new high temperature TES materials.

ABSTRACT:

The traditional quarry mining process causes considerable climate effects owing to the processes involved in the extraction, processing, transport, and disposal of the materials used in construction activities. With an increase in the number of mineral resource demands, there is a rise in greenhouse gases, large energy consumption, disturbance of the land, and more environmental pressures. To mitigate climate change and practice sustainability in managing the mineral resource demands, urban mining has become critical to the current times. Urban mining is associated with recycling and reuse of secondary mineral materials like construction and demolition of debris, recycled aggregates, and excavated soils. The reuse of such materials as opposed to quarrying can result in minimized climate impact due to the reduction in energy consumption, shorter distance to transportation, less need for landfill disposal, and reduced dependency on virgin resources. Urban mining plays an important role in supporting circular flow of materials and climate-friendly activities in the construction and geotechnical industries.In Germany, urban mining receives great support from the national Mantelverordnung. In particular, the synergy between the Ersatzbaustoffverordnung (EBV) and the Deponieverordnung (DepV) has been instrumental. EBV provides technical and environmental requirements that are necessary for the safe reuse of mineral substitute construction materials, whereas DepV aims at promoting sustainable landfill management and recycling mineral waste to minimize its disposal. Thus, urban mining receives significant legal support in Germany.

Keywords: Quarry Mining, Climate Change, Urban Mining, Ersatzbaustoffverordnung (EBV), Deponieverordnung (DepV).

ABX₃-Perovskites have numerous physical, magnetic and electronic properties and offer a wide range of technological applications due to their chemical and structural variability.

Most perovskites do not exhibit the ideal cubic aristotype structure at ambient conditions but a distorted one of lower symmetry.

Mitchell et al. [1] studied various natural latrappites and concluded that the minerals are complex quaternary solid solutions between CaTiO₃, NaNbO₃, Ca₂FeNbO₆ and Ca₂NbO₇. All latrappites crystallise in the orthorhombic crystal system with space group Pbnm (62) and are isostructural to CaTiO₃. However, recent studies within the system CaTi_1-2xFe_xNb_xO₃ have shown that in the range 0.4 ≤ x ≤ 0.5 the hkl and h0l diffraction lines are broadened and reduced in intensity, indicating a further reduction of symmetry to monoclinic with P2₁/n [2].

To understand the ordering process in the presence of manganese, members of the binary system were synthesised in the range 0 ≤ x ≤ 1 using the Pechini method. Powder X-ray diffraction techniques (Mo and Cu radiation) were employed to determine the crystal systems lattice parameters and subsequently refine the crystal structures of each synthesized phase Ca₂Fe_1-xMn_xNbO6. Raman spectroscopy was applied to understand the distortion phenomena, which arise due to the ordering process of Nb/Fe in connection with the Mn/Fe substitution.

[1] Mitchell, R. H., Choi, I. K., Hawthorne F, C., McGammon C, A., Burns, P. C. The Canadian Mineralogist (1998) 36 (1): 107–116

[2] Chakhmouradian, A. R., Mitchell, R. H. Journal of Solid State Chemistry (1998), Vol. 138, No. 2 p. 272-277

Global demand for mineral resources is increasing rapidly, particularly for critical raw materials required for the energy transition. At the same time, newly developed ore deposits, which are generally lower in grade and more variable in mineralogical composition, require complex beneficiation routes and efficient processing strategies. Geometallurgy, in this context, provides a quantitative framework by linking ore characteristics with processing performance. However, its success depends on robust mineralogical information, including mineral chemistry.

SEM-based automated mineralogy enables high-throughput quantification of modal abundance, mineral size, liberation, and mineral association. However, the quantification of elemental chemistry derived from energy-dispersive X-ray spectroscopy (EDS) still relies largely on standardless methods, limiting its reliability for quantitative elemental analysis. Since mineral distribution calculations combine the relative abundance of minerals with their specific chemical composition, uncertainties and systematic errors in EDS data directly affect result accuracy.

This study describes the development-steps of a standard-based quantitative EDS workflow on a TESCAN TIMA system. The workflow combines analysis of reference materials, detector calibration and verification, and spectrum quantification by DTSA-II software, followed by statistical evaluation of accuracy and uncertainty. Validation uses representative ore samples characterized by optical microscopy, bulk chemistry, X-ray powder diffraction, and electron probe microanalysis. These mineral chemistry data are then re-integrated into automated mineralogy datasets to deliver uncertainty-aware multi-element deportment. The expected result is a traceable workflow that produces mineral chemistry with complete uncertainty budgets alongside modal data, improving the reliability of elemental deportment estimates and supporting reproducible geometallurgical studies of complex, low-grade ores.

Closing material cycles is a key strategy for achieving a more sustainable construction sector. The recycling of mineral waste as a substitute for clinker in cement production offers significant potential to reduce CO₂ emissions while simultaneously conserving limited landfill capacity. This study focuses on the activation of mineral waste materials to enhance their reactivity and to evaluate their potential as supplementary cementitious materials. A detailed characterization of various gravel-washing sludges using XRD and XRF serves as the basis for identifying suitable activation methods for low kaolinitic clays, since gravel-washing sludges (GWS) contain little or no kaolinite and are dominated by illite due to the geology of Switzerland. Besides the low kaolinite amount GWS also contains significant amounts of carbonates (limestone, dolomite) which release CO₂ at temperatures over ~600°C. This contrasts with the thermal activation temperature of illite, which is significantly higher. Therefore, appropriate activation methods (e.g. mechanical activation) are systematically identified, and their overall feasibility requires comprehensive evaluation based on the environmental impact of such activation methods.

The stable carbon isotopic composition (δ¹³C) of carbonation products is increasingly regarded as a diagnostic parameter in cementitious systems, with potential applications in carbonation curing and the characterization of recycled concrete fines. A robust interpretation of such signatures requires reference data on isotopic fractionation during carbonation across the relevant constituent phases of cement, which to date are only sparsely available.

The present study quantifies stable isotopic fractionation and mineralogical phase evolution during wet carbonation of two major cementitious phases: β-dicalcium silicate (C₂S), a clinker phase, and ettringite, a sulfate- and aluminium-bearing cement hydrate phase. Carbonation experiments were conducted in aqueous suspension in an open system continuously supplied with isotopically characterized CO₂ at different flow rates. δ¹³C of solid carbonates, the dissolved inorganic carbon (DIC) and headspace gas was determined by IRMS. The solid phase assemblage was quantified by Rietveld-XRD (QXRD) and TGA, and pH and electrical conductivity were monitored in situ. The dataset was compared with PHREEQC and GEMS thermodynamic modelling.

Both phases show reproducible inter-phase fractionation throughout the reaction, accompanied by the formation of polymorphic carbonate assemblages, in good agreement with the thermodynamic modelling. The combined dataset provides a quantitative reference for the interpretation of carbon isotope signatures in cementitious systems.

Soils impacted by long-term mining activities can accumulate and release potentially toxic elements. One good example is the Harz Mountains in central Germany due to significant mining activities from the Bronze Age to the 20th century. Long-term extraction and processing of metal ores led to widespread contamination of soils with As and heavy metals like Pb, Zn, Cd, while unmanaged mining wastes enhanced contaminant dispersion through soil erosion. This study investigates soil profiles from the mine areas of Grube Gottes Segen (Sankt Andreasberg), the Rammelsberg near Goslar, and the former smelting at Silberhütte in the Harz Mountains to assess element enrichment and evaluate element mobility.

Geochemical and mineralogical analyses, together with magnetic susceptibility measurements, are used to evaluate contamination levels in the investigated soil profiles. Magnetic susceptibility values range from 7.317*10^-5 to 30.88 SI, which indicate a strong, spatially varying level of contamination. Further geochemical and mineralogical analyses will allow identification of the heavy metal enrichment in the soil. Heavy metal mobility and potential contaminant release are assessed through leaching experiments and spatially resolved geochemical analyses.

These combined investigations aim to evaluate distribution, mobility and mineral association of potentially toxic elements in mine-affected soil profiles from the Harz Mountains. The results are going to provide insight into the environmental impact of historical mining and smelting activities, particularly the processes controlling heavy metal dispersion and release under varying geochemical conditions, and may contribute to future monitoring and remediation strategies in contaminated mining areas but also to assess its secondary resource potential.

The growing demand for critical metals (CMs) such as lithium (Li), manganese (Mn), cobalt (Co), and nickel (Ni) drives the search for alternative and locally available resources. This study examines shallow geothermal waters in Baden-Württemberg, occurring at depths below 1 km and originating from deeper basin fluids that migrate to the surface along fault systems. The collected waters are predominantly Na–Cl type, with an average pH of 6.7 and temperatures ranging from 20 to 51 °C. Total CM concentrations, determined by ICP-MS and ICP-OES, show average values of 10 mg/L Li, 0.5 mg/L Mn, 0.7 µg/L Co, and 3 µg/L Ni, which are higher than typical seawater concentrations. To assess the selective extraction potential of these CMs from geothermal water, batch sorption experiments were studied under varying conditions using water from the Baden-Baden spa and different sorbents, including inhouse-synthesized hydrous manganese oxide (HMO) as well as commercial biochar (BC) and activated carbon (AC). The results show that HMO enables the most efficient and selective Li removal, achieving up to 60 % extraction within 1 h, while BC and AC have lower selectivity but broader metal uptake. Experiments conducted between 20 and 60 °C highlight the role of temperature in optimizing sorption performance. Based on a daily flow rate of 800 m³, up to 1.6 tons of Li could be extracted annually from a single Baden-Baden spa; when scaled to nearly 60 spa facilities in Baden-Württemberg and around 250 across Germany, this highlights a substantial cumulative resource potential of CMs.

Layered lithium nickel manganese cobalt oxide/NMC has replaced lithium cobalt oxide/LCO as the cathode active material in Li-ion batteries. This is due to the lower production cost, higher specific capacity and lower potential for environmental damage of the former. Direct recycling is proposed as a responsible and sustainable supplement to lithium and transition metal primary production to counteract the increasing demand for Li-ion batteries and these raw materials. Intercalation of magnesium and calcium in the cathode material is hypothesized to be linked to direct recycling pre-processing of NMC in specialized solvents during ultrasonication. Configurational entropy calculations and ab initio first-principle methods are utilized to investigate the potential effects of Mg²⁺ and Ca²⁺ intercalation on the crystal structure and Li-ion diffusion capability of the NMC. Preliminary density functional theory results show that the incorporation of Mg²⁺ and/or Ca²⁺ in the Li-layer of a fully lithiated NMC811, when below 0.05 apfu, agrees with refined XRD data. Specifically, in the case of Mg²⁺ intercalation, antisite Li-Ni defects in the [Li]_3a sites also seem to be partially inhibited. The intercalation of Mg²⁺ and/or Ca²⁺ increases the configuration possibilities; however, effects on Li-diffusion is highly dependent on the spatial distribution of the intercalated cations. Magnesium doping to NMC is expected to prevent the collapse of the Li-layer during excess delithiation. Our thermodynamic and computational chemistry results combined with experimental data could fill the research gaps for predicting the crystallography and crystal chemistry of the NMC material under the effect of hydrometallurgical or direct recycling processes.

The Rammelsberg Zn-Pb-Cu deposit in the Harz Massif (Germany) is an exceptionally high-grade (27 Mt at 19% Zn, 9% Pb, 160 g/t Ag) clastic-dominated (CD-type) deposit hosted in the Wissenbachschiefer, a Middle Devonian black shale locally enriched in barite. Previous studies suggest that barite and sulfide mineralization are coeval and formed by sedimentary exhalative processes. In this ongoing study, preliminary petrographic and SEM results from 34 samples reveal a more complex, multi-stage paragenetic sequence, in which two pre-ore (diagenetic) stages are followed by at least two hydrothermal ore stages. The diagenetic stages include fine-grained framboidal pyrite and early barite inclusions (Stage 1), followed by pyrite overgrowths and euhedral celsian (Stage 2). The main ore stage (Stage 3) mineralization (sphalerite, galena, chalcopyrite, pyrite) forms coarse-grained massive aggregates. Stage 4 comprises precious metals (native gold, electrum) and Sb-Ni-Co-bearing phases (e.g., boulangerite, tetrahedrite, cobaltite), which formed via fracture filling and replacement of earlier sulfide assemblages. In barite-rich samples, Stage 4 also includes late-stage pyrite filling secondary voids created by barite replacement. Both barite replacement in Stage 3 and the crosscutting nature of Stage 4 suggest a multi-stage evolution for the Rammelsberg deposit. This contrasts with previous models, which inferred that barium and ore-stage metals were transported together by reduced, H₂S-rich basinal brines and precipitated after hydrothermal venting from an euxinic water column. Continued petrographic work will further refine and test this paragenesis, and provide a framework for in situ analytical work on key sulfur-bearing phases.

Evaluating crystalline rock bodies as potential host rock for a nuclear waste repository requires a detailed understanding of fracture-controlled permeability. This study aims to improve the understanding of fracture and fault development within the Ramberg Granite (Eastern Harz Mountains), which is considered a potential host lithology. The area contains numerous near-vertical fluorite veins related to structures that crosscut the gently dipping pluton–host rock contact. Structural and mineralogical data were collected on the first level of the former Hohewarte fluorite mine. Data include observations from granite and adjacent contact-metamorphosed slate from the mine, surface outcrops and historical records.

Structural data (open joints, faults, and related features) are analyzed across the lithologies. The joint orientation varies widely with a maximum dip direction towards W and SW and a dip angle of 50 to 80°. Hydrothermal mineralization along fractures is characterized by multi-stage fluorite formation, with subordinate quartz, pyrite and carbonates.

A major 30–50 cm thick, deep blue fluorite vein was emplaced along a major WNW-ESE-striking steep to vertical fault zone. This main fluorite vein is crosscut by a conjugate set of subordinate faults with related purple fluorite veins that are up to 1 cm thick. Throughout the mine, subordinate veins along gently to moderately dipping fractures with variable strike orientations hosting purple, blue, and white fluorite occur.

Further geochemical analyses are planned to constrain fluid sources and crystallization history. Overall, the vein system records paleo-fluid migration and fracture zones that may remain significant for future tectonic reactivation and fluid pathways.

