LITHOSPHERE (Russia)最新文献

{"title":"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","authors":"N. G. Soloshenko, M. V. Streletskaya, M. Chervyakovskaya, D. V. Kiseleva","doi":"10.24930/1681-9004-2024-24-2-364-375","DOIUrl":"https://doi.org/10.24930/1681-9004-2024-24-2-364-375","url":null,"abstract":"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.","PeriodicalId":18202,"journal":{"name":"LITHOSPHERE (Russia)","volume":"24 S52","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141003604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Regular relations of the composition, structure and properties of crystals of hydrogen-containing compounds","authors":"I. P. Makarova, E. Selezneva, A. Tolstikhina, R. Gainutdinov","doi":"10.24930/1681-9004-2024-24-2-398-405","DOIUrl":"https://doi.org/10.24930/1681-9004-2024-24-2-398-405","url":null,"abstract":"Research subject. Crystals of hydrogen-containing compounds belonging to the superprotonic family. Aim. To obtain knowledge about regular relations between composition, atomic structure, real structure and physical properties of materials, with the purpose of elucidating processes occurring in condensed state and forming the basis for modification of known or obtaining new compounds. Materials and methods. Experimental data were obtained using a set of complementary physical methods, including structural analysis using X-rays, synchrotron radiation and neutrons, optical microscopy, and atomic force microscopy. Results. Experimental data on the atomic structure, real structure, and physical properties of superprotonic crystals, including systems of hydrogen bonds and their changes, were obtained. Conclusions. The physical properties of superprotonic crystals are significantly affected by hydrogen bonding systems and their changes, primarily by the formation of dynamically disordered hydrogen bonds with energetically equivalent positions of hydrogen atoms. When carrying out diagnostics of crystalline samples, account should be taken of their real structure, including the structure of surface layers and the presence of crystallization water. These factors may affect the measured physical parameters, the boundaries of existence of phases, the formation of a multiphase state under variations in temperature.","PeriodicalId":18202,"journal":{"name":"LITHOSPHERE (Russia)","volume":"30 40","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141005417","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Synthesis of sulfide mineral crystals by incongruent methods using the example of Cu-Fe-S and Cu-Fe-Se systems","authors":"I. G. Puzanova, E. A. Pankrushina, M. S. Pechurin, D. A. Chareev","doi":"10.24930/1681-9004-2024-24-2-406-415","DOIUrl":"https://doi.org/10.24930/1681-9004-2024-24-2-406-415","url":null,"abstract":"Research subject. Understanding the structure and thermodynamic properties of sulfide minerals is important for studying the paragenesis of sulfide formation on Earth and in space, as well as for analyzing technological issues in the processing of ores and polysulfide product concentrates. There is a lack of experimental and theoretical information on many representatives of the Cu-Fe-S and Cu-Fe-Se systems. Aim. To synthesize crystals in the Cu-Fe-S and Cu-Fe-Se systems at the lowest possible temperatures for the subsequent study of their physical properties, while solving the main problem of materials science related to interrelations between composition, structure, and properties. Materials and methods. Crystal synthesis was carried out by the solution-melt method in a stationary temperature gradient, in evacuated sealed quartz glass ampoules. Two types of ampoules were used in the experiment, standard and long. The ampoules were filled with a charge and a salt mixture of RbCl-LiCl of eutectic composition, evacuated and sealed, then placed in several quartz or ceramic glasses. The glasses were placed in tubular furnaces such that the ends of the ampoules with the charge were located closer to the center of the furnace, and the opposite ends were closer to the edge to create a temperature gradient. For standard ampoules, the hot end temperature was 520–469℃, and the cold end was 456–415℃. For long ones: 470℃ – hot end and 340℃ – cold. The synthesis duration ranged from three to four months. Results. Depending on the composition of the charge, crystals of chalcocine Cu2S, bornite Cu5FeS4, chalcopyrite CuFeS2, isocubanite CuFe2S3, and iron-containing dicopper sulfide with an iron content of up to 8 at % and various equilibrium associations with their participation and with the participation of pyrite FeS2 and pyrrhotites Fe1–xS were obtained. Copper dendrites were also found in some samples. In addition, crystals of a