Das Jura-Museum widmet sich den Fossilien im weltberühmten Solnhofener Plattenkalk. Hier wird ein neues Exponat vorgestellt, dass sich den Solnhofener Plattenkalken über die Fossilien hinaus widmet. Es handelt sich um ein Festgesteins--Transferpräparat aus dem Steinbruch Ettling, das während der Forschungsgrabung angefertigt wurde und die Gesteinsabfolge im Original dokumentiert. Daraus wird ein Exponat, das dem Publikum Einblicke geben soll, wie sedimentäre Abfolgen datiert und interpretiert werden. Der Steinbruch Ettling ist bekannt für seine außerordentlich gut erhaltenen Fische mit Farbmustern. Der einzige Ammonit, der als Altersanzeiger dienen kann, kommt aus einer Bank, die im Transferpräparat enthalten ist. So kann Biostratigraphie anschaulich vermittelt werden. Weitere Forschungsdatenwerden in Zukunft direkt auf das Transferpräparat übertragen. Derzeitige Analysenumfassen mineralogische Zusammensetzung, Nannofazies, Chemostratigraphie und quantitative Auswertungen aus der Forschungsgrabung. Die Ergebnisse, die allein sehr abstrakt wären, sind so anschaulich am Profil vermittelbar. Das Exponat dient somit zur Vermittlung vielfältiger geowissenschaftlicher Ansätze und Fragestellungen weit über den Fossilbestand hinaus und liefert direkte Einblicke in die Forschung.

Ein Museum will eine Öffentlichkeit erreichen. Doch das ist leichter gesagt als getan, denn aus soziologischer Sicht zeigt sich die Öffentlichkeit nicht als monolithischer Block, sondern als ein Konglomerat aus sozialen Milieus, die Informationen sehr unterschiedlich aufnehmen und verarbeiten. Das Wahlkapfteam Barack Obamas z.B. war dementsprechend auf über 80 solcher ÖffentlichkeitEN eingestellt und sprach sie jeweils unterschiedlich an. Wie kann die Soziologie mit ihren Modellen von dem, was man gemeinhin "Gesellschaft" nennt der Wissenschaft, die genau weiß, "wie man mit dem Hammer philosopirt" (Nietzsche) ggf. dabei helfen, ihre Öffentlichkeiten zu erkennen und erfolgreich mit ihnen zu kommunzieren? Dieser Frage würde ich gerne in meinem Beitrag diskutieren.

Kleine Museen mit eingeschränkter Finanzierung können oft nur geringe Mittel aufbringen, um mit weiterführenden Material Vitrinen und Ausstellungsobjekte zu ergänzen, zum Beispiel englische Texte oder Tonmaterial für Sehbehinderte. Um spezielle Zielgruppen, wie z. B. Kinder und Schülerinnen und Schüler anzusprechen und ihnen Sammlungsobjekte zugänglich zu machen, bieten sich kurze Videos an, die wissenschaftliche Zusammenhänge erläutern. Ferner können Forschungsmethoden in solchen Videos erklärt werden. Die Einbindung von ergänzenden Visualisierungen kann u a. über QR-Codes oder an geeigneten Stellen mit Monitoren erfolgen.

Wir präsentieren anhand von Fallbeispielen Ansätze, wie mit geringem technischen Aufwand und weit verbreiteter, zum Teil frei verfügbarer Software ergänzendes Videomaterial erzeugt und in Ausstellungen eingesetzt werden kann. Das Poster bietet über QR-Codes Zugang zu auf diese Art generierte Videodateien.

To meet the global commitments for net zero carbon emissions our energy mix must transition from fossil fuels. Hydrogen is gaining increasing recognition as a low carbon energy option to support this energy transition. Hydrogen is considered a low-carbon substitute for fossil fuels to decarbonise domestic and industrial heat, power generation and heavy-duty transport. It can also promote increased renewable energy uptake by acting as an energy store to balance supply and demand.

For hydrogen to be deployed at the scales required for net zero, we will need access to large-scale geological storage. This talk will present an overview of the most recent findings from research working to establish the feasibility of storing hydrogen in underground porous reservoirs. The talk will cover the results of research into the key biological and chemical reactions between the reservoir rocks, formation fluids and injected hydrogen that could compromise the storage complex and the key flow processes that influence hydrogen migration and trapping during injection and withdrawal. It will also consider the role of hydrogen storage within an integrated energy system.

The first Hydrogen storage caverns of Germany are planned to be constructed at the salt cavern field Epe in NRW, where 114 caverns, of which more than 50 are currently used for natural gas storage, are located. Since gas filled caverns experience convergence over time and thus cause subsidence at the surface, it is important to have a monitoring concept with high spatial and temporal resolution, to predict future subsidence and potential damage to infrastructure, but also to detect unexpected subsidence quickly and assist in identifying the cause.

Epe displays a complex surface deformation field, consisting of cavern convergence caused linear trends, as well as precipitation dependent seasonal and cavern pressure dependent contributions as shown in previous studies of the area.

As part of the SAMUH2-Project, funded by the German Federal Ministry of Economics and Climate Protection, we are working on a monitoring concept to incorporate the already established methods of yearly levelling and GNSS measurements into our approach of using Interferometric SAR (InSAR) time series, which provide not only high spatial, but also good temporal resolution. Here, we use Sentinel-1 SAR data from 2015 to 2022, and process time series by using a joint approach of persistent scatterer (PS) and distributed scatterer (DS) techniques.

Our results show good agreement of the InSAR time series with other geodetic measuring methods. We can distinguish the signals of the different source mechanisms well and can even model varying cavern convergence rates, depending on the extent of the yearly cavern depletion and filling.

In the current global race towards achieving self-sufficiency and sustainability in meeting energy demands with net-zero emissions, hydrogen has emerged as a promising solution. However, hydrogen's volumetric energy density is lower compared to conventional energy sources, and the storage conditions (pressure and temperature) for hydrogen on the surface are expensive and technically challenging.

To overcome the challenge of large-scale hydrogen storage, researchers around the world have proposed storing hydrogen in subsurface geological structures, such as salt caverns and porous reservoir rocks. While hydrogen storage in salt caverns is a more advanced concept, storing hydrogen in porous rocks such as depleted reservoirs and aquifers requires further research attention. This paper outlines a preliminary workflow for a feasibility study on the use of depleted gas reservoirs for hydrogen storage. Two different fields in Germany are used as examples to illustrate the process. One of the case study fields is still producing from the carbonates of the Zechstein Group, while the other is a decommissioned field that previously produced from unconsolidated Neogene sands. The workflow involves creating a static geological model and populating it with petrophysical parameters, followed by dynamic flow simulation for history matching. Hydrodynamical parameters for hydrogen are then introduced to simulate hypothetical storage cycles. A geomechanical model is then created incorporating the pore pressure data and material properties, to assess storage integrity, fault activity, and surface deflection in response to hydrogen filling. Overall, this workflow provides a comprehensive approach to evaluate the potential for hydrogen storage in depleted reservoirs.

In the frame of the SAMUH2 project water samples were taken at a geological pore gas storage. In the course of the abandonment of a natural gas storage, deep fluids could be recovered from a depth of 500 - 600 meters. A total of eight boreholes were sampled from injection and observation wells. The focus of the investigations was on the analysis of the chemical composition of the fluids as well as the characterization of the microbial biocoenosis and partly also their metabolic activity.

