Rock Samples Research Articles

A novel proposed classification system for rock slope stability assessment

The present study introduces “rock slope instability score (RSIS)” a novel classification system for assessing rock slope stability. It takes into account geological and geotechnical parameters, as well as the impact of human activities and triggering parameters, which have become more frequent due to climate change and few of them have been ignored in existing classifications. The study focuses on rock slopes of various lithologies from the Indian Himalayas. The development of this new classification system is based on the examination of 81 different rock slopes from various states of the Indian Himalayas. Extensive field surveys, rock sampling, geotechnical laboratory tests, and ground measurements have been conducted at the various slope sites to establish a comprehensive scoring system for the stability assessment. The distributions of weightage to each parameter have been considered, corresponding to its degree of impact in causing slope instability. Sensitivity analysis of all defined parameters of RSIS system has revealed that the majority of the parameters exhibit a strong positive correlation, with Pearson correlation coefficients ranging from 0.74 to 0.61. However, two parameters, namely discontinuity dip and the relationship between slope & discontinuity direction, gives moderate relationship with correlation coefficient values of 0.48 and 0.41, respectively. To avoid any designer biasness in the system, several individuals gathered data set at different times. The proposed classification system has demonstrated a strong correlation with the actual slope condition, and it is quite promising. The outcome of RSIS classification for studied 81 slopes classified 2 slopes under stable condition, 21 slopes as partially stable, 44 as unstable, and 14 as completely unstable.

Physico-mechanical parameters of rock materials used in open pit reclamation – a case study of CTL Maczki-Bór S.A. mine in Poland

The aim of the research was to assess the variability of selected physical and mechanical properties of Carboniferous barren rocks in the Upper Silesian Coal Basin and to analyze the impact of time and increasing vertical pressure on the mechanical parameters of the mixture of these rocks used in the reclamation of the open pit. Both type of tests were conducted in a strength press. For lithologically and stratigraphically differentiated rock samples, strength parameters in various states of humidity (air-dried and capillary saturation state) were determined, including compressive strength, cohesion and the angle of internal friction. It was found that the strength of all types of rock increases with geological age, however saturation of these rocks with water causes their structural weakening, which is especially noticeable in the case of sandstone and claystone. In the case of mudstone, due to their structure, the reduction of strength after saturation with water is not so significantly noticeable. In the second part of the laboratory tests, 5 samples of Carboniferous post-mining waste with different storage times in the open pit were subjected to the assessment of changes in density and compressibility in relation to increasing values of vertical pressure. It was found that the long-term depositing of waste in the excavation is conducive to the intensive development of hypergenic processes. This contributes to the disintegration of sedimentary rocks, which causes changes in their physical and mechanical parameters. This phenomenon is additionally intensified by the increasing vertical pressure with thickness of waste layers.

Diffusion in Porous Rock Is Anomalous.

Molecular diffusion of chemical species in subsurface environments─rock formations, soil sediments, marine, river, and lake sediments─plays a critical role in a variety of dynamic processes, many of which affect water chemistry. We investigate and demonstrate the occurrence of anomalous (non-Fickian) diffusion behavior, distinct from classically assumed Fickian diffusion. We measured molecular diffusion through a series of five chalk and dolomite rock samples over a period of about two months. We demonstrate that in all cases, diffusion behavior is significantly different than Fickian. We then analyze the results using a continuous time random walk framework that can describe anomalous diffusion in heterogeneous porous materials such as rock. This methodology shows extreme long-time tailing of tracer advance as compared to conventional Fickian diffusion processes. The finding that distinct anomalous diffusion occurs ubiquitously implies that diffusion-driven processes in subsurface zones should be analyzed using tools that account for non-Fickian diffusion.

