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The transition metal silicide coatings have excellent oxidation resistance. In the high-temperature oxidization environment, the "anomalous" diffusion phenomenon of the reverse concentration gradient occurs in the multilayer silicide coating structure, which has a significant impact on the coating degradation. This study is to explore the physical mechanism of "anomalous" diffusion phase transformation in the MoSi2–NbSi2 bilayer silicide coating on the Nb alloy substrate. Through vacuum annealing experiments, combined with micro-Raman spectroscopy and electron probe microanalysis measurements, the diffuisonal phase transformation of multilayer silicide coating in the oxygen-free environment at high temperatures was studied. By decoupling the oxidation and diffusion, the experiments indicate that high-temperature oxidation is not the dominant driving factor for the "anomalous" diffusion of atoms. The thermodynamic analysis reveals that the reduction in the nucleation barrier of the silicide-poor layer due to multicomponent solid solution and the non-uniform distribution of component chemical potential provide the driving force for the "anomalous" diffusion growth. Based on the diffusion kinetic modeling, the simulation of diffusion-controlled phase transformation in multilayer silicide coating was carried out, and the effect of tracer diffusion coefficients on the growth of the silicide-poor phase was analyzed. The research will have guiding significance for the recognition of failure mechanisms of silicide coating systems and performance improvement. [ABSTRACT FROM AUTHOR]

Series of gadolinium tantalum niobates activated with Eu3+ and Tb3+ ((Gd 1-y-z Eu y Tb z)Nb x Ta 1-x O 4 (x = 0, 0.3, 1; y = 0.6; z = 0.06; 0.15; 0.3)) were obtained for the first time. The formation of substitutional solid solutions was demonstrated. The obtained ceramic solid solutions had a monoclinic structure with I2/a space group. Electron probe microanalysis, photoluminescence (PL) and cathodoluminescence (CL) were used for studies of gadolinium tantalates and tantalum niobates series activated with Eu3++Tb3+. CL and PL spectra, concentration dependences of CL intensity and decay times, as well as excitation spectra for 5D 0 -7F 2 Eu3+ and 5D 4 -7F 5 Tb3+ bands were analyzed. It was shown for the first time that both energy transfer from Tb3+ to Eu3+ ions, and a reverse process – energy transfer from Eu3+ to Tb3+ ions are observed. This reverse process led to a decrease in CL intensity and decay times of europium bands in the presence of terbium 3+ in these materials. Presumably this phenomenon is influenced by anti-Stokes luminescence. This is confirmed by the dependences of anti-Stokes luminescence probability on temperature and excitation density. [ABSTRACT FROM AUTHOR]

New experimental measurements of phase equilibria in the CaO-FeO-Fe 2 O 3 system at 1120–1740 °C over a wide range of oxygen partial pressures (pO 2 = 1, 10−0.68, 10−2, 10−6, 10−8, 10−10 atm) and in equilibrium with metallic Fe has been obtained. The study was undertaken using equilibration/quenching and electron probe X-ray microanalysis (EPMA) technique enabling the compositions of the liquid and solid phases in equilibrium at temperature to be accurately measured. The data have been used to define the liquidus of hematite (Fe 2 O 3), spinel (Fe,Ca) 3 O 4+x , lime (Ca,Fe)O, wustite (Fe,Ca)O 1+x , 2CaO·Fe 2 O 3 (C 2 F), CaO·Fe 2 O 3 (CF), CaO·2Fe 2 O 3 (CF 2), and a solid phase with composition close to (CaO) 15 (FeO) 8 (FeO 1.5) 77 , which is believed to belong to the Silico-Ferrite of Calcium and Aluminium (SFCA-I) solid solution. Direct oxygen concentration measurements in the liquid and solid phases using EPMA were also undertaken in the present study to determine the Fe2+/Fe3+ ratio in these phases. The experimental data obtained in the present study will be used for thermodynamic re-optimisation of the CaO-FeO-Fe 2 O 3 system, undertaken as part of the study of the 20-component Pb-Zn-Cu-Fe-Si-Ca-O-S-Al-Mg-Cr-Na-As-Sn-Sb-Bi-Ag-Au-Ni-Co system directly relevant to the applications in the ferrous and non-ferrous metallurgical industries. [ABSTRACT FROM AUTHOR]

Nitrogen (N) is an essential element for life. Yet the processes of planet formation and early planetary evolution through which rocky planets like Earth obtained their atmospheric and surface nitrogen inventory are poorly understood. In order to understand the effect of early silicate differentiation of the rocky bodies on N inventory, here we study the elemental partitioning of N between the silicate minerals and melts. We conducted laboratory experiments using tholeiitic basalts and Fe + Si alloy mixtures at 1.5 – 4.0 GPa and 1300 to 1550 °C under graphite saturation at an oxygen fugacity range of IW–1.1 to IW–3.0. The experiments yielded an assemblage of Fe-rich alloy melt (am) + silicate melt (sm) + clinopyroxene (cpx) ± garnet (grt) ± orthopyroxene (opx) ± plagioclase (plag). Using electron microprobe, we determine that under the experimental conditions, N act as an incompatible element with D N c p x / s m (0.11 – 0.47) > D N p l a g / s m (0.41) > D N o p x / s m (0.25) > D N g r t / s m (0.06 – 0.21). The D N m i n e r a l / s m do not show any strong dependence on temperature, pressure, and melt composition. However, through comparison with previous estimates, it appears that with decreasing f O 2 , N becomes less incompatible. Under our experimental conditions of alloy melt-mineral equilibria, N behaves as a siderophile element (D N a m / m i n e r a l ranging from 4.1 to 60.6) with f O 2 playing the strongest control on D N a m / m i n e r a l . Our data suggest that under reducing conditions, in the early stages of a magma ocean (MO) and/or deeper mantle, silicate minerals would hold a non-negligible fraction of N as N becomes less atmophile and siderophile. Therefore, reduced parent bodies could also retain substantial N in the residual mantle during partial melting. The extraction of N from an internal MO or a solid planetary mantle is thus enhanced only as the system becomes more oxidizing, enriching the surficial reservoirs in N. Thus, Earth's N 2 -rich atmosphere may be intrinsically linked to its mantle oxidation, whereas other rocky planets of the Solar System, such as Mars and Mercury, may have retained a significant portion of their N inventory in nominally N-free mantle silicates through episodes of MO crystallization and mantle melting. [ABSTRACT FROM AUTHOR]