Organic acids were detected in varying concentrations and compositions in both the fluid samples taken at the injection and observation wells. Organic acid concentrations ranged from 0.1 to 730 mg/L. Gen copies of Bacteria, sulfate reducers (SRB) and methanogenic archaea were detected in all fluids by qPCR. A detailed characterization of the microbial community was carried out by microbiome analysis. A diverse microbial community was detected on fermenters and methanogenic archea. Sulfate reducers, on the other hand, were identified predominantly in the observation wells.

Several laboratory experiments demonstrated that the fluids of injection wells contained an active biocenosis capable of hydrogenotrophic methanogenesis. In contrast, only one observation well fluid demonstrated the activity of hydrogenotrophic methanogenic archaea. The capability of underground storage facilities for producing eco- ("green") methane is a further topic of this study.

Underground H₂ storage (UHS) in salt caverns, deep saline formations, and depleted oil/gas reservoirs has emerged as a reliable and safe technology for storing renewable energy and reducing carbon dioxide emissions. H₂ gas, however, is one of the most important electron donors for many subsurface microorganisms. During the multiple cycles of H₂ injection and withdrawal operations, a certain amount of H₂ is permanently lost due to various physical, chemical, and biological mechanisms. Although research in UHS in porous media is evolving, our understanding of the impacts of cyclic loading and microbial activity on H₂ recovery and loss mechanisms remains inadequate.

In this study, we present recent findings from a quantitative investigation of H₂ reconnection and recovery mechanisms in repeated injection-withdrawal cycles using a microfluidic pore network simulating shallow reservoir storage conditions (30 barg). Our results reveal that H₂ storage capacities increase with higher injection rates, ranging between approximately 10% and 60%. Additionally, we observed the growth of a typical halophilic sulfate-reducing bacterium in the hydrogen-saturated pore network for 9 days. Significant H₂ loss occurred due to microbial consumption within 2 days following injection into the microfluidic device. These results may have significant implications for hydrogen recovery and gas injectivity. Microvisual experiments provide critical observations of bubble-liquid interfacial area and reaction rate that are essential to the modeling that is needed to make long-term predictions. Our results contribute to improving the selection criteria for future storage sites, ensuring optimized and efficient H₂ storage and utilization.

The southern Baltic Sea between the German and Polish coast in the south and the Danish and Swedish coast in the north comprises the well-investigated structural-geological situation along the Tornquist Fan area. Different tectonic features tell the story of this polyphase activated weakness zone, like the Paleozoic Tornquist Zone in the NW, Mesozoic NE trending fault zones or salt structures with crestal grabens above, such as various Late Cretaceous to Paleogene inversion structures.

Time-migrated reflection seismic sections indicate neotectonic activity and fault reactivation, a fact supported by recent earthquakes and ongoing isostatic movements of up to 1 cm/a. Due to the reduced resolution of this thin Quaternary layer within the seismic sections, the fault activation could not be dated more precisely so far. Stress variations of the existing background stress are assumed to result from glacial isostatic adjustment (GIA) processes within the lithosphere. This study analyses fault reactivation due to GIA, covering the past 200 ka. For the first time, this glacially triggered faulting could be studied and compared on a variety of faults that differ in their strike and dip direction, age, depth, and character. Using finite element simulations, we tested if and when faults were reactivated during ice advances and retreats within the European Saalian and Weichselian glacial phases.

So-called ‘blind’ faults, which are not visible at the Earth’s surface may be the source of unexpected and potentially disastrous earthquakes and thus represent a major hazard, especially in urban areas. Detecting such hidden faults is highly important for the seismic hazard assessment of a region, but often remains a challenge, because the faults are covered by young sediments. To overcome this limitation, we visualize blind faults in the area of the Sorgenfrei-Tornquist Zone in northern Denmark with shear-wave seismic reflection surveys. The faults on the seismic surveys are interpreted based on systematic reflector offsets, the presence of continuous transparent zones that separate individual fault blocks, abrupt lateral changes in the reflector pattern, and the presence of fault shadows. The seismic surveys give evidence for a near-surface strike-slip fault system, based on the presence of flower structures and the dominance of steep faults. The distribution of the faults on the seismic surveys and the occurrence of fault-related shear-deformations bands that occur in outcrops along the nearby seas-cliff, together with fault-related basins that are developed in the study area, indicate that the northern boundary fault of the Sorgenfrei-Tornquist Zone is not an isolated fault, but a wider fault array. The study demonstrates that the shear-wave reflection seismic method is a powerful tool to image near-surface faults and is very suitable for palaeoseismological studies. The significantly improved resolution of shear-wave seismic surveys compared to those of the common P-wave reflection method is an advantage, especially in the case of small fault displacements.

The drive towards net-zero emissions as per the Paris 2015 agreement has resulted in significant efforts to develop sustainable energy resources. In order to change the current energy system, alternative resources need to replace wood, coal, oil and gas. One of the recent new findings in the Geo-Energy sector is natural hydrogen which can be found in many places around the globe as seeps.

Reasons for the lack of interest in hydrogen exploration so far are multi-fold, like nobody considered natural hydrogen as a viable option, hydrogen cannot be detected easily, other energy resources were available in large quantities and at low cost and more. However, many indications point towards a major clean energy resource of the future considering that in the last few years some 300 seeps have been reported. One of the most famous ones is the eternal fires of Chimaera in Turkey, know to burn since more than 2500 years. In the meantime, the first hydrogen exploration companies have formed and even a first long-term production test is ongoing.

Natural (white) hydrogen was until now not considered in the energy transition. If further developments turn out to be successful, this may result in another unexpected game changer in the energy sector similar to coal replacing peat in 1880. However, the question remains, what such a potential new energy opportunity could look like as part of the future energy mix. This talk will highlight the current status and potential ways forward on this new energy resource.

The results of the application of the mobile direct-prospecting technology of frequency-resonance processing and interpretation of satellite images and photographs in large areas and local areas of hydrogen degassing in German various regions are presented. Experimental reconnaissance studies were carried out to study the features of the deep structure of hydrogen-degassing areas.

Instrumental measurements confirmed the presence of large zones of hydrogen degassing in the areas of basalt volcanoes in Bavaria. Signals at the frequencies of hydrogen, basalts and healing water were recorded at the sites performed for the hydrogen migration. Measurements recorded the facts of hydrogen migration into the atmosphere. When scanning the cross-section, responses from hydrogen are recorded from the upper edges of basaltic volcanoes to their roots. Signals at hydrogen frequencies were also recorded from limestones, dolomites, and marls overlying the basalts from above (including at shallow depths). Experimental studies have also shown that siliceous rocks can be a good seal for hydrogen. There is no hydrogen migration into the atmosphere within basalts, overlapped by siliceous rocks. The obtained results of experimental work are also additional evidence in favour of the "volcanic" model of the formation of various structural elements and the external appearance of the Earth, as well as deposits of combustible and ore minerals (including hydrogen and water).

The use of mobile and low-cost technology will significantly speed up the exploration process for hydrogen, as well as reduce the financial costs for its implementation.

Keywords. Hydrogen,basalts, limestones,healing water, abiogenic genesis,volcano,direct searching,remote sensing data

The activation of methanogenic Archaea in the context of subsurface hydrogen storage may lead to permanent hydrogen conversion to methane. The objective of this proof-of-concept study is to experimentally investigate these activities, and it is focused on reservoir analogues from the Cretaceous and Triassic periods. These analogues have been selected based on their varying porosities, which range from 8% to 24%. Methanothermococcus thermolithotrophicus was used as the model organism due to its relatively high activity and growth rate. The microbial activities in various water-saturated reservoir rocks with either similar bulk or pore volumes, as well as inoculated media containing sand particles and rock fragments, were experimentally studied and compared to values obtained in bulk solutions. Measured activities in the water-saturated rock specimens with identical bulk volumes varied between 0.17 and 1.22 mM H₂ /h largely correlating with the pore volume. Furthermore, the results indicated that activities in the water-filled pore space of the respective rocks were higher by a factor of 8-10 compared to activities in bulk solutions. This observation, in conjunction with the measured activities in inoculated media containing sand particles and rock fragments, as well as in rocks with similar pore volume, supported the notion that the surface area available for microbial colonization is another factor in controlling activity when the amount of substance is held constant. Additionally, the study suggests that methanogenic activities used to quantify hydrogen conversion in reservoirs must potentially be revisited because they are typically measured on bulk solution rather than within intact rocks.

Hydrogen (H₂) was injected into a shallow aquifer at the TestUM field site (close to Wittstock, Brandenburg, Germany) in order to simulate a H₂ gas leakage scenario. The resulting biogeochemical processes were monitored in space and time by analyses of stables hydrogen isotopes, groundwater microbial community composition and geochemical parameters in two monitoring wells (D04, D06) close to the injection wells, and a reference well (D11) not directly affected by the injected H₂. During the injection, initial shifts in the isotope signature of H₂ were observed, probably caused by dissolution of H₂ in the water phase and the migration of the gas phase through pores and channels in the aquifer. After the injection, H₂ concentrations in D04 and D06 decreased within less than 80 days from maximal 850 µmol/L below the detection limit, accompanied by an equilibrium isotope exchange with water leading to a strong isotopic depletion of H₂, a reaction typically catalyzed by the H₂-cleaving enzyme hydrogenase. Microbial H₂ oxidation and subsequent growth of hydrogenotrophic prokaryotes was further indicated by temporally increasing abundances of putative H₂-oxidizing sulfate reducers, acetogens, nitrate reducers and aerobes, accompanied by nitrate disappearance and transiently increasing acetate concentrations. In summary, the results confirm our expectation that H₂, being an excellent energy source for many microorganisms, is quickly microbiologically consumed in an aquifer after a leakage.

Natural hydrogen (H₂) exploration is particularly focused on surface emissions (seeps) and soil-gas prospections, similar to early petroleum reservoir explorations. However, defining the amount of H₂ at the surface that indicates a potentially economic resource is impossible, and identifying its origin is challenging due to the fact that geological H₂ concentrations and isotopic composition can overlap with the in-situ biological signature. The potential for H₂ generation in surface environments as a result of microorganisms, corrosion of iron particles or minerals, or even drilling (artificial H₂) must be extensively evaluated. Despite these limitations, similarities to hydrocarbon systems suggest that certain seeps, which typically occur in correspondence with faults, are an expression of advection (not diffusion), driven by pressure gradients, and thus can disclose the existence of pressurized pools (Etiope, 2023). The fluid dynamics of gas seeps can therefore reveal the nature of the H₂ supply system. Comparing seep flux rates with potential H₂ generation rates, either via radiolysis or serpentinization, is a fundamental exercise for determining whether the H₂ system must include a reservoir, similar to conventional natural gas systems, or if the H₂ observed at the surface originates from continuous flow crossing short-term accumulations or directly from the source rock, as some scholars have hypothesized. However, analyses of the gases associated with H₂ (such as CO₂, CH₄, N₂ and He) are always advised. Assessing the potential of a geological H₂ resource necessitates a holistic approach that integrates multiple geochemical, ecosystem, and geological data.

References

Etiope G., (2023) https://doi.org/10.1016/j.ijhydene.2022.12.025

Even if measurements of high H₂ concentrations in continental rocks have significantly increased in the last decade, the origin of H₂ remains enigmatic in this context. Here we show that the localities in continental rocks where H₂-rich gases have been reported are mainly located near orogenic gold deposits. Two types of geomorphological features were identified near orogenic gold deposits on satellite images. They consist in both barren ground depressions and high densities of self-organized, small (< 20 m in diameter) circular- and comet-shaped white spots in 32 and 7 localities, respectively. Fe-carbonates commonly occur near gold deposits since gold is transported in CO₂-rich fluids. Thermodynamic modelling reveal here that they can further dissolve in the presence of aqueous fluid to produce magnetite and up to ~ 1 mole of H₂ per kg of rock. This reaction leads to a volume decrease of ~ 50 %. Based on these findings, we propose that Fe-carbonate dissolution could be the primary source of H₂ in orogenic gold deposit areas, and involved in the formation of the geomorphological structures reported here. The association between H₂-rich gas and ground depressions was also observed near other formations containing Fe-carbonates such as iron formations and carbonatites. This suggests that H₂ production through Fe-carbonate dissolution is not restricted to gold deposits. The global H₂ production in crustal rocks associated with Fe-carbonate alteration is estimated to 3 x 10⁵ mol/yr.

H₂-bearing fluids (pH 10 – 12) issued in alkaline springs found in several ophiolitic complexes worldwide are believed to result from the alteration of ultramafic rocks by infiltration of meteoric waters. The mineralogical fingerprint of the reactive percolation of such an alkaline fluid is revealed by veinlet mineralization occurring in the New Caledonian ophiolite (Massif du Sud). In two localities separated by ~ 15 km (Georges Pile and GR2H mines), late veins in a partially serpentinized peridotite contain magnetite crystals younger than 2 Ma as inferred from (U-Th)/He geochronometry. While the serpentinite host at Georges Pile is largely overprinted by lateritic weathering, primary parageneses are preserved at GR2H. There, magnetite occurs along with dolomite and Fe-poor lizardite as filling in millimeter sized veins cross-cutting the mesh texture of the partially serpentinized dunite. Temperature of the aqueous fluid from which the vein material precipitated is estimated to be ~95°C from in situ δ¹⁸O data on the magnetite-dolomite pair, indicating a low-temperature alteration process. Thermochemical calculation shows that this aqueous fluid was alkaline and most likely H₂-bearing. Chemically, it strongly resembles waters that are issued today in H₂ and CH₄ – bearing (hyper)alkaline springs of the Massif du Sud. δ¹³C isotopic composition of dolomite is exceptionally high, between 7.1 and up to 17.3 ‰ and is interpreted as evidence for low-temperature methanogenesis.

The alteration of ferroan brucite, a common by-product of serpentinization, has been proposed as a H₂ source at low temperature. Here, synthetic ferroan brucite with Fe/(Fe+Mg) = 0.2 was reacted with pure water at temperatures ranging from 348 to 573 K in 29 experiments either conducted in gold capsules or in Ti-based reactors. H₂ production monitoring with time and characterization of the reaction products revealed the occurrence of the following reaction: 3 Fe(OH)₂^brucite = Fe₃O₄ + H₂ + 2 H₂O. This reaction proceeded completely in ~ 2 months at 378 K and was thermally activated. The small grain size of the synthetic brucite (40-100 nm) was similar to observations in natural samples, and was probably responsible for the high reaction rate measured. H₂ production reached a plateau and Fe-bearing brucite also precipitated as a reaction product, suggesting the achievement of equilibrium. The thermodynamic properties of Fe(OH)₂ were refined based on the experimental dataset and differ by less than 5 % from previous estimates. However, ferroan brucite is predicted to be stable at an hydrogen activity one order of magnitude lower than previously calculated. As a result, significant H₂ production during ferroan brucite alteration at low temperature requires efficient fluid renewal. Such a mechanism strongly differs from olivine serpentinization which can occur even at high activity in H₂ and thus with limited water renewal.

Carbon Capture and Storage (CCS) as well as subsurface energy storage in the form of hydrogen are measures to lower carbon emissions to the atmosphere. Large-scale implementation is underway, especially for CCS, and first hydrogen storage projects have been announced recently.

With most CCS projects being planned for offshore locations, public acceptance is less of a determining factor than it used to be 10-20 years ago, where discussions were rather for onshore locations. CO2 leakage has always been a risk highlighted in the public debate, while no or minimal leakage has been reported for current CCS projects worldwide. However, as scientific community, we need to realistically highlight the risk of leakage across sealing units for any fluids stored in the subsurface to inform various stakeholders like regulators, the public and of course also operating companies.

Caprock leakage needs to be studied across various length and time scales, considering the undisturbed matrix as well as fracture networks and faults; we need to consider advective and diffusive flow and transport and incorporate mineral alterations, potentially leading to changes in hydraulic or mechanical properties.

This talk will highlight the current state of research, advancements and future research required for a realistic evaluation of caprock leakage. It will be based on past research related to matrix transport as well as current research focusing on single and multiphase flow along faults and fractures.

In many applications a fluid is injected into rocks for example for CO₂ storage, in enhanced geothermal reservoirs, or during oil and gas recovery. The fluid may be out of equilibrium with the rock resulting in chemical reactions at depth. The correct prediction of reaction front velocities depends on a thorough understanding of the theory of chromatography and the changes of density and porosity in reactive transport models. We study the systematics of reaction fronts in multi-component systems. The methodology is based on a finite difference approach for solving the transport problem in combination with precomputed thermodynamic equilibria. These lookup tables are calculated using Gibbs’ minimization and a linear programming approach. They are validated against full analytical solutions of the Gibbs minimization problem. Porosity and density evolution is predicted based on mass conservation. We focus on ternary ideal fluid or melt solutions in equilibrium with pure phases as exact solutions are feasible and here first consider the isothermal case. For a fixed incoming fluid composition, over twelve reaction sequences may form depending on initial rock composition. Within one type of reaction sequence, bulk rock composition still plays are role in determining the speed of the reaction front as well as the fluid compositions that develop along the path. This theoretical understanding allows better predictions of the formation of reaction sequences and the consequences on rock properties upon injection of fluids with dissolved chemical components.

The Upper Cretaceous Campanian limestones from the Ahlen-Fm. (Beckum-Fm. Submember) of the Münsterland Cretaceous Basin in NW Germany are former high porosity limestones, which consist mostly of detrital components. This study focuses on the petrophysical assessment of these limestones in combination with diagenetic studies to understand the potential interaction with rising mine-water as they unconformably overlie Upper Carboniferous coal-bearing strata. Therefore, outcrop analyses were carried out and samples were taken to study the heterogeneity and controlling factors, as well as diagenetic para-sequence in tight limestones. We show that diagenesis, compaction, authigenic cementation and the detrital composition affect petrophysical properties. Mechanical compaction is seen by elliptically deformed calcispheres and foraminifera at the transition to ductile clay laminae, forming compaction bands. Mechanical compaction and early diagenetic precipitation of inter- and intragranular sparry ferroan calcite reduces porosity and permeability. Porosity ranges between 1.0% to 18.7%, permeability between <0.0001 mD to 0.2 mD, and p-wave velocity ranges between 2089 m/s and 5843 m/s. Furthermore, natural fractures are filled by either ferroan calcite and/or strontianite. Thus, the studied lithologies of the Beckum-Fm. can be considered as seals for potential rising mine-water levels. Furthermore, results indicate, that they may not be potential targets for geothermal utilization. However, open fractures formed during exhumation overprinted the rocks which may enhance the reservoir quality by generating potential fluid pathways close to the present day surface.

Models and simulations allow a prognosis of how processes in the geosphere might occur in the future, considering physical and chemical processes. They are the only way to test future scenarios and hypotheses and to evaluate the long-term evolution of a repository site, e.g. by quantifying potential radionuclide migration in the hydrogeological system of the containment providing rock unit.

An example is used to demonstrate the extent to which simulated migration lengths can vary for a million years, depending on the model concept as well as on the underlying data and parameters. In the case of uranium in the potential host rock Opalinus Clay (Switzerland), the range extends from 5 m applying experimentally determined transport parameters, over 50 m using process-based approaches and taking hydrogeology into account and up to 80 m depending on the thermodynamic data set used.

The degree of reliability of the models is derived from comparison with laboratory tests and data from boreholes and underground laboratories. This is the only way to assess the simulation results. In addition, indications can be provided where new data need to be collected. To reduce the uncertainty related to the migration length of uranium in the Opalinus Clay, the calcite-carbonate ion system as well as the hydrogeological setting at a potential disposal site need to be known, whereas the amount of clay minerals plays a subordinate role as long as it is enough, which is the case in argillaceous formations.

Aquifer thermal energy storage (ATES) is comparatively rarely used in Germany. Since there is a lack of demonstration plants nationally, the goal of our BMBF-funded joint project “DemoSpeicher” (Development and Monitoring of Seasonal Heat and Cold Storage for the Demonstration of Aquifer Storage) is to implement and scientifically accompany a near-surface LT-ATES. Within the scope of the project, the entire construction cycle of an LT-ATES is to be covered, which ranges from design and planning to grid integration and commissioning to thermal energy supply. Legal admission requirements are developed in the process. An urban site in Germanys capital Berlin-Mitte was selected for the implementation of the demonstration plant. An extensive monitoring program is planned for the thermal-hydraulic underground processes. Another focus of the project will be possible changes in groundwater chemistry and temperature-sensitive groundwater ecology because of thermal loading. Monitoring of energy flows is also planned to estimate the thermal energy exchange between the aquifer reservoir and the building's systems engineering. This will include a heating and cooling demand analysis, as well as an assessment of potential synergistic use effects with other technologies that could be used, for example, for thermal loading of aquifer storage. All results will be presented in a coupled thermal-hydraulic modeling. The project and the first results of the implementation of an LT-ATES in a densely populated urban area will be presented and discussed in this presentation.

In progressively decarbonized district heating systems with high shares of renewable energies, seasonal large-scale heat storage systems are a central component for overcoming the seasonal offset between heat generation and demand. In addition to Pit Thermal Energy Storages (PTES), which often encounter high spatial resistance in urban contexts, Aquifer Thermal Energy Storages (ATES) in the three geothermal regions in Germany offer a suitable solution for large-scale and cost-effective thermal energy storage with high surface area efficiency. Currently, however, there is no operating high-temperature ATES in Germany that is integrated into an urban heating network. The focus of this presentation is on aspects of interaction between aquifer storage, large-scale heat pumps and district heating networks in Germany.

The framework conditions for the technical integration of heat from aquifer storage are subject to constant change. On the one hand, district heating systems are usually operated with sliding supply and return temperatures, on the other hand, the temperature continuously decreases during discharging period.

This requires different solutions for the integration of aquifer storage, which are to be systematized and classified. Central integration possibilities are the direct use in supply line, the increase of the return temperature as well as the use of large heat pumps.

The lecture will present the findings from the research project "OptInAquiFer" on reasonable integration possibilities of aquifer storage in German district heating networks. In addition, current research on large-scale HP configurations will be highlighted to identify suitable and efficient HP capacities, refrigerants and HP configurations for ATES applications.

Achieving sustainable and climate-friendly space heating and cooling is essential to the energy transition. Aquifer Thermal Energy Storage (ATES) is a promising technology to significantly reduce greenhouse gas emissions compared to conventional heating and cooling technologies. Therefore, in this study the technical potential of shallow low-temperature ATES systems is quantified for the city of Freiburg im Breisgau, Germany in terms of reclaimable energy. Using 3D heat transport models, heating and cooling power densities are determined accounting for several different ATES configurations in various hydrogeological subsurface conditions. High groundwater flow velocities of up to 13 m d^-1 lead to a significant loss of stored energy limiting power densities to a maximum of 3.2 W m^-2. Nevertheless, comparing these power densities to the existing demands of heating and cooling energy reveals that substantial heating and cooling supply rates are possible with ATES. While heating energy supply rates of larger than 60 % are determined for about 50 % of all residential buildings, the cooling energy demand could be supplied entirely by ATES systems for 92 % of the buildings. For ATES heating alone, this results in greenhouse gas emission savings of up to 70,000 tCO₂eq a^-1. This equals about 40 % of the current greenhouse gas emissions caused by space and water heating in the study area’s residential building stock. In the future, the application of the modeling approach proposed in this study for other regions with similar hydrogeological conditions could obtain estimations of local ATES supply rates supporting city-scale energy planning.

High-temperature aquifer thermal energy storage (HT-ATES) in the geological subsurface can help bridge the temporal mismatch between production and demand of energy from renewable sources. Despite great importance for energy system transformation in the heat supply sector, HT-ATES faces some challenges and risks such as regulatory challenges. The heat input experiments at the TestUM –Aquifer test site provide a basis for characterization and verification of hydraulic, thermal, geophysical, microbiological, and geochemical process understanding. A HT-ATES system was experimentally simulated at the field site, representing three phases with varying loading and unloading cycles at injection temperatures of 80°C. More than 500 thermocouples were used to record temperature data over a 579-day period between July 2021 and February 2023. A total of eleven operating cycles divided into three phases were performed, representing a total heat input of 155 MWh. The temperature records are highly resolved spatially, especially in the vicinity of the injection well, with intervals as low as 0.5 m in the vertical and horizontal directions, and a temporal resolution of 10 min. Thus, the temperature distribution in the subsurface and the position of the heat plume is well characterized at any time. Results show, that the temperature distribution is affected by density driven convection, caused by the temperature differences, as well as heat loss to the confining unit. The storage efficiency was determined by measuring return flow rates and temperatures, showing that storage efficiency decreases with cycle length and with downtimes between charging and discharging.

Seasonal ATES systems enable the efficient integration of climate-neutral heat sources into urban heat-supply systems. However, secure and efficient operation presupposes the detection as well as realistic evaluation and prediction of induced hydraulic, thermal, geochemical and microbial effects and their impacts on operation and environment.

To provide the database for extending field-scale process understanding and deriving suitable monitoring strategies, a cyclic HT-ATES field test was conducted. In six fortnight-long charging periods ~300 m³ of water were infiltrated (~15 L/min; ~80 °C) into the storage aquifer (6-15 bgs) and recovered directly or after 21 storage days. Induced hydrogeochemical effects and their reversibility were tracked with a temporal and spatially high-resolute monitoring of ~90 measurement points.

Within ~7 m around the „hot well“, superimposition of formerly stratified calcium and sulphate concentrations in combination with the spatial spreading-patterns of elevated silica concentrations point towards the build-up of a density-driven convection cell, which was also predicted by accompanying numerical thermo-hydraulic simulations. In storage periods, but more so in post operation, decreases in temperature go along with a decline of previously elevated concentrations of e.g. silica, potassium, selenium and vanadium. Moreover, potassium and selenium concentration-peaks drop after the first cycles, indicating depletion of their releasable pools. Although simulated tracers indicate passage of infiltrated water, no induced temperature or concentration changes were monitored 30 m downstream so far.

Overall, highly dynamic flow conditions dominate the hot well’s vicinity and despite scale dependent low heat recovery rates, reversibility of induced effects keeps the wider surrounding geochemically unaffected.

Throughout the past two decades, aquifer thermal energy storage (ATES) has grown increasingly into focus as a suitable geo-energy storage method. In this context, many carbonate aquifers are useable for storing and later retrieval of thermal energy due to their potential natural porosity and adequate permeability. However, numerous ATES projects suffer from operational and maintenance issues or failures. For instance, a reduction in reservoir permeability and clogging (caused by scaling, sintering, flocculation, and microbial growth) belong to the main threats to sustainable and reliable functioning.

In the BMBF-funded research project “UnClog-ATES”, both the aforementioned threats and their practical countermeasures (e.g., adding scaling inhibitors, acids, CO₂) are thoroughly investigated using a combination of flow-through column and batch experiments. These experiments are temperature-controlled to simulate realistic ATES cycles of alternating heating and cooling while monitoring them continuously.

A critical point when assessing ATES systems specifically for carbonate aquifers is that significant inconsistencies exist regarding the kinetics and intensities of mineral dissolution/precipitation processes observed in the laboratory (using pure/synthetic minerals) and those observed in reality. This is because factors such as specific surface, dislodgement from equilibrium, presence of inhibitors as well as the rock’s chemical purity play important roles. For that reason, i.e., to represent natural ATES materials and to gain realistic reaction data, limestone from the Malm (Upper Jurassic), Germany (“Treuchtlinger Marmor”), is used for our experiments.

The overall project results aim towards gaining a variety of insights that are essential for planning, effective implementation, and sustainable operation of ATES in carbonate aquifers.

Geothermal facilities in the North German Basin are frequently affected by corrosion and scaling due to high salinity as well as microbial induced corrosion. To study biofilm formation, corrosion processes and countermeasures, a mobile bypass system was installed at the Neubrandenburg geothermal heat storage plant. The reservoir was located in a depth of 1300m in a saline aquifer (~130g/L NaCl). Operation was conducted in two different seasonal modes. In the warm months, heat was stored, while in the winter months the direction of flow was reversed and heat was recovered. At temperatures lower than 60°C, at the cold side of the aquifer, corrosion was promoted by microbial activity, which led to the formation of biofilms on plant components and pipes. Biofilms consisted mainly of various genera of fermentative, sulfate reducing and hydrogen consuming bacteria. Longer incubation time as well as inoculation with fresh biofilm showed an independency of seasonal mode and enrichment of highly adapted community composition with the dominating sulfate-reducing genus Desulfallas.

As a countermeasure to corrosion, heat shocks were evaluated in the bypass system and tested also two times at the large scale plant. Heat shocks led to significantly reduced biofilm formation on corrosion coupons and correspondingly reduced iron sulfide precipitates and corrosion rates from 0.538mm/a to 0.170mm/a over an observation period of 48 days. The impact of one heat shock lasted for more than four weeks. Overall the use of periodic heat shocks showed its preventative measure against microbial induced corrosion and scaling in geothermal plants.

Column and field tests related to ATES found significantly elevated Mo, V, and other oxo-anions that could not be explained by reductive dissolution of Fe oxyhydroxides. A common hypothesis levied was that the oxo-anion mobilization appears to be related to a thermal desorption process. However, for an accurate prediction of the concentration changes, there is a lack of thermodynamic parameters to prove that hypothesis which was the aim of this study.

Batch equilibrium adsorption experiments with oxo-anions such as molybdate and vanadate were performed using goethite suspensions with different concentrations, ionic strengths, pH values, and at four temperatures between 10 and 75 °C. The results of this large number (>500) of individual batch equilibrium experiments showed that the amount of an oxo-anion adsorbed decreased with increasing temperature. The experimental data were fitted using the CD-MUSIC surface complexation model framework. Temperature variations in the complexation constants were in turn fitted using the two-term van’t Hoff equation to obtain molar enthalpies and entropies. The enthalpies were negative, indicating that the adsorption of the oxo-anions is exothermic and therefore the adsorption affinity decreases with increasing temperature. The entropies could be correlated to the adsorbate molecule volumes together with those previously determined for other oxo-anions, which can be used to extrapolate the adsorption entropies of many other oxo-anions for which EXAFS-based adsorbate structures are available, but for which such data are not yet available. Hydration differences across the bivalent oxo-anion molecule series apparently affect the derived enthalpies and hence the adsorption energies for oxo-anions.

A thorough characterization of aquifer parameters is crucial for long-term predictions of the ATES system's functioning. Single well tests, also known as push-pull tests, have been widely used to identify effective porosity, flow velocity, decay constants, sorption coefficients, and heat storage capacity of the aquifer. For more than fifty years, multiple analytical and numerical approaches have been developed to validate push-pull test data and to identify model sensitivity. Despite the relatively straightforward approach, the main bottleneck of the push-pull test calibration is the non-uniqueness of the inverse problem solution. Especially in a deep ATES system data scarcity induces the parametric uncertainty and thus calls for the stochastic parameter optimization. To address this issue, a sensitivity-acknowledging surrogate modeling-based optimization technique for stochastic parameter optimization has been developed. Based on the analytical solution for heat and conservative tracer, a surrogate modeling-based optimization approach was developed to identify the heat storage from the push-pull test data. The optimization procedure has been validated against a synthetic dataset with parameter ranges from one of the ATES sites in Berlin. Results confirm that doing a push-pull test with heat and conservative tracer together enables uncertainty reduction. At the same time, sensitivity acknowledging optimization results in a much narrower posterior parameter distribution than the instant fusion of all available data. The modeling procedure highlights that objective function selection, as well as measurement accuracy, define the confidence interval and calibration precision.

High-temperature aquifer thermal energy storage (HT-ATES) is a heat storage technology utilising the subsurface, which can reduce greenhouse gas emissions in renewable-dominated heating sectors. Since the temperature difference between the surrounding groundwater and the injected water (> 50 °C) leads to density differences, HT-ATES can induce buoyancy flow. This process results in uneven heat distribution across the aquifer thickness, lower storage efficiency, and increased thermal impacts. The occurrence and intensity of buoyancy flow depends on, among others, vertical and horizontal permeability.

The proposed HT-ATES storage site in Hamburg, Germany, utilizes the Miocene Lower Braunkohlensande (brown coal sands) as the storage aquifer. This geological formation was formed in a coastal transition regime between terrestrial and shallow marine settings and is primarily composed of sands. Layers of brown coal, silt, and clay, embedded in the main storage aquifer, as identified from borehole information, were formed from peat swamps and lagoons and may impede convection due to their low permeability. The influence of these low permeability layers, also considering their lateral extension and position relative to the warm well, on induced convection and on HT-ATES efficiency and thermal impacts is examined in this work by employing a site-specific numerical HT-ATES model representing the coupled thermo-hydraulic processes.

Results show, that including even thin low permeability layers can effectively hinder temperature induced thermal convection, thus increasing thermal efficiency of a HT-ATES. The scenario simulations also show, that convection is already significantly dampened if the layers extend only up to the thermal radius.

Aquifer thermal energy storage (ATES) is a promising technique for the short- to long-term storage of reusable thermal energy in the subsurface. Many ATES projects suffer from operational issues or failures. Main causes are clogging, mineral precipitation and corrosion affecting both the aquifer matrix and technical infrastructure (e.g., pipes, heat exchangers), as well as unfavourable recovery rates due to convective and conductive heat energy losses across natural system boundaries.

While most systems address natural porous aquifers, a range of formerly active underground mines has been considered for ATES as well. The ongoing research project “MineATES” focuses on chances and limitations of such man-made systems.

Specifically, an in-situ real laboratory has been set up at the former silver mine “Reiche Zeche” in Freiberg, Germany, to simulate periodical heat exchange between mine water and surrounding rock. Hydro-/geochemistry changes will be logged simultaneously to the monitoring of heat propagation in both water and rock. In parallel, laboratory-scale flow-through column and batch experiments with multiple combinations of rock types and mine water compositions will be carried out at defined temperatures (~ 5°C to 50°C) to identify scales, types and locations of possible mineralization and further chemical alteration. Reference materials (rocks and mining waters) from the “Reiche Zeche” will be compared to materials from the Saxonian mines “Ehrenfriedersdorf” (former tin ore mine) and “Lugau/Oelsnitz” (former hard coal mine).

The project results are to be compiled into a criteria catalogue, providing guidelines for assessing if and how a mine could be used as an ATES system.

The Winzer project investigates the opportunities and challenges of implementing ATES systems in old groundwater-filled coal mines. For this purpose, a near-surface (<80 m) small coal mine in Bochum, Germany at the Fraunhofer IEG is used as the pilot site. The mine was tapped by three boreholes through which the groundwater is lifted and reinjected. The implementation of geothermal reuse in the old mine building in combination with a concentrated solar power system (CSP) is unique in the world. This allows seasonal storage of fluids with temperatures up to 60°C. In addition, a comprehensive condition monitoring was implemented. The measurement data and findings obtained will be used to make qualitative and quantitative statements on the hydrochemical, microbiological, geo-mechanical and ecological conditions during cyclic operations. The newly developed concepts and technologies will enhance the efficiency of the existing ATES system with regard to scalings and biofoulings at the heat exchangers as well as the safety, i.e. with regard to the mobilization potential of contaminants. Within the project the upscaling from the pilot site at the IEG through the planned development of the site of the former Dannenbaum mine is evaluated. There the hydraulic and geomechanical properties and changes in the ATES system can also be examined during the seasonal heat storage. By including numerical simulations, an optimization of the operation management concepts for the overall system is achieved and potentials for transferability to many other cities and networks in former coal mining regions in Europe will be shown.

The Kupferschiefer districts in Central Europe contain some of the world’s largest sediment-hosted stratiform Cu deposits. The fine-grained sulfides are hosted by the Rotliegend sandstone (S1), organic matter-rich Kupferschiefer (T1) mudstones and Zechstein Limestone (Ca1). In this study, standard and high-resolution microscopy techniques (reflected-transmitted light, SEM, FIB-TEM) are combined with quantitative mineralogical data (X-ray diffraction, QXRD) to characterize the key mineral assemblages and styles of sulfide mineralization in drill core samples from different localities (Sangerhausen, Allstedt, Wallendorf) of the Saale subbasin, Eastern Germany. Our QXRD data show a progressive decrease in calcite abundance from the underlying S1 into the T1 in the Sangerhausen and Allstedt drill cores and an upward increase in calcite in the Wallendorf drill core. Petrographic data show extensive in situ alteration of rock fragments and detrital feldspar in the S1. Diagenetic calcite has formed intergranular pore-filling cement that occludes primary porosity in the S1 and T1. The ore-stage sulfides (bornite, sphalerite, galena, ± pyrite) in the S1 and T1 are mostly formed as a replacement of calcite cement and, to a lesser extent, feldspar. High-resolution TEM data has helped to identify hematite and magnetite within particular calcite growth zones in the S1, which likely corresponds with the “Rote Fäule” alteration associated with the Cu sulfide mineralization. Nanoscale Cu-chloride complexes have also been identified, intergrown with pore-filling illite in the T1. In summary, the distribution and dissolution of calcite cement were critical to the secondary porosity development and migration of the mineralizing fluids in the Saale subbasin.

The Spremberg-Graustein-Schleife deposit is part of the Kupferschiefer district in the southern Permian Basin and comprises copper and silver mineralized rocks hosted by pre-Zechstein sandstones, Kupferschiefer, and Zechstein carbonates. As there is still significant exploration potential across the southern Permian basin, the goal of the present study is to identify mineralogical signatures, which may be usable as exploration vectors. The specific focus in this study is on the gangue mineralogy, since it is more likely to provide a larger detectable footprint in the mineralizing system.

Multiple analytical methods were combined to investigate samples from three mineralized and non-mineralized drill-cores. Scanning Electron Microscope (SEM) based image analysis (MLA) was carried out to obtain quantitative data on mineralogy as well as major-element carbonate chemistry of each stratigraphic unit. Quantitative bulk-powder XRD was performed as an external validation. In addition, the SEM-MLA data are being integrated with hyperspectral core-scans for upscaling observations.

Zechstein carbonate rocks in the well-mineralized drill-hole are dominantly composed of dolomite, in contrast to the weakly-mineralized drill-hole that contains more calcite. In the mineralized sandstones, three successive generations of carbonate cement have been identified from backscatter electron imaging and semi-quantitative EDX measurements, comprising i) dolomite to ii) Mn-Fe dolomite, and finally the deposition of iii) ankerite rims. Kaolinite, one of the main cement minerals in the sandstones, appears more abundantly in the mineralized than in the barren sandstones. The occurrence of ankerite and kaolinite may indicate overprinting by the mineralizing fluids and may thus be useable vectors towards mineralization.

The sediment-hosted Spremberg-Graustein-Schleife deposit is located in Lusatia, eastern Germany. Mineralization occurs in the lower Zechstein units, extending from the Grauliegend conglomerates and sandstones into the overlying organic-rich Kupferschiefer black shales and Zechstein carbonates. Around 100 Mt of Cu-Ag ore is present within the deposit. The ore is also enriched in Pb, Zn, Co, Ni, Au, Bi, Se, Re, and Ge (in addition to Cu and Ag). Despite the metal endowment, detailed quantitative metal deportment studies have not been carried out for this deposit, or indeed any other Kupferschiefer deposit. This study aims to bridge the gap. Core samples representing the complete mineralization interval (31 m in total) at three different sites within the deposit were mineralogically and geochemically analyzed. To ensure a comprehensive, high-quality and internally consistent dataset, various analytical methods including X-ray fluorescence (XRF), ICP-OES, ICP-MS, X-ray diffraction (XRD), Mineral Liberation Analysis (MLA), electron probe micro-analysis (EPMA) and laser ablation ICP-MS (LA-ICP-MS) were performed. The results reveal that the concentration and main hosts of copper and potential by-products vary vertically between the stratigraphical units, and spatially at different locations of the deposit. Such information will eventually help to predict deportments across the deposit, track each element within the minerals processing plants and also to get an idea of expected recoveries and thus optimizing the procedure.

Sphalerite (ZnS) is the main ore mineral in clastic-dominant (CD-type) massive sulfide deposits. However, the precise physicochemical conditions of ore formation are often poorly constrained. This study uses sphalerite mineral chemistry and fluid inclusion microthermometry to constrain conditions of Zn mineralization at the Boundary Zone prospect of Macmillan Pass district, Canada.

The sulfide mineralization comprises pyrite, sphalerite, galena, and minor chalcopyrite. Sphalerite with contrasting trace element compositions is hosted in Late Ordovician-Early Silurian (Duo Lake Formation) and Late Devonian (Portrait Lake Formation) black mudstones. Different paragenetic stages of sphalerite formation preserve distinct trace element patterns within and between host rock intervals, and overall, Ge, Ga, Cu, and Cd, are relatively enriched compared to In. Trace element incorporation mechanisms vary, with both direct and coupled substitution (e.g., 3Zn²⁺ ↔ (Ge)⁴⁺ + 2Cu⁺) pathways suggestive of compositional and fluid temperature differences during sphalerite precipitation.

Homogenization temperatures (T_h) of CO₂-N₂-bearing, 2-phase primary aqueous fluid inclusions in Portrait Lake sphalerite range between 154 – 249°C (median= 179°C). The T_h values of quartz-hosted CO₂-N₂-H₂S-CH₄-bearing aqueous inclusions from late veins are in the range of 207 – 236°C (median= 223°C). These temperatures are consistent with sphalerite trace element geothermometry (GGIMFis; 163 – 279°C) and are comparable to nearby Tom and Jason CD-type deposits in the Macmillan Pass district.

The Zinnwald/Cinovec Sn-W-Li greisen deposit on the border between Germany and Czech Republic in the eastern part of Krušné Hory/Erzgebirge represents a fluorine-rich hydrothermal alteration of a granite-rhyolite association. We investigated the effects of fluid-rock interaction on distal rhyolites of the deposit, using petrological and mineralogical data to constrain the process of greisenization in detail. The samples were selected from the contact between granite and rhyolite. Three distinct zones of high- and low-degree topaz-greisenization and albitization developed with different textures, mineral assemblages and mineral compositions. Beyond the albitization zone, a continuous transition to the least altered rhyolite was observed. In the greisen part, the predominant minerals are quartz (~80 vol%) and topaz (~10 vol%) with minor mica (~5 vol%). We employed a reactive transport model based on mass conservation and local equilibrium to unravel the detailed process of greisenization. We integrated solution models and endmember thermodynamic data for topaz in recent thermodynamic datasets. The model accounts for fluid flow, porosity and density evolution. The model is used to emulated the sequence of observed petrological zones as obtained with automated mineralogy to constrain the original fluid chemistry and reconstruct elements redistribution during greisenization. By comparing fluid-rock interaction models producing topaz greisen and topaz-free mica greisen, we quantify the F-content necessary to form the greisen at Zinnwald/Cínovec. The comparison implies that F content has a great influence on the greisenization types, which may be related to different metallogenic processes and give insights into W-Sn ore deposits.

Future exploration for mineral resources will target greater depths and submarine settings, which is costly and technically challenging. For this development, numerical modeling can be used to identify the governing processes within entire ore-forming systems. Capturing the dynamics of magmatic-hydrothermal interface processes requires to resolve mass and energy fluxes as a continuum that extends beyond the roots of hydrothermal systems and bridges the gaps between fluid flow and magma dynamics. Magma is mobile during intrusion events and can convect until it reaches a crystal lockup due to cooling and crystallization. During this process, the magma reservoir reaches fluid saturation and exsolves metal-bearing magmatic volatiles to the host rock. We developed a consistent formulation for fluid generation and transport in a coupled model for viscous flow according to the Navier-Stokes-Equations and porous flow with Darcy’s Law, using an up-scaled description of volatile release from reservoir to host rock and realistic magma properties from published experimental and modelling works. We explore the consequences of exsolved volatile phases on magma dynamics and its implications on fluid release and ore formation within the host rock. We distinguish three distinct stages during the evolution of magmatic bodies and their associated porphyry copper deposits with a preparation, a brecciation-stockwork-veining and an ore-formation stage.

Mineralogy evaluation is critical to understand a deposit’s mineralogical variability, and inform decisions associated with ore beneficiation. Elemental-to-mineral conversion techniques (EMC) are a popular method to rapidly estimate a sample’s modal mineralogy from an assay dataset. EMC techniques are based in the principle that the bulk chemistry of a sample is proportional to the product of its modal mineralogy and the mineral’s elemental composition.

In this work, we present a Baeysian framework to infer modal mineralogy from compositional data, Pedras. It builds upon the works of Escolme et al. (2019) and Berry et al. (2011), an EMC method that uses linear programming to minimize coefficients representing the energy required to generate a given mineral assemblage. The minimization process implies thermodynamic equilibrium, which is rarely the case for hydrothermal environments. Instead, the thermodynamic coefficients are defined as a logistic probability distribution function, centred at the mineral assemblage’s equilibrium, which relaxes the thermodynamic coefficient’s minimization.

The framework is tested on synthetic alteration assemblages within a porphyry copper deposit and applied to a geochemical dataset from the Wainaulo porphyry copper deposit (Fiji). The results show that by relaxing thermodynamic minimization constraint, accurate modal mineralogy can be approximated at different stages of hydrothermal alteration in porphyry copper deposit systems. Major mineralogical domains are obtained from mineral approximations, reflecting different lithotypes, alteration and mineralization patterns. The modal mineralogy outputs also provide invaluable insights of mineral associations that vector towards mineralization, The method’s accuracy is enhanced when prior knowledge is objectively included in the modelling stage.

The Ruwai Pb-Zn-Ag skarn deposit is located within the Schwaner Mountain Complex in Central Kalimantan, Indonesia. It is the largest polymetallic skarn deposit in Kalimantan with the resources is estimated up to 14.43 Mt. at 4.94 wt.% Zn, 3.28 wt.% Pb, 108.11 g/t Ag which hosted by Jurassic limestones of the Ketapang Complex and Cretaceous granitoids of Sukadana Complex. In order to study the complex mineralogy and deportment of critical-elements (Ag, Bi, Sb, In, Te, Cd) pulp samples from the main stages of the processing plant (Ball mill/feed, Pb concentrate, Zn concentrate, Pb scavenger, Zn scavenger, Fe screw, and tailings) as well as 66 core samples of Pb-Zn-Ag mineralization were obtained.

Preliminary results on the pulp samples from X-ray diffraction (XRD), X-ray fluorescence (XRF) and mineral liberation analysis (MLA) agree within analytical uncertainties. The data allows a preliminary assessment of the deportment and distribution of Ag and Bi in the skarn ores and processing products. Particularly, acanthite (Ag₂S) and freibergite ((Ag,Cu,Fe)₁₂(Sb,As)₄S₁₃) are likely to be important hosts of Ag, while Bi occurs within bismuthinite (Bi₂S₃) and native bismuth (Bi). For the core samples, µ-XRF measurements of slabs have so far provided a broad overview of elemental distribution within the samples, while XRD results indicate more complex mineralogical compositions than the pulp samples.

Further analytical work including electron probe microanalysis (EPMA) and laser ablation ICP-MS are planned for all samples to be also able to evaluate the resource potential of other critical elements of interest such as Sb, In, Te, Cd.

Indonesian laterite deposits are a major source of Ni and Co. Here, we present new geological data on the Sebuku laterites (SE Kalimantan, Indonesia), with a resource of ~390 Mt at 42.5 wt.% Fe, 0.9 wt.% Ni, and 0.15 wt.% Co. The deposits are mostly limonitic, oxide-dominated Fe-Ni-Co-rich horizons, which formed by weathering of Jurassic-Cretaceous ophiolitic units. Although the Fe ore has been mined since 2006, little mineralogical and geochemical data are available, which would allow optimizing beneficiation and recovery of Ni and Co.

Typical laterite profiles at Sebuku consist of: 1) weathered bedrock composed of serpentinized dunites and harzburgites overlain by 2) a 0.2-7 m-thick saprolite zone, 3) a 2-8.5 m-thick yellow limonite zone, and 4) a 1-3.5 m-thick red-limonite zone.

Preliminary XRF, XRD, and mineral liberation analysis (MLA) data show a decrease in Mg and Si and an increase in Fe moving upwards through the laterite profile, corresponding to a transition from silicate- to oxide-rich mineralogy. Oxides and (oxy)-hydroxides comprise goethite, maghemite, hematite, magnetite, chromium spinel, gibbsite/bayerite, and various Mn-minerals, whereas silicates consist of serpentine, chlorite, talc, quartz, pyroxene, olivine, and clay minerals. Ni is hosted by various minerals, which include goethite, Mn-oxides, serpentine, and clays, whereas Co is mainly hosted by Mn-oxides.

Mineral chemical analyses (EPMA) are planned to further understand critical metal variability and distribution within the host minerals and throughout the deposits. Our ultimate goal is to characterize and quantify the distribution of Ni and Co in order to develop more efficient beneficiation processes.

Securing a predictable and affordable supply of critical metals for the high-tech industry, coupled with tightening supplies and augmented competition for available resources, leads to increasing exploration of complex and/or unconventional deposits. Complex ores often require extensive metallurgical processing and thus suffer from high capital and/or operational expenditures (CAPEX and OPEX). The Fe, Co, Ni, and Sc extraction from Sebuku Fe-(Ni)-Laterite was studied. The study compares conventional and alternative extraction methods, considering both the metal value of the deposit and the operational expenditures involved.

Conventional methods, such as roasting, stirred leaching, and pressure leaching, showed high extraction efficiencies for the target elements but also a significant demand in energy and chemicals. Alternative reducing agents in combination with conventional methods benefit faster leaching times and reduced energy demand at similar extraction efficiencies and might result in a more cost-effective and environmentally friendly process chain. Unconventional approaches, such as ionic liquids and deep eutectic solvents, report lower recovery rates necessitating further basic investigations to optimize the leaching agents and/or to develop efficient process designs with respect to the specific requirements.

Independent on the approach used, a basic process design including the implementation of potential recycling processes and waste/wastewater streams is mandatory for a first economic assessment of the individual routes. Based on this evaluation, the study highlights the need for further optimization to make beneficiation approaches feasible and attractive for potential investors especially viewing the current market prices for metals and chemicals.

This study is part of the StratOre Project (Client II).