Geochemical data from intermediate volcanic rocks of the Lower Rotliegend Subgroup in northeastern Germany and from volcanic rocks of the intersected extramontane basins to the south indicate an arc-related tectonomagmatic affinity (e.g. Halle volcanic complex, Romer et al., 2001). The mostly andesitic lavas of Lower Rotliegend volcanic rocks exhibit porphyritic textures, a trait commonly associated with subduction zones (e.g. Tatsumi & Takahashi 2006; Zhu et al., 2013), although alternative tectonic settings – such as hotspot-related (Bhushan 2000) or intraplate environments – cannot be entirely excluded. However, subduction related to the Variscan- and Caledonian orogenies had ceased earlier. Subsequently, rifting processes due to the post-orogenic stress regime, including mejor dextral translation between North Africa and Europe (see Wilson et al., 2015) dominated the Variscan foreland. Rhyolitic and ignimbritic sequences in southeastern Germany also display affinities to OIB-type magmatism (Wenzel et al 1997). The apparent mismatch between the tectonic setting and magma geochemical signature was already recognized in the 1980s (Hübscher 1983). More recent literature explains this by the influence of older subduction-modified basaltic magma reservoirs derived from magmatic underplating (Benek et al. 1996). The latter has been geophysically evidenced by the detection of a lower velocity zone in the lower crust of Avalonia in northern Germany (Smit et al., 2016).
Here, by analyzing both existing and new geochemical data, along with rock core and thin-section descriptions, we aim to shed light on magma generation of Lower Rotliegend volcanic rocks. Additionally, we investigate trace-element distributions with potential economic significance.

In the area between Berlin and Zossen, the current state of exploration and knowledge have evolved to such an extent since 1974, that a reinterpretation of the stratigraphic boundaries is necessary. Here, based on the Dabendorf Ug Df 2/74 well, the chronostratigraphic boundaries in the Lower Jurassic and its base, as well as the lithostratigraphic boundaries in the Rhätkeuper Formation (Uppermost Triassic) of the federal state Brandenburg, were redefined. To this end, the depths of distinctive lithological boundaries were adjusted and the lithology within intervals of missing core recovery was inferred from the geophysical logs. Furthermore, a detailed core description was performed, considering the results of geophysical logging as well as palynological and paleozoological studies. The redefinition of both lithostratigraphic and chronostratigraphic boundaries was based on the correlation of interpreted sequences using third-order global eustatic cycles (Haq 2017, 2018) as well as the incorporation of new biostratigraphic results.

The recognition of Amaltheus cf. stokesi as evidence for the lower margaritatus Zone permitted the base of the Upper Pliensbachian to be constrained to a significantly greater depth than previously inferred.

Based on the palynological results of Schulz (1974), the base of the Hettangian was identified and clearly distinguished from the Rhätkeuper. Similarly, the deposits of the Rhätkeuper Formation in Brandenburg were assigned to the Triletes and contorta Member.

Precise stratigraphic assignments are a requirement for 3D modeling of the subsurface and the assessment of its utilization potential, specifically regarding sandstone reservoirs and aquifers.

ERCOSPLAN recently supervised an exploration campaign with a focus on potash and borate resources of a salt dome in the Caspian Basin, Central Asia. Particular focus was placed on the geological modelling of an internal structure because of its impact on the mining method. The input data for the modelling were taken from 70 vertical drill holes, accompanied by lithological descriptions and chemical analyses of the salt rocks that were drilled. The drill holes penetrated depths of up to 1,200 metres, with a layer of evaporite rocks extending between 500 and 850 metres.

An essential element for understanding the internal structure was the reconstruction of the hanging wall/footwall positions by identification of the original evaporation sequence based on the geochemical signatures of the evaporites, i.e. Br and Sr content in halite. As a result, the style of folding as well as the presence of faults and detachment zones of the entire salt dome have been discovered. This initial step made it possible to identify those parts of the salt dome in which commercially viable potash was likely to be found. Such parts were subject to more detailed exploration by further drilling and sampling, resulting in a 3D model of the potash horizons’ structure. It was determined by means of this geological model that the drill hole spacing of approximately 1 × 1 km represents the maximum spacing that would still allow the correlation of structural and litho-/tectono-stratigraphic elements between neighbouring drill holes.

Conventional approaches to 3D modeling and visualization often struggle to effectively communicate complex spatial information beyond expert communities. Limited accessibility of specialized tools and the abstract nature of digital models can hinder intuitive understanding, particularly for non-expert audiences.

Recent developments in visualization technologies provide new opportunities to address these challenges. In particular, 3D printing enables the transformation of digital models into tangible objects, allowing users to physically explore complex geometries. At the same time, interactive visualization techniques - such as web-based applications and immersive environments including virtual and augmented reality - complement physical models by enabling dynamic exploration and contextual analysis.

This poster presents an integrated, open-source workflow that combines Python-based data processing, geospatial analysis using QGIS, 3D modeling in Blender, and real-time rendering with OpenGL. A special focus is placed on the preparation of 3D-printable models, including optimization, simplification, and conversion of complex datasets into physically realizable forms.

The combined approach demonstrates how digital and physical visualization methods can be effectively linked to enhance both scientific analysis and communication. By transforming abstract data into interactive and tangible representations, this workflow contributes to improved accessibility, engagement, and knowledge transfer across disciplines.

Understanding igneous phase relationships is fundamental to cast light on melting and crystallization sequences. Lectures, textbooks and computer programs illustrate related phase diagrams in 2D. However, not all students can translate 2D to 3D; limiting students’ capability to fully understand these complex systems. 3D printing can change this. As highlighted by Ishutov et al. (2021) 3D printing has in recent years become a critical tool in geoscience research, education, and technical communication. Guo et al. (2022) demonstrates that 3D-printed models enhance spatial visualization. We present 3D printed models of multiphase diagrams (e.g. forsterite–diopside–anorthite), designed to enable more innovative and efficient knowledge sharing.

Because it is challenging to visualize 3D models with 2D means, the knowledge about phase diagrams is often limited or even abstract for many students. Published figures use 2D cuts from 3D models or diagrams are perspective drawings of the 3D model. In contrast, as individual phases can be taken out of our 3D printed models, students can easier identify phase stability fields and trace crystallization sequences (e.g. dunite-troctolite-gabbro); enabling them to better understand the geometry of ternary systems beyond static textbook figures. Finally, our 3D printed models will be displayed in the drill core archive visitor center in Nuuk or can be transported into the field and document the formation of magmatic rocks to students and non-experts. This work highlights the potential of 3D printing in geoscience education by bridging the gap between theoretical phase equilibria and intuitive understanding.

As part of the joint project TUNB Velo 2.0, a regional three-dimensional seismic velocity model of the North German Basin was developed. The project aimed to provide consistent interval velocities for the time-depth conversion of seismic data and their application in structural geological modelling. It was coordinated by the Federal Institute for Geosciences and Natural Resources in cooperation with the geological surveys of Schleswig-Holstein, Mecklenburg-Western Pomerania, Saxony-Anhalt, and Lower Saxony.

The State Authority for Mining, Energy and Geology developed a regional velocity model for Lower Saxony and Bremen. Interval velocities were derived following the approach of Jaritz et al. (1991), using the v0-k method to calculate interval velocities from theoretical surface velocities and vertical velocity gradients. The structural framework was based on the TUNB3D-NI model, which includes 14 lithostratigraphic horizons, ranging from the base of the Zechstein to the present-day surface, as well as salt structures and major faults.

Modelling was carried out using Aspen SKUA®, where a geological volume model was first generated and subsequently parameterized with seismic velocity data.

The new velocity model provides a first comprehensive regional framework for time-depth conversion at an overview scale. Through the harmonization of different datasets and methodological approaches across state borders, a consistent cross-border velocity model of the North German Basin was established. While not intended to replace local velocity studies, it can be used as a regional reference model and supports a range of geoscientific applications, including structural geological and seismological analyses.

The Pannonian Basin System includes sub-basins developed during Miocene extensional phases at the Alpine-Dinaride-Carpathians transition.

The westernmost subbasin of the Pannonian Basin System, the Styrian Basin, has a varied volcanic history coeval with extensional tectonics. Therefore, dating volcanic activity provides temporal insight into basin initiation and the main deformational phases.

To place new constraints on the timing of volcanism in the Styrian Basin and the initiation of basin formation, we investigated zircon populations from volcanic rocks (lavas and volcaniclastics) and overlying sandstone from three boreholes: St. Nikolai 1, Wiersdorf 1 and St. Peter 1 in the south-eastern Styrian Basin. The zircons were analysed for their typology after Pupin (1980) and selected grains subsequently dated by LA-ICP-MS.

The zircon typologies reveal significant differences between the volcanic rocks from the different boreholes, reflected by variations in crystallization temperatures and Typology Evolutionary Trend (TET). Results of U-Pb dating further indicate that volcanism in the study area occurred during three stages over >1 Myrs in the Early Badenian (Langhian).

Detrital zircon populations additionally show that sandstone from the overlying marine succession was mainly supplied from remote pre-Mesozoic basement sources and does not result from reworking of the volcaniclastic rocks.

Reference: Pupin, J.-P. (1980). Zircon and granite petrology. Contributions to Mineralogy and Petrology, 73(3), 207–220. https://doi.org/10.1007/BF00381441

The processes governing denudation rates throughout the Quaternary remain poorly understood, particularly in the European Alps. Although a large proportion of the Alpine range comprises carbonate rocks, the landscape evolution and associated denudation mechanisms remain largely underexplored. This is due to limitations of current methods, which struggle to accurately measure denudation rates over timescales of the last million years (i.e., Quaternary period), particularly in carbonate-dominated regions.

Electron spin resonance (ESR) thermochronometry offers a new method to address this gap. A proof-of-concept study using carbonate bedrock samples from the Rhône Valley (Swiss Alps) demonstrates the potential of this approach. Six samples were characterised using X-ray fluorescence and cathodoluminescence prior to ESR measurements, including dose response and isothermal decay experiments.

The project further focuses on samples collected from the Aare, Reuss and Rhine valleys in the central Alps, with the aim of constraining rock cooling histories along a west-east transect and quantifying Quaternary exhumation rates in the carbonate-dominated Alpine valleys.

Preliminary results emphasize the potential of ESR thermochronometry for carbonate rocks, offering key advantages such as: (i) measuring multiple ESR signals with different thermal sensitivities within a single sample, (ii) high upper dating limits (10⁶-10⁷ years), (iii) low closure temperatures (<80 °C), suitable for recent denudation studies, and (iv) the capacity to constrain low exhumation rates (<1 mm/yr). This method provides a reliable framework to estimate carbonate exhumation rates and better understand the interactions between tectonics, climate, and surface processes during the Quaternary.

Radiometric dating requires the measurement of related parent and daughter isotopes to produce meaningful ages. The alpha ejection during the decay of uranium and thorium spatially separates the parent and daughter nuclides analysed in (U-Th)/He dating by a few tens of microns within the crystals. In-situ (U-Th)/He dating applies two superimposed laser ablation spots to analyse the liberated parent and daughter nuclides sequentially, assuming that the analysed He is derived from the analysed U and Th. However, computer simulation considering alpha ejection visualizes the helium source volume around the helium-pit and reveals that in-situ (U-Th)/He dating undermines that assumption. Only a fraction of the parent nuclei that produced the measured volume of helium are probed during analysis. Furthermore, while those parent nuclei contribute equally to the analysed radionuclide budget, their contribution to the helium budget is a complex function depending on the relative location of the alpha emitter to the laser ablation spots, as well as the geometry of the latter. This geometry controls the overdispersion of in-situ (U-Th)/He ages produced by radionuclide zonation, which can be reduced to a minimum by optimizing the geometries. This contribution serves as a guideline on how to minimize age overdispersion produced by the interplay of radionuclide zonation and the geometry of the laser ablation spots and demonstrates how to assess the reliability of in-situ (U-Th)/He ages by optimizing the laser pit geometry.

In-situ (U-Th)/He analyses, performed using two laser-ablation spot analyses for sequential determination of radiogenic ⁴He and radioactive U+Th(+Sm), significantly increases analytical throughput and reduces bias introduced during mineral picking. This technique, however, is especially susceptible to the impact of crystal zonation combined with the dislocation of ⁴He during alpha decay, which typically occurs at a scale of a few tens of micrometers. In this contribution, we demonstrate that this effect can generate overwhelming and non-systematic dispersion, with apparent age offsets multiple times older than U-Pb age under unfavorable analytical conditions, by performing in-situ analyses in crystals from a single granitic sample with a well-constrained thermochronological history. We also show that this process has a more pronounced impact in controlling date dispersion than intracrystalline diffusive migration in the study sampled. The observed age offset can be reproduced by simulating alpha redistribution for a range of zonation patterns, confirming our observations and exemplifying how estimating the magnitude of date dispersion due to intra-crystalline ⁴He redistribution is a necessary step towards accurately describing the uncertainty of in-situ (U-Th)/He data. In addition, we demonstrate empirically that changes in spot size geometry have an impact in (U-Th)/He dates, confirming previous modelling results.

Intramontane basins are vital for studying Earth's surface processes related to climate and tectonics. Understanding their transition from endorheic to exorheic drainage is key to interpreting landscape changes in the Late Cenozoic. The Guadix-Baza (GB) basin in southern Spain (Betic Cordillera) features a sedimentary record from the Miocene to the Pleistocene. Despite extensive research into basin evolution and the shift from endorheic to exorheic drainage, as well as how landscapes respond to surface process changes, debates persist largely due to the limited temporal resolution of the sediments. The basin contains fluvial archives crucial for studying landscape evolution after basin capture, however these deposits are poorly dated.

To fill the chronological gap, sediment samples from fluvial terraces and basin infill units at the top of the GB basin and Guadalquivir River catchment were collected for trapped-charge dating. This involved a multi-method approach combining luminescence and electron spin resonance (ESR) dating. Initial results indicate that optically stimulated luminescence (OSL) dating of quartz produced moderate to dim signals and low saturation doses, limiting its working range to the last ~100 ka. Conversely, infrared stimulated luminescence (IRSL) of feldspar showed favourable properties for dating deposits from the Middle Pleistocene. If required, the timeline will be further refined beyond the luminescence dating limit through ESR dating of quartz using a Multiple Centre approach. Overall, this study provides important insights into the post-capture landscape evolution, and especially the reorganisation of the fluvial network, in the GB basin.

Establishing precise chronologies for mid-to-late Pleistocene volcanic events (10⁴–10⁶ years) remains a fundamental geochronological challenge. Conventional radiometric methods such as U-Pb and ⁴⁰Ar/³⁹Ar are restricted by low daughter isotope concentrations and initial chemical disequilibrium, while other approaches such as radiocarbon dating or tephrochronology offer only indirect or temporally limited estimates. Consequently, establishing alternative direct dating approaches is critical.

Electron spin resonance (ESR) offers a promising alternative by utilizing mineral grains as natural dosimeters. Zircons are highly viable candidates as they are commonly present in mafic-to-intermediate deposits and possess crystal lattices capable of trapping charges. Specifically, the SiO₄-Y³⁺ center can capture electrons ionized by natural background radiation, acting as a geologic clock. However, the specific charge trapping and de-trapping kinetics of natural, non-metamict zircons remain poorly constrained.

To evaluate the practical dating limits of this method, we investigated the thermal stability and dose-response behavior of the ESR signals from the SiO₄-Y³⁺ center under laboratory X-ray irradiation. Our findings reveal that although dose-response behavior can be successfully reconstructed, severe application challenges are prevalent. The evolution of the ESR signal immediately after irradiation and the prevalence of shallow electron trap depths severely limit chronological accuracy. Therefore, more in-depth investigations are necessary to reliably develop the ESR dating of zircons.

The South Iceland Seismic Zone (SISZ) and the Reykjanes Peninsula, located along the active plate boundary between the North American and Eurasian plates, exhibit distinct tectonic behaviors. The Reykjanes Peninsula, an oblique rift zone, experiences volcanic, and seismic activities, whereas the SISZ, a transform fault zone, is characterized by significant seismic activity (up to M_w 7) nucleating on NS-oriented faults but lacks volcanism. Both regions form a 140 km long E-W left-lateral shear zone oriented N070, with NS right-lateral strike-slip faults, indicative of a common tectonic mechanism. Structural continuity between the two zones remains uncertain, raising concerns about potential large earthquakes propagating toward the Reykjavik area.

We used drone photogrammetry to map and analyze NS fault systems, producing high-resolution DEMs and orthophotos. We examined fault populations to obtain detailed structural maps. We found that 20 NS fault zones distributed in both areas exhibit comparable en-echelon fractures and compressional push-ups, supporting a structural continuity between the SISZ and Reykjanes. We then combined our results with seismic data and observed a westward decrease of fault segment lengths, earthquake magnitudes and epicenter depths.

We suggest that these structural differences in the faults’ systems are likely influenced by a plate boundary rotation. An angle exceeding approximately 20° between the boundary and the spreading direction, due to a higher normal component, may promote volcanic activity. This activity increases the geothermal gradient, thereby expanding the ductile area and reducing the risk of large earthquakes, which is crucial for assessing seismic hazards in this densely populated region.

Sedimentary basins are often sites of high exposure to seismic hazard and characterizing these hazards is a high priority. In the near-field, the seismic sources are often the basin-bounding faults which project to the surface, allowing them to be studied using established paleoseismic techniques. Near-horizontal detachments between the sediments and crystalline basement represent a more challenging hazard, as slip along these low-angle faults may not reach the surface. Whether this slip is accommodated seismically or aseismically, and the factors that govern this, are essential questions for a complete understanding of seismic hazard within sedimentary basins. The Tajik Basin is situated within the India Eurasia collision zone and has been well studied using geodesy, seismology and geological mapping. Geodetic studies have shown basin bounding faults to be creeping, and seismic lines show a significant layer of salt at the basin detachment, which is thought to promote a velocity strengthening rheology on the fault. Salt diapirism and apparently co-located low angle earthquakes in the Tajik Basin suggest the possibility that salt can migrate away from the detachment via buoyancy, leading a previously aseismic fault to become seismogenic. To test the control of salt diapirism on detachment seismicity, we construct a new seismic catalog within the Tajik Basin reaching back to the mid-20th Century using calibrated earthquake relocation methods. We use statistical methods to more robustly test the co-location of earthquakes with diapirism to assess whether this hypothesis requires further study.

Fault systems record the temporal and kinematic evolution of orogenic belts and provide an important record of late- to post-orogenic tectonic processes. However, resolving whether structural diversity expressed as contrasting fault orientations and kinematics reflects conjugated systems or progressive stress field transitions remains a challenge in polyphase orogenic settings. This can only be solved by acquiring robust geochronological datasets constraining the timing of faults. In the Dom Feliciano Belt, the Neoproterozoic sub-metamorphic Itajaí Basin preserves a wide range of brittle to brittle-ductile fault geometries whose temporal relationships remain to be constrained. Here we present K-Ar geochronology of grain-size-fractionated illite from fault rocks and interlayered tuffs across the Itajaí Basin, integrated with structural analysis, textural characterization and illite crystallinity data. The analyzed structures span distinct fault orientations and kinematic regimes. Our results show that fault rocks of contrasting kinematics yield distinct K-Ar age populations, with most samples displaying limited evidence of detrital mixing, corroborated by constraints from interlayered and fault-related tuff. The ages and textural results might indicate multiple episodes of illite recrystallization associated with successive fault reactivations under Epizonal to diagenesis conditions. The data suggests a special relevance of ca. 520 Ma ages.

The rise in the atmospheric CO₂ concentration is pushing Earth’s climate to a critical state. By 2030, global climate is expected to mirror mid-Pliocene conditions. However, reconstructions of early Pliocene climate and its transition to the Pleistocene so far mainly depend on Mediterranean marine proxies. This PhD project aims to reconstruct past climate variability in Central Europe using the Heidelberg Basin in the northern Upper Rhine Graben as a high-resolution terrestrial archive. Its well-preserved and nearly continuous sedimentary record and variable lithology allow orbital to sub-orbital-scale temporal resolution.

Baseline sedimentological characterization identifies various clastic lithofacies, including massive and distorted sands, gravel-dominated facies, cross-bedded and ripple cross-laminated sands, flaser- and horizontally bedded sands, alongside massive, mottled, lenticular-, and horizontally bedded fines. These deposits compose typical fluvial architectural elements such as channel fills, crevasse splay, lateral accretions, sediment gravity flows, and floodplain fines. The succession records fluctuating energy conditions with repeated floodplain–crevasse–levee development. Upsection, increasingly incomplete crevasse–floodplain cycles suggest alterations in hydrological regime and/or accommodation space dynamics. Preliminary insights from heavy mineral analysis and detrital garnet geochemistry suggest a dominant local source within Lower Triassic sandstones and metamorphic rocks of the southern Odenwald and northern Black Forest. Higher in the stratigraphic section, increased metamorphic input emerges, possibly reflecting a basin-wide tectonic signal.

The overall results highlight the Heidelberg Basin as a potential European terrestrial climate archive, with mostly proximal sediment reflecting local climate signals. Future XRD analyses would extend this framework to quantify Pliocene weathering regime and reconstruct dry–wet palaeoclimate trends.

The IODP-ICDP Expedition 364 drill core is characterized by the pervasive presence of cataclasite zones in shocked target rocks underlying the peak ring of the Chicxulub crater. The formation of these zones is attributed to the transition from acoustic fluidization to localized shear faulting during cratering. Hence, the question arises to what extent cataclasis is the result of acoustic pressure fluctuations, possibly leading to pure crushing of target rock, and comminution of rock caused by zone-parallel shearing. We applied a novel semi-automated workflow for the 2D image analysis of thin section microphotographs to characterize shapes and orientations of fragments in cataclasite zones to better comprehend the possible change in the deformation mechanisms. Pure crushing is expected to produce random orientations of fragments with diverse shapes, while shearing may result in shape-preferred orientations of elongate fragments. The analyses indicate that the fragment ellipticity can vary significantly within any cataclasite zone, while a preferred orientation of elliptical fragments is evident. Furthermore, cataclasite zones from different depths of the core appear to mostly exhibit shape-preferred orientations. These observations suggest that shearing may have played a significant role in cataclasite formation. This implies that zone-parallel shearing may have indeed triggered a reorientation of elliptical fragments formed by initial crushing. Therefore, acoustic fluidization may have ceased at an earlier stage than previously thought.

Coarse-grained Gilbert-type deltas with steep foresets often develop in marginal-marine basins adjacent to active faults, being affected by the interplay of syn-sedimentary tectonics, riverine inputs and marine processes. In the Early Pleistocene of southern Italy, such deposits are found interfingered with mixed bioclastic-siliciclastic arenites within the Calcareniti di Vinco Formation, and are attached to the SW–NE-striking Oliveto Fault. In this system, eight facies were defined based on 17 sedimentary logs, supported by thin-section analysis and drone-derived orthomosaics. Steeply inclined, clast- to matrix-supported pebble and cobble conglomerates form a prograding Gilbert-type delta. The siliciclastic fraction is derived from the erosion of the adjacent Aspromonte Massif, transported through fluvial processes and deposited by gravity (i.e. concentrated and hyperconcentrated) flows during episodic discharge. The bioclastic fraction is indicative of an active carbonate production by the heterozoan assemblage located in the delta top and on the distal foreset. Organisms develop during periods of depositional quiescence, and are subsequently mixed and buried by waves and currents. The stratigraphic architecture records three phases of relative sea-level rise, marking system back-stepping from proximal deltaic conditions to more distal shallow-marine deposits. The succession documents the evolution through longer-term, relative sea-level rise in the Early Pleistocene.

This project is part of the ICDP initiative Gabon and Oxygenation of Earth – Drilling Early Earth Project (GOE-DEEP) and investigates the Francevillian Basin (Gabon) as a key archive of environmental and tectonic change during the Great Oxidation Event (GOE, ~2.4 Ga). The study focuses on establishing a coherent basin-scale framework to better understand how sedimentation, tectonics, and environmental change are linked during this critical interval of Earth history.

The Francevillian succession preserves evidence of major perturbations in the carbon cycle, early oxygenation, and microbial ecosystem evolution. However, the spatial and temporal relationships between these processes remain insufficiently constrained. This project aims to address this gap by using newly acquired geophysical downhole logging data from eight boreholes drilled in 2025 to (i) establish stratigraphic correlations across sub-basins, (ii) characterize sedimentary successions, and (iii) reconstruct aspects of basin evolution.

Geophysical logging data provide continuous records that enable high-resolution correlation and facies characterization beyond core recovery. These data will be integrated to develop a consistent stratigraphic framework and to assess basin architecture and its evolution.

By directly linking stratigraphic architecture, tectonic processes, and environmental signals, this project contributes to the overarching goals of GOE-DEEP: understanding the interplay between geodynamics, surface environments, and early life during the GOE. The study hast the potential to provide a framework for integrating borehole data with core and geochemical datasets, thereby enabling a more robust reconstruction of early Proterozoic Earth system evolution.

The Deep Dust Drilling Project will provide log- and core data from terrestrial sediments in the Anadarko Basin, Oklahoma, U.S.A. These data will enable refinement of Permian chronostratigraphy, and help better establish the presence of magnetic reversals at least in the younger (post-Kiaman) part of the stratigraphic succession. While the large-scale magnetostratigraphic patterns are established for the Permian, shorter magnetozones in the Lower Permian are not yet globally established consistently. Our contribution to the Deep Dust initiative is twofold and aims to improve Permian stratigraphy. We will conduct magnetostratigraphy and cyclostratigraphy in parallel to establish a timing for normal/reverse polarity intervals. In addition, it is our aim to establish an orbital eccentricity template for at least parts of the Permian using the novel TimeOptTemplate tool, ideally with absolute age control from dateable ash layers reported from the area.

The eruption of the Laacher See volcano (13 ka BP) resulted in the formation of a large caldera lake. The most prominent indicators of ongoing volcanic activity are the continuous release of gases (≈ 99% CO₂) in the form of mofettes and soil degassing, as well as strong gas seepages at various depths within the lake, some of which reach the surface.

Events such as earthquakes, landslides or a drop in the water level can cause a sudden release of gas stored at depth. This poses a particular risk from spring until late autumn when the lake is stratified and the region is visited by many tourists. With this motivation, three CO₂ flux campaigns covering the entire lake surface were conducted in summer (2024) and winter (2025) to obtain an initial estimate of the total CO₂ released by the lake. Results indicate that winter CO₂ emissions are an order of magnitude higher than those measured in summer, suggesting substantial accumulation of dissolved CO₂ in the hypolimnion during summer. In parallel, summer water column profiles of dissolved inorganic carbon (DIC) and its δ¹³C signature show gradients up to 10mM in the deep waters. Based on water chemistry we calculated that during summer p(CO₂) ranges from 2,000 µatm in the epilimnion to 102,000 µatm in the hypolimnion, independently supporting CO₂ accumulation at depth. We discuss scenarios under which gas pressure can exceed hydrostatic pressure resulting in sudden gas release - a potential risk posed by the lake.

Glycerol dialkyl glycerol tetraethers (GDGTs) are well-established biomarkers widely used for temperature and environmental reconstructions. Isoprenoid GDGTs (isoGDGTs), produced by Archaea, are the basis for valuable organic proxies like the TEX₈₆ or the methane index (MI), while branched GDGTs (brGDGTs), synthesized by Acidobacteria, form the basis of proxies (MBT’_5Me, IR_6Me and CBT) used for the reconstruction of temperature and pH. However, complex environmental interactions result in equally complex GDGT distributions, necessitating further studies into the global distribution of these components.

This study analyzes surface sediments from ~60 lakes worldwide for both brGDGT and isoGDGT distributions and investigates the robust application of GDGT-based proxies. The lakes are located on an altitudinal gradient with elevations ranging from 0 to 4060 m and mean annual air temperatures varying from -5°C to 25°C. Both isoprenoid and branched GDGTs were ubiquitously distributed and showed high variability between lake environments, reflected in BIT values ranging from 0.33 to 0.99. Additionally, OH-GDGTs, GGDs and branched GMGTs were detected in some of the lakes. MBT’_5Me values range from 0.21 to 0.92 showing a correlation with MAAT. IR_6Me values range from 0.16 to 0.84, while ratios of cyclisation show two groups, with a high temperature grouping (MAAT > 13°) characterized by very low abundances of hexamethylated brGDGTs. The results of this study showcase the high variability of GDGT distributions in lacustrine environments, advancing our understanding of proxy principles and highlighting the influence of environmental factors such as altitude, terrestrial organic matter input and temperature on proxy applications.