phase with the approximate composition of CuFeSe2 were obtained. It is shown that due to different combinations of oxidation states of all three elements dissolved in a salt electrolyte, it is possible to obtain phases with almost any stoichiometric ratio. Chalcopyrite and isocubanite are reliably detected using Raman spectroscopy. In this case, some samples are locally characterized by the “absence” of a spectrum, which probably indicates the metallic (semi-metallic) properties of the samples. Conclusion. Using the Cu-Fe-S and Cu-Fe-Se systems as an example, the possibility of obtaining sulfide crystals in a RbCl-LiCl salt melt up to a eutectic temperature of 313℃ is shown. Due to the low synthesis temperature, the synthesis should be carried out over several months, resulting in crystals a fraction of a millimeter in size.","PeriodicalId":18202,"journal":{"name":"LITHOSPHERE (Russia)","volume":"126 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141002013","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thermal metamorphism of metal assemblage in the light lithology of the Chelyabinsk LL5 meteorite","authors":"E. V. Brusnitsyna, R. Muftakhetdinova, G. Yakovlev, V. Grokhovsky","doi":"10.24930/1681-9004-2024-24-2-341-346","DOIUrl":"https://doi.org/10.24930/1681-9004-2024-24-2-341-346","url":null,"abstract":"Research subject. Metal assemblage in the light lithology of the Chelyabinsk ordinary chondrite (LL5). Aim. The study of the structure of kamacite (α-Fe(Ni, Co)) and taenite (γ-Fe(Ni, Co)), as well as identification of the morphological features resulting from heating of chondrite matter. Materials and methods. Samples from the unaltered light lithology of the Chelyabinsk meteorite. The chemical composition of the samples was studied using optical microscopy (Zeiss Axiovert 40 MAT) and scanning electron microscopy (FE-SEM ∑IGMA VP) with an EDS unit. Results. The studied fragments can be divided into three groups depending on their structural composition: 1) metal grains with an unchanged structure; a zonal structure is observed in taenite (tetrataenite, cloudy zone); 2) metal grains with a taenite structure similar to the zonal one; 3) fragments in which no grains with a zonal structure were found; martensite-like structures formed during reheating were present. The structure of metal assemblage in the Chelyabinsk chondrite is compared with the structure of metal assemblage obtained in previous experiments with the Seymchan iron meteorite. It was established that heating to a temperature of 400°C for 6 h causes no changes in the metal grain structure. Heating to temperatures of 500 and 600°C for 6 h initiates transformation processes of the cloudy zone, which disappears completely after heated to 700°C for 6 h. Conclusions. Fragments of the light lithology of the Chelyabinsk ordinary chondrite were heating unevenly as a result of an impact event in its cosmic history. The presence of tetrataenite and a cloudy zone in one of the fragments means that temperature in this area didn’t exceed 400°C. Some areas underwent heating in the temperature range of 500–600°C and above 700°C.","PeriodicalId":18202,"journal":{"name":"LITHOSPHERE (Russia)","volume":"59 30","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141009497","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Copper and zinc isotopic variations in Ni-Cu-PGE ores of the Noril’sk Province (Russia)","authors":"K. Malitch, I. Badanina, N. G. Soloshenko, S. Sluzhenikin","doi":"10.24930/1681-9004-2024-24-2-300-325","DOIUrl":"https://doi.org/10.24930/1681-9004-2024-24-2-300-325","url":null,"abstract":"Research subject. Mineral assemblages of sulfides from massive and disseminated sulfide nickel-copper-platinum-group element (Ni-Cu-PGE) and low-sulfide PGE ores of the Noril’sk Province, which hosts the richest complex deposits of platinum-group metals, nickel, and copper. Aim. In order to identify sources of ore material and explore new forecasting approaches for Ni-Cu-PGE deposits, we study the Cu- and Zn isotopic compositions of sulfides from economic Kharaelakh and Noril’sk-1 intrusions containing unique and large sulphide Ni-Cu-PGE deposits (Oktyabr’sk and Noril’sk-1, respectively), subeconmic Zub-Marksheider and Vologochan intrusions containing small- to medium-size Ni-Cu-PGE deposits, and non-economic Nizhny Talnakh and Nizhny Noril’sk intrusions containing low grade disseminated Ni-Cu mineralization. Results. The analyzed samples are characterized by sulfide mineral assemblages, which contain mainly chalcopyrite, pyrrhotite, pentlandite, troilite, cubanite, and galena. Sulfide Ni-Cu-PGE ores of the Oktyabr’sk and Noril’sk-1 deposits, associated with economic intrusions (i.e., Kharaelakh and Noril’sk-1), demonstrate distinct δ65Cu values from –2.42 to –1.40‰ and from –0.33 to 0.60‰, respectively, which differ from the δ65Cu values for sulfides from other Ni-Cu-PGE deposits and ore occurrences of the Noril’sk Province (data comprise 36 analyses). We note that the Cu-isotopic composition for sulfide minerals of massive and disseminated ores from the Kharaelakh intrusion has similar “isotope-light” characteristics. The most pronounced shift towards “isotope-heavy” copper was found in the horizon of low-sulfide PGE ores of the Noril’sk-1 intrusion (δ65Cu = 0.51–0.60‰). The isotopic composition of Zn (δ66Zn) for the studied sulfide samples from economic, subeconomic, and non-economic intrusions, with the exception of one sample (0.73 ± 0.14‰), is characterized by similar “isotope-light” values (from –0.65 to –0.03‰). Conclusions. The revealed variations in the Cu- and Zn-isotopic composition in the studied sulfide assemblages from all types of ores reflect their primary characteristics; however, for the unique Oktyabr’sk Ni-Cu-PGE deposit, characterized by the most “isotopically light” composition of copper (δ65Cu = –1.9 ± 0.34‰), the possibility of assimilation of an external source of Cu during the formation of sulfide Ni-Cu-PGE ores cannot be excluded. The combined use of Cu and Zn isotopic parameters proved to be a weakly informative predictive indicator for the detection of high-grade sulfide ores, primarily due to the similarity of the Zn isotopic composition of the ore material in all investigated intrusions of the Noril’sk Province.","PeriodicalId":18202,"journal":{"name":"LITHOSPHERE (Russia)","volume":"47 17","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141010311","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Optical-spectroscopic and isotope-geochemical characteristics of zircons from diamond-bearing placers in Yakutia as indicators of diamond ore bodies","authors":"A. Agashev, M. Chervyakovskaya, S. L. Votyakov, R. Zhelonkin, V. Chervyakovskiy, E. A. Pankrushina, A. L. Zemnukhov, N. Pokhilenko","doi":"10.24930/1681-9004-2024-24-2-284-299","DOIUrl":"https://doi.org/10.24930/1681-9004-2024-24-2-284-299","url":null,"abstract":"Research subject. Zircon grains from diamond placers of the Molodo and Ebelyakh rivers of the Yakut Arctic. Aim. To study the indicator characteristics of zircon to determine sources of diamonds and ways of their transfer to placers; to analyze optical-spectroscopic and isotope-geochemical parameters of zircon grains, their microelemental, U-Pb, and Lu-Hf isotope composition. Materials and methods. A LA-ICP-MS analysis of the U-Pb isotopic and trace element composition of zircon was carried out using a NexION 300S mass spectrometer with an NWR 213 attachment. An analysis of the Lu-Hf isotope system was carried out using a Neptune Plus mass spectrometer with an NWR 213 attachment, located in a room of cleanliness class 7 ISO at the Geoanalitik Center for Collective Use (IGG Ural Branch of the Russian Academy of Sciences, Ekaterinburg). Raman spectra were obtained using a LabRAM HR800 Evolution confocal spectrometer. CL spectra were obtained using a Jeol JSM6390LV scanning electron microscope equipped with a Horiba H-CLUE iHR500 attachment. Results. The local optical spectroscopic characteristics (Raman spectra and catholuminescence) of zircon grains were established, which made it possible to substantiate the conclusion about their high crystallinity and homogeneity (monochrony), as well as to select international zircon standards with similar characteristics for use in LA-ICP-MS analysis to ensure similar conditions for evaporation of the substance and fractionation parameters of the U and Pb elements. LA-ICPMS data on the microimpurity, U-Pb and Lu-Hf isotopic composition of zircon grains from diamond placers, as well as the dose values of their self-irradiation, are presented. Conclusions. The obtained U-Pb dating contributes to reconstructing a more precise history, character, and sequence of manifestation of kimberlite magmatism, tectonic processes, and migration routes of kimberlite material and diamonds across the Siberian craton, within the Yakut kimberlite province.","PeriodicalId":18202,"journal":{"name":"LITHOSPHERE (Russia)","volume":"50 49","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141009911","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reedmergnerite and stillwellite-(Ce) from the Dara-i-Pioz alkaline massif: insights into high-temperature behavior of borosilicates","authors":"E. V. Kaneva, O. Belozerova, T. Radomskaya, R. Shendrik","doi":"10.24930/1681-9004-2024-24-2-326-340","DOIUrl":"https://doi.org/10.24930/1681-9004-2024-24-2-326-340","url":null,"abstract":"Research subject. Reedmergnerite and stillwellite-(Ce) were obtained from the rocks of the Dara-i-Pioz alkaline massif located on the southern slope of the Alai Range in Tajikistan, which is characterized by the presence of rare mineral species including borosilicates and lithium minerals. Aim. To investigate the thermal behavior of reedmergnerite and stillwellite-(Ce) using high-temperature X-ray diffraction, including the determination of phase transition temperatures and expansion/compression of the unit cell parameters, as well as the calculation of thermal expansion coefficients. Materials and methods. Chemical analysis was performed using a TESCAN MIRA 3 microscope (EDS mode) and a JEOL JXA-8230 electron probe microanalyzer (WDS mode). High-temperature powder X-ray diffraction data were collected using a D8 ADVANCE Bruker diffractometer with an HTK16 heating chamber, covering temperatures from 30°C to 750°C in ambient air. Results. The thermal expansion coefficients of reedmergnerite and stillwellite-(Ce) were determined. Heating reedmergnerite resulted in slight changes in the unit cell parameters, with the parameter c experiencing the smallest change and the parameter a showing the greatest increase. The unit cell volume increased by 1.8% when heated to 750°C and returned to its initial value upon cooling. When stillwellite-(Ce) is heated in the temperature range of 400–450°C, a phase transition occurs, which is confirmed by previously recorded temperature values. The conducted heating and subsequent cooling experiments revealed that the volume and unit cell parameters of stillwellite-(Ce) did not fully revert to their original values. Conclusions. The coefficients of thermal expansion tensor (αij) of rhodmerdgnertite and stillwellite-(Ce) were investigated as a function of temperature using high-temperature in-situ experiments. The phases exhibited relatively low values of thermal expansion parameters compared to the general data for feldspars and borosilicates obtained from literature. These findings contribute to the understanding of the thermoelastic behavior of this group of minerals and their potential applications in various fields.","PeriodicalId":18202,"journal":{"name":"LITHOSPHERE (Russia)","volume":"66 11","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141007813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Current problems in the field of structure, properties of minerals and methods of their investigation","authors":"S. L. Votyakov","doi":"10.24930/1681-9004-2024-24-2-203-213","DOIUrl":"https://doi.org/10.24930/1681-9004-2024-24-2-203-213","url":null,"abstract":"The main goal of research into the structure and properties of minerals, as well as their crystal chemistry and physics, consists in obtaining fundamental information about the actual atomic and electronic structure of mineral objects and physical regularities of their transformations under the influence of external factors (temperature, pressure, radiation, and environmental chemistry). Such information forms the basis for mineral typification and restoration of mineral crystallization conditions and their evolution in a certain geological situation. This information is widely used in petrogenetic and geochronological constructions. Such studies are also relevant to the development of nature-like technologies for obtaining new promising functional materials. Knowledge of the structure, crystal chemistry, and physics of minerals, typomorphism of their spectroscopic properties, as well as the development of analytical techniques and methods for the synthesis of mineral-like materials are of particular significance. This thematic issue of the Lithosphere journal aims to review of these problems in the context of the materials reported at the XIII All-Russian Scientific Conference “Minerals: Structure, Properties, Research Methods” held in 2023 at the Institute of Geology and Geochemistry of the Ural Branch of the Russian Academy of Sciences in Yekaterinburg.","PeriodicalId":18202,"journal":{"name":"LITHOSPHERE (Russia)","volume":"66 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141016390","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Oxoborates of the ludwigite group: Natural and mineral-like compounds as prospective materials","authors":"Y. Biryukov, A. L. Zinnatullin, R. S. Bubnova, F. Vagizov, A. Shablinskii, S. K. Filatov, I. Pekov","doi":"10.24930/1681-9004-2024-24-2-226-239","DOIUrl":"https://doi.org/10.24930/1681-9004-2024-24-2-226-239","url":null,"abstract":"Research subject. Natural oxoborates of the ludwigite group, including azoproite, ludwigite, and vonsenite. Their empirical formulas based on five oxygen atoms have the following form: azoproite (Mg1.81Fe2+0.19)∑2.00(Fe3+0.36Ti0.26Mg0.26Al0.12)∑1.00 O2(BO3), ludwigite (Mg1.69Fe2+0.30Mn2+0.01)Σ2.00(Fe3+0.90Al0.07Mg0.02Sn0.01)Σ1.00O2(BO3) and vonsenite (Fe2+1.86Mg0.13)∑1.99 (Fe3+0.92Mn2+0.05Sn4+0.02Al0.02)∑1.01O2(BO3). Aim. To establish the relationship between the composition, crystal structure, and thermal behavior (293–1373 K) of the minerals. Materials and methods. Ludwigite was collected at the Iten’yurginskoe tin skarn deposit; vonsenite was collected at the Titovskoe magnesium-skarn boron deposit; azoproite was collected at magnesian skarns of the Tazheran alkaline massif. The methods of single crystal X-ray diffraction, energy dispersive X-ray spectroscopy, high-temperature X-ray diffraction, Mössbauer spectroscopy, and thermal analysis were used. Results. Low-charge cations (Fe2+, Fe2.5+, Mg2+) tend to occupy the M(1)–M(3) sites, and high-charge cations (Fe3+, Al3+, Ti4+, Sn4+) generally occupy the M(4) site. Azoproite is characterized by the highest melting temperature Tm > 1650 K. Due to the low Fe2+ content, azoproite does not undergo solid-phase decomposition across the investigated temperature range. The melting point of ludwigite exceeds 1582 K, which is due to the high Mg content; as a result of the Fe2+ → Fe3+ oxidation, it gradually decomposes with the formation of hematite, warwickite, and magnetite. The temperatures of oxidation and solid-phase decomposition in the Fe2+-rich vonsenite are approximately 100 K lower than those in ludwigite. The melting point of vonsenite is 1571 K. All the minerals are characterized by a weak degree of thermal expansion anisotropy. The main contribution to the thermal expansion anisotropy is due to the preferred orientation of the [BO3]3– triangles. Conclusions. The thermal properties of the oxoborates depend on their chemical composition. It was established that Tm increases with an increase in the Mg and Ti4+ content, and decreases with an increase in the Fe2+ content. The Fe2+ → Fe3+ oxidation is observed when the FeO component in the minerals exceeds 10 wt %, which leads to the solid-phase decomposition starting at temperatures of about 500–600 K. The values of the 293KαV volume thermal expansion of ludwigite and azoproite are comparable, while the largest values were observed for vonsenite. This is associated with the largest average bond lengths, primarily those of 6.","PeriodicalId":18202,"journal":{"name":"LITHOSPHERE (Russia)","volume":"122 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141015292","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Negative thermal expansion of β-Rb2SO4","authors":"A. Shablinskii, S. Demina, R. S. Bubnova, S. K. Filatov","doi":"10.24930/1681-9004-2024-24-2-254-263","DOIUrl":"https://doi.org/10.24930/1681-9004-2024-24-2-254-263","url":null,"abstract":"Research subject. The low-temperature modification of β-Rb2SO4 sulfate (Pmcn). Aim. Low-temperature study of the thermal expansion of β-Rb2SO4 by high-temperature powder X-ray diffraction in comparison with the crystal structure, as well as interpretation of the anisotropy of β-Rb2SO4 thermal expansion. Materials and Method. Powder X-ray diffraction and high-temperature powder X-ray diffraction. Results. The thermal expansion of β-Rb2SO4 sulfate was studied for the first time using low-temperature powder thermal X-ray diffraction in comparison with the crystal structure. The phase composition was confirmed by powder X-ray diffraction. The thermal expansion of β-Rb2SO4 is practically isotropic. Across the temperature range from –177 to –140°C, the sulfate experiences negative thermal expansion. A further increase in temperature leads to a change in its thermal expansion, which becomes positive. It is proposed to consider the crystal structure of β-Rb2SO4 sulfate as a mixed framework of [RbSO4]–1, which, in turn, consists of fundamental building units (microblocks) of Rb(SO4)6. Across the temperature range from room temperature to –100°C, the maximum expansion of β-Rb2SO4 sulfate occurs along the a axis. The minimum thermal expansion is observed along the c-axis, along the columns consisting of microblocks (αa = 65.4(3)∙10–6°C–1, αb = 59.7(2)∙10–6°C–1, αc = 58.6(2)∙10–6°C–1 at +25°C). In the temperature range from –177 to –140°C, thermal expansion is negative in all three directions (αa = –10.3(3)∙10–6°C–1, αb = –8.6(2)∙10–6°C–1, αc = –9.7(2)∙10–6°C–1 at –170°C). Conclusion. The thermal expansion of β-Rb2SO4 sulfate in the low-temperature range (from –177 to –25°C) was studied for the first time, its structural interpretation was performed. A comparison was given with the thermal expansion of isostructural β-K2SO4.","PeriodicalId":18202,"journal":{"name":"LITHOSPHERE (Russia)","volume":"39 158","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141016410","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}