An Integrated Petrographic, Geomatic and Geophysical Approach for the Characterization of the Carbonate Rocks of the Calcari di Cagliari Formation

Non-invasive techniques, such as close-range photogrammetry (CRP) and 3D ultrasonic tomography complemented with optical and scanning electron microscopy and mercury porosimetry, were applied to characterize the carbonate rock samples of the Calcari di Cagliari formation. The integrated approach started with the computation of high-resolution 3D models of the carbonate samples using the CRP technique to produce 3D high-resolution models texturized both with natural colors and intensity. Starting from the 3D models from previous techniques, a 3D ultrasonic tomography on each rock sample was accurately planned and carried out in order to detect the elastic properties of such rocks and relate them to textural heterogeneity or internal defects. The results indicate that the relationship between longitudinal velocity and rock properties is complex even in the same carbonate formation. Understanding the relationship between the geomatic and geophysical responses in the investigated rock properties, such as textural characteristics and especially structure and geometry of pores, type of pores, tortuosity and cementing material, is important for many practical applications and especially in the diagnostic process of the conservation state of monumental structures. The integration of the above non-invasive techniques complemented by petrographical–petrophysical data proved to be a powerful method to associate each lithotype with a different susceptibility to degradation. The results presented in this paper demonstrate that the proposed integrated use of complementary methodologies would guarantee the reproducibility of the measurements both at the laboratory and field scale for the monitoring in time of the rock condition while giving a useful contribution in making decisions on an appropriate remedial strategy.

Morphostructural, Chemical and Genetic Features of Native Gold in Brown Coals from the Yerkovetsky Deposit, Far East Russia

We studied the morphostructural features and chemical composition of micron and submicron particles of native gold from brown coals and overcoal sediments of the Yerkovetsky deposit (Zeya-Bureya sedimentary basin, Far East Russia). The samples of coal and host rocks in the form of thin sections, as well as coal particles and grains of native gold obtained during the process of dispersion and the fractionation of loose and crushed samples divided according to size and density, were analyzed using scanning electron microscopy in combination with X-ray microanalysis, involving various visualization modes. It was revealed that native gold is syngenetic with the mineralization of brown coals, and microphases dispersed in the minerals of overcoal loose and sandy-clay sediments were the source of native gold. In coal, gold is accumulated at the stages of formation (alluvial and eolian, including terrigenous and ionogenic subtypes) and the diagenesis of coal deposits (ground-infiltration subtype). A significant part of the mineralization process of coals and the formation of microparticles of native gold was contributed to by the descending water infiltration of polycomponent colloid solutions. During the dehydration of hydroxysiliconized iron-based hydrogels, mineral phases have an unstable composition and floccular structure and contain submicron gold particles. The coatings of all gold microparticles have identical origin and composition. Coal beds that border host rocks are an open system with a constant inflow of the substance, which leads to the gradual formation of polycomponent aggregated particles in micro cavities. Part of the gold in coals occurs as sulfur-bearing complexes dissolved in pore water. The key factor in the migration and deposition of gold in coals is the inorganic substances involved in the processes of coal mineralization. Organic substances play a more passive role and have medium-forming, fractionating (colloid, molecular, and ionic sieves), and accumulation functions.

Analysis of the Sedimentary and Geochemical Characteristics of Sedimentary Clastic Rock Samples from the Alpha–Mendeleev Rise

Analysis of the Sedimentary and Geochemical Characteristics of Sedimentary Clastic Rock Samples from the Alpha–Mendeleev Rise

Fluid‐rock interaction experiments with andesite at 100°C for potential carbon storage in geothermal reservoirs

AbstractGeothermal energy extraction often results in the release of naturally occurring carbon dioxide (CO2) as a byproduct. Research on carbon storage using volcanic rock types other than basalt under both acidic and elevated temperature conditions has been limited so far. Our study uses batch reactor experiments at 100°C to investigate the dissolution of andesite rock samples obtained from an active geothermal reservoir in Sumatra (Indonesia). The samples are subjected to reactions with neutral‐pH fluids and acidic fluids, mimicking the geochemical responses upon reinjection of geothermal fluids, either without or with dissolved acidic gases, respectively. Chemical elemental analysis reveals the release of Ca2+ ions into the fluids through the dissolution of feldspar. The overall dissolution rate of the rock samples is 2.4 × 10–11 mol/(m2 · s) to 4.2 × 10–11 mol/(m2 · s), based on the Si release during the initial 7 h of the experiment. The dissolution rates are about two orders of magnitude lower than those reported for basaltic rocks under similar reaction conditions. This study offers valuable insights into the potential utilization of andesite reservoirs for effective CO2 storage via mineralization.

Thermo‐physical characterisation of natural rocks and impact analysis of variations in their thermo‐physical properties on thermal storage performance

AbstractIn this study, the thermal characterisation of natural rock samples from Zimbabwe for low‐temperature industrial thermal energy storage (TES) applications was carried out. Thermal stability, specific heat capacity, thermal diffusivity, thermal conductivity and density were determined. Variations in these parameters were evaluated and their impact on thermal storage performance was analysed. Basalt and dolerite samples from different locations were found to have average specific heat capacities of 826 and 853 J/kg K, respectively, at room temperature. Insignificant variations were observed with differences of 3.4% for basalt and 1.7% for dolerite samples. Also, negligible differences of 0.3% and 0.7% in densities for rocks of the same type but of different origins were obtained for basalt and dolerite samples, respectively. However, significant variations in thermal diffusivity of all the igneous and metamorphic samples were observed with quartzite rock exhibiting the highest value of 2.1 × 10−6 m2/s, while the values for the other samples range from 0.9 × 10−6 to 1.6 × 10−6 m2/s. This implies that the thermal efficiency of sensible TES systems that use different or the same rock types from different locations can be significantly high to be overlooked. Thermo‐gravimetric analysis results revealed that the rock samples studied have good thermal stability for low‐temperature heat storage applications.

Experimental study on the damage characteristics of cyclic disturbance and acoustic emission characteristics of different types of sandstones under high stress in deep mines

AbstractThree sandstone specimens common in rock engineering were selected to study the differences in the mechanical properties of rocks with different lithologies. The development and expansion of the internal cracks in the specimens were observed by combining the simulation system with the acoustic emission system. Through the combination of dynamic and static stresses, the deformation and damage of rocks under deep rock excavation and blasting were simulated. As the results show, the acoustic emission events of specimens with different lithologies under combined static and dynamic cyclic loading can be roughly divided into three phases: weakening, stabilizing, and surging periods. In addition, the acoustic emission characteristics of specimens with different lithologies show general consistency in different compression phases. The degree of fragmentation of specimens increases with the applied stress level; therefore, the stress level is one of the important factors influencing the damage pattern of specimens. The acoustic emission system was used to simulate the deformation and damage of rocks subjected to deep rock body excavation and engineering blasting. Cyclic dynamic perturbations under sinusoidal waves with a frequency of 5 Hz, a loading rate of 0.1 mm/min, a cyclic amplitude of 5 MPa, and a loading rate of 0.1 mm/min were applied to the three rock samples during the experiments. Among them, the fine‐grained sandstones are the most sensitive to the sinusoidal cyclic perturbation, followed by the muddy siltstone and the medium‐grained sandstones. On this basis, the acoustic emission energy release characteristics were analyzed, and the waveform characteristics in the damage evolution of the specimen under dynamic perturbation were studied by extracting the key points and searching for the main frequency eigenvalues.

Study and Application of Rock Drilling Resistance Characteristics in the Jiyang Depression Formation

In response to the unclear drilling resistance characteristics of rocks in the Ji’yang Depression, low drilling efficiency of PDC drill bits, and difficulties in drill bit selection, this study selected rock samples from different depths in the area for indoor drilling resistance analysis testing. Based on logging data, a prediction model was established for drilling resistance characteristics parameters of the strata in the area, and a graph of drilling resistance characteristic parameters of the rocks in the area was drawn. The study showed that the uniaxial compressive strength of the strata rocks was 50–110 MPa, with a hardness of 500–1300 MPa, a plasticity coefficient ranging from 1 to 2, a rock drillability grade of 8–20, and an abrasiveness index of 5–20. Combining the analysis of on-site drilling bit failures, PDC drill bits adapted to the strata in the area were selected, and the mechanical drilling speed of the selected bits reached 12.58 m/h, successfully drilling through the target layer. The above research results are of guiding significance for understanding the reasons for the difficulty of drilling into the Jiyang Depression strata and for improving mechanical drilling speed and drill bit selection in this area.