The Middle Jurassic is a pivotal interval in dinosaur evolution, yet terrestrial fossil sites are rare, even more so in Central Asia. This study reconstructs Jurassic paleoenvironmental conditions in the Fergana Basin, Kyrgyzstan, with a focus on the fossil-bearing Tashkumyr area. Despite the international significance of the Tashkumyr site for vertebrate paleontology, high-resolution sedimentological analyses that clarify the ecological context of the findings remain incompletely understood. This project integrates field-based stratigraphic correlation, sediment petrography, clast counts, facies analysis, and paleocurrent measurements from the Balabansai, Igrysai, and Tashkumyr formations to refine the depositional history of the basin.

Preliminary results indicate pronounced lateral and vertical facies variability, with rapid transitions between individual sections. The succession records a climatic shift from humid, coal-forming lowland conditions in the Tashkumyr Formation to more seasonal and increasingly arid fluvial environments in the overlying units. This transition is reflected by the disappearance of coal, the dominance of greenish-grey fluvial sediments in the Igrysai Formation, and later red-brown mudstones with channel fills and calcic paleosols with limited marine ingressions in the Balabansai Formation. The observed facies patterns suggest changing river dynamics, from meandering systems and floodplains to more braided and locally confined channels. The fluvial channels, regardless of the fluvial style, appear to be fixed throughout all formations. Clast-count data further indicate changes in sediment provenance through time.

These results provide a new sedimentological framework for the dinosaur-bearing strata of Tashkumyr and improve the understanding of the Middle Jurassic basin evolution in Central Asia.

Seawater hydrogen and oxygen isotopes are linked to salinity and reflect changes in the global hydrological cycle. The hydrogen isotopic composition of long-chain alkenones (δ²H_C37), produced by marine haptophyte algae, depends on both the hydrogen isotopic composition of seawater and salinity, allowing reconstruction of past surface seawater isotope variability from marine sediments. Here, we present a compilation of published and newly generated δ²H_C37 records from Ocean Drilling Program (ODP) and International Ocean Discovery Program (IODP) sediment cores spanning climate transitions of the Cenozoic.

Quaternary records consistently show lower reconstructed seawater isotope values during deglaciations, reflecting the release of isotopically depleted meltwater and changes in surface ocean hydrology. In contrast, reconstructed seawater isotopes remain comparably stable across the Middle Miocene Climate Transition at IODP Site U1318 (eastern North Atlantic) despite a pronounced increase in benthic δ¹⁸O, suggesting that much of this shift reflects deep-ocean cooling. Across the EOT and Early Oligocene, Atlantic records indicate larger seawater isotope variability than inferred from existing δ¹⁸O-based reconstructions, suggesting substantial reorganization of the oceanic hydrological cycle during the onset of Antarctic glaciation.

The compilation also highlights ecological and evolutionary influences on δ²H_C37 records. Data from IODP Site U1338 indicate effects of subsurface alkenone production, while highly enriched and variable Oligocene values observed at ODP Site 959 and other Atlantic sites may reflect evolutionary changes in alkenone-producing haptophytes. Together, these records show both the potential and limitations of alkenone hydrogen isotopes for reconstructing the Cenozoic surface seawater isotope evolution.

Environmental instability across the Triassic–Jurassic boundary (TJB) is closely associated with major perturbations of the global carbon cycle and widespread ecological turnover triggered by volcanism of the Central Atlantic Magmatic Province. Recurrent negative carbon-isotope excursions (NCIEs) preserved in organic and inorganic carbon records provide key evidence for these disturbances and are widely used for chemostratigraphic correlation. However, the expression of NCIEs may differ considerably depending on depositional environment, especially within shallow epicontinental basins affected by changing sea level and incomplete sedimentation. This study examines how local depositional controls influenced the preservation of TJB carbon-cycle signals in the North German Basin (NGB) through investigation of a proximal–distal transect including Barth, Moseberg, and Schandelah. Integrated TOC, Rock-Eval, and δ^¹³C_org analyses combined with palynostratigraphic and sequence-stratigraphic data reveal strong links between sea-level dynamics, flooding phases, hiatus development, and the accumulation of transgressive organic-rich black shales. A pronounced negative δ^¹³C_org excursion occurs in all studied sections near the latest Rhaetian–earliest Hettangian regression–transgression transition. At Barth, the condensed and truncated transitional interval records only a subdued ~3.6‰ excursion within a thin black-shale layer assigned to the Deltoidospora–Concavisporites palynozone. In contrast, the more complete Moseberg and Schandelah records preserve larger ~5‰ excursions within a transgressive organic-rich shale interval of the Hettangian Pinuspollenites–Trachysporites Zone together with elevated TOC, HI, and hydrogen-rich marine organic matter. These results highlight the critical role of accommodation space and stratigraphic completeness in controlling the timing, magnitude, and preservation of TJB carbon-cycle signatures in the NGB.

The North German subterraneous hydrogeology is strongly influenced by evaporites that occur at different depths. Most of these precipitated about 250 million years ago in a marginal marine basin in the Upper Permian containing thick series of carbonate-, sulphate-, and chloride-minerals. Interaction with meteoric waters often leads to the development of salty brines and underground voids causing sinkholes, such as in the town of Lüneburg or along the southwestern border of the Harz Mountains as well as to large karst-springs such as those near Förste and the Rhume Spring. Salt brines occurring at depth in Bad Sülze, Heringsdorf among other sites are brought to the surface and used for recreation and health applications. Therefore, underground evaporite dissolution at the interface between atmosphere, hydrosphere, lithosphere is impacted by anthropogenic activity and possibly by climate change. Understanding the hydrogeochemical water-rock interaction is of fundamental importance for the prediction of future quality developments of water resources.

Here, we combine stable isotope (H, C, O, S) and trace element results with dating from the mentioned surface and ground water systems and discuss results in terms of sources and sinks for dissolved constituents and the potential release of carbon dioxide. A physico-chemical meta-analysis of measurements allows for a characterization of (dis)equilibrium between mineral, solution, and gas phase. Some results can be compared with historical reports, and for the gypsum karst of the SW Harz Mountains with detailed investigations of the carbon and sulphur cycles a few decades ago, allowing for a possible climate change perspective.

Antimony (Sb) is a toxic element, and contamination from abandoned mines can persist long after mining activities ceased. In this regard, stable Sb isotopes emerged as valuable tracers for mineral exploration and environmental investigations, enabling the identification of ore-forming processes but also contamination sources in mining-impacted environments. In contrast, the biogeochemical Sb cycle in low-contaminated (<1 μg/L) aqueous systems remains poorly constrained.

This study investigates Sb concentrations and isotopic compositions in rivers of the Harz Mountains in relation to Sb ores and mine waters from the historic Wolfsberg Sb mine. Water samples collected in spring 2024 and summer 2025 revealed dissolved Sb ranging from <1 μg/L in unpolluted waters to ~105 μg/L in mine drainage waters. Contaminated waters (0.50–1.11 ‰, n = 7) and Fe oxides (0.70 ‰, 0.6 wt.% Sb) exhibited systematically heavier isotopic signatures than both the dominant ore mineral stibnite of the Wolfsberg area (0.00–0.30 ‰) and unpolluted waters (0.18 ± 0.06 ‰, 2SE, n = 24). This enrichment in heavy isotopes presumably indicates preferential release of heavy Sb isotopes during stibnite weathering.

At 500 m downstream of the mine drainage discharged into the creek, Sb concentrations and δ¹²³Sb values increased from background levels (~0.8 μg/L; ~0.14 ‰ before confluence) to elevated values (~7 μg/L; ~0.50 ‰), reflecting mixing and dilution between uncontaminated river water and mine effluent. These results demonstrate that combined Sb concentration and isotope data provide a sensitive tool for tracing the proximity and direction of Sb ore-derived inputs in mining-impacted catchments.

Amorphous calcium carbonate (ACC) and its magnesium-bearing analogue (ACMC05) play key roles in biomineralization, element cycling, and materials science. Recent advances using fast differential scanning calorimetry (FDSC) have revealed that synthetic ACC and ACMC05 exhibit a glass transition, confirming their nature as structural glasses, although they were not produced by quenching a melt but by lyophilization.

FDSC measurements at extremely fast heating rates up to 2000°C/s demonstrate that ACC and ACMC05 undergo a glass transition, with glass transition temperatures (T_g) strongly dependent on water content. For example, synthetic nominally anhydrous ACC exhibits a T_g of 339 °C. For hydrous samples, T_g decreases significantly with increasing water content. The relationship between water content and glass transition temperature is well described by the Gordon-Taylor equation, which provides a tool for predicting the glass formation, i.e. T_g, as a function of temperature and water content.

These findings suggest that dehydration-driven glass formation is a key mechanism in the production of glassy ACC and ACMC05, thereby bridging the gap between supersaturated aqueous solutions and crystalline calcium carbonate polymorphs. This process is particularly relevant for biomineralization, where ACC acts as a transient precursor.

Our latest FDSC analysis of biogenic ACC from a sea slug (Baptodoris cinnabarina) also exposes a glass transition signal, which confirms that natural ACC, which was formed by a living organism and not synthesized under laboratory conditions, is also a structural glass. Consequently, the isothermal crossing of the glass transition by dehydration is a plausible mechanism by which organisms produce metastable ACC.

Albeit being a well-documented process in ancient carbonate rocks from the Precambrian to the Cenozoic, early marine diagenetic dolomitisation is not clearly understood with respect to its occurrence and timing. It is also considered that early marine diagenetic dolomites cannot be mindlessly accounted as ancient seawater archives, as their geochemistry often reflects their evolution throughout their burial. In the Lombardy Basin (Northern Italy), the Norian Dolomia Principale platform underwent pervasive, mimetic dolomitisation soon after sediment deposition, making it an exemplary case study of early marine dolomitisation. Identifying the palaeoenvironmental parameters influencing the features of early marine replacement dolomites in Triassic shallow marine settings requires a comprehensive multi-proxy analysis. Samples were collected from various depositional environments, including restricted lagoon, inner platform, outer platform/margin, slope, and intraplatform basin. To unravel the diagenetic history and distinguish early diagenetic features from later alterations, a paragenetic sequence was established based on petrographic observations, cathodoluminescence, fluid inclusion microthermometry, U-Pb dating, and stable isotope measurements (d¹³C, d¹⁸O, and ⁸⁷Sr/⁸⁶Sr). Although the intensity of these events varied according to the original carbonate’s depositional environment, four main diagenetic events were identified: (i) early marine dolomitisation, replacing precursor sediment and marine cement; (ii) a succession of late dolomite cement precipitations; (iii) burial calcite cement precipitation; and (iv) late meteoric calcite precipitation. A comparative study of geochemical, textural and stoichiometric properties of early marine dolomites was also performed, revealing that geochemistry is often overprinted during burial, while the texture-stoichiometry combination of early dolomites may constitute an interesting proxy for ancient environments.

Lacustrine carbonates are essential yet understudied archives within the broader field of carbonate research. The low-Mg calcite shells of non-marine ostracods represent an invaluable source of authigenic biogenic carbonate in lake systems. Because ostracod valves are precipitated and deposited in close proximity to the sediment surface, they are especially prone to early (syn- and post-depositional) diagenetic alteration, potentially overprinting primary environmental signals. Although ostracod carbonate has been widely used in paleoclimatic studies for the last three decades, only a limited number of investigations have addressed the effects of sedimentary diagenesis on valve preservation and composition. Our study adopts an experimental approach to investigate sedimentary and mineralogical influences on the preservation and geochemical composition of non-marine ostracod valves. Here, we use living specimens of Cyprideis torosa, as they provide the most pristine valve conditions. The experiment consists of six distinct setups, each focusing on a specific water parameter: two temperature ranges (high: 40-50°C; low: 25°C), two pH conditions, and two dissolved salts (NaCl and MgCl₂). Additionally, clay mineral buffers will also be incorporated to simulate burial conditions and assess mineralogical influences. Initial experiments will run for more than five weeks, after which the valves will be analysed for structural changes using an electron microscope and for variations in trace element and isotope ratios. Results will be compared with unaltered valves from the same population to identify parameter-specific diagenetic effects, improving the reliability of ostracod calcite as a paleolimnological archive.

Speleothems are among the most reliable terrestrial archives for paleoclimate. A wide range of geochemical and petrographic proxies enables both precise dating and detailed reconstructions of past environmental conditions. Although previous studies have investigated the petrographic characteristics of speleothems, the relationship between drip-water geochemistry and speleothem petrography remains insufficiently understood. Research indicates that the mineralogy and crystal morphology of cave carbonates depend on various physicochemical parameters. The drip-water Mg/Ca ratio is the most influential factor, directly affecting crystal morphology and serving as a proxy for prior calcite precipitation (PCP). In a natural cave environment, multiple factors influence drip-water Mg/Ca ratios. Hence, cave analogue experiments were conducted to disentangle these effects. The setup was housed in a climate cabinet, with parameters of 15 °C and 70% humidity under atmospheric CO2 conditions. The solutions were purified of organic material and prepared at pH 7.9, with a steady drip rate of 98 µL/min. For 90 days, carbonate precipitated on roughened watch glasses while temperature, humidity, CO2 level, drip rate, conductivity, pH, and outflow element concentrations were continuously monitored. Between experiments, the fluid Mg/Ca ratio varied (0.5, 0.375, 0.25, 0.125), and each Mg/Ca ratio was tested with and without PCP. The precipitated carbonates were analysed utilising SEM, EBSD, and EMPA. Preliminary results indicate that the Mg/Ca ratio strongly controls crystal morphology. Moreover, aragonite was detected exclusively in experiments conducted under PCP conditions.

Carbonates of norsethite-type structure (Ba(Mg,Mn,Fe)[CO₃]₂) are used as crystal chemical and geochemical analogues for the prominent Ca-bearing double carbonates dolomite (CaMg[CO₃]₂), ankerite (CaFe[CO₃]₂), and kutnahorite (CaMn[CO₃]₂). Selected solid-solution members have been observed to occur in low- and high-temperature natural systems, like Baltic Sea sediments or different types of ore deposits. For most of these carbonates, neither the thermodynamic nor the reaction kinetic properties are well constrained or even known, so far.

