Subjects -> MINES AND MINING INDUSTRY (Total: 82 journals)
 Showing 1 - 42 of 42 Journals sorted alphabetically Applied Earth Science : Transactions of the Institutions of Mining and Metallurgy       (Followers: 4) Archives of Mining Sciences       (Followers: 1) BHM Berg- und Hüttenmännische Monatshefte       (Followers: 1) Canadian Mineralogist       (Followers: 5) CIM Journal Clay Minerals       (Followers: 8) Contributions to Mineralogy and Petrology       (Followers: 11) Environmental Geochemistry and Health       (Followers: 2) European Journal of Mineralogy       (Followers: 12) Extractive Industries and Society       (Followers: 2) Gems & Gemology       (Followers: 1) Geology of Ore Deposits       (Followers: 3) Geomaterials       (Followers: 2) Geotechnical and Geological Engineering       (Followers: 8) Ghana Mining Journal       (Followers: 3) Gold Bulletin International Journal of Coal Geology       (Followers: 2) International Journal of Coal Preparation and Utilization       (Followers: 1) International Journal of Coal Science & Technology       (Followers: 1) International Journal of Hospitality & Tourism Administration       (Followers: 14) International Journal of Minerals, Metallurgy, and Materials       (Followers: 8) International Journal of Mining and Geo-Engineering International Journal of Mining and Mineral Engineering       (Followers: 5) International Journal of Mining Engineering and Mineral Processing       (Followers: 5) International Journal of Mining Science and Technology       (Followers: 4) International Journal of Mining, Reclamation and Environment       (Followers: 4) International Journal of Rock Mechanics and Mining Sciences       (Followers: 6) Journal of Analytical and Numerical Methods in Mining Engineering Journal of Applied Geophysics       (Followers: 15) Journal of Central South University       (Followers: 1) Journal of China Coal Society Journal of Convention & Event Tourism       (Followers: 4) Journal of Geology and Mining Research       (Followers: 11) Journal of Human Resources in Hospitality & Tourism       (Followers: 8) Journal of Materials Research and Technology       (Followers: 2) Journal of Metamorphic Geology       (Followers: 15) Journal of Mining Institute Journal of Mining Science       (Followers: 2) Journal of Quality Assurance in Hospitality & Tourism       (Followers: 5) Journal of Sustainable Mining       (Followers: 2) Journal of the Southern African Institute of Mining and Metallurgy       (Followers: 5) Lithology and Mineral Resources       (Followers: 3) Lithos       (Followers: 9) Mine Water and the Environment       (Followers: 4) Mineral Economics Mineral Processing and Extractive Metallurgy : Transactions of the Institutions of Mining and Metallurgy       (Followers: 11) Mineral Processing and Extractive Metallurgy Review       (Followers: 4) Mineralium Deposita       (Followers: 4) Mineralogia       (Followers: 2) Mineralogical Magazine       (Followers: 1) Mineralogy and Petrology       (Followers: 2) Minerals Minerals & Energy - Raw Materials Report Minerals Engineering       (Followers: 9) Mining Engineering       (Followers: 5) Mining Journal       (Followers: 3) Mining Report       (Followers: 2) Mining Technology : Transactions of the Institutions of Mining and Metallurgy       (Followers: 2) Mining, Metallurgy & Exploration Natural Resources & Engineering Natural Resources Research       (Followers: 8) Neues Jahrbuch für Mineralogie - Abhandlungen       (Followers: 1) Physics and Chemistry of Minerals       (Followers: 4) Podzemni Radovi Rangeland Journal       (Followers: 1) Réalités industrielles Resources Policy       (Followers: 4) Reviews in Mineralogy and Geochemistry       (Followers: 4) Revista del Instituto de Investigación de la Facultad de Ingeniería Geológica, Minera, Metalurgica y Geográfica Rock Mechanics and Rock Engineering       (Followers: 6) Rocks & Minerals       (Followers: 2) Rudarsko-geološko-naftni Zbornik Stainless Steel World       (Followers: 17) Transactions of Nonferrous Metals Society of China       (Followers: 9)
Similar Journals
 Physics and Chemistry of MineralsJournal Prestige (SJR): 0.702 Citation Impact (citeScore): 2Number of Followers: 4      Hybrid journal (It can contain Open Access articles) ISSN (Print) 1432-2021 - ISSN (Online) 0342-1791 Published by Springer-Verlag  [2469 journals]
• Chemical analysis of trace elements at the nanoscale in samples recovered
from laser-heated diamond anvil cell experiments

Abstract: Abstract High pressure and high temperature experiments performed with laser-heated diamond anvil cells (LH-DAC) are being extensively used in geosciences to study matter at conditions prevailing in planetary interiors. Due to the size of the apparatus itself, the samples that are produced are extremely small, on the order of few tens of micrometers. There are several ways to analyze the samples and extract physical, chemical or structural information, using either in situ or ex situ methods. In this paper, we compare two nanoprobe techniques, namely nano-XRF and NanoSIMS, that can be used to analyze recovered samples synthetized in a LH-DAC. With these techniques, it is possible to extract the spatial distribution of chemical elements in the samples. We show the results for several standards and discuss the importance of proper calibration for the acquisition of quantifiable results. We used these two nanoprobe techniques to retrieve elemental ratios of dilute species (few tens of ppm) in quenched experimental molten samples relevant for the formation of the iron-rich core of the Earth. We finally discuss the applications of such probes to constrain the partitioning of trace elements between metal and silicate phases, with a focus on moderately siderophile elements, tungsten and molybdenum.
PubDate: 2022-05-20

• Compressional wave velocity for iron hydrides to 100 gigapascals via
picosecond acoustics

Abstract: Abstract We performed synchrotron X-ray diffraction (XRD) and picosecond acoustic measurements on iron hydrides (FeHX) synthesized in laser-heated diamond anvil cells at pressures up to 100 GPa and 300 K. The obtained XRD data reveals that hcp FeH1.1, hcp FeH0.3, and fcc FeH1.0 were synthesized, and we determined the compressional wave velocities (VP) of the latter two phases. We discovered that the VP–density (ρ) relationships for fcc FeH1.0 changed between 8.7 and 9.2 g/cm3 (at about 60 GPa), which may be due to a magnetic transition. A comparison of the preliminary reference Earth model (PREM) with a Birch’s law extrapolation considering the temperature effect of our experimental VP–ρ results support the hypothesis of hydrogen presence in the Earth’s inner core.
PubDate: 2022-05-04

• LiquidDiffract: software for liquid total scattering analysis

Abstract: Abstract LiquidDiffract is an open source, Python-based graphical application for X-ray total scattering analysis of liquids and disordered solids. The software implements procedures to obtain information on macroscopic bulk properties and local atomic-scale structure of monatomic or polyatomic samples from X-ray total scattering data. LiquidDiffract provides an easy to use interface with tools to perform background subtraction; calculation, normalisation, and refinement of the reciprocal-space structure factor and real-space correlation functions; and the extraction of structural information such as bond lengths, coordination number, and bulk density. The software is well suited to investigations of amorphous materials at extreme conditions, such as studies of high-pressure melt structure, polyamorphic phase transitions, and liquid equations of state. The open-source distribution and graphical interface will be of particular benefit to researchers who are new to the field. In this article we describe the distribution, system requirements, and installation of LiquidDiffract, and detail the data processing workflow and underlying numerical methods.
PubDate: 2022-05-03

• Equations of state of α-SiC (6H) and βʹ-Mg2Si1.1 from single-crystal
X-ray diffraction data and novel high-pressure magnesium silicide Mg2Si7

Abstract: Abstract SiC and (Fe, Mg)-silicide are candidate phases forming under reducing conditions in the Earth and planetary interiors. However, structural studies of SiC and Mg2Si at high pressure and their thermal stability are presently lacking. In this work, we applied single-crystal X-ray diffraction in a diamond anvil cell at high pressure and determined the equations of state of α-SiC (6H) and βʹ-Mg2Si1.1 up to 60 and 40 GPa, respectively, yielding bulk moduli of 226.0(4) and 56(1) GPa. We also report the formation of a novel orthorhombic Mg2Si7 phase upon laser heating βʹ-Mg2Si1.1 at ~ 45 GPa and 2000 °C [Pbam, a = 7.16(1) Å, b = 12.490(3) Å, c = 2.6545(3) Å, V = 237.5(3) Å3]. The structure of this compound contains layers formed by irregular 12-member silicon rings, which are arranged in channels filled with both Mg and Si atoms. No signs of the Mg2Si7 phase were detected upon releasing the pressure in the DAC, which suggests that this phase is unstable under ambient conditions.
PubDate: 2022-05-03

Abstract: Abstract In this study, we use laser-driven shock compression coupled with in situ X-ray diffraction to interrogate the phase transition dynamics of shock-compressed zircon (ZrSiO4) for the first time. A phase transition from zircon to the high-pressure reidite phase was observed during the nanosecond timescale of a laser-driven shock. At high laser power, diffraction peaks of zircon and reidite appeared superimposed on two broad features. This diffuse background was ascribed to liquid scattering from a partial melt. At the highest laser power, the diffuse scattering dominated, with minimal evidence for crystal diffraction. On release, the melt recrystallized into a combination of zircon and reidite. Decomposition of zircon to SiO2 and ZrO2 was not observed. This study revealed that on laser-shock timescales, the zircon–reidite phase transition readily occurs. However, the decomposition of zircon into ZrO2 and SiO2 is kinetically inhibited.
PubDate: 2022-05-03

• Control of deviatoric stress in the diamond anvil cell through thermal
expansion mismatch stress in thin films

Abstract: Abstract Elastic and plastic properties of materials and phase transitions at extreme conditions vary with both hydrostatic pressure and deviatoric stress. To generate and measure controlled deviatoric stress at pressures beyond those accessible with large volume differential and rotational presses and optical access for spectroscopy, experiments tested the combination of diamond anvil cell and thin film technology. Thin films of polycrystalline Cr-doped Al2O3 ruby were prepared using pulsed laser deposition on single-crystal substrates of either Al2O3 sapphire or yttria-stabilized cubic zirconia for contrasting initial film stress, and loaded in diamond anvil cells for confining stress. The piezospectroscopic response of the ruby films demonstrates consistently higher deviatoric stress in the film on zirconia relative to the film on the control sapphire, and an increase in deviatoric stress with applied load. Complementary synchrotron X-ray diffraction of the zirconia substrate confirmed that no pressure-induced phase transitions impacted the stress state of the ruby film, but differences in compressibility of film and substrate result in changes in film stress analogous to thermal expansion mismatch. This technique may be applied to evaluate elastic and plastic response of thin films of a variety of materials under extreme stress.
PubDate: 2022-05-03

• Structure and thermodynamics of calcium rare earth silicate oxyapatites,
Ca2RE8(SiO4)6O2 (RE = Pr, Tb, Ho, Tm)

Abstract: Abstract Calcium rare earth silicate oxyapatites, (Ca2RE8(SiO4)6O2), are of interest as components of glass–ceramic nuclear waste forms. To assess their long-term behavior in a geologic repository, it is essential to determine their structure and thermodynamic stability at relevant conditions. In this work, we performed detailed structural and thermodynamic investigations on Ca2Pr8(SiO4)6O2, Ca2Tb8(SiO4)6O2, Ca2Ho8(SiO4)6O2, and Ca2Tm8(SiO4)6O2 by high energy synchrotron powder X-ray diffraction combined with Rietveld analysis and high temperature oxide melt drop solution calorimetry. Enthalpies of formation from constituent oxides (∆Hf,ox) were determined to be − 765.1 ± 22.8 kJ/mol for Ca2Pr8(SiO4)6O2; − 638.9 ± 20.5 kJ/mol for Ca2Tb8(SiO4)6O2; − 643.3 ± 10.3 kJ/mol for Ca2Ho8(SiO4)6O2; and − 403.2 ± 5.1 kJ/mol for Ca2Tm8(SiO4)6O2. These thermodynamic parameters were used in assessing the thermochemical stability of these phases in the presence of water vapor from room temperature to 600 K, as encountered in the subsurface environments of a geological repository.
PubDate: 2022-05-03

• A chondrule formation experiment aboard the ISS: microtomography, scanning
electron microscopy and Raman spectroscopy on Mg $$_2$$ 2 SiO $$_4$$ 4
dust aggregates

Abstract: Abstract We performed an experiment under long-term microgravity conditions aboard the International Space Station (ISS) to obtain information on the energetics and experimental constraints required for the formation of chondrules in the solar nebula by ’nebular lightning’. As a simplified model system, we exposed porous forsterite (Mg $$_2$$ SiO $$_4$$ ) dust particles to high-energetic arc discharges. The characterization of the samples after their return by synchrotron microtomography and scanning electron microscopy revealed that aggregates had formed, consisting of several fused Mg $$_2$$ SiO $$_4$$ particles. The partial melting and fusing of Mg $$_2$$ SiO $$_4$$ dust particles under microgravity conditions leads to a strong reduction of their porosity. The experimental outcomes vary strongly in their appearance from small spherical melt-droplets ( $$\varnothing \approx$$  90 µm) to bigger and irregularly shaped aggregates ( $$\varnothing \approx$$  350 µm). Our results provided new constraints with respect to energetic aspects of chondrule formation and a roadmap for future and more complex experiments on Earth and in microgravity conditions.
PubDate: 2022-05-03

• The electrical conductivity of Fe4O5, Fe5O6, and Fe7O9 up to 60 GPa

Abstract: Abstract The electrical conductivities of iron-bearing minerals are important for understanding the chemical and thermal heterogeneity of the Earth’s mantle. Recent high-pressure experiments have shown that the new iron oxide group (FeO)m(Fe2O3)n is stable under mantle conditions. Although the new iron oxides possibly play an important role in the subduction zone, the physical properties of these iron oxides are still unclear. Here, we determined the electrical conductivities of Fe4O5, Fe5O6, and Fe7O9 at pressures up to 60 GPa using diamond anvil cells. The electrical conductivities of the iron oxides generally increased with increasing pressure, and the values were comparable with previous data for Fe3O4 and FeO at high pressures. Although iron oxides with a mixed-valence state are generally highly conductive, Fe7O9 was less conductive than Fe4O5 and Fe5O6. This difference is likely due to the ordered sites and valences in the structures of Fe4O5 and Fe5O6. The results show that the new iron oxides were not metallic under the experimental conditions. The iron oxides in the subducted materials may cause anomalies in the electrical conductivity of the deep mantle along with the melt and water.
PubDate: 2022-05-03

• Transformation of natural pollucite into hexacelsian under high pressure
and temperature

Abstract: Abstract Synchrotron X-ray powder diffraction experiments were performed on natural pollucite to observe its transition into hexacelsian-like phase at high pressure and temperature conditions under water pressure medium. When heated to 100 °C at 1.3(1) GPa, the natural cubic pollucite, (Cs, Na)16Al16Si16O96 (Ia $$\overline{3 }$$ d), transformed to its triclinic phase (P $$\overline{1 }$$ ) with discontinuous unit cell volume contraction by ca. 4.4%. After further compression to 4.1(1) GPa and heating up to 250 °C, a new hexagonal phase with a hexacelsian framework, Cs1.28(1)Na0.44(1)Al1.72(1)Si6.28(1)O16 (P63/mcm, (Cs, Na)-HEX), formed with unit cell volume contraction by ca. 6.1% based on 96 oxygen atoms of the framework (Of). The structural model of the newly formed hexacelsian-like phase, (Cs, Na)-HEX, was refined by the Rietveld method to show the disordered distribution of cesium and sodium cations between the double six-membered rings (D6R). Further details of the (Cs, Na)-HEX model are compared to those of the natural Ba-hexacelsian (Ba-HEX) and synthetic Cs-hexacelsian (Cs-HEX).
PubDate: 2022-05-03

• Evolution of chemically induced cracks in alkali feldspar: thermodynamic
analysis

Abstract: Abstract A system of edge cracks was applied to polished (010) surfaces of K-rich gem-quality alkali feldspar by diffusion-mediated cation exchange between oriented feldspar plates and a Na-rich NaCl–KCl salt melt. The cation exchange produced a Na-rich layer at and beneath the specimen surface, and the associated strongly anisotropic lattice contraction lead to a tensile stress state at the specimen surface, which induced fracturing. Cation exchange along the newly formed crack flanks produced Na-enriched diffusion halos around the cracks, and the associated lattice contraction and tensile stress state caused continuous crack growth. The cracks nucleated with non-uniform spacing on the sample surface and quickly attained nearly uniform spacing below the surface by systematic turning along their early propagation paths. In places, conspicuous wavy cracks oscillating several times before attaining their final position between the neighboring cracks were produced. It is shown that the evolution of irregularly spaced towards regularly spaced cracks including the systematic turning and wavyness along the early propagation paths maximizes the rate of free energy dissipation in every evolutionary stage of the system. Maximization of the dissipation rate is suggested as a criterion for selection of the most probable evolution path for a system undergoing chemically induced diffusion mediated fracturing in an anisotropic homogeneous brittle material.
PubDate: 2022-05-03

• Controls on the distribution of hydrous defects in forsterite from a
thermodynamic model

Abstract: Abstract The distribution of hydrogen across different crystallographic sites and point defects in forsterite determines how many properties, such as rheology, conductivity and diffusion are affected by water. In this study, we use lattice dynamics and Density Functional Theory (DFT) to build a thermodynamic model of H-bearing defects in Al,Ti bearing forsterite. From this, the distribution of hydrogen in forsterite as a function of pressure (P), temperature (T), water, Al and Ti concentration is determined. Primarily, hydrogen distribution in forsterite is complex and highly varied in different P, T and composition regimes. Therefore, extrapolation of properties that depend upon water between these different regimes is non-trivial. This extrapolation has often been done by determining exponents which describe how defect-specific defect concentrations or properties dependent upon them vary with water concentration/fugacity. We show here that these exponents can vary radically across common experimental and geophysical P, T and [H2O]bulk ranges as the favoured hydrogen-bearing defects change. In general, at low pressures hydrogen favours Mg vacancies (high temperatures) or complexes with titanium (low temperatures) whilst at high pressures, hydrogen favours Si vacancies regardless of all other conditions. Higher values of [H2O]bulk also favours hydrated Si vacancies. We evaluate these distributions along geotherms and find that hydrogen distribution and thus its effect on forsterite properties is highly varied across the expected conditions of the upper mantle and thus cannot be simply represented. No such distribution of hydrogen has been previously constructed and it is essential to consider this hydrogen distribution when considering the properties of a wet mantle.
PubDate: 2022-03-28

• Vibrational and structural insight into silicate minerals by mid-infrared
absorption and emission spectroscopies

Abstract: Abstract Silicate minerals are essential bricks of solid planets, which have been studied deeply by infrared absorption spectroscopy. Along with the rapid development of planetary exploration, infrared emission spectroscopy and corresponding radiation properties of minerals have been receiving attention. However, systematic research on silicate minerals using infrared emission spectroscopy has been absent so far. In this work, various silicate minerals (totally ten in five series included nesosilicates, eyclosilicates, inosilicates, phyllosilicates and tectosilicates) were investigated infrared spectral characteristics and infrared radiation properties using X-ray diffraction, X-ray fluorescence, and infrared spectroscopy (absorption and emission spectroscopy). Results indicated that the assignment of each band in infrared emission spectra of all samples could be obtainable referring to the well-known infrared absorption spectra, presenting a dominant absorption band near 1000 cm−1 related with the stretching of Si–O bonds and several weak bending-driven absorption bands in the range of 400–650 cm−1. A good linear relationship (coefficient of determination R2 = 0.996) between two corresponding wavenumbers suggested emission bands of silicate minerals have great correspondence with their absorption bands. Both vibrational stretching and bending of Si–O bonds in both spectra regularly shifted to higher frequencies as the increase of Si/O from 0.25 for nesosilicates and 0.50 for tectosilicates. The average emissivity of silicates, obtained from radiation energy spectra from 400 to 2000 cm−1 in the temperature range of 50–140 °C, showed all silicate minerals presented relatively higher emissivity (> 0.910) and displayed a remarkable reduction from nesosilicates (e.g., 0.981 for forsterite) to tectosilicates minerals (e.g., 0.913 for quartz). It was thus concluded that higher emissivity of silicates was attributed to the decrease of polymerization degree of SiO4 tetrahedron (R2 = 0.86), vibrational frequency and range for Si–O stretching (R2 = 0.88, 0.92, respectively), and vibrational range for Si–O bending (R2 = 0.85). This work gets insight into the relationship among spectral characteristics, crystal chemistry, and radiation properties of silicate minerals, and would help accurately identify and distinguish various silicate minerals in remote sensing analysis for understanding the composition of planetary surfaces and their evolutionary path.
PubDate: 2022-03-03
DOI: 10.1007/s00269-022-01180-y

• Effect of second Si–O vibrational overtones/combinations on quantifying
water in silicate and silica minerals using infrared spectroscopy, and an
experimental method for its removal

Abstract: Abstract Infrared spectroscopy (IR) is the most widely used analytical tool to quantify trace water in silicate and silica minerals. A prerequisite for highly accurate IR measurements of trace water is a good understanding of the effect of the second Si–O vibrational overtones/combination bands (2nd Si–O VOCBs) on the water peaks. Silicate and silica minerals can be divided as isolated (Q0), paired (Q1), ring (Q2), chain (Q1 or Q2), sheet (Q3) and framework (Q4) structures according to the polymerization of their SiO4 tetrahedral units, and the 2nd Si–O VOCBs of these different structural types attain different vibrational features which are expected to affect the water peaks to different extents. Here, we selected olivine (Q0) and α-quartz (Q4) as two endmember-like structural examples, performed extensive IR measurements on both pristine and heat-treated thin sections prepared for these two minerals, and explored the vibrational features of the 2nd Si–O VOCBs. We have found that the 2nd Si–O VOCBs are well separated from the water peaks in olivine, but severely overlap with the water peaks in α-quartz, confirming the different roles that the 2nd Si–O VOCBs play in quantifying trace water in silicate and silica minerals with different structural polymerizations. To remove the influence of the 2nd Si–O VOCBs (or any other species rather than water), an experimental protocol has been successfully developed, as approved by some fundamental equations and verified by the data of α-quartz in the literature. This development should lead to significant accuracy improvement in quantifying trace amounts of water in Earth and planetary materials.
PubDate: 2022-02-11
DOI: 10.1007/s00269-022-01179-5

• High-pressure behaviour and atomic-scale deformation mechanisms in
inyoite, CaB3O3(OH)5·4H2O

Abstract: Abstract The compressional behaviour of inyoite, ideally CaB3O3(OH)5·4H2O, has been studied by an in-situ high-pressure single-crystal X-ray experiment, at the ESRF large-scale facility, up to 19.80(5) GPa. Inyoite undergoes a first-order phase transition to inyoite-II, bracketed between 8.25(5) and 8.86(5) GPa, with a large volume discontinuity (ΔV ⁓ 7.5%). The structure of the high-pressure polymorph has not been solved due to a significant decrease in the number of Bragg reflections. The isothermal bulk modulus (KV0 = β−1P0,T0, where βP0,T0 is the volume compressibility coefficient) of inyoite was found to be KV0 = 26.9(8) GPa, whereas in inyoite-II, the KV0 value increases to 52(5) GPa. The increase of the bulk modulus is paired with a sharp decrease of the anisotropy of compressibility, as shown by the magnitude of the Eulerian finite unit-strain ellipsoid with: ε1:ε2:ε3 = 3.5:2.1:1 in inyoite and ε1:ε2:ε3 = 1.5:1.1:1 in inyoite-II. The P-induced deformation mechanisms controlling, at the atomic scale, the bulk compression of inyoite are here described on the basis of a series of structure refinements.
PubDate: 2022-01-23
DOI: 10.1007/s00269-021-01173-3

• Comment on: Melting behavior of SiO2 up to 120 GPa (Andrault et al.
2020)

Abstract: Abstract The additional work we have done using our new laser heating in the diamond anvil cell system since the publication of Andrault et al. (Phys Chem Mineral 47(2), 2020) leads us to the conclusion that there was a systematic bias in the determination of temperature. First, the temperature of the W-lamp used for the calibration of the optical system was overestimated by ~ 22 K at 2273 K. Then, we made the assumption that hot SiO2 was a grey-body (constant emissivity ε(λ)), while the available measurements suggest instead that ε(λ) of SiO2 is similar to that of tungsten. Applying these two corrections lowers the SiO2 melting temperatures significantly. In LMV, we performed a new experimental determination of the SiO2 melting temperature, at 5000 (200) K and ~ 70 (4) GPa, which is well compatible with the amplitude of the correction proposed. The reevaluation of the melting temperature profile does not affect largely the interpretations or the main conclusions presented in Andrault et al. (Phys Chem Mineral 47(2), 2020). Within the stability field of stishovite, the melting curve still presents a relatively sharp change of slope at P–T recalculated as ~ 40 GPa and ~ 4800 K. It is related to a change of the melt structure. At higher pressures, the melting curve is almost flat up to the subsolidus transition from stishovite to the CaCl2-form around 85 GPa, where the slope of the melting curve increases again up to ~ 120 GPa. We present corrected figures and tables of the original publication.
PubDate: 2022-01-19
DOI: 10.1007/s00269-021-01174-2

• Equation of state of a new calcium magnesium silicate compound with the
composition Ca3MgSi2O8 at pressures up to 23 GPa and ambient T

Abstract: Abstract Interaction between the Ca-rich and Ca-poor (or Mg-rich) domains in the mantle may lead to formation of some special calcium magnesium silicates (CMS), as indicated by the unusual mineral inclusion with the chemical formula Ca2.85Mg0.96Fe0.11Si2.04O8 enclosed in a super-deep diamond from Brazil. The equations of state (EoS) of these CMS compounds are thus important. With a diamond-anvil cell, here we performed in situ synchrotron X-ray diffraction experiments at high P (up to ~ 23 GPa) and ambient T to constrain the EoS of a new CMS compound with the composition Ca3MgSi2O8 and the space group C2/c. The obtained P–V data were fitted to the third-order Birch–Murnaghan EoS, yielding an isothermal bulk modulus $${K}_{T}$$ = 108(2) GPa, its first pressure derivative $${K}_{T}^{^{\prime}}$$ = 4.0(3) and room-P volume V0 = 658.0(4) Å3. If $${K}_{T}^{^{\prime}}$$ is fixed as 4, then $${K}_{T}$$ = 108(1) GPa and V0 = 658.0(3) Å3. In addition, no phase transition has been observed for this new CMS compound in the investigated P interval.
PubDate: 2022-01-19
DOI: 10.1007/s00269-021-01175-1

• Steudelite, (Na3☐)[(K,Na)17Ca7]Ca4(Al24Si24O96)(SO3)6F6·4H2O, a new
cancrinite-group mineral with afghanite-type framework topology

Abstract: Abstract The new cancrinite-group mineral steudelite, ideally (Na3☐)[(K,Na)17Ca7]Ca4(Al24Si24O96)(SO3)6F6·4H2O, was discovered in syenite ejectum from the Sacrofano paleovolcano, Latium region, Italy. The associated minerals are sanidine, diopside, andradite, biotite, leucite, haüyne, sacrofanite, biachellaite, liottite, and secondary dioctahedral smectite. Steudelite forms colourless, thick-tabular, isometric and short-prismatic crystals up to 7 mm across. Cleavage is distinct on {10 $$\overline{1}$$ 0}; perfect parting on {0001} is observed. Steudelite is brittle, with uneven fracture. The Mohs’ hardness is 5. Measured and calculated density are equal to 2.51 (1) and 2.511 g cm–3, respectively. The IR spectrum shows the presence of H2O molecules, SO32– and minor SO42– anionic groups. The chemical composition of steudelite is (wt%; electron microprobe, H2O determined by the modified Penfield method; total sulfur apportioned between SO2 and SO3 based on structural data): Na2O 7.40, K2O, 8.42, CaO 3.54, Al2O3 26.46, Fe2O3 0.18, SiO2 30.96, SO2 4.74, SO3 5.18, F 1.66, Cl 0.84, H2O 1.6, –O≡Cl,F − 0.89, total 100.09. The empirical formula is H8.22Na11.06K8.28Ca11.18(Al24.04Fe3+0.10Si23.86O96)(SO3)3.43(SO4)3.00F4.04Cl1.10O3.89. The crystal structure of steudelite is based on the afghanite-type aluminosilicate framework containing a column of cancrinite cages and isolated cancrinite and liottite cages whose populations are {Na3.14Ca0.14☐0.72[(H2O,OH)3.72Cl0.28]}, {Ca4F4.02Cl0.60}, and {K8.40Na8.13Ca7.10(SO3)3.24(SO4)2.76}, respectively. The SO32– and SO42– groups occur in the liottite cage, at two sites with the occupancies S1[(SO4)0.69(SO3)0.31] and S2[SO3]2. Steudelite is hexagonal, space group P-62c, with a = 12.89529 (15), c = 21.2778 (3) Å, V = 3064.21 (8) Å3, and Z = 1. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 11.15 (28) (100), 4.799 (25) (104), 3.973 (16) (105), 3.721 (47) (300), 3.305 (100) (214, 303, 400), 2.661 (17) (008), 2.149 (21) (330). The mineral is named in honour of the outstanding German chemist, a specialist in chemistry of sulfur Prof. Ralf Steudel (1937–2021).
PubDate: 2021-12-22
DOI: 10.1007/s00269-021-01172-4

• Aluminum solubility in rutile (TiO2)

Abstract: Abstract The solubility of aluminum in rutile has been studied in the systems Al2O3–TiO2–H2O and Al2O3–SiO2–TiO2–H2O at 700–1200 °C and 0.075–3.3 GPa. Electron probe microanalysis (EPMA) measurements of rutile crystals grown in equilibrium with corundum show that the concentration of Al increases with increasing temperature, pressure, and oxygen fugacity. Solubility is enhanced by the addition of Nb and reduced by the addition of trivalent cations. These results are consistent with the substitution of Al3+ for Ti4+ on normal cation sites and the simultaneous incorporation of positively charged hydrous defects for charge compensation. Parameters for a thermodynamic model of Al substitution in rutile are calculated and the merits of using the model as a geochemical tool are discussed.
PubDate: 2021-11-11
DOI: 10.1007/s00269-021-01169-z

• A critical assessment of interatomic potentials for modelling lattice
defects in forsterite Mg $$_2$$ 2 SiO $$_4$$ 4 from 0 to 12 GPa

Abstract: Abstract Five different interatomic potentials designed for modelling forsterite Mg $$_2$$ SiO $$_4$$ are compared to ab initio and experimental data. The set of tested properties include lattice constants, material density, elastic wave velocity, elastic stiffness tensor, free surface energies, generalized stacking faults, neutral Frenkel and Schottky defects, in the pressure range $$0-12$$  GPa relevant to the Earth’s upper mantle. We conclude that all interatomic potentials are reliable and applicable to the study of point defects. Stacking faults are correctly described by the THB1 potential, and qualitatively by the Pedone2006 potential. Other rigid-ion potentials give a poor account of stacking fault energies, and should not be used to model planar defects or dislocations. These results constitute a database on the transferability of rigid-ion potentials, and provide strong physical ground for simulating diffusion, dislocations, or grain boundaries.
PubDate: 2021-11-11
DOI: 10.1007/s00269-021-01170-6

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