Adding titanium oxide has become a common practice in modern blast furnace operating procedures. The blast furnace slag is based on the CaO–MgO–Al 2 O 3 –SiO 2 –TiO 2 low titanium slag system rather than CaO–MgO–Al 2 O 3 –SiO 2 system. Phase equilibria in the CaO–SiO 2 –Al 2 O 3 –MgO–TiO 2 system in the low-TiO 2 part have been experimentally determined by means of high temperature equilibration and quenching technique followed by electron probe X-ray microanalysis. Introducing a small quantity of titanium-bearing materials can lower the liquidus temperature. The TiO 2 content in the slag should be controlled below 4.6 wt%, otherwise it will enter the perovskite phase region where the liquidus temperatures increases rapidly. The compositions of the solid solutions corresponding to the liquidus have been precisely measured and should be utilized for developing the thermodynamic database. [ABSTRACT FROM AUTHOR]

The phase equilibria in the SiO2‐rich region of the Li2O‐, Na2O‐, and K2O‐SiO2 systems at 1550°C to 1650°C were experimentally studied to determine accurate liquidus of SiO2 in the systems. A classical equilibration/quenching method was used, and the equilibrated samples were analyzed by X‐ray diffraction (XRD) and electron probe microanalysis (EPMA). Samples were contained in sealed Pt crucibles and held at the target temperatures for 7–21 days to reach equilibrium condition. Sealed Pt crucibles were employed to avoid the volatile loss of alkali oxides during high temperature phase equilibration and hydration upon quenching. Accurate liquidus of SiO2 in alkali‐silicate systems was determined for the first time, and the results were analyzed using the limiting slope rule in order to understand the dissolution behavior of alkali oxides in SiO2 melt. It was confirmed that alkali oxide dissolves in SiO2 melt by producing Li+, Na+, and K+ cationic species rather than Li22+, Na22+ and K22+ species. [ABSTRACT FROM AUTHOR]

Basaltic shergottites are the most abundant rock type of Martian meteorites, and pyroxene grains within shergottites commonly show a zoned structure. Here, the detailed microscopic mineralogical characteristics of patchy zoned pyroxene in basaltic shergottite NWA 12522 were investigated by a combination of scanning electron microscopy, electron microprobe, Raman spectroscopy, and transmission electron microscopy. The results show that the cores of zoned pyroxene in NWA 12522 have a homogeneous Mg# value and consist mainly of augite and pigeonite. By contrast, the rim of zoned pyroxene is extremely ferroan and can be further divided into two regions based on quite distinct mineralogy and textures (i.e., far‐core and near‐core pyroxene rims). The near‐core rim shows narrow exsolution lamellae (~35 nm) that were cross‐cut by thin pigeonite veinlets and contain abundant nano‐sized particles of metastable pyroxferroite and pigeonite. Only relatively coarse exsolution lamellae (~80 nm) were observed in the far‐core pyroxene rim regions. The distinct mineralogical characteristics of the pyroxene rims and cores in NWA 12522 imply different crystallization conditions, and the homogeneous Mg‐rich pyroxene cores should have slowly crystallized from magma within a deep‐seated chamber, followed by an overgrown evolved melt on these pyroxene cores during their ascent to the Martian surface, and disequilibrium crystallization of nano‐sized metastable phase (pyroxferroite) occurred in the near‐core region. The abnormally low ΣREE contents and steep REE pattern (high Yb/La ratio) of the pyroxene rims in NWA 12522 imply that merrillite should have crystallized prior to the pyroxene rims, making the residual melt become REE‐depleted and HREE‐enriched. [ABSTRACT FROM AUTHOR]

Azurite, a historical blue mineral pigment, has previously been described to contain certain elemental impurities. These may originate from host rocks, vein fillings, or the primary copper ore mineralization. In this study, azurites (and also green malachites) from three important Central European deposits with a potential of being exploited for pigment usage already in the Middle Ages have been studied, together with azurite from Chessy, France, with a different geological setting. Using electron probe microanalysis and, more importantly, laser ablation inductively coupled plasma mass spectroscopy for trace elemental analysis, several indicators were pinpointed as important for provenance: characteristic elemental fingerprint of the deposit, e.g., elevated lead (Pb) in combination with rare earth elements, may be combined with zinc (Zn)/arsenic (As) ratio (indicating sources of excess Zn in the primary deposit) and the overall amount of metal impurities (suggesting the source mineral of copper for azurite formation). In addition, malachites from the same deposits were found to preferentially incorporate primary ore metal elements as well as Cd, Mg, Mn, or U. Therefore, if azurite pigment contains an elevated amount of malachite as an impurity, it may significantly influence the overall elemental composition. The results obtained on geological samples were applied to two micro-samples of works of art containing azurite-rich layers originating from the 13th–14th and 16th centuries. It was shown that it is highly beneficial to focus on the overall trace elemental composition of the paint layer and not on the admixed mineral grains, as their presence, especially in minute micro-samples, is largely accidental and thus not representative. Although a higher number of samples need to be studied in the future, the newly described criteria made it possible to exclude some of the localities of the employed azurite pigment. This confirmed the key importance of trace elements analysis of mineral pigments for the provenance studies of fine arts. [ABSTRACT FROM AUTHOR]

Hydropyrochlore, ideally (H2O,□)2Nb2(O,OH)6(H2O), is a cubic mineral (space group Fd 3 m, a = 10.56–10.59 Å, Z = 8) belonging to the pyrochlore supergroup (general formula: A2–mB2X6–wY1–n). The K-rich variety of this species is unique to the Lueshe syenitic-carbonatitic deposit (D.R. Congo), where it occurs as the alteration product of primary (Ca,Na)2Nb2O6F pyrochlores. The structure of this mineral is made of a B2X6 (B = Nb, Ti; X = O, OH) framework that generates tunnels along the [110] direction, where the interstitial sites are partially occupied by water molecules and minor amounts of different cations. These features form the basis for the ion-exchange properties of hydropyrochlore, making it a promising candidate as a mineral sink for heavy metals (e.g., Tl+) dispersed in aqueous matrices, with interesting environmental implications. Tl+ incorporation was induced through imbibition experiments in a diluted Clerici solution using single crystals of hydropyrochlore from Lueshe (D.R. Congo); the modifications induced by Tl+ incorporation were then evaluated using single-crystal X-ray diffraction (SCXRD), electron microprobe analyses (EMPA), and Fourier transform infrared (FTIR) spectroscopy. After Tl+ imbibition, a dramatic increase of the A-site electron density (n.e– from ~4 to ~60) confirms the entry of a substantial amount of Tl+ at this site (up to about 70%), leading to a lengthening of the A-X distances and the consequent expansion of the unit cell. A decrease of the site scattering at the Y′ site (from ~9 to ~4 e–) also occurs, suggesting a loss of aqueous species. Although the predominance of neutral H2O molecules at the interstitial sites of hydropyrochlore from Lueshe is widely accepted by the mineralogical community, our crystal-chemical and FTIR data provide evidence that the dominant species might be the hydronium ion, with significant implications on the nomenclature of the pyrochlore supergroup. Understanding the crystallographic aspects of hydropyrochlore as a potential waste form for monovalent thallium immobilization not only addresses a pressing environmental concern but also contributes to the broader field of waste management. [ABSTRACT FROM AUTHOR]