In the present study, the dissolution behaviour of double and triple carbonate members of the norsethite family were dissolved in CO₂-saturated solutions at 25°C and 1 atm total pressure. The carbonates were synthesized at high P and T and characterized, e.g. via FTIR spectroscopy. Free-drift batch-type reactors were used. At the end of the experiment, carbonate solid-solutions were precipitated by forcing strong disequilibrium via CO₂ degassing. Both, the congruent and incongruent parts of the dissolution process were investigated and the partitioning of metals and stable isotopes was followed by aqueous and solid phase analysis.

The dissolution in aqueous solutions was found to be initially congruent with respect to metal stoichiometry. Extrapolation of experimental congruent reaction parts give the solubility product and the free energy of formation of the respective carbonate and the time-dependent reaction path allows for the extraction of dissolution kinetic parameters. Secondary carbonates differed in their composition compared to precursor phases.

These new experimental results will help to include these carbonate phases into codes for modelling reactive-transport during natural or underground CO₂-storage systems.

Lithium‑bearing brines are a key resource for lithium extraction, where the precipitation of zabuyelite (Li₂CO₃) acts as a major recovery route of Li feedstocks for subsequent processing. The efficiency of zabuyelite precipitation depends strongly on the solution chemistry, as non-constituent ions can compete for Li or carbonate ions as well as interact with the growing surface of zabuyelite in an antagonistic manner, altering nucleation and crystal growth. This contribution will highlight experimental and computational results that examine the role of different brine ions (Ca{^2+}, Mg{^2+}, Na{^+} and SO{_4}) on the growth of zabuyelite. The experiments demonstrate evidence that Ca²⁺ and SO₄²⁻ are incorporated into zabuyelite. Whereas, sulfate is expected to adsorb to distinct surface sites, altering growth, as well as form ion pairs with Li⁺ in solution. Na⁺ may alter the accessibility of carbonate in the solutions tested through the formation of ion pairs, whereas K⁺ and Cl⁻ interact weakly with growing crystals. These findings demonstrate how ion‑specific interactions at mineral–solution interfaces control the precipitation and purity of Li₂CO₃ products, providing mechanistic insight crucial for optimising lithium recovery from natural brines.

Speleothems (cave carbonates), such as stalagmites, serve as excellent archives for reconstructing palaeoclimate variability. However, the number of stalagmite records from glacial periods is significantly lower than from interglacial periods. By contrast, cryogenic cave carbonates (CCC), formed as water freezes in caves, can be used to infer palaeoenvironmental change during glacial periods. Although the number of studies on CCCs has increased over the past decades, studies of CCC element concentrations remain very rare. Here, we present CCCs collected in Windloch Cave in Western Germany. These were analysed via scanning electron microscopy (SEM), and thin sections were used for transmitted, polarised, fluorescence and cathodoluminescence microscopy. Finally, element concentrations of bulk CCCs were determined via ICP-OES, and those of thin-section CCCs were measured with EMPA. The calcite crystal morphologies of CCCs from Windloch Cave range from rhombohedra with varying degrees of steepness to spherulitic forms. Some rhombohedral types are partially or completely overgrown by microcrystalline calcite, reminiscent of the spherulitic CCCs. These overgrowths appear to consist of two to three distinct growth phases. The bulk Mg concentration of CCCs increases in the order: (i) rhombohedra, (ii) rhombohedra with partial overgrowth, (iii) rhombohedra with complete overgrowth and (iv) spherulites. All CCCs show an increase in Mg concentration from the interior outwards. The incorporation of Mg into the calcite crystal lattice increases the number of defects, leading to steeper rhombohedra and, at very high Mg concentrations, even spherulitic forms.

Hard water springs emerge to the surface saturated with respect to CaCO₃ and supersaturated with respect to the partial pressure of atmospheric CO₂. Overall, the path of surface water flows is in a delicate balance between degassing and precipitation, eventually leading to carbonate precipitation. These processes lead to geochemical proxy-containing mineral formation and the enhanced liberation of CO₂. At the Nohn (Dreimühlen) waterfall in the Eifel Region, the rate of these processes is enhanced in one major step, thereby originating the travertine formation within a complex moss matrix - an important geotope for local tourism.

Here, we investigated the partitioning of stable isotopes (CHOS) and trace elements upon surface water evolution of this hard water creek leading to carbonate travertine formation. Besides water in-situ parameters, the alkalinity, major and trace elements, nutrients, and the stable isotope composition of dissolved and solid phases were analyzed. Further textural and chemical compositions of solid phases were further analyzed by SEM-EDX in detail.

The evolution of the hard-water creek at Nohn is characterized by an induction period where degassing of carbon dioxide dominates, followed by a step-like calcite formation at the waterfall itself, further driving degassing. Stable isotope signatures allow for an element source identification and mechanistic interpretation of the processes controlling the carbonate system. Process rates may vary due to changes in topography and/or biological activity. The dissolved sulfate at Nohn originates from the oxidation of metal sulfides in the aquifer that may be incorporated into the carbonate lattice (CAS).

Carbonates from Gale Crater on Mars exhibit exceptionally high δ¹³C (110 ± 3 ‰) and δ¹⁸O (91 ± 4 ‰) values, which are difficult to explain by evaporation, Rayleigh fractionation, and cryogenic brine models alone [1]. Here, we experimentally test whether progressive freezing of bicarbonate brines under low pressure can induce carbonate precipitation. Saturated Ca- and Ca-Mg-bicarbonate solutions were placed in a freeze-dryer, where CO₂ degassing, evaporative cooling, and progressive freeze concentration promoted carbonate precipitation. Freezing over several hours induced precipitation of amorphous Ca- and Ca-Mg-carbonates (ACC, ACMC) preferentially at the ice-brine interface. Slower freezing rates promoted coarsening of ACC spherules. Magnesium-bearing brines produced unusually large ACMC domains of over 100 µm, suggesting that Mg stabilizes or promotes the persistence of amorphous carbonate during progressive freezing. Whereas cryogenic ACC has previously been produced by liquid-nitrogen quenching of bicarbonate solutions [2], our experiments show that amorphous carbonates also form during slower, progressive freezing under low pressure. Preliminary carbon and triple oxygen isotope data suggest that cryogenic amorphous carbonates can record C- and O-isotope compositions heavier than expected from equilibrium carbonate-water fractionation. ACC-to-calcite transformation may increase δ¹⁸O [3], implying that an amorphous precursor could amplify isotope enrichments acquired during evaporation and freezing. While this effect cannot explain the full Gale Crater δ¹⁸O enrichment on its own, it may contribute to the combined effects of evaporation, freezing, and Rayleigh-type fractionation.

[1] Burtt et al. PNAS 121.42 (2024). [2] Ihli et al. AFM 23.12 (2013), 1575-1585. [3] Asta et al. GCA 386 (2024), 96-109.

Calcite twins are referred to as e-, r-, and f- twins, which are contact twins with planar twin boundaries on {018}, {104}, and {012} planes, respectively, when indexed with respect to the hexagonal setting of the unit cell. Fine-lamellar (<1µm) mechanical e-, and r- twins occur together in one calcite crystal in fault rocks from the Talea Ori, Crete. In the Nördlinger Ries, Germany, impact breccias contain shocked calcite with e-, f- and r- twins. Mechanical twinning is a dislocation glide-controlled plastic deformation mechanism, where the nucleation and growth of twins (in length and thickness) in a host grain are facilitated by the generation and glide of dislocations, activated by deviatoric stress. In the theory of ferroelasticity, a spontaneous strain is reversible under deviatoric stress. Domains with crystallographically controlled different orientation (i.e., twins) form when a ferroelastic crystal undergoes a structural phase transition from a high-symmetry paraelastic phase to a low-symmetry ferroelastic phase, where the symmetry element of the twin law is combined with the symmetry elements of the structures to form the symmetry of the high-symmetry paraelastic phase. Here, we apply the theory of ferroelasticity to the calcite pseudosymmetries to the cubic NaCl- and CsCl-type structures to evaluate e-, r-, and f- mechanical twins and their relationship to each other in deformed calcite from fault rocks as well as shocked calcite. An understanding of mechanical twinning of calcite is important to infer the deformation conditions during faulting as well as the shock and aftershock conditions during impact cratering.

Fe-bearing carbonates are increasingly recognized as key phases for iron and carbon storage in Earth’s deep interior. Their physical properties at high pressure remain poorly constrained, particularly in compositionally complex and structurally disordered systems such as ankerite. Cation order strongly influences the physical properties and phase-stability [1,2]. Constraining the effects may help to explain the observed seismic anisotropic anomalies in the mantle wedge [3] and contributes to the detectability of carbonates in the deep Earth [4]. In this study, we investigate the high-pressure behavior of both ordered and disordered ankerite, Ca(Mg_0.3Fe_0.7)(CO₃)₂, using a combination of synchrotron-based X-ray diffraction and X-ray emission spectroscopy. Our goal is to assess the influence of cation ordering on both structural evolution and Fe spin behavior [1,2]. Experiments were conducted by compressing the samples in diamond anvil cells (DACs) up to ~80 GPa, exceeding the pressure range typically associated with the Fe spin crossover in the system FeₓMg₁₋_ₓCO₃ (~43 GPa at room temperature) [5,6]. The results show that both ordered and disordered ankerite remain in the high-spin state throughout the investigated pressure range and do not undergo a pressure-induced spin transition.

[1] Zucchini A et al. (2014) Phys Chem Miner 41:783-793; [2] Zucchini A et al. (2017) Eur J Mineral 29:227-238; [3] Liu X and Zhao D (2017) Geophys J Int 210:1410-1431; [4] Chariton S et al (2020) Am Miner 105:325-332.; [5] Cerantola V et al. (2017) Nat Commun 8:15960; [6] Liu J et al. (2014) Am Mineral 99:84-93

Carbon Capture and Storage (CCS) is widely regarded as a key technological approach for addressing global climate change by permanently storing or fixing greenhouse gas emissions underground. Presently the Government of Greenland assigned GEUS to prospect its integral geology regarding is potential to implement CCS technologies. At the same time Greenland investigates, within the framework of the EU Green Growth Cooperation Program especially into W Greenland Disko Island and the surrounding Disko–Nuussuaq basin as a suitable geological formation for long-term CO₂ sequestration. In 2025, two boreholes were drilled to depths of more than 500 m, recovering a previously undocumented thick succession of Paleogene picritic lava flows. These cores are presently studied to better characterize the volcanic stratigraphy with the included latite horizons, petrology, geochemistry and also the secondary (zeolite) mineralization’s of the volcanic successions. This intrinsic information is important to better understand the potential to fix CO2 as a stable mineral phase within these igneous lithologies. As in contrast to classical methodologies of CO2 storage in its gas and/or supercritical fluid phase, Greenland follows the technology of CarbFix to crystallize the CO2 with calcium, magnesium, and iron from the injected lithological units. This approach, in which CO₂ is immobilized through mineral carbonation, is more sustainable in Arctic regions than dependence on costly, long‑term, technology‑ and labor‑intensive monitoring systems required to mitigate leakage risks from subsurface CO₂ reservoirs.

Understanding alteration in crystalline rocks is important for geothermal energy utilization, as alteration can modify mineralogical, geochemical, petrophysical, thermophysical, and mechanical properties, influence the mechanical stability of rock masses, and provide insights into paleofluid migration in geothermal reservoirs.

This study investigates alteration processes in the Tromm Granite (Odenwald, SW Germany) through an integrated analysis of subsurface core material of the GeoLaB-1 wellbore and outcrop analogs from the same region. The primary objective is to identify altered horizons at depth and characterize alteration features observed in surface exposures to evaluate their implications on the integrity and long-term behavior of crystalline rocks considered for underground research applications.

The study combines field observations with laboratory-based mineralogical, geochemical, and mechanical characterization to establish links between alteration intensity, mineral transformations, as well as modifications in geochemical composition and rock properties. Subsurface core material is evaluated alongside representative outcrop analogs to improve understanding of the spatial variability of alteration within the crystalline body. Analytical methods include thin-section petrography, X-ray diffraction (XRD), X-ray fluorescence (XRF), inductively coupled plasma mass spectrometry (ICP-MS), electron microprobe analysis (EMPA), and mechanical testing to assess mineralogical and geochemical changes associated with alteration and their effects on rock strength.

By integrating subsurface and outcrop observations, this work aims to provide insights into alteration pathways in crystalline geothermal environments and their implications for the characterization and sustainable utilization of crystalline geothermal reservoirs.

Enhanced Geothermal Systems (EGS) rely on efficient fluid flow through natural or engineered fracture networks in crystalline basement rocks. These fractures are often poorly connected and flow-limited by asperities and small apertures. Therefore, chemical stimulation provides a promising approach to widen flow paths by selective mineral dissolution, potentially reducing seismic risks associated with purely hydraulic stimulation methods.

Within the framework of the Helmholtz research infrastructure project GeoLaB, this study investigates the hydrothermal reactivity of the Tromm granite exposed to bio-degradable N, N-bis(carboxymethyl)-L-glutamic acid (GLDA)-bearing fluids at 150°C and varying pH conditions. The investigated granite is characterised by a distinct dark-red colouration caused by a pervasive distribution of iron (Fe)-bearing alteration phases, i.e. hematite. Previous studies on light-coloured granites showed that quartz and feldspar exhibit only limited reactivity during GLDA treatment, thereby preserving a resilient structural framework after the dissolution of Fe-bearing phases, such as biotite. The present study specifically addresses whether this stability persists, when framework minerals are intergrown with biotite and streaked with hematite-enriched domains, focussing particularly on the role of such micro-scale heterogeneities in creating localised reactive domains that alter the overall geochemical behaviour of the Tromm granite relative to light-coloured granites.

Mineralogical and microtextural changes are characterised before and after the experiments using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. Evolving fluid chemistry and dissolution kinetics are quantified via ICP-OES analysis. The results provide a basis for subsequent flow-through studies investigating reactive transport and permeability evolution in Fe-bearing crystalline geothermal reservoirs rocks.

Predictive geochemical characterization of geothermal fluids during early exploration stages requires understanding of fluid–rock interactions and paleofluid circulation. Chemical species, including valuable metals such as Li, Pb, Zn, and Mn, as well as CO₂ and H₂S, can be mobilized, transported, trapped, or redistributed depending on physicochemical conditions. Reliable modeling of geothermal fluid composition depends on constraining pressure–temperature (P–T) conditions and reaction kinetics (Dezayes & Lerouge, 2019; Boschetti, 2023). However, a key limitation in modeling lithium behavior is the scarcity of kinetic data for the dissolution of Li-bearing minerals, particularly phases.

To address this limitation, controlled batch dissolution experiments were conducted on Li-bearing biotites, a key mineral due to its abundance in granitic reservoirs and its role as one of the main hosts for lithium in crustal rocks. The Upper Rhine Graben (URG, Europe) is used as a representative case study, where lithium-rich brines (up to ~200 mg/L at 250 °C) are associated with alteration of Li-rich micas in the granitic basement (Sanjuan et al., 2022; Drüppel et al., 2020; Dugamin et al., 2024; Lerouge et al., 2025).

Experiments were parameterized using geochemical numerical simulations and performed at 75, 90, and 150 °C under varying pH (acidic–neutral), water-to-mineral ratios (5–100), and reactive surface areas. Preliminary results obtained over one month (80–100 µm grain size; W/M = 100; distilled water) show a progressive increase in dissolved lithium. These data will be used to determine Li release mechanisms and estimate release rates for future reactive transport modeling.

Fracture permeability controls injectivity, productivity, and pressure management in crystalline geothermal reservoirs. Its evolution during circulation depends on fracture aperture, connected fracture volume, mineral reaction, and effective thermomechanical stress. These parameters are measured at core scale, but they enter reservoir forecasts through highly non-linear upscaling. This study develops a conservative geothermal digital twin for upscaling core-scale processes in crystalline rock to reservoir-relevant permeability constraints. The digital twin is calibrated against a high-temperature granite core flow-through X-ray computed tomography dataset under confinement. It integrates fracture geometry before and after reaction, laboratory flow response, effluent chemistry, mineralogy, temperature, pressure, and stress conditions. The conservative formulation preserves three independent constraints: imaged change in connected void volume, mineral volume loss inferred from aqueous chemistry, and aperture change expected from pressure and effective stress. These contributions are reconciled separately and evaluated against the observed hydraulic response. This provides a physically constrained interpretation of permeability enhancement. The key challenge is non-uniqueness. In crystalline rocks, small aperture changes can dominate permeability. Yet aperture is commonly near imaging resolution. Hydraulic aperture may also differ from geometric aperture. Fracture contact area, roughness, reactive surface accessibility, connected flow paths, and thermal-stress boundary conditions remain poorly constrained. Using the calibrated digital twin, the study shows that similar permeability enhancement can arise from dissolution, mechanical opening, improved connectivity, or their combined action. The framework identifies which quantities are measured, which are inferred, and which uncertainties dominate reservoir-scale interpretation. This supports more defensible geothermal forecasts and guides future measurements for reservoir design.

In the course of the cooperative research projects STIMTEC and STIMTEC-X, extensive acoustic-borehole televiewer (aBTV) logging was performed in the boreholes drilled in the research mine Reiche Zeche, Freiberg, Germany, including repeat-logs before and after hydraulic stimulation of selected borehole sections. Here, we report on the comparative analyses of aBTV images of intact borehole sections and sections with natural joints and fractures, performed with the objective to complement in-situ stress measurements. The intact sections offer an opportunity for a strain determination based on image correlation and travel-time analyses. Sections with fractures are examined for evidence of slip, i.e., localized strain, between the instants of taking the images. Restricted to an extended depth range of about 15 m, enclosed by two natural fault zones, in the more than 60 m long borehole BH10, we observe evidence for incipient borehole breakouts in the repeat images providing constraints on time-dependent failure of the penetrated gneiss and on stress orientation and its variability. Our study shows how repeat logging can contribute to an integrated stress analysis.

Thermo-mechanical and thermo-chemical processes strongly influence fracture evolution, permeability, and elastic properties in geothermal reservoirs. To better understand these processes at laboratory scale, we develop an integrated software framework for the analysis of acoustic emissions (AE) recorded during mechanical deformation experiments on geothermal reservoir analogue rocks. The work is conducted within the German collaborative research project TRIGGER, which investigates the effects of large thermal gradients on fracture formation and fluid–rock interactions in geothermal systems.

The workflow combines event detection, arrival-time picking, localization, and waveform modelling within a unified and open framework. Instead of conventional threshold-trigger methods, segmented waveforms from all sensors are cross-correlated to identify coherent signal portions across the acquisition network. Relative arrival times are then estimated using eigenvalue decomposition of the correlation matrices, enabling robust and precise picks even for weak or emergent events.

The resulting picks are used for high-resolution localization of AE hypocenters within laboratory samples, providing insights into fracture initiation, propagation, and clustering during thermal stressing experiments. In addition, we present a finite-difference waveform-modelling tool for fully anisotropic elastic media at laboratory scale. The modelling framework allows investigation of waveform distortions, travel-time variations, and amplitude effects caused by anisotropy and evolving internal structures.

Together, the presented tools establish a quantitative framework for linking thermal stimulation, fracture evolution, and elastic properties in geothermal reservoir rocks, thereby improving the interpretation of laboratory experiments and supporting the upscaling of sample-scale observations toward reservoir-scale applications.

Modeling subsurface reservoirs requires input parameters for the relevant physical properties of rocks. Regarding elastic properties, a discrepancy exists between values derived from elastic wave measurements (e.g., seismic surveys, sonic logging, and laboratory experiments) and those obtained from quasi-static loading in deformation apparatus. Frequency and strain amplitude are among the factors controlling differences between dynamic and static elastic parameters. Here, we report a suite of laboratory tests on samples of Gildehaus Bentheim sandstone, an analogue for siliciclastic hydrothermal-reservoir rocks, performed at mean stress levels of 10, 20, and 30 MPa, with loading amplitudes of 10, 30, 50, and 80% of the mean stress, corresponding to strain amplitudes from 6×10^-5 to 5×10^-4, at frequencies of 0.01, 1, and 10 Hz, complemented by ultrasonic measurements. Samples were tested dry, oil-saturated, and water-saturated to investigate the role of pore fluids and their viscosity for energy dissipation during cyclic loading. Under quasi-static monotonic loading, the dry sandstone samples exhibited an elastic modulus of approximately 14 GPa. Under oscillatory loading, the samples exhibited higher apparent stiffness. Storage and loss moduli are determined applying Fast Fourier transformation to the stress-strain records. The storage and loss moduli are more sensitive to strain amplitude than to excitation frequency, decreasing systematically with increasing strain amplitude. With a comparative analysis of our results from quasi-static and dynamic testing as wells ultrasonic measurements we aim to diminish the gap in frequency range covered by the various approaches to support parameter selection for modelling of subsurface reservoirs experiencing a complex stress history.

Geothermal energy provision from hydrothermal reservoirs relies on fluid transport through networks of discontinuities. The successful development and sustainable use of such reservoirs is supported by numerical simulations that upscale parameters from laboratory or monitoring scales to the reservoir dimension, typically based on laboratory measurements on intact rock specimens. At larger scales, the hydromechanical properties of the rock mass are increasingly controlled by the presence of discontinuities.

Previous studies have investigated the mechanical behaviour of fractured rock in uniaxial and triaxial deformation experiments, e.g., with varying number and geometries of pre-existing cracks, artificially induced defects, or discontinuity sets. These studies revealed that the rock failure pattern of the specimens shows a tendency towards coplanar shear failure with increasing angle of inclination of the pre-existing crack with respect to the direction of maximum principal stress, while pure tensile failure occurs at a dip angle of 90°.

This experimental study investigates how discontinuity sets with different orientations affect the hydromechanical bulk rock properties across spatial scales. The hydraulic, elastic and frictional properties of saw-cut and naturally fractured discontinuities are determined for two rock varieties from the Upper Rhine Graben using both direct shear tests and post-failure triaxial deformation experiments on specimens with different dimensions. The results of this study contribute to numerical upscaling approaches, relevant for geothermal reservoirs that rely on pre-existing fracture networks and subsurface applications based on equivalent principles.

Within the framework of the collaborative project TRIGGER, we aim to establish a petrophysical database for rocks relevant to the Upper Rhine Graben. Several lithologies were selected from Rotliegend drill cores of the Saar-Nahe Basin, which serves as an analogue for potential geothermal reservoir formations in the Upper Rhine Graben. About a dozen lithologies were investigated in this study, but detailed investigations were restricted to two sandstone varieties, volcanics, and a conglomerate. The experimental work was complemented by in-depth thin-section analyses. In addition to inspecting cores, we examined prepared samples including those from a fracture halo to decipher the chemical degradation processes. Basic petrophysical characterization included determinations of porosity, density, P-wave velocity, and velocity anisotropy. Bulk densities range from approximately 2410 to 2760 kg/m³, with the volcanic samples showing the highest densities and the sandstones generally exhibiting lower values. Porosity varies between approximately 5% and 10%, with the grey sandstone showing the highest average porosity and the conglomerate the lowest. The volcanic samples exhibit the highest average P-wave velocities under both dry and saturated conditions (5.5 and 5.7 km/s, respectively) and show nearly isotropic behaviour. In contrast, the grey sandstone displays the lowest average velocities (3.6 and 4.3 km/s) and relatively weak anisotropy, whereas the conglomerate and especially the reddish sandstone exhibit stronger directional dependence of P-wave velocity. With our work, we aim at constraining property variability, to be transferred into parameter uncertainty in modelling frameworks.

Temporarily negative electricity prices in spot market trading caused by a renewable energy surplus highlight the need for increased energy storage capacities. Supercharged hybrid gas-based energy storage (SH-GES) is a concept storing excess electricity as coupled thermo-mechanical energy in the geological subsurface, e.g., using CO₂ as a working fluid. Storage-induced pressure and temperature variations introduce geomechanical risks, including potential deterioration of reservoir and caprock integrity.

This study presents a thermo-hydro-mechanically coupled numerical analysis to identify the most influential petrophysical parameters controlling rock mass stability in both reservoir and seal formations. A total of 270 parameter combinations were evaluated using machine learning. Reservoir Young’s modulus, Biot coefficient, Poisson’s ratio, thermal expansion coefficient, and permeability were varied for a representative clastic system. Results indicate that the reservoir’s Young's modulus is a dominant control on system integrity. Higher stiffness leads to increased thermo-elastic stress redistribution, elevating the likelihood of mechanical failure in both the reservoir and overlying seal. Complementary laboratory observations suggest that most key rock properties remain largely stable under cyclic thermal loading up to 200 °C, but minor changes in elastic properties were documented. These results emphasise the sensitivity of system stability to rock mass properties, and the sensitivity of rock mass properties to temperature. Overall, the study highlights the importance of careful site characterisation to mitigate geomechanical risks during storage operations.

Shallow geothermal energy can contribute to a more sustainable heating and cooling supply, particularly when borehole heat exchanger (BHE) fields are part of local energy concepts. This master’s thesis investigates whether the use of pure water as a heat carrier fluid can provide an environmentally safer alternative to conventional water-glycol mixtures. Water minimizes the groundwater risk in sensitive areas but requires stricter thermal design to prevent freezing. The main question is whether water-operated BHE fields with borehole depths of up to 400 m can remain safe and cost-effective while maintaining minimum temperature limits over long-term operation.

The study is based on a site-specific case study of the city of Schwerte, Germany, and focuses on optimizing long-term thermal simulation using Earth Energy Designer (EED). Using hourly load profiles as input data, EED is applied to simulate and optimize various borehole field configurations, considering borehole depth, borehole count, total borehole length, and field geometry. Three scenarios are compared: a conventional water-glycol reference system, a water-operated system without active regeneration, and a water-operated system with seasonal thermal regeneration. The results are evaluated with respect to thermal stability, specific heat extraction, viscosity-dependent energy pumping demand, and overall techno-economic feasibility.

Underground hydrogen storage (UHS) in porous media is essential for large-scale renewable energy storage. However, hydrogen loss and alterations in reservoir rock properties such as porosity and permeability, driven by microbial activities, remain critical challenges. Although these biological risks are recognized, how microbial metabolism interacts with abiotic geochemical reactions and subsequently alters reservoir petrophysical properties during periodic injection is still poorly understood.

To investigate these coupled phenomena, a newly developed core-flooding apparatus is utilized to simulate hydrogen/water flow regimes in sandstone samples. Initial experiments focus on low-pressure conditions with methanogens, using sterile control groups to distinguish biological reactions from purely chemical effects. By monitoring effluent chemistry and gas pressure changes over extended cycling periods, we quantify reaction kinetics and track the evolution of core permeability to evaluate potential periodic variations in biofilm dynamics. This experimental framework will subsequently be extended to high-temperature and high-pressure environments.

Anticipated results will clarify the biogeochemical coupling mechanisms and petrophysical impacts under periodic flow conditions. This work aims to identify operational windows to either mitigate detrimental microbial growth or leverage beneficial pathways, offering practical benchmarks for reservoir screening, and risk management.

The present-day crustal stress state is a key parameter in assessing a potential siting region for a deep geological repository for radioactive waste since it is crucial for designing and evaluating long-term safety.

We present results from a new, Germany-wide, 3D geomechanical numerical model that provides a prediction of the present-day stress state. The model geometry is based on a new geological model of Germany and comprises 50 individually parameterized units. We assume linear elasticity and that the stress state is a superposition of gravitational and plate-tectonics-related forces. We solve the resulting partial differential equations describing force equilibrium numerically using the finite element method. The model consists of approximately 10⁷ hexahedral finite elements, which allow for a vertical resolution of ~50 m within the uppermost 5 km of the model. For model calibration, we use a new compilation of stress magnitude data records.

The model results show good agreement with the mean S_Hmax orientation of the new WSM release 2025 with a mean of the absolute differences of ~10°. Furthermore, our model results indicate an improved prediction of S_hmin in comparison to previous models with a mean of the absolute stress differences of 3 MPa. The modeled S_Hmax magnitudes exhibit larger deviations from the calibration data with a mean of the absolute differences of 7 MPa.

For geological engineering applications in general, and for final nuclear waste disposals in particular, temporal upscaling is necessary to derive rock mass properties and their changes with time from laboratory and field data. However, upscaling procedures based on physical data is scarce.

We present results from a combined physical and numerical modelling study on a granitic rock. The laboratory campaign comprised a) experiments to determine fracture toughness of the granitic rock and further fundamental physical rock parameters, and b) a set of specimens that were uniaxially deformed up to different levels of axial stress, and c) at different strain rates to macroscopic failure. Specimens were subsequently characterised with respect to their microstructural fracture patterns. The numerical campaign utilised laboratory results to translate laboratory data into model parameters and simulated fracture activation and propagation leading to failure using the phase field approach.

The laboratory results from uniaxial deformation experiments indicate an expected systematic relation of the crack inventory to the level of axial stress, and a systematic relation to the rate of deformation spanning five orders of magnitude. Accordingly, the numerical phase-field modelling approach considered tensile and shear failure to simulate brittle deformation in specimens containing multiple, randomly distributed, closed pre-existing microcracks, by employing the principal stress criterion in the phase-field evolution equation. By successfully simulating the strain-rate dependence of uniaxial strength and comparing the numerical crack inventory with those experimentally observed, this study contributes to a better understanding of long-term deformation processes forming the basis for temporal numerical upscaling.

Evaluating the clay mineralogy of Lower and Middle Jurassic clay rocks is essential for the site‑selection process in Germany. While only limited core material is available from the Lower Saxony Basin (LSB), cuttings from the Groß Buchholz Gt1 drilling provide an additional dataset. However, these cuttings were embedded in smectitic drilling fluids, which complicates the assessment of expandable clay minerals—precisely the components that control key barrier properties such as swelling, self‑sealing and sorption.

This poster contribution outlines the methodological limitations of using such cuttings and evaluates the effectiveness of intensive sample preparation and analysis of lithic fragments in sandy particle‑size fractions. To assess data reliability, Lower Cretaceous cuttings from Gt1 were compared with 555 core samples from four LSB boreholes quantified using Rietveld refinement [1-2]. Bulk samples show expandable illite–smectite contents of 21 wt% (Valanginian), 23–29 wt% (Hauterivian), 28 wt% (Berriasian), 31 wt% (Barremian) and 34 wt% (Aptian). These values closely match the 20–35 wt% range found in sand‑sized cuttings residues from the same units. Although the number of cuttings samples is small, the consistent overall range supports the plausibility of the results.

Applying the same analytical approach to sandy fractions of Lower and Middle Jurassic cuttings—where no core material is available—yields 25–40 wt% expandable illite–smectite minerals. These findings suggest that, despite inherent limitations, carefully processed cuttings can provide meaningful mineralogical information for stratigraphic units lacking core samples.

[1] Ufer K et al. (2012a). https://doi.org/10.1346/CCMN.2012.0600507

[2] Ufer K et al. (2012b). https://doi.org/10.1346/CCMN.2012.0600508

Ensuring the safe disposal of high-level radioactive waste in a suitable host rock requires compliance with several legally defined criteria. These criteria are established by the German Site Selection Act (Standortauswahlgesetz – StandAG). Section 22 of StandAG defines the exclusion criterion “volcanic activity”. Magmatic and volcanic activity present a risk of a potential integrity loss of the host rocks with barrier function and of the surrounding rocks and therefore may result in the release of stored radioactive materials. Accordingly, areas with known Quaternary volcanism or expected volcanic activity within the next one million years must be excluded (Eifel and Vogtland). The evaluation is based on the study of Schreiber and Jentzsch (2021). In addition, the combined risk associated with magmatic and eventually volcanic activity is analyzed. Additionally, the probability of magmatic hazards occurring is classified into five categories based on a five-year project by BGR (Magmatism Project, u.a. Rummel et al 2024 und Bartels et al 2024). The probability of occurring magmatic and volcanic processes is categorized based on the following three processes: potential for magma formation in the mantle, presence of volcanic rocks on the surface and formation of migration paths in the lithosphere. Thus, a map providing an assessment of magmatic and volcanic hazards on a national scale was developed and will be presented.

The long-term safety of deep geological repositories for high-level radioactive waste relies on the stability of the engineered barrier system, including the metallic canister and the surrounding bentonite buffer. In crystalline host rock environments, the hydrogeochemical composition of deep water is expected to vary significantly and may influence corrosion processes at the metal–bentonite interface.

This study investigates the corrosion behavior of cast iron with spheroidal graphite in bentonite suspensions under repository-relevant conditions, with a particular focus on the influence of the hydrogeochemistry. Experiments are conducted under anoxic conditions at elevated temperature (60 °C) using artificial waters with varying salinity representative of crystalline rock environments.

A multi-analytical approach is applied to characterize corrosion processes and associated alterations in both, the metal and the surrounding bentonite. Surface and cross-sectional analyses are performed using optical microscopy and scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM-EDS). Mineralogical phase identification is carried out by X-ray diffraction (XRD) and µ-Raman spectroscopy, while elemental distribution patterns are assessed using micro-X-ray fluorescence (µ-XRF).

The study systematically evaluates how variations in hydrogeochemical conditions affect corrosion mechanisms, corrosion products, and element migration at the metal–bentonite interface. It provides insights into the coupled processes controlling material degradation in engineered barrier systems and supports the assessment of long-term repository performance.

Implementing the German site selection act (StandAG) requires a comprehensive understanding of the composition and properties of potentially suitable claystone formations. In recent years, the database on repository-relevant properties of German claystones has improved significantly.

For this study, samples from southern Germany and the Mont Terri site (Switzerland) were investigated using a facies-based approach including structural, mineralogical and geochemical analyses. The results support the classification of the Opalinus Clay into several (sub-)facies types. The clay mineral content fraction (by XRD quantitative analysis using the Rietveld method) controls radionuclide sorption and swelling behavior, varies between facies, and correlates with variations in cation exchange capacity (CEC). Rietveld crystal structure analysis of illite-smectite interstratified phases indicates that the proportion of illitic layers in these mineral phases ranges between 77% and 83% across all refinements and ordering types. Remaining 17-23% of this “mixed layer clay mineral” are smectitic layers with large interlayer surface areas and the ability to exchange hydrated cations allowing the clay rock to swell and shrink upon changes in water content. No significant differences in the illite:smectite ratio were observed between the studied sites; however, variations in the degree of ordering may reflect differences in burial history.

Building on these results, as well as data from other claystone formations, we aim to establish a standardized evaluation framework, focusing on the predictability of repository-relevant properties. Central to this approach is the development of simplified, quantitative proxies (e.g., CEC, XRF data and selected borehole logs) derived from the multidisciplinary datasets.

The interaction between cementitious pore water and high-level waste glasses, together with the self-irradiation damage caused by radionuclides, can significantly reduce the structural durability of the glass, thereby accelerating the aqueous corrosion process. In this study, the International Simple Glass (ISG) was irradiated with ~ 950 MeV gold ions (penetration depth ~ 60 µm) to simulate processes arising from alpha-decay processes. The Au-irradiated ISG was corroded in a NaOH (0.5 M) - Na₂CO₃ (0.25 M) solution (pH_18.6°C = 13) at about 81 °C for 360 hours, using fluid-cell Raman spectroscopy (FCRS). Real-time and space-resolved (operando) observations by FCRS revealed: (i) enhanced dissolution kinetics of the irradiated glass, (ii) precipitation of vaterite, (iii) formation of a water-rich interface between the dissolving glass and the surface alteration layer (SAL), accompanied by (iv) vaterite-calcite transformation. Post-mortem scanning electron microscopy and energy-dispersive X-ray spectroscopy confirmed the stabilization of vaterite by silica, and the formation of calcite, revealing further Ca-rich and Zr-Si-rich layers. FCRS enabled the study of the direct link between irradiation-induced structural modifications of the borosilicate glass network, the dissolution rate kinetics and SAL-formation, and vice versa. The operando observations of the evolving water-rich interface and lamellar patterns support the interface-coupled dissolution-precipitation model. These findings are crucial for improving models used to predict the long-term behavior of nuclear waste glasses in a geological repository.

Permeability and capillary sealing behaviour are key transport properties controlling fluid flow in claystone host rocks considered for deep geological disposal of radioactive waste. Their dependence on stress, anisotropy, and burial history is critical for evaluating their containment potential.

This study investigates water permeability (k_water) and hydrogen capillary sealing behaviour in the Amaltheen Claystone (Hils and Sack synclines, Lower Saxony Basin, Germany). The area acts as a natural laboratory, where variations in thermal maturity and thus maximum palaeo-burial depth (d_max), define a south–north thermal maturity gradient, enabling systematic investigation of burial-dependent behaviour. Core samples were prepared parallel and perpendicular to bedding to assess anisotropy.

k_water was determined using steady-state and pulse-decay methods under confining pressures of 1–20 MPa through loading–unloading paths. Stepwise hydrogen gas breakthrough (P_breakthrough) tests assessed capillary sealing behaviour in water-saturated samples.

k_water (∙10^-19–∙10^-23 m² for up to 4.8 km d_max ) decreases with increasing stress, reflecting partial plastic and elastic closure of fractures and pores during loading. Limited recovery during unloading indicates mostly elastic changes. k_water also decreases with maximum burial depth, reflecting mostly plastic deformation due to mechanical and chemical compaction. Anisotropy is more pronounced at low stress. P_breakthrough increases with confining pressure and thermal maturity (3–5.5 MPa across samples spanning ~1.7–2.8 km d_max) with negligible anisotropy.

These initial results demonstrate that k_water and P_breakthrough are governed by effective stress and burial history, providing experimentally constrained parameters for evaluating the containment potential of claystones.

To guarantee the safety of long-term storage of radioactive waste in the geosphere, the integrity of geological formations and technical barriers must be maintained over long periods. In order to investigate the microstructural failure properties relevant to long-term nuclear waste disposal, nine granite specimens were subjected to triaxial deformation up to failure under three strain rates (10^-7 to 10^-3 s^-1) and confining pressures (3, 5, 9 MPa) and subsequently prepared as thin sections.

A total of 54,546 individual crack structures were manually identified and analysed. The number of cracks, crack length, crack orientation, crack density, crack intensity and the ratio of tensile to shear cracks were digitally quantified. The results demonstrated a direct systematic relationship between the crack-length frequency distribution and both strain rate and confining pressure. Short cracks dominated at all investigated conditions, although comparatively more long cracks occurred at lower strain rates. The observed fractal relationship between the fracture-length frequency distribution with strain rate and confining pressure suggests that microscale fracture processes can be extrapolated to larger temporal scales and can therefore be incorporated into long-term numerical safety analyses. Furthermore, microcracks act as pathways for fluid migration, which could compromise the integrity of subsurface structures for the long-term underground disposal of radioactive waste. Based on fracture profiles across the investigated thin sections, upper limits of intrinsic permeabilities were estimated.

The results show that two-dimensional microstructural analyses enable a link to be established between laboratory testing, natural crack development and the prediction of rock failure over geological timescales.

In the context of the site selection procedure for a high-level radioactive waste repository in Germany, the fluid content of rock salt is an important parameter to evaluate the potential of gas formation and the tendency to form fluid pathways. Knowing the composition and quantity of the fluids in salt rocks is important (1) to estimate gas generation due to temperature increase, (2) to understand the mechanical behaviour of the rock salt or (3) to predict future scenarios, such as an interaction of highly-saline brines with the technical barriers. Aqueous fluids in rock salt are typically present in small unconnected fluid inclusions located within the crystals or arranged along crystal boundaries. In addition to this “free water”, there is mineral-bound water for example in anhydrite or clay minerals. When estimating the fluid content of rock salt the main challenges are (i) the general low fluid contents, (ii) the low permeability of the rock preventing fluid extraction and (iii) the spatial heterogeneous fluid distribution. We are working on an improved non-destructive and rapid method to characterise the fluid contents in rock salt by nuclear magnetic relaxation (NMR) relaxometry. We present a compilation of NMR measurements on rock salt samples from various locations, settings and formations. In addition, typical NMR relaxation times are identified that correlated with the mineralogy of minor components (e.g., anhydrite, clay minerals) as well as with microscopically visible fluid inclusions. These findings form the basis for the quantification and discrimination of “free” and mineral-bound water in salt rocks.

The Continental Deep Drilling Project (KTB) in northeastern Bavaria is Germany's only deep scientific drilling in crystalline rock. It has provided insights into continental crustal mechanics, including unique geomechanical data down to 9 km depth. The observed influence of the host rock and intersected fault zones on the stress state provides a valuable basis for studying geomechanics in a crystalline setting. This is particularly relevant to the site-selection process for a deep geological repository.

We present the first high-resolution 3D geomechanical-numerical model of the KTB drill site, covering approximately 20 × 20 × 12 km³, discretised with ~6 million elements. The model incorporates five lithological units and three fault zones (SE1, SE2, SE4), parameterised with contrasting stiffness values, and is calibrated against available stress magnitude data to yield a continuous 3D stress field across the model volume.

The model advances understanding of geomechanics in several key aspects. It quantifies the sensitivity of the modelled stress state to variability in rock properties, particularly the Young's modulus, constraining inherent uncertainties arising from the heterogeneity in the rock volume. It also allows comparison of the modelled rotation of principal stress axes with borehole breakout orientations, which enables the estimation of the minimum and maximum stiffness contrasts. Furthermore, it allows the simultaneous constraining of several model parameters, using, in addition to stress magnitude data, the rock property measurements and indirect observations of the stress state.

The work was funded by the DFG (PHYSALIS 523456847), the BGE (SpannEnD 2.0) and the BMUKN project SQuaRe (02E12062B).

Potash deposits have been formed and preserved in numerous basin structures around the world over the course of the Earth's geological history. Due to the role of economically viable potash deposits in the production of potash fertilisers and, consequently, global food security, potash salts are considered to be among the most significant raw materials.

The main potash deposits presently in production formed during the Devonian (e.g. Elk Point Basin, Pripyat Basin), the Permian (e.g. Kama Basin, Zechstein Basin) and the Quaternary (e.g. Dead Sea Region). Moreover, numerous exploration campaigns for further deposits in South America, Central Africa, as well as in Southeast and Central Asia have been undertaken in recent times.,

Modern exploration of potash deposits is characterised by a sequence – and often a combination – of the following steps: prospecting to find the right geological setting, archive studies to obtain as much information as possible about the subsurface in the area before expensive field investigations are started, geophysical investigations to evaluate the continuity and depth of the deposit or the brine host rocks, exploration drilling to obtain material for detailed investigations of the deposit and hydrogeological studies. The data obtained from this exploration serves as input for the subsequent steps in the evaluation of the deposit.

It is evident that a numerous of geoscientific disciplines are involved in the exploration and exploitation of potash deposits. Areas of responsibility undertaken by geologists include lithology, tectonics, microstructur, 3D-modeling, geophysics, geochemistry, water and environmental law, mining law and raw material economics.

The GEOROC (Geochemistry of Rocks of the Oceans and Continents) database is the largest publicly accessible geochemical database and is providing researchers with geochemical datasets tailored to their specific needs. Rock classifications are stored in the database as the authors of the original publications reported them. This can lead to perceived inconsistencies, especially due to the multiple pathways of rock classification – be it classification by petrological hand specimen observations or based on (semi-)quantitative rock modes or chemical analysis.

To address this problem and to allow the users and providers of geochemical and geological data more freedom in classification-based queries on a multitude of chemical parameters, we present an automated process leveraging geospatial and geometric functions to rapidly classify geochemical datasets. The workflow utilises a PostgreSQL database with the PostGIS extension to treat datapoints as locations and classification polygons as areas on a compositional map. Using spatial intersection SQL functions in the database we can automatically identify which polygon any sample datapoint falls into, thereby assigning the datapoint to a chosen classification convention.

A set of predefined polygons for a large amount of well-established geochemical classification diagrams allows the user to utilise the classification based on the parameters they choose, thereby increasing comparability and interoperability of compiled individual datasets.

To demonstrate this, we apply this methodology to a comprehensive dataset of igneous rocks from the Aeolian Arc, Italy, compiled from GEOROC. Using a Python-based ecosystem connected to Postgres, the data is extracted, classified and mapped directly in one pipeline.

The increasing volume and complexity of geochemical literature pose major challenges for the sustainable curation of domain-specific databases such as GEOROC (Geochemistry of Rocks of the Oceans and Continents). GEOROC is the world's largest database of geochemical and isotopic data from igneous and metamorphic rocks and minerals, and supports a wide range of geochemical and petrological research. However, curation and data input to GEOROC still relies heavily on manual effort, limiting scalability and consistency.

In this contribution, we present an information extraction architecture implemented as a multi-agent system, orchestrating specialized agents around a large language model backbone. A layout-aware parser (MinerU) decomposes PDF manuscripts into geometrically grounded primitive blocks, preserving the structural context essential for interpreting complex data tables. A text-filter agent groups these blocks into titled sections, while a dedicated table-processing agent extracts samples and measurements from tabular content, handling wide tables through column-batch chunking to remain within model context limits.

Central to the framework is a context-aware enrichment strategy in which each extracted field carries metadata distinguishing high-confidence values anchored in tables from those derived from surrounding text. A text-enrichment agent iteratively traverses text sections, filling missing attributes and replacing weaker information when stronger evidence emerges, while preserving the document context. A final merge-and-normalization agent performs deduplication and unit harmonization, producing a database-ready JSON representation that preserves both extracted values and their evidential context. By combining these components, the framework supports scalable curation while improving consistency, traceability, and interoperability, strengthening GEOROC's role as a FAIR-compliant reference infrastructure.

Historical groundwater quality records from Lusatia, collected between 1950 and 1990, were digitized and now integrated into a modern geospatial framework. The dataset includes measurements of key hydrochemical parameters: iron, sulfate, nitrogen species, and various potentially toxic elements (PTEs) from irregularly located sampling spots and discontinuous temporal intervals across mining-impacted areas. The dataset as a result is sporadic and scattered, with missing values due to these specific, targeted campaigns focused on particular measurements at times and locations. These heterogeneous characteristics add complexities for data processing and make it challenging to select an appropriate approach a priori.

In this study, we first employ a set of exploratory visualization techniques to investigate the spatial and geochemical variabilities in the region. Building on these insights, we evaluate the suitability of several classification approaches (e.g., k-means and data clustering) for interpreting the dataset. The resulting workflow contributes further to the interpretation of long-term groundwater quality trends, providing insight into anthropogenic impacts on regional geochemical dynamics. The overarching goal is to better understand the groundwater-soil interactions in Lusatia, and to evaluate the extent to which mining activities have influenced water quality across the region.

Computational geochemistry plays an increasingly important role in understanding magmatic, volcanic, and broader Earth system processes. These approaches depend on integrating diverse geochemical datasets that vary in scale, analytical methods, and material types. However, data reuse is often hindered by inconsistent metadata, unclear terminology, and limited interoperability among some major data providers.

The Digital Geochemical Data Infrastructure (DIGIS) addresses these limitations by modernizing and linking two key databases: GEOROC and GeoReM. GEOROC provides extensive open-access geochemical data for rocks, minerals, and glasses, while GeoReM compiles high-quality reference material data essential for calibration and analytical quality control. Strengthening interoperability between these complementary resources is crucial for ensuring reproducibility and robustness in computational studies.

Central to this effort is the development of shared, machine-readable controlled vocabularies spanning sample descriptions, lithology, mineralogy, analytical methods, and reference materials. These vocabularies harmonize legacy datasets while remaining aligned with international data standards. The resulting integration enhances data filtering, supports uncertainty-aware modelling, and enables reproducible benchmarking.

Recent studies demonstrate the benefits of such harmonization. Machine learning applied to large geochemical datasets has improved classification of tectono-magmatic environments and revealed patterns in magma evolution. Similarly, standardized datasets support emerging petrological models that infer magma storage conditions from compositional data.

Overall, interoperable, FAIR-aligned geochemical infrastructures provide a critical foundation for advancing data-driven and computational magmatic research.

The GeoReM (Geological and Environmental Reference Material) database was initiated in 2005 by Klaus Peter Jochum and developed at the Max Planck Institute for Chemistry in Mainz, Germany. Following Jochum’s passing, responsibility for GeoReM was transferred to the International Association of Geoanalysts (IAG) in August 2025, with infrastructure support now provided by the Digital Geochemical Data Infrastructure (DIGIS) team at the University of Göttingen.

Since the early 2020s, GeoReM has faced new challenges due to rising publication volumes, the proliferation of insufficiently reviewed papers in predatory journals, increasing data volumes driven by FAIR principles, and rapidly expanding geoanalytical datasets enabled by methodological advances and automation.

For GeoReM 2.0, data curation must adapt. Previously, curation relied on experience-based searches in a curated list of journals, supported by voluntary submissions. To address increasing data volumes, we evaluated data completeness using IGG-B1 to B8 boron isotope reference materials [1,2]. An extended citation map was used to assess whether relevant data from original and subsequent publications were integrated into GeoReM. Results are complemented by a statistical analysis showing how newly added datasets refine the characterization of these eight reference materials. This approach also facilitates identification of missing data for other materials.

Additionally, GeoReM citation data are analyzed using a knowledge that visualizing reference material usage and clustering in the geoanalytical community. Integration of RIS-format bibliographic data enables systematic citation mapping and automated detection of newly published studies, enhancing traditional manual “combing” approaches.

[1] Tonarini et al. (2003) https://doi.org/10.1111/j.1751-908X.2003.tb00710.x
[2] Gonfiantini et al. (2003) https://doi.org/10.1111/j.1751-908X.2003.tb00711.x

The GEOROC database is a cornerstone resource for geochemical research, providing freely accessible, curated sample data spanning a wide range of rock types, locations, and geological ages. However, its current interface is limited to structured queries using predefined metadata filters, preventing researchers from exploring the database through natural-language research concepts. A geoscientist interested in, for example, “magma plumbing systems at multiple crustal levels” has no direct query pathway within the existing system.

This contribution presents a proof-of-concept semantic search prototype designed to bridge this gap. The system links pre-trained embedding models to GEOROC-associated data sources, enabling free-text retrieval over geoscience research abstracts. A four-stage pipeline, formed by reference data import, abstract retrieval via the Crossref API, embedding generation, and vector similarity search via PostgreSQL/pgvector,is implemented in Python and deployed in a fully reproducible, containerised environment.

Four general-purpose embedding models were evaluated across 48 retrieval experiments, covering expert-formulated geoscience queries, full abstracts, title-only inputs, and out-of-domain control texts. All models returned geoscientifically plausible results for domain queries without any domain-specific fine-tuning, and dimension reduction revealed how shared abstract topics clustered into themes in vector space. Furthermore, we observe correlation between question length, domain topic and similarity scores. Crucially, specific search questions linked back to GEOROC sample locations reveal geographically and geologically coherent matches, for example when looking for polybaric magma plumbing systems which correlates to the Pacific Ring of Fire.

GEOROC and PetDB offer access to over 48 million individual data points from approximately 27,000 publications covering oceanic islands, continental environments, and subduction zones. The DIGIS project is modernizing GEOROC in accordance with the FAIR principles. Thematic global compilations are extracted as datasets with DOI identifiers and regularly updated via the GFZ data services. GEOROC is reconnected to the reference material database GeoReM. New tools for data analysis quality assessment are developed (Ernst Styn et al., 2025; Traun et al, in prep.). PetDB was migrated to a new architecture with simplified search interface in 2025. The EarthChem-Library offers data publication and archiving. In the EarthChem portal, PetDB and GEOROC together with several smaller databases provides access to nearly 50 million geochemical data points through a single point of entry.

These global geochemical data services provide curated domain-specific databases and extensive, thematically curated datasets and data publications that were developed over many years and are maintained by the research community on the basis of individual proposals for third-party funding. While community use of this service remains on the rise and obviously the data systems contribute to exciting research also beyond the “hard-rock” Earth Sciences, future funding and further development is not secured unless a sustained funding format is in place.

This contribution seeks to strengthen the recognition of the geochemical data services as an important research tool with many opportunities also in applied sciences, attempts to foster discussions and involvement of the Earth Science Community in the discussion about their future.

The most effective way to reach the largest number of young learners is to engage the largest number of teachers and educators. Unfortunately, the limited presence of geoscientific topics in university programs for geography teachers and in German School curricula represents a major obstacle to integrating geosciences into German schools. However, this is not only a German issue. In other countries, where geoscience is included within the curricula of other natural sciences, teachers often lack sufficient geoscientific background (Bonaccorsi et al., 2020, European Geologist, 50).

To overcome these differences and with the aim of providing a greater number of teachers with a solid background in geosciences, the European Geosciences Union (EGU) and International Union of Geological Sciences (IUGS) have been promoting a training program in six countries since 2019. It is based on a network of field officers (one from each member country), who aim to organise and carry out at least four workshops for teachers per year in their respective countries. Currently, 12 European Countries are part of this initiative (Correira et al. 2023, EGU General Assembly 2023; https://www.egu.eu/education/)

Germany has been part of this program since 2022. Since its beginning, 16 workshops have been organised across 10 of the 16 federal states. This contribution aims to summarise the first four years of activities and provide an overview of future initiatives. All those interested in this topic are also invited to attend the training day for teachers organised on Wednesday, 23^rd September, within the framework of this conference.

Teaching materials on the topic of "Earth System" are available for free download on the website of the German Geological Society (DGGV). The project has been under development since 2024. 24 chapters on geological topics, currently focusing on the fundamentals of geodynamics, have already been completed and are available in three languages: German, English, and Spanish German version (https://www.dggv.de/das-system-erde/themen-zum-system-erde/, and the links therein). Further chapters will follow shortly. The content is primarily aimed at teachers and pupils in schools, but also at university students and anyone else interested in geological topics. Trials in the classroom by individual teachers have shown that the materials provide useful and welcome support for teaching.

Each chapter contains explanatory text and illustrations or short movie clips, as well as a direct link to the corresponding instructional video available on the YouTube channel "Lehrvideos System Erde". The instructional videos are 6 to 15 minutes long.

After two years, the YouTube channel now has 530 subscribers and more than 35.000 views. The website had recorded more than 90.000 views. I hope that the interest in the website and the YouTube channel continues to grow and would be pleased if information about this project were shared.

Pores that form in the liquid metal and slag phases during the pyrometallurgical smelting process can provide information on various characteristics of the process and the potential weathering of stockpiled slag. This study analyses the formation, morphology, and interconnection of pores during the pyrometallurgical processing of secondary Waelz slag, emphasising their impact on the efficiency of metal-slag separation. The morphology of the pores, including their shape, sphericity, and size distribution, is governed, among other factors, by the interplay between melt viscosity and surface tension during the liquid stage.

Micro-computed tomography (μ-CT) enables non-destructive, comprehensive three-dimensional volume analysis of representative sample volumes. Quenched slag samples are characterised by μ-CT, and the resulting image stacks are processed using advanced segmentation protocols to isolate pore populations from the slag matrix and metallic phases. Along with pores, metal droplets are also isolated through segmentation and analysed. Characteristics of individual phases derived from μ-CT are correlated with results from chemical analysis using µ-XRF and with results from phase analysis using X-ray diffraction. The resulting dataset constitutes a multi-scale, quantitative framework for understanding microstructural development in Waelz slag as a function of pyrometallurgical processing conditions, with the ultimate aim of identifying processing parameters that optimise metal recovery.

Today’s quality of life and technological advancement in the world depend on access to a variety of raw materials, including chromium. The European Union is subject to a high risk of supply disruption because it imports most of the critical raw materials. In addition, because of numerous constraints in exploration and extraction activities in Europe, opening new mining operations has become quite burdensome. In this study, we reviewed chromite deposits in Albania, Turkey, Cyprus, Greece, and Finland.

Major chromite producers are South Africa and Kazakhstan, with about 70% of world production. In Cyprus, chromite production ceased in 1982 and since then the country has been unable to compete in world chromium production. Turkey, Finland and Albania are the major chromium producers in Europe and still belong to the top 10 chromite producers worldwide; however, they cannot meet Europe's full demand for chromium on their own.

To better understand the genesis of chromite deposits and their associated ophiolites, chromite compositions are typically analyzed using electron microprobe techniques. While effective, this method is time-consuming and requires specialized analytical facilities. In this study, Raman spectroscopy was applied as an alternative approach to obtain comparable compositional information in a more efficient manner. The results demonstrate that Raman spectroscopy yields outcomes consistent with electron microprobe analyses and, additionally, enables the identification of chromite alteration rims.