Study on the physical and mechanical properties of recycled weathered rock materials in expressway subgrade in permafrost areas

In view of the specialized climatic conditions in high-cold and high-altitude regions, the direct, repeated freeze-thaw and freezing processes resulting from diurnal and seasonal temperature changes pose a significant threat to the integrity of the roadbed stones in these areas. Weathering and fragmentation constitute a form of rock damage. Rock damage negatively impacts the air convection within the rock subgrade, rendering it incapable of safeguarding frozen soil. The objective of this study is to investigate the mechanical properties and the constitutive model for freeze-thaw damage of three recycled weathered rock materials subjected to varying freeze-thaw cycles. Additionally, it aims to examine the damage and degradation mechanism of recycled weathered rock materials under the combined influence of freeze-thaw and load. The model is then employed to validate the experimental data. Research indicates that with an increase in the number of freeze-thaw cycles, the quality of the three types of recycled weathered rock samples exhibits a gradual decrease, accompanied by a corresponding reduction in P-wave speed. The elastic modulus and compressive strength of the three recycled weathered rock materials show an increase with rising confining pressure and a decrease with a growing number of freeze-thaw cycles. The types of damage include splitting and shear damage. The presented damage model can elucidate the pattern of damage evolution in the specimen under varying confining pressures and freeze-thaw cycles. The expansion of internal micro-cracks is influenced differently by freeze-thaw cycles and loads; moreover, the coupling effect of damage exhibits pronounced nonlinear characteristics. Substantiated by experimental results, the damage constitutive model demonstrates both reasonability and feasibility.

Waveform Complexity and Positioning Analysis of Acoustic Emission Events during the Compression Failure Process of a Rock Burst Prone Sample

The localization results of acoustic emission (AE) events can reflect the location and pattern of burst-prone rock failures. However, event localization heavily depends on the quality of the original waveform of the sensor. Therefore, this study analyzed the AE waveform of a rock sample under compression to evaluate its failure localization and quality. From the research results, it could be seen that the initial failure was relatively calm, with clear take-off points, which can be better used for accurate AE event positioning. However, the later failure was severe, causing the take-off points of most sensors to be very unclear, and positioning methods that rely on take-off points cannot be used for positioning, let alone simply using the positioning results of the built-in software. This research result reminds researchers who use AE signals for event localization to first examine the quality and status of the original waveform, providing a basis for obtaining accurate localization results, in order to further accurately study the subsequent failure patterns. The above facts indicate that the initial failure is small and scattered, while the later failure is large and concentrated, with certain fractal characteristics.

Implementation and experience of using methods for analyzing the isotopic composition of Sm and Nd, Rb and Sr in rock samples at the Geoanalitik Center for Collective Use

Research subject. AGV-2 and BHVO-2 geochemical reference materials for studying the Sm, Nd and Rb, Sr isotope systems along with various rocks and mineral samples. Materials and Methods. An analysis of the isotopic composition of Sm, Nd and Rb, Sr was carried out using Neptune Plus and Triton Plus mass spectrometers. Aim. To implement analytical techniques for the isotopic composition of Sm and Nd, Rb, and Sr in various rock and mineral samples using two types of multicollector mass spectrometers – inductively coupled plasma NeptunePlus and thermal ionization TritonPlus (Thermo-Fisher), as well as a description of the procedure of processing experimental data and the experience in using techniques at the “Geoanalitik” shared research facilities of the IGG UB RAS for the period 2015-2023. Results. The analytical techniques implemented included (1) column chromatography using various ion-exchange resins, optimised for the ratio of labour costs/quality of analytical results; (2) the measurement of isotope ratios using two types of mass spectrometers; (3) the correction of mass bias of isotope ratios and the determination of Sm and Nd, Rb, and Sr concentrations by the isotope dilution method using 149Sm+150Nd and 85Rb+84Sr spikes. Testing of the techniques was carried out using the AGV-2 and BHVO-2 geochemical reference materials; their metrological characteristics were presented. When using TritonPlus, the reproducibility (BHVO-2, n=60) of measurements of 143Nd/144Nd, 147Sm/144Nd isotope ratios and Sm and Nd concentrations are ±0.000020, ±0.0004, ±1.3 and ±0.4, respectively; indicators of correctness of determining the ratios 143Nd/144Nd and 147Sm/144Nd – 0.001 and 0.25% and concentrations of Sm and Nd – 2%; the reproducibility (BHVO-2, n=63) of measurements of 87Sr/86Sr, 87Rb/86Sr isotope ratios and concentrations (Rb and Sr) are ±0.0025%, ±1.5%, ±2%, respectively. The uncertainty of a single measurement of the 143Nd/144Nd and 87Sr/86Sr isotope ratio, represented by the standard error of the average single measurement in the sample, does not exceed 0.0025%. Conclusions: the results obtained for the geochemical reference materials are in satisfactory agreement with those provided in the GeoReM database, as well as with the certified values provided by the United States Geological Survey (USGS). The described analytical techniques are used at the “Geoanalitik” shared research facilities of the IGG UB RAS to analyse various rock and mineral samples. The work presents a number of experimental results obtained, which are subsequently used in geochronological applications.