Louisfuchsite (IMA 2022-024), with an end-member formula Ca2(Mg4Ti2)(Al4Si2)O20, is a new refractory mineral identified in a Ca-Al-rich inclusion (CAI) from the NWA 4964 CK3.8 carbonaceous chondrite. Louisfuchsite occurs with spinel, perovskite, grossmanite, plus secondary rutile, titanite, and ilmenite in three regions in the CAI. The mean chemical composition of type louisfuchsite by electron probe microanalysis is (wt%) Al2O3 25.48, SiO2 18.40, MgO 17.92, TiO2 15.36, Ti2O3 3.13, CaO 14.92, FeO 3.30, V2O3 0.67, Cr2O3 0.08, total 99.26, giving rise to an empirical formula of C a 2.00 (M g 3.44 T i 1.49 4 + F e 0.36 T i 0.34 3 + A l 0.24 V 0.07 3 + C a 0.06 C r 0.01 ) Σ 6.01 (A l 3.63 S i 2.37 ) Σ 6.00 O 20 . Louisfuchsite has the P 1 rhönite structure with a = 10.37(1) Å, b = 10.76(1) Å, c = 8.90(1) Å, α = 106.0(1)°, β = 96.0(1)°, γ= 124.7(1)°, V = 741(2) Å3, and Z = 2, as revealed by electron backscatter diffraction. The calculated density using the measured composition is 3.44 g/cm3. Louisfuchsite is a new refractory phase from the solar nebula, crystallized from an 16O-rich (Δ17O ~ –24 ± 2‰) refractory melt with the initial 26Al/27Al ratio of (5.09 ± 0.58) × 10–5 under reduced conditions. The mineral name is in honor of Louis Fuchs (1915–1991), a mineralogist at Argonne National Laboratory, for his many contributions to mineralogical research on meteorites. [ABSTRACT FROM AUTHOR]

The article discusses the mineral downsite, a hydrated potassium molybdate sulfate found in Utah, named after Dr. Robert Downs for his contributions to mineralogy. Downs, a professor emeritus at the University of Arizona, has made significant advancements in crystal structure databases and mineral research. He has received numerous awards and honors for his work, including the Leonard G. Berry Medal and the Carnegie Mineralogical Award. Additionally, Downs has been involved in projects such as the RRUFF database and the Alfie Norville Gem and Mineral Museum, showcasing his dedication to mineralogy and education. [Extracted from the article]

The results of studying the sulfur isotope system in platinum-group minerals (PGM) are rare and generally limited to S-isotope data for Ru-Os sulfides from dunite-harzburgite massifs. To partially fill this gap, we for the first time characterized features of the S-isotopic composition of kuvaevite (Ir5Ni10S16) and tolovkite (IrSbS) from the Verkh-Neivinsk dunite-harzburgite massif, a typical representative of the ophiolitic association at the Middle Urals. The study employed a number of analytical techniques, including scanning electron microscopy, electron microprobe analysis and a femtosecond laser ablation with a gas source isotope ratio mass spectrometry. The primary PGM assemblage is formed by osmium and iridium minerals, laurite, kuvaevite and Pt–Fe alloys, which are replaced by As-bearing laurite, irarsite, tolovkite and other PGM of secondary origin. Kuvaevite is characterized by a predominance of Ni over Fe, Cu, and Co (Ni/(Ni + Fe + Cu + Co from 0.56 to 0.58), as well as Ir over other platinum-group elements (PGE) (i.e., Ir/(Ir + Rh + Os + Ru + Pt + Pd) = 1.00); tolovkite is characterized by trace amounts of Pt (0.51–2.86 wt %), Rh (0.58–1.36 wt %), Ru (0.31–1.47 wt %), Ni (0.34–0.74 wt %), Cu (0.06–1.10 wt %), and As (0.06–1.44 wt %). Particularities of the isotopic composition of sulfur in kuvaevite (δ34S from 0.9 to 2.1‰, mean δ34S 1.5 ± 0.5‰, n = 4) are indicative of the mantle source with a chondritic isotope composition. The heavy sulfur isotope composition of tolovkite (δ34S from 5.0 to 7.8‰; mean δ34S 5.9 ± 0.9‰, n = 8) indicates the participation of sulfur of crustal origin (for example, isotopically heavy sulfur derived from host sedimentary rocks), being consistent with the secondary origin of the tolovkite. New data support the conclusion about contrasting sources of sulfur and a multistage evolution of PGE mineralization. [ABSTRACT FROM AUTHOR]

This study investigates the influence of super-fast heating rate and holding time on the microstructure and mechanical properties of dual-phase (DP) Fe-0.16C-1.4Mn sheet steel. Super-fast heating and cooling rates were achieved via induction heating and gas quenching. The results were also compared with those for a conventional low-speed heat treatment. The microstructures were characterized in detail using X-ray diffraction, scanning electron microscopy, electron backscatter diffraction, and electron probe microanalysis. The results showed that the layered structure of the DP Fe-0.16C-1.4Mn steel after super-fast heating was mainly composed of recrystallized ferrite, martensite clusters, and a small amount of residual austenite. Compared with the conventional method, super-fast heating significantly refined the grains and improved yield and tensile strength, but it slightly reduced the elongation. The fraction of martensite, which depends on the nucleation and growth behavior of austenite, was significantly affected by the heating rate and holding time. The DP structure of Fe-0.16C-1.4Mn steel had an atypical layered heterogeneous structure, with an uneven plastic strain between the two phases occurring during the deformation process, which is something that can improve fracture elongation. [ABSTRACT FROM AUTHOR]

The potential of Fe‐rich non‐ferrous metallurgical slag (NFMS) in alkali‐activated materials has been demonstrated, exhibiting promising mechanical strength and fire resistance. However, the durability of alkali‐activated NFMS (AA‐NFMS) in terms of sulfate salt resistance remains unexplored. Additionally, the variability in the chemical composition of NFMS presents challenges in directly assessing the durability of AA‐NFMS. This study investigates the interplay between the Ca/Si and Mg/Ca ratios in Fe‐rich NFMS and the resulting MgSO4 resistance of the AA‐NFMS made thereof. To do so, mass change and compressive strength retention were monitored for six months on AA‐NFMS immersed in 5 wt% MgSO4, whereas microstructure was investigated using scanning electron microscope (SEM) and electron probe microanalyzer (EPMA). The results show that the MgSO4 solution attacked selectively the reacted binder matrix of AA‐NFMS rather than the unreacted slag. The corrosion primarily occurs at the sulfate exposure surface of AA‐NFMS, forming a dense, thin layer of Mg(OH)2, which acts as a barrier and impedes further attack. Dissolution of Ca is the most pronounced among the major elements (Ca, Fe, Al, and Si) in the NFMS. The mass of the specimens increased linearly with the initial Ca content. The medium Ca concentration (∼10%) retained the highest strength. [ABSTRACT FROM AUTHOR]

I have done major element analyses by electron microprobe, in-situ trace element analyses by laser ablation inductively coupled plasma mass spectrometry, and instrumental neutron activation analyses on bulk samples of olivine grains separated from main-group and Eagle-Station pallasites. Most main-group pallasite olivines have homogeneous Fe/Mg yet have varying Fe/Mn. Those few with anomalously ferroan olivine have Fe/Mn within the range of other main-group pallasites. High-temperature redox process coupled with diffusional exchange resulted in the homogeneous compositions of most main-group pallasites; simple diffusional exchange alone is insufficient. The Eagle-Station pallasites have Fe/Mn twice that of main-group pallasites with similar Fe/Mg, a result of having roughly half the Mn content. The Ni/Co ratio of main-group pallasite olivines is relatively constant and was imposed by the same high-temperature redox/diffusion process that established Fe/Mg-Fe/Mn relationships. Variability in trace lithophile element contents within individual pallasites and within individual olivine grains, coupled with very low contents for some that are inconsistent with formation from a magma, indicate that the current mm-sized olivine grains were recrystallized from a fragmental olivine breccia; grain fragments from different portions of an original dunitic mantle were juxtaposed in the breccia. Main-group pallasites are dimict breccias formed of fragmented and mixed monomict dunite breccia and metallic breccia that were formed in the walls and floor of a large basin that penetrated the mantle of their parent asteroid. Limited data indicate that Eagle-Station pallasites may have been formed by a similar process. Given that Eagle-Station and main-group pallasites were formed in distinct regions of the early Solar System, the pallasite forming process likely was common in early Solar System history. [ABSTRACT FROM AUTHOR]

Considering the urgency of resource utilization and environmental protection, the geochemistry of anomalous trace transition metal elements in coal formed in terrestrial environments has been studied using methods such as inductively coupled plasma atomic emission spectrometry analysis, electron probe micro-area analysis, sequential chemical extraction procedures, and correlation analysis. The results indicate that minerals in the coal samples included pyrite, kaolinite, quartz, dolomite, calcite, and celestite. Furthermore, compared with the average values of coals in China and the upper continental crust, the coal samples were rich in transition metal trace elements such as Ni, Cr, and Sr and were deficient in Be, Cd, Cu, Co, Ga, Mo, Sb, Tl, V, Zn, and Ti. We found that Ni preferentially occurred in the organic matter over minerals, while Cr primarily bonded with sulfide minerals and to a lesser extent with the iron-manganese oxide minerals. Sr had a low correlation with organic matter but adhered to clay minerals and celestite. Ni enrichment in coal samples was the result of terrigenous input, while the Cr enrichment was related to intrusion of magmatic hydrothermal fluids. Sr enrichment was caused by the presence of SO42- in the terrigenous debris and the influence of Sr-rich water underground. [ABSTRACT FROM AUTHOR]

In the present paper, the Al–Fe-Mo phase diagram was studied by X-ray diffraction (XRD), differential thermal analysis, differential scanning calorimetry, scanning electron microscopy and electron probe microanalysis. For the first time, isothermal sections at 1450, 1300 and 1200 °C were experimentally determined over the entire range of compositions. A ternary intermetallic compound τ (Mo3FeAl8) with a TiAl3-type structure was observed at all above temperatures. It has been shown that isostructural disordered bcc (A2) phases of pure elements Fe and Mo (W-type structure, cI2- I m 3 ¯ m) in the ternary system at 1450 °C form a continuous solid solution (Mo,Fe,Al), dissolving up to 50 at.% Al. When cooled, it decomposes into a Mo-rich part and an elongated area (Fe,Al) along Fe-Al side. As the temperature decreases, their homogeneity regions reduce in size and shift toward higher Mo and Fe contents, respectively. The μ (Mo6Fe7) phase, which in the Fe-Mo binary system is formed in the solid state at 1368 °C, deeply extends into the ternary system, up to 16 and 15 at.% at 1300 and 1200 °C, respectively, where Al substitutes for Fe. Since the addition of Mo stabilizes the ε (Fe5Al8) phase, and the temperature of its formation in the ternary system is higher than in the binary (1331 and 1234 °C, respectively), the isothermal section at 1300 °C contains a narrow homogeneity region of this phase. In contrast, the solubility of Mo in ε at 1200 °C is no less than 14.4 at.%. The boundary Al-Mo binary and Al–Fe-Mo ternary systems are thermodynamically remodeled based on our experimental results and novel information reported in literature. Thermodynamic modeling was carried out by the CALPHAD (CALculation of PHAse Diagrams) approach using Thermo-Calc software. Calculations performed using the proposed thermodynamic description well reproduce most of the experimental data, including data from the available literature. Based on the developed description, phase diagrams of the constituent binary systems, as well as liquidus and solidus projections, selected isothermal and isopleths sections and the reaction scheme of the ternary system were calculated. [ABSTRACT FROM AUTHOR]

This work proposes an original method that reveals the transformation dynamics of nanosized Bi films into semiconductor films of bismuth oxide (Bi2O3) and the factors affecting the low‐energy cold plasma on the electro‐optical properties of Bi2O3. In the plasma microreactor with a photosensitive GaAs:Cr electrode, the transformed Bi films 400–1100 nm thick are analyzed by X‐ray diffraction to determine the crystal structure of Bi2O3 and by an electron probe microanalyzer to explore the evolution of the composition. The morphological properties of the Bi films exposed to electron–ion flow are examined by processing the scanning electron microscope images. It is found that as a result of the combined effect of photoactive illumination, charged particles, and active plasma components: 1) an absorption spectrum of a new substance is formed in the range λ = 330–1100 nm; 2) the optical width of the bandgap of the resulting substance is Eg ≈ 3 eV, which satisfactorily coincides with the width of the bandgap of Bi2O3; and 3) to overcome the potential barrier and formation of semiconducting Bi2O3 film energy is required, which is provided by the combined kinetic energy of electrons and negatively charged oxygen ions bombarding on the Bi film. [ABSTRACT FROM AUTHOR]

The Mediterranean region has been characterized by intense explosive volcanism since the Eocene. These eruptions ejected tephra, including fine-grained ash, which were thrown into the air and dispersed over wide areas to later be deposited as ash layers, many of which are preserved in some continental and marine sedimentary basins. Their study provides crucial insights into past volcanic activity, yet, for many of such ash layers, the understanding of their sources remains challenging. The presence of many ash layers across central Italy is widely recognized in literature although not uniquely associated with a specific volcanic source. We investigate in detail upper Tortonian (~ 7.6 Ma) ash layers sampled from three different localities, from the Tyrrhenian to the Adriatic coast of Italy, comparing our results with others already described in the literature. Electron microprobe geochemical analyses on biotite crystals, U–Pb ID-TIMS and LA-ICP-MS geochronological dating, and trace elements/Lu–Hf isotope analyses on zircons permitted us to expand our knowledge of these ancient ash deposits. Several potential volcanic centers were active during the late Tortonian, including the Massif Central (France), the Valencia trough (Spain), the Betics-Rif orogen (Spain-Morocco), and eastern Carpathians (Romania) and Capraia island (Italy). Through detailed radioisotopic dating and geochemical comparisons, we narrow down the possible source to the Upper Miocene Capraia island volcano (Tuscan archipelago), located in the northern Tyrrhenian basin. [ABSTRACT FROM AUTHOR]

Over 30 small, discontinuous, tabular carbonatite bodies are located in the Sheep Creek area, Ravalli County, southwest Montana. The age and origin of these REE-Nb-rich deposits are currently being investigated. The purpose of this paper is to document the occurrence of several rare minerals, including daqingshanite, törnebohmite, biraite, sahamalite, and ferriperbøeite, in two of the carbonatite bodies. These minerals are found in association with monazite, hydroxylbastnäsite, ferriallanite, calcite, dolomite, baryte, quartz, actinolite, apatite, celsian, and Sr-rich aragonite. Automated SEM-EDS was used to target the areas of interest in polished specimens for more detailed spot SEM-EDS and electron probe microanalysis. Raman spectra were also acquired for each of the rare minerals. The complex mineralogy of the Sheep Creek carbonatites is most likely due to several overlapping thermal events, including primary magmatic, overprinting hydrothermal, and supergene weathering stages. The rare minerals described in this study are believed to be hydrothermal and/or carbothermal in origin, although no estimates of temperature are available at this time. [ABSTRACT FROM AUTHOR]

The Václav vein (Březové Hory deposit, Příbram ore area, Czech Republic) is a base–metal vein containing minor Cu-Zn-Pb-Ag-Sb sulfidic mineralization in a usually hematitized gangue. A detailed mineralogical study using an electron microprobe revealed a complicated multistage evolution of the vein. Early siderite and Fe-rich dolomite were strongly replaced by assemblages of hematite+rhodochrosite and hematite+kutnohorite/Mn-rich dolomite, respectively. In addition, siderite also experienced strong silicification. These changes were associated with the dissolution of associated sulfides (sphalerite, galena). The following portion of the vein contains low-Mn dolomite and calcite gangue with Zn-rich chlorite, wittichenite, tetrahedrite-group minerals, chalcopyrite, bornite, and djurleite, again showing common replacement textures in case of sulfides. The latest stage was characterized by the input of Ag and Hg, giving rise to Ag-Cu sulfides, native silver (partly Hg-rich), balkanite, and (meta)cinnabar. We explain the formation of hematite-bearing oxidized assemblages at the expense of pre-existing "normal" Příbram mineralization due to repeated episodic infiltration of oxygenated surface waters during the vein evolution. Episodic mixing of ore fluids with surface waters was suggested from previous stable isotope and fluid inclusion studies in the Příbram ore area. Our mineralogical study thus strengthens this genetic scenario, illustrates the dynamics of fluid movement during the evolution of a distinct ore vein structure, and shows that the low content of ore minerals cannot be necessarily a primary feature of a vein. [ABSTRACT FROM AUTHOR]

The liquidus surface, melting diagram (superposition of the liquidus and solidus surfaces) and Scheil diagram of the Hf-Rh-Ir system are presented for the first time based on results of the study of as-cast alloys using optical microscopy, scanning electron microscopy, electron probe microanalysis, differential thermal analysis and x-ray diffraction techniques taking into account the constitution of the solidus surface. In the Hf-Rh-Ir system a continuous series of solid solutions between isostructural compounds Hf2Rh and Hf2Ir (with the Ti2Ni-type structure), high-temperature modifications of compounds HfRh and HfIr (CsCl-type), HfRh3 and HfIr3 (AuCu3-type), iridium and rhodium (Cu-type), as well as solid solutions based on βHf, compounds Hf5Ir3 and Hf3Rh5 take part in phase equilibria. Two invariant four-phase reactions (peritectic at 1958 °C and transition at 1655 °C) involving liquid and corresponding three-phase equilibria take place in this system. [ABSTRACT FROM AUTHOR]

This study aimed to assess the antibiofilm effects of dentin desensitizers using a modified Robbins device flow cell system. The test desensitizers were Saforide, Caredyne Shield, and Clinpro White Varnish. Standardized dentin specimens were prepared from human single-rooted premolars, treated with one of the materials, and mounted on the modified Robbins device flow cell system. Streptococcus mutans biofilms were developed for 24 h at 37 °C under anaerobic conditions. Scanning electron microscopy, fluorescence confocal laser scanning microscopy, viable and total cell counts, acid production, and gene expression analyses were performed. A wavelength-dispersive X-ray spectroscopy electron probe microanalyzer was used to analyze the ion incorporations. Clinpro White Varnish showed the greatest inhibition, suggesting its suppression of bacterial adherence and transcription of genes related to biofilm formation. Saforide reduced only the number of viable bacteria, but other results showed no significant difference. The antibiofilm effects of Caredyne Shield were limited. The uptake of ions released from a material into dentin varies depending on the element. Clinpro White Varnish is effective for the short-term treatment of tooth sensitivity due to dentin demineralization. It prioritizes remineralization by supplying calcium and fluoride ions while resisting biofilm formation. [ABSTRACT FROM AUTHOR]

The first in‐depth geochemical and petrological analyses of new lunar meteorite Northwest Africa (NWA) 11788 were conducted with the aim of better understanding the diversity of lunar rock types. Petrography, microcomputed tomography, electron probe microanalysis, and laser ablation inductively coupled plasma mass spectrometry were employed to analyze mineralogic/elemental makeup, petrologic profile, melt history, and inferred composition of the lunar mantle from which the crystals in this sample originated from. Geochemical maps of the lunar surface were generated to constrain potential lunar launch locations for NWA 11788. Potential launch locations are concentrated in the outer rims of impact basins on the lunar Eastern nearside limb (e.g., Crisium, Fecunditatis, Marginis, Smythii) and around the South Pole–Aitken Basin. Similarities in the major, minor, and trace element chemistry of NWA 11788 along with its potential launch locations suggest a petrogenetic relationship with regolith samples returned from the Luna 20 mission and the Apollo 16 and 17 magnesian granulites. Additionally, the results of this study add to the growing body of evidence that KREEP (potassium, rare earth elements, phosphorous)‐poor, Mg‐suite‐"like" lithologies are common in non‐Apollo‐type locales, that KREEP may not be required to generate lithologies like the Mg‐suite, and that KREEP is not globally distributed at present. [ABSTRACT FROM AUTHOR]

Cobalt is a critical and strategic metal mainly found as associated element in several types of deposits, of which skarn‐type deposits are the major sources. Han‐Xing type skarn iron deposit, having high grade iron ore and associated cobalt, is a typical skarn‐type iron ore in China. But the complete recovery and exploitation of cobalt are restricted because of the lower grade of related cobalt and the dearth of prior research on its occurrence condition and enrichment mechanism. In this paper, pyrite from five typical ore deposits in the Han‐Xing area was studied by using electron probe microanalysis (EPMA) and laser‐ablation inductively‐coupled‐plasma mass‐spectrometry (LA–ICP–MS) techniques to decipher the occurrence state and enrichment mechanism of associated cobalt in skarn‐type iron deposits. The results show that Co2+ replaces Fe2+ in pyrite through isomorphism. The distribution of cobalt in pyrite from different deposits varies greatly, that is, in the Xishimen iron deposit, the cobalt content is comparatively enriched in the pyrite's core. In contrast, in other deposits, the cobalt content is concentrated in the pyrite's rims, where it can be up to 1000 times higher than in the core. The cobalt mineralization in Han‐Xing area can be divided into several stages. The sulphur element of sulphide is mainly derived from evaporite, while cobalt mineralization occurred in the early stage with pyrite formation or in the late stage by metasomatism/cementation of Co‐rich ore‐forming fluid. The magma assimilated with the Ordovician evaporite not only promoted iron mineralization, but also became the main controlling factor for cobalt enrichment. [ABSTRACT FROM AUTHOR]

In this study, D2 steel (Cr12Mo1V1) with different yttrium (Y) contents was designed, and the effects of Y on the inclusions and eutectic carbides of D2 steel after casting were analyzed by scanning electron microscopy, ASPEX, and electron probe microanalyzer. The results reveal that the inclusions in D2 steel without Y are mainly Al2O3 and MnS, while the inclusions with Y are mainly Y2S3, Y2O2S, and complex inclusions. When the Y content increased from 0 to 0.021%, the quantity of inclusions with an average grain size of 1–2 microns gradually increased from 47.6 to 64.7%. The chain eutectic carbides in D2 were broken and tend to be spheroidized after adding Y, which was attributed to the fact that the submicron Y-rich inclusions help to slow down the segregation of carbon and alloying elements. The inclusion is beneficial to the heterogeneous nucleation of M7C3 eutectic carbides and the decrease in eutectic reaction temperature. [ABSTRACT FROM AUTHOR]

Advancements in scanning electron microscopy and energy dispersive X-ray analysis (SEM-EDX) technologies have reached the point where rapid, fully quantitative, non-destructive and high-resolution acquisition of effectively all major element chemical information from polished sample material is possible. Here, we discuss optimisation parameters and demonstrate the data quality that can be achieved for SEM-EDX analysis of magmatic glass samples; glass represents a particular challenge due its lack of stoichiometry and potential for beam-induced element mobilisation. We test our approach through analysis of reference materials and demonstrate the advantages of SEM-EDX for several volcanic glasses that were previously investigated with electron probe micro-analysis (EPMA). SEM-EDX analysis is typically undertaken at a much lower beam current than EPMA, allowing for non-destructive analysis of geologic material that are sensitive to a higher beam current, such as sodium-rich glass. With careful instrument set-up, robust standardisation, and optimal experiment parameters, SEM-EDX analysis can achieve major and minor element data comparable with that collected via EPMA, with the exception of low abundance elements (those below 0.2 wt%). In addition, SEM-EDX analysis typically uses a smaller beam diameter and so permits analysis of smaller features than EPMA. Our results show that this technique can be potentially used as a quantitative tool on a wide range of geological materials with faster analysis, improved spatial resolution and cost advantages making it a complementary or alternative analytical method to EPMA. [ABSTRACT FROM AUTHOR]

Copper possesses very strong chacophile properties, but under the conditions found in meteorites, its behavior is like that of siderophile elements. The Suizhou meteorite is a highly shocked L6 chondrite. Troilite and taenite are considered the main primary carrier of copper in this meteorite, and the post-shock thermal episode is considered the main reason that elemental Cu migrates from its original host phase and forms metallic grains. The Suizhou meteorite contains a few very thin shock melt veins. The occurrence and behavior of metallic copper in this meteorite were studied by optical microscopic examination, electron microprobe analyses, and high-resolution X-ray elemental intensity mapping. Our results show that metallic copper is abundant in the Suizhou chondritic rock. Metallic copper grains adjacent to small troilite grains inside FeNi metal are the most common occurrence, and those at the FeNi metal–troilite interface are the second most common case. The metallic copper grains occurring at the interface of FeNi metal/troililte and silicate are rather rare. Metallic copper grains are not observed within the Suizhou shock veins, Instead, Cu in elemental form is transferred through shock metamorphism into FeNi metal + troilite intergrowths. Four different occurrence types of Cu in the FeNi metal + troilite intergrowths have been identified: the concentrations of Cu in the FeNi + FeS intergrowths for four occurrence types are rather close, we estimate it might be lower than 1 wt%. [ABSTRACT FROM AUTHOR]

• The waste-with-waste treatment is used to successfully remove heavy metals from slag. • Separation at high-temperature with Si-Cu additives recovered more than 90% of metals. • EPMA analyses allowed for quantifiable comparisons of all elements present in slag. • Concentrations of heavy metals reduced from 2400 ppm to 41.7 ppm in the remaining slag. The smelting processes account for over 80 % of global copper production, generating various slags in large quantities. Most of these slags do not contain the required amounts of valuable metals to justify economic revalorization, yet the concentrations present may negatively affect the environment. In this study, heavy and potentially toxic metals were removed by keeping the liquefied slag at 1300 °C for four hours, while the metals gathering was enhanced by adding silicon-copper compounds. Crystallography, metallography, gravimetric, thermogravimetric, and differential thermal analysis were employed to characterize the slag. Electron probe microanalysis was utilized to examine the distribution of heavy and potentially toxic metals from the original copper slag to the remaining slag and mattes formed in the lower portion of the containing vessel. In all instances, concentrations of the arsenic and zinc were reduced below the detection limit. Moreover, the cumulative concentrations of six heavy metals were reduced from 2400 ppm in the initial slag to 41.7 ppm in the remaining slag when using 30 wt%Si70wt%Cu additive. All potentially valuable or toxic metals gathered in the mattes that had oxygen concentrations about 50 times lower than in the initial slag, at 0.82, 0.56, and 0.68 wt% after the mixing slag with 10 wt%Si90%Cu, 30 wt%Si70wt%Cu, and 50 wt%Si50wt%Cu additives, respectively. Investigated practices can mitigate the threat of heavy and potentially toxic metals associated with the disposal of copper slags while also enabling the recovery of valuable metals and rendering the remaining slag suitable for construction or mine backfill purposes. [ABSTRACT FROM AUTHOR]

A long-term foundational study aimed at developing a thermodynamic database for continuous basalt fiber systems is in progress. In this work, the equilibrium phase relations of the SiO 2 –Al 2 O 3 –Fe 3 O 4 -5 wt.% CaO system at 1400 °C in air atmosphere were determined experimentally using the equilibrium-quenching technique. Subsequent analyses were conducted using Electron Probe Micro-Analysis (EPMA), X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM) to validate the experimental results and further investigate the microstructural characteristics. The results revealed a single liquid region and three distinct two-phase regions as Liquid-Cristobalite, Liquid-Mullite solid solution, and Liquid-Spinel solid solution. Additionally, two three-phase regions were identified as liquid-cristobalite-mullite solid solution, and liquid-mullite solid solution-spinel solid solution. This work contributes to a deeper understanding of the phase behavior during the melting of basalt ore systems, which is crucial for optimizing their production and enhancing their applications. [ABSTRACT FROM AUTHOR]

In recent years, high entropy alloys (HEAs), also known as multi-principal component alloys (MPCAs) have emerged as a new and exciting class of materials. This paper reports on the solid state reduction synthesis of a series of CoFeNiMn-based MPCA compositions, starting from a mixture of the corresponding oxides. One of the aims of the study was to test whether the degree of reduction of MnO, a highly stable oxide, could be enhanced by tailoring the alloy composition. Specifically, the influence of Ni content was studied because Ni exhibits a significant negative enthalpy of mixing with Mn. High purity precursor powders of Co(OH)2, Fe2O3, MnO2, and NiO were milled and mixed using standard ceramic processing methods. The nominal sample compositions (assuming complete oxide reduction) were (CoFeMn)xNi(1−x), for x = 0, 0.083, 0.166, and 0.25. The oxide samples were subjected to a series of isothermal reduction anneals in flowing 3 pct H2–Ar at 1100 °C. The resulting microstructures were characterized using scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The composition of the resulting MPCAs was determined quantitatively using wavelength dispersive spectroscopy (WDS) in the electron microprobe. The study revealed that for each of the initial oxide compositions studied, it was possible to achieve an MPCA with ~ 25 at. pct Mn. These results were found to be consistent with the predictions of a thermodynamic model whereby a negative enthalpy of mixing (ΔHmix), combined with a contribution from configurational entropy, can offset a positive free energy of reduction (ΔGred). The incorporation of vibrational entropy into first principles calculations was found to have a significant effect on the predicted crystal structure of the MPCAs. [ABSTRACT FROM AUTHOR]

High-phosphorus (P) iron ore, particularly oolitic hematite, has remained unexploited due to technological and cost limitations in mining. Effectively developing this ore involves not just utilizing its iron content but crucially extracting P to reduce exploitation costs. Here, we applied a direct reduction-magnetic separation process to recover these valuable elements efficiently. The phase transition and morphology evolution of phosphorus and iron were investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and electron probe microanalysis (EPMA). Subsequently, a quantitative mass balance analysis described the migration and recovery performance of P after magnetic separation. The results show that during the direct reduction process, the phosphorus underwent a series of transformations from Ca5(PO4)3F in the ore to Ca3(PO4)2, then to a dissolved state in molten slag, enrichment in metallic iron, and finally its escape to the gas phase. Under optimal conditions of 1400 °C, a reduction time of 60 minutes, a C/O molar ratio of 1.2, and an addition of 4 wt pct Al2O3, a high concentrations of P-rich iron was obtained with 2.63 wt pct P with a recovery of 95.19 pct Fe and 90.06 pct P was achieved. This method offers a more efficient pathway to reduce P loss compared to traditional mineral separation techniques, presenting a competitive method for processing refractory high-phosphorus oolitic hematite. [ABSTRACT FROM AUTHOR]

The coloring process of monolithic dental zirconia caused considerable debate on the possible effects of different coloring methods. The main objective of this study was to investigate the influence of pigments in 3 multilayer 5-mol% yttria partially stabilized zirconia (5Y-PSZ) disks (Lava Esthetic A2 [Zr-AGG_A2] and Bleach [Zr-AGG_BL], both 3M Oral Care, and Katana STML A2 [Zr-NoAGG], Kuraray Noritake). The influence of pigment addition on the translucency parameter (TP00), fracture toughness, Vickers hardness, biaxial strength, and hydrothermal stability was assessed and correlated with the microstructure and phase composition. The pigment composition and distribution were evaluated by light and fluorescence microscopy, electron probe microanalysis, and nano–scanning electron microscopy. The chemical and phase composition and aging behavior were assessed using X-ray fluorescence and X-ray diffraction, respectively, while the aging sensitivity of the pigments was evaluated using micro-Raman spectroscopy. In contrast to Zr-NoAGG, possessing a typical 5Y-PSZ microstructure, the pigment additions in both Zr-AGG_A2/BL zirconia resulted in large yellow and blue fluorescent Er-, Hf-, and Al-containing agglomerates composed of small grains (0.57 µm and 0.38 µm, respectively, vs. 0.92 µm for the surrounding grains) with lower Y2O3 content. Zr-AGG_A2 had the lowest aging resistance, with transformation degradation occurring exclusively within the pigment agglomerates. All zirconia grades had a high Y2O3 content (4.2%–5.7 mol%) tetragonal ZrO2 phase and a high (42%–55 wt%) cubic ZrO2 phase content. Although no statistical differences were measured for hardness and toughness, Zr-NoAGG had a significantly higher TP00, higher flexural strength, and lower mechanical reliability compared to both Zr-AGG_A2/BL zirconia. The rare-earth oxide-containing zirconia agglomerates that were added as pigments to the multilayered monolithic Zr-AGG_A2/BL zirconia are the cause for their lower optical and mechanical properties and reduced aging resistance. [ABSTRACT FROM AUTHOR]

The objects of the study were converter slags from the Balkhash copper plant in their initial state and after heat treatment. Using mineralogical and X-ray phase analysis, scanning electron microscopy (SEM), and electron probe microanalysis (EPMA), it was found that the initial converter slag and its thermally treated samples have identical matrices with almost complete coincidence in mineral and phase compositions. The distinguishing feature is the quantitative ratio of mineral components in the slag mass. Almost all of the iron is oxidized and present in the form of fayalite, magnetite, and magnetite, with other elements (silicon, copper, zinc, and aluminum) incorporated into its lattice. The structure of all slag samples indicates an association of sulfur exclusively with copper. Copper in the slags was identified in both metallic and sulfide forms. Slow cooling of the converter slag after its remelting contributes to the reduction in the sulfide–metal suspension in the volume of the melt and its coarsening. During slow cooling, structural changes occur not only in the main oxide part of the slag but also in the polymetallic globules. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) pollutes natural waters, but some impacted systems show natural attenuation. We sought to identify the biogeochemical mechanisms responsible for the natural attenuation of AMD. We hypothesized that biogenic sulfide-mediated iron reduction is one mechanism and tested this in an experimental model system. We found sulfate reduction occurred under acidic conditions and identified a suite of sulfate-reducing bacteria (SRB) belonging to the groups Desulfotomaculum, Desulfobacter, Desulfovibrio, and Desulfobulbus. Iron reduction was not detected in microcosms when iron-reducing bacteria or SRB were selectively inhibited. SRB also did not reduce iron enzymatically. Rather, the biogenic sulfide produced by SRB was found to be responsible for the reduction of iron at low pH. Addition of organic substrates and nutrients stimulated iron reduction and increased the pH. X-ray diffraction and an electron microprobe analysis revealed that the polycrystalline, black precipitate from SRB bioactive samples exhibited a greater diversity of iron chalcogenide minerals with reduced iron oxidation states, and minerals incorporating multiple metals compared to abiotic controls. The implication of this study is that iron reduction mediated by biogenic sulfide may be more significant than previously thought in acidic environments. This study not only describes an additional mechanism by which SRB attenuate AMD, which has practical implications for AMD-impacted sites, but also provides a link between the biogeochemical cycling of iron and sulfur. [ABSTRACT FROM AUTHOR]

ABSTRACT Carbonate cementation in the Upper Permian sandstones informs the timing and temperature of hydrothermal activity in the south‐western Ordos Basin. This study presents a detailed examination of these hydrothermally influenced carbonate cements, constraining their age, carbonate diagenesis and relationship with regional geodynamic evolution. Sedimentological analyses demonstrate the development of deltaic plain and front sand bodies in the study area, which resulted in interbeds of volcanic matrix‐rich sandstones with matrix‐free sandstones. Petrography and electron microprobe analysis reveal four carbonate mineral growth phases of matrix‐free sandstones in the following sequence; scarce pure siderite, scarce Mg‐rich siderite, abundant blocky calcite and moderately abundant grain‐replacing calcite. The fluid inclusion data show anomalies of homogenization temperature of blocky carbonate cements during early diagenesis, over a wide range of ca 148 to 228°C. In addition, blocky carbonate cements show low δ13C (−5.9 to −13.1‰ Vienna PeeDee Belemnite) and δ18O (clustered tightly from −12.4 to −14.6‰ Vienna PeeDee Belemnite) values, interpreted to result from elevated temperatures during cementation, associated with activation of basement faults and concomitant hydrothermal fluid intrusion triggered by oceanic crust subduction in the south‐west margin of the Ordos Basin. Using in situ calcite U–Pb geochronology, the timing of hydrothermal activity was constrained to ca 247.0 ± 11 to 248.2 ± 4.7 Ma. This work provides a case study for applying intergranular calcite U–Pb dating to determine the absolute timing of fluid flow in sedimentary basins, offering tremendous potential to capture snapshots of various diagenetic evolution stages in sediments. The proposed diagenetic model can also provide new insights and understanding regarding hydrothermally influenced sediments. More importantly, hydrothermal activity may have commenced earlier than previously thought. The North Qinling Orogen uplift and associated Mianlue oceanic crust subduction may have begun at the Permian–Triassic transition with a protracted hydrothermal event in the south‐western Ordos Basin. [ABSTRACT FROM AUTHOR]

CaO–SiO 2 is the key system in ferrous and non-ferrous metallurgy, ceramic manufacture, cement production, and other applications. A number of discrepancies and gaps in knowledge has been identified and resolved since the last thermodynamic optimization of this system. This study reports new experimental phase equilibria data measured using recent advances in equilibration, sample quenching, and Electron Probe X-ray Microanalysis (EPMA) technique. An updated self-consistent set of thermodynamic model parameters is provided. Most importantly, these updates are integrated with a complete re-assessment of the 20-component Cu–Pb–Zn–Fe–Ca–Si–O–S–Al–Mg–Cr–Na–As–Sn–Sb–Bi–Ag–Au–Ni–Co system directly relevant to applications in the ferrous and non-ferrous metallurgical industries. To obtain a large single set of model parameters, significant advances were made in the computational approach, with a focus on simultaneous parallel optimization of binary and ternary model parameters using an experimental dataset combining binary, ternary, and multicomponent information. The Modified Quasichemical Formalism is used for the liquid slag phase. Thermodynamic properties of solid phases and liquid endmembers are completely revised following the recommendations for the third generation of CALPHAD databases. Other notable changes include the revision of the melting temperature of CaO, justified by extrapolations from the multicomponent systems, as well as a physically realistic heat capacity function for metastable SiO 2 below the glass transition temperature. These updated properties expand the areas of application of the database to amorphous and partially crystallized slags at ambient temperatures, such as thermodynamics and kinetics of leaching of toxic elements in an aqueous environment. The fundamental limitations of the existing Modified Quasichemical Formalism are also discussed, along with strategies for addressing them. [ABSTRACT FROM AUTHOR]

Ce3+-doped lithium alumino-silicate (Li-Al-Si) scintillating glass was prepared using a melting method and crystallized via heat treatment. X-ray diffraction and transmission electron microscopy confirmed the presence of nanocrystals in the materials. Radioluminescence spectra, obtained by X-ray excitation, and luminescence spectra, obtained by 338 nm excitation, showed that the luminescence intensity increased after crystallization. The glass was combined with pure silica as the inner cladding to fabricate a hybrid fiber core using a melt-in-tube technique. The composition of the fiber core was examined using an electron probe microanalyzer. The glass fiber produced strong blue luminescence under UV excitation. After a micro-crystallizing heat treatment of the hybrid fiber at 850 °C in a reducing atmosphere, a Ce3+-doped lithium alumino-silicate glass–ceramic scintillating hybrid fiber was obtained. The nanocrystal structure of the fiber core was examined using micro-Raman spectroscopy. Excitation and luminescence spectra of the hybrid fiber before and after micro-crystallization were measured using microspectrofluorimetry. The results demonstrated that the fiber remained luminous after micro-crystallization. Hence, this work provides a new way to prepare scintillating glass–ceramic hybrid fibers for neutron detection. [ABSTRACT FROM AUTHOR]

The Phase diagram of ternary Na 2 O-B 2 O 3 -ZnO system was investigated for the first time using the classical equilibration/quenching method and differential thermal analysis followed by the phase analysis using the Electron Probe Micro-Analysis (EPMA) and X-Ray Diffraction (XRD). The isothermal phase diagrams of this ternary system at 900, 1000 and 1100 °C were determined, and the melting temperatures of two ternary compounds were investigated using Differential Thermal Analysis (DTA). The thermodynamic modeling of ternary Na 2 O-B 2 O 3 -ZnO system was carried out based on the present ternary phase diagram data and the optimized model parameters of binary systems. Thermodynamic models with optimized model parameters were used to predict the phase diagram of the ternary Na 2 O-B 2 O 3 -ZnO system. [ABSTRACT FROM AUTHