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X-ray computed tomography has established itself as a crucial tool in the analysis of rock materials, providing the ability to visualise intricate 3D microstructures and capture quantitative information about internal phenomena such as structural damage, mineral reactions, and fluid-rock interactions. The efficacy of this tool, however, depends significantly on the precision of image segmentation, a process that has seen varied results across different methodologies, ranging from simple histogram thresholding to more complex machine learning and deep learning strategies. The irregularity in these segmentation outcomes raises concerns about the reproducibility of the results, a challenge that we aim to address in this work. In our study, we employ the mass balance of a metamorphic reaction as an internal standard to verify segmentation accuracy and shed light on the advantages of deep learning approaches, particularly their capacity to efficiently process expansive datasets. Our methodology utilises deep learning to achieve accurate segmentation of time-resolved volumetric images of the gypsum dehydration reaction, a process that traditional segmentation techniques have struggled with due to poor contrast between reactants and products.We utilise a 2D U-net architecture for segmentation and introduce machine learning-obtained labelled data (specifically, from random forest classification) as an innovative solution to the limitations of training data obtained from imaging. The deep learning algorithm we developed has demonstrated remarkable resilience, consistently segmenting volume phases across all experiments. Furthermore, our trained neural network exhibits impressively short run times on a standard workstation equipped with a Graphic Processing Unit (GPU). To evaluate the precision of our workflow, we compared the theoretical and measured molar evolution of gypsum to bassanite during dehydration. The errors between the predicted and segmented volumes in all time-series experiments fell within the 2% confidence intervals of the theoretical curves, affirming the accuracy of our methodology. We also compared the results obtained by the proposed method with standard segmentation methods and found a significant improvement in precision and accuracy of segmented volumes. This makes the segmented CT images suited for extracting quantitative data, such as variations in mineral growth rate and pore size during the reaction. In this work, we introduce a distinctive approach by using an internal standard to validate the accuracy of a segmentation model, demonstrating its potential as a robust and reliable method for image segmentation in this field. This ability to measure the volumetric evolution during a reaction with precision paves the way for advanced modelling and verification of the physical properties of rock materials, particularly those involved in tectono-metamorphic processes. Our work underscores the promise of deep learning approaches in elevating the quality and reproducibility of research in the geosciences. [ABSTRACT FROM AUTHOR]

The regulation of anthropogenic carbon dioxide (CO 2) is an urgent issue – continuously increasing atmospheric CO 2 from burning fossil fuels is leading to significant warming and acidification of the surface ocean. Timely and effective measures to curb CO 2 increases are thus needed in order to mitigate the potential degradation of natural ecosystems, food security, and livelihood caused by anthropogenic release of CO 2. Enhanced rock weathering (ERW) on croplands and hinterlands may be one of the most economically and ecologically effective ways to sequester CO 2 from the atmosphere, given that these soil environments generally favor mineral dissolution and because amending soils with crushed rock can result in a number of co-benefits to plant growth and crop yield. However, robust quantitative evaluation of CO 2 capture by ERW in terrestrial soil systems that can lead to coherent policy implementation will require an ensemble of traceable mechanistic models that are optimized for simulating ERW in managed systems. Here, we present a new 1D reactive transport model – SCEPTER. The model is designed to (1) mechanistically simulate natural weathering, including dissolution/precipitation of minerals along with uplift/erosion of solid phases, advection plus diffusion of aqueous phases and diffusion of gas phases, (2) allow targeted addition of solid phases at the soil–atmosphere interface, including multiple forms of organic matter (OM) and crushed mineral/rock feedstocks, (3) implement a range of soil mixing regimes as catalyzed by soil surface fauna (e.g., bioturbation) or humans (e.g., various forms of tilling), and (4) enable calculation of solid mineral surface area based on controlled initial particle size distributions coupled to a shrinking core framework. Here we describe the model structure and intrinsic thermodynamic/kinetic data, provide a series of idealized simulations to demonstrate the basic behavior of the code, and evaluate the computational and mechanistic performance of the model against observational data. We also provide selected example applications to highlight model features particularly useful for future prediction of CO 2 sequestration by ERW in soil systems. [ABSTRACT FROM AUTHOR]

Regulation of anthropogenic carbon dioxide (CO2) is an urgent issue-continuously increasing atmospheric CO2 from burning fossil fuels is leading to significant warming and acidification of the surface ocean. Timely and effective measures to curb CO2 increases are thus needed in order to mitigate the potential degradation of natural ecosystems, food security, and livelihood caused by anthropogenic release of CO2. Enhanced rock weathering (ERW) on croplands and hinterlands may be one of the most economically and ecologically effective ways to sequester CO2 from the atmosphere, given that these soil environments generally favor mineral dissolution and because amending soils with crushed rock can result in a number of co-benefits on plant growth and crop yield. However, quantitative evaluation of CO2 capture by ERW in terrestrial soil systems to date has been conducted with tools that are mechanistically very simplified and/or allow limited flexibility. With the goal of working towards a more mechanistically grounded understanding of the geoengineering potential of terrestrial ERW, we developed new 1D reactive transport model - SCEPTER. The model is designed to: (1) mechanistically simulate natural weathering, including dissolution/precipitation of minerals along with uplift/erosion of solid phases, advection plus diffusion of aqueous phases and diffusion of gas phases; (2) allow targeted addition of solid phases at the soil-atmosphere interface, including multiple forms of organic matter (OM) and crushed mineral/rock feedstocks; (3) implement a range of soil mixing regimes as catalyzed by soil surface fauna (e.g., bioturbation) or humans (e.g., various forms of tilling); and (4) enable calculation of solid mineral surface area based on controlled initial particle size distributions coupled to a shrinking core framework. Here we describe the model structure and intrinsic thermodynamic/kinetic data, provide a series of idealized simulations to demonstrate the basic behavior of the code, and evaluate the computational and mechanistic performance of the model against observational data. We also provide selected example applications to highlight model features particularly useful for future prediction of CO2 sequestration by ERW in soil systems. [ABSTRACT FROM AUTHOR]

Kahlenbergite, ideally KAl11O17, and Fe-rich hibonite, CaAl10Fe2O19, are high-temperature minerals found in "olive" subunits of pyrometamorphic rocks, in the Hatrurim Basin, the Negev desert, Israel. The crystal structures of both minerals are refined using synchrotron radiation single-crystal diffraction data. The structure of kahlenbergite (P63=mmc; a D 5:6486.1/Å; b D 22:8970.3/Å; Z D 2) exhibits triple spinel blocks and so-called R blocks. The spinel blocks show mixed layers with AlO6 octahedra and (Al0:56Fe0:44/O4 tetrahedra and kagome layers with (Al0:92Fe0:08/O6 octahedra. One-dimensional diffuse scattering observed parallel to c* implies stacking faults in the structure. Also, in one of the investigated kahlenbergite crystals additional reflections can be identified, which obviously belong to a second phase with a smaller lattice parameter c: Fe3C-rich hibonite. The structure of hibonite contains the same spinel blocks as kahlenbergite. The R blocks in hibonite contain Ca atoms, AlO5 bipyramids, and AlO6 octahedra, whereas the R blocks in kahlenbergite contain potassium atoms and AlO4 tetrahedra. [ABSTRACT FROM AUTHOR]

Population growth, together with overall improvement of life standards, greater level of environmental awareness and energy transition towards green technologies, result in globally increasing demand for mineral resources on a yearly basis. Considering that most of the shallow large-scale deposits have likely already been explored and mined out (or are being mined), there is a great interest to explore for deeper-seated deposits. For this purpose, the SIT4ME project, through EIT Raw Material Program was established, aiming to promote, improve and further establish seismic methods for mineral exploration in hard rock environments. In November 2018, a multi-method seismic dataset was acquired in the Zinkgruvan mining area in the Bergslagen mineral province of Sweden. Both active (32t seismic vibrator truck as source) and passive data were acquired using a combination of sparse 3D grid and dense 2D profiles in an area of approximately 6 km2 enabling reasonable 3D subsurface illumination. For the data acquisition, a total of 1300 receivers were used across the study area, distributed along ten 2D-crooked-seismic lines and in a 3D mesh. This provided us with a comprehensive dataset, which would be used for a multitude of processing and imaging approaches. The objectives are to image any deep (> 500 m depth) massive sulphide mineralization and structures hosting them within this complex three-dimensionally deformed hard rock setting. Here, we present the acquisition setup, preliminary reflection seismic processing results obtained from active part of the dataset. [ABSTRACT FROM AUTHOR]

Occurrences of alkali not diamondiferous ultramafic lamprhophyres, which recently were found on southwest edge of Siberian craton [Kargin et al., 2016], are very informative and may help us to understand origin mechanisms and evolutions of such rocks, their connections to other ultramafic types, so comprehensive study of this case are important. Especially, experimental works on nature samples might model the system, which have been done in this work.In this paper the results of experimental study of natural sample of aillikites from Irkeneeva-Chadobets trough are presented. This sample represented collection of rocks from Ilbokich uplifts, where the rocks form dykes. The rocks are classified, according classification scheme [Tappe et al.,2005], as aillikites. Aillikites are characterized by porphyritic an/or globular texture, enriched in magmatic carbonates (up to 25 wt.% of CO2 whole rock composition), olivine macro- and/or phenocrysts, and rarely pyroxene phenocrysts. Mineral compositions are presented in groundmass: carbonates, phlogopites, clinopyroxenes, spinel, ilmenite, rutile, perovskite, Ti-garnets, K-feldspar. Aillikites characterized higher concentrations of CO2 than kimberlites and differ from lamproite by lower alkali content. Variety of minerals, their composition and morphology indicates multi-stage evolution, which can be distinguished to magmatic and late magmatic stages, on which many autometasomatic processes occurred. The studied rocks are rich in volatile substances and late-stage processes strongly effect on paragenesis, which makes the determination of solid minerals difficult, but it is very important to unders--tand the mechanism of origin. To solve this problem, melting experiments have been made. Thermodynamic parameters of anticipated first phase were rough estimated using monomineral olivine thermometer [Smirnova et al., 2017]. That estimations and literature data [Tappe et al., 2006] suggested that the pressure - near 5 GPa and temperature varies from 1200 up to 1400C. The experiments were conducted under 5 and 4 GPa and temperatures 1000 – 1500C with the high-pressure toroidal "anvil-with-hole" apparatus. For experiments least altered and not containing macro- and phenocrysts samples were chosen. Natural samples were crushed into powder and stored in platinum capsules. The time of the experiment was from 3 to 10 hours under predetermined pressure and temperature. As a result of the experiments, the following conclusions were made: we found that two types of paragenesis are characteristic: (1) under high-pressure and low-temperature clinohumite + Ti-garnet + clinopyroxene + carbonate, and (2) olivine + clinopyroxene + mica + carbonate ± Ti-garnet ± Ti-phase. Ti and F play important role in forming process, namely in the stabilization of phases such as Ti-clinohumite/olivine/Ti-garnet/F-mica. Our experiments confirm that studied aillikites from Southwestern Siberia can be formed under estimated conditions. Apparently the most important differences between aillikites' magmas and kimberlites and lamproites can be associated with various influence of activities F, Ti and CO2.Authors thank Anna Nosova, Ludmila Sazonova and Alexei Kargin for Ilbokich's samples. This work was partially supported bu RFBR (19-05-00195). [ABSTRACT FROM AUTHOR]

The factors influencing uranium migration in water-rock systems during acid in-situ leaching (ISL) were studied at the Kujieertai uranium deposit in Xinjiang. Using an ISL unit, we tested the sequential effects of a leaching solution without oxidant (H2SO4 solution 4–8 g/L) and a leaching solution with oxidant (H2SO4 3–7 g/L, and Fe (III) 2–6 g/L). The observation of the leaching process revealed clearly defined stages of uranium migration from the solid mineral to solution. At the beginning of the acid ISL process, the oxidant was not added to the leaching solution and the dissolution of hexavalent uranium at the mineral surface led to a rapid increase in uranium concentration followed by a decrease in uranium concentration in the solution. This change occurred when the pH value was less than 4.5 and there was sufficient SO42- ligand. Following the decrease in hexavalent uranium at the ore surface and a decline in uranium migration intensity, the addition of Fe(III) oxidant facilitated the oxidation of tetravalent uranium, which enabled strong uranium migration again. In this process, the dissolution of uranium had a strong positive correlation with the reduction of Fe(III), and the ratio of the uranium dissolution to the Fe(III) reduction ranged between 0.041 and 0.091. Furthermore, the deportment of uranium was another important factor affecting uranium migration. Uranium located on the mineral surface can be completely exposed to the solution and the dissolution and migration intensity was significantly affected by hydrogeochemical conditions. The uranium present in microfissures and in the ore matrix could not be fully exposed to the solution, and the intensity of uranium migration in the microfissure was primarily controlled by corrosion and permeability of the ore. Therefore, the hydrogeochemical conditions and the deportment of uranium were the external and internal factors that significantly affected the dissolution and migration of uranium in the early and middle stages of the experiment. However, in later stages, as the concentration of uranium in the ore decreased, increases in the chemical potential of the solution, specifically acidity and the amount of oxidant, had a limited or insignificant impact on the dissolution of uranium. [ABSTRACT FROM AUTHOR]