Exploration Vectors and Indicators Extracted by Factor Analysis and Association Rule Algorithms at the Lintan Carlin-Type Gold Deposit, Youjiang Basin, China

The Youjiang Basin in China is the world’s second-largest concentrated area of Carlin-type Au deposits after Nevada, USA, boasting cumulative Au reserves nearing 1000 t. This study examined the recently unearthed Lintan Carlin-type Au deposit within the Youjiang Basin. Factor analysis and association rule algorithms were used to identify exploration vectors and indicators essential for navigating this promising geological territory. In the Lintan mining area, the geological strata encompass the Triassic Bianyang, Niluo, and Xuman formations comprised clastic rocks, followed by the deeper Permian Wujiaping Formation with massive carbonate rocks. The orebodies are restricted to the F14 inverse fault, cutting through the Xuman Formation, with an additional F7 fault between the Wujiaping and Xuman formations. A total of 125 rock samples from the F14 fault and a representative cross-section were analyzed for 15 elements (Au, Ag, As, Bi, Cd, Co, Cu, Hg, Mo, Ni, Pb, Sb, Tl, W, and Zn). The elements were divided into four groups based on cluster and factor analysis. Group 1 (Co, Cu, Zn, Ni, Tl, W, and Bi) was mainly enriched in the Xuman, Niluo, and Bianyang formations controlled by sedimentary diagenesis. Group 2 (Au, As, Hg, and Sb) was concentrated in the F14 and F7 faults, representing Au mineralization. Group 3 (Pb, Ag, and Mo) was mostly enriched near the F14 and F7 faults, displaying a peripheral halo of Au mineralization, and was probability controlled by ore-forming hydrothermal activities. Group 4 (Cd and Mo) exhibited extreme enrichment along the periphery of the F7 fault. This pattern indicates the presence of a substantial hydrothermal alteration zone surrounding the fault, likely influenced by ore-forming hydrothermal processes. Additionally, Pb, Ag, Cd, Mo, and W are considered essential indicators for ore formation besides Au, As, Sb, Hg, and Tl. Twelve effective association rules were derived using the association rule algorithm, which can aid in discriminating Au mineralization. The spatial distributions of the 15 elements indicated that the F14 fault is the main ore-bearing fracture zone, while the F7 fault serves as the ore-conducting structure, channeling ore-forming fluids into the F14 fault. Faults between the Wujiaping and Xuman formations, along with their associated reverse faults, present potential prospecting targets both within and outside the Lintan Au deposit in the Youjiang Basin. Exploration geochemical data can be fully utilized by combining factor analysis and association rule algorithms, offering key guidance for prospecting Carlin-type gold and similar deposits.

Direct mineral content prediction from drill core images via transfer learning

Deep subsurface exploration is important for mining, oil and gas industries, as well as in the assessment of geological units for the disposal of chemical or nuclear waste, or the viability of geothermal energy systems. Typically, detailed examinations of subsurface formations or units are performed on cuttings or core materials extracted during drilling campaigns, as well as on geophysical borehole data, which provide detailed information about the petrophysical properties of the rocks. Depending on the volume of rock samples and the analytical program, the laboratory analysis and diagnostics can be very time-consuming. This study investigates the potential of utilizing machine learning, specifically convolutional neural networks (CNN), to assess the lithology and mineral content solely from analysis of drill core images, aiming to support and expedite the subsurface geological exploration. The paper outlines a comprehensive methodology, encompassing data preprocessing, machine learning methods, and transfer learning techniques. The outcome reveals a remarkable 96.7% accuracy in the classification of drill core segments into distinct formation classes. Furthermore, a CNN model was trained for the evaluation of mineral content using a learning data set from multidimensional log analysis data (silicate, total clay, carbonate). When benchmarked against laboratory XRD measurements on samples from the cores, both the advanced multidimensional log analysis model and the neural network approach developed here provide equally good performance. This work demonstrates that deep learning and particularly transfer learning can support extracting petrophysical properties, including mineral content and formation classification, from drill core images, thus offering a road map for enhancing model performance and data set quality in image-based analysis of drill cores.

Effects of changing water content of clay-content rocks on field cutter consumption rate of roadheaders: a case study of porous ignimbrites

The changing formation characteristics during excavation can cause a higher cutter consumption rate (CCR) of mechanical excavators than theoretically estimated before the project begins. This study investigates the adhesive potential of clay-content porous ignimbrites in increasing water content and their effects on the CCR of roadheaders. For this purpose, the actual field CCR data of roadheaders were recorded for ten cold storage caverns (CSC) projects during the excavation in dry and wet conditions. Then, laboratory tests were carried out on the rock samples collected from project areas. CCRs of roadheaders were theoretically estimated based on the Cerchar abrasivity index of rocks using three different empirical models. The laboratory test results showed that increasing water content reduces the abrasivity and strength of the rocks. The theoretically estimated results also showed that CCR is to be less under saturated conditions. However, actual field data revealed higher CCRs for all CSC projects in wet conditions. Therefore, the adhesion potential of rocks in different water contents was analyzed, and positive relationships were obtained between the field CCR in wet conditions and the adhesion potentials of excavated rocks with 15%, 20%, and 25% water content. New equations were developed to estimate the CCR of roadheaders, especially in excavating rocks that have an adhesive potential to cutters, such as clay-content rocks. It has been concluded that for an accurate CCR estimation, more than theoretical calculations will be required, and changing formation conditions should also be analyzed in detail.

CAPILLARY PROCESSES DURING FLOODING OF LAYERED-HETEROMOGENEOUS PRODUCTIVE FORMATIONS

The paper presents an analysis of existing laboratory methods for determining capillary pressure functions used in mathematical and computer modeling of the processes of capillary impregnation of low-permeability layers of layered heterogeneous hydrophilic reservoirs during their flooding.It is shown that in existing methods for determining capillary pressure functions in rock samples using capillarimeters and high-speed centrifuges, the factor of the formation of residual oil in the pore space of the rock is not taken into account. At the same time, the processes of displacement of oil by water from productive formations and, in particular, the processes of capillary impregnation of the rock, are characterized by the processes of formation of microvolumes precisely of immobile residual oil in its pore space. Meanwhile, when conducting laboratory studies of rock samples using existing methods, another process is physically reproduced — the process of displacement of water by oil, during which microvolumes of residual water, rather than oil, are formed.This difference in the structure of the oil-water medium leads to a significant difference between the capillary pressure functions determined by traditional methods and the capillary pressure functions that control the distribution of oil and water phases in the pore space of rocks in the processes of displacement of oil from them by water pumped into the reservoir.This difference is especially significant when flooding low-permeability rocks characterized by high capillary pressure values.The work suggests possible approaches to conducting laboratory studies of rock cores that are more consistent with the structural features of the oil-water environment during flooding of productive formations.For the most complete capillary impregnation of low-permeable layers of a layered heterogeneous formation with water from quickly watered high-permeability layers, a method is proposed that consists in the fact that the water pumped into the formation must contain the minimum required amount of oil, ensuring the mobility (connectivity) of the oil phase in the watered high-permeability layers.For this purpose, water from production wells containing a certain amount of residual oil can be used for injection into the reservoir. The economic feasibility of the proposed method should be justified by the results of computer modeling of capillary impregnation processes, taking into account the described features of capillary pressure functions characteristic ofprocesses of oil displacement from productive formations during their waterflooding.

Refinement of the crystal structure of christofschäferite-(Ce) and the modular aspect of the chevkinite polysomatic series with the general formula of {A<sub>4</sub>B(T<sub>2</sub>O<sub>7</sub>)<sub>2</sub>}{C<sub>2</sub>D<sub>2</sub>O<sub>8</sub>}<sub>m</sub> (m = 1, 2)

Research subject. The crystal structure of christofschäferite-(Ce) was previously refined in terms of the P21/m low-symmetrical space group, which allowed the local features of cationic arrangements to be determined. In this work, we set out to refine the crystal structure of christofschäferite-(Ce) in terms of the P21/a high-symmetrical space group based on the previously collected diffraction data. A topology-symmetrical analysis of the members of the chevkinite group with the general formula of A4BC2D2(Si2O7)2O8 was conducted. Materials and methods. A magmatic rock sample with christofschäferite-(Ce) inclusions was found in the vicinity of the Laacher See volcano, near Mendig, Eifel Mountains, Rhineland-Palatinate (Rheinland-Pfalz), Germany. The crystal structure was studied using single-crystal X-ray analysis. Results. Despite an increase in the symmetry to the P21/a space group (in comparison with the previous data with the P21/m space group), the main patterns of cation distribution between the octahedral and tetrahedral sites are preserved. However, due to the lover number of cationic sites, this distribution becomes more disordered. Based on a crystal chemical analysis of the crystal structures of natural and synthetic members of the chevkinite group in the framework of the OD theory, it is possible to combine them into a united OD family with the same OD groupoid. Conclusions. According to the OD theory, there are two structural OD-subgroups of the chevkinite group (chevkinite and perrierite). The crystal structure and symmetry of possible MDO-polytypes are predicted.

Postprocessing Workflow for Laboratory Diffraction Contrast Tomography: A Case Study on Chromite Geomaterials.

Texture stands as a fundamental descriptor in the realms of geology and earth and planetary science. Beyond offering insights into the geological processes underlying mineral formation, its characterization plays a pivotal role in advancing engineering applications, notably in mining, mineral processing, and metal extraction, by providing quantitative data for predictive modeling. Laboratory diffraction contrast tomography (LabDCT), a recently developed 3D characterization technique, offers nondestructive measurement of grain phases including their morphology, distribution, and crystal orientation. It has recently shown its potential to assess 3D textures in complex natural rock samples. This study looks at improving on previous work by examining the artifacts and presents a novel postprocessing workflow designed to correct them. The workflow is developed to rectify inaccurate grain boundaries and interpolate partially reconstructed grains to provide more accurate results and is illustrated using multi-scan examples on chromite sands and natural chromitite from the Upper Group 2 Reef layer in South Africa. The postcorrected LabDCT results were validated through qualitative and quantitative assessment using 2D electron back-scattered diffraction on polished sample surfaces. The successful implementation of this postprocessing workflow underscores its substantial potential in achieving precise textural characterization and will provide valuable insights for both earth science and engineering applications.

Chemical element analysis of Arjuno-Welirang igneous rocks.

Mount Arjuno-Welirang has a geological structure consisting of volcanic breccia, lava, tufan breccia, and tuff. This research focuses on exploring the chemical content of Arjuno-Welirang igneous rocks. The mapping of chemical element content is carried out to provide information on the distribution of Arjuno-Welirang dominant elements which are very important for exploitation and industry. The results of X-ray fluorescence (XRF) analysis of seven igneous rock samples showed that there were Al, Si, P, K, Ca, Ti, V, Cr, Mn, Fe, Cu, Zn, Sr, Ba, Eu, and Re. The dominant elements (Wt% > 10%) are Si (44.4-51.6%), Al (14-19%), Ca (12.1-17.1%), and Fe (12.4-20.4%). In addition, rare earth element REE europium (Eu) content was also found with an average of 0.23 Wt%. The discovery of REE Eu indicates the presence of other REE elements and needs further analysis. The presence of several oxide elements SiO2 and K2O was compared to the surrounding mountains, where SiO2 indicates a greater content of Bromo-Semeru, while K2O is larger than Semeru and smaller than Bromo. This provides an overview of the difference in magma properties, where the results of Arjuno-Welirang igneous rock analysis show alkaline properties while Bromo-Semeru ultrabase. The Fe2O3 content of Arjuno-Welirang shows a smaller tendency than Bromo-Semeru. This shows that Arjuno-Welirang magma is magnetically higher than Bromo-Semeru. The average depth of magma from igneous rocks is calculated between ± 147.7 and ± 225.1km below the earth's surface. These results correlate significantly with K2O compounds where the deeper the magma origin of the sample, the higher the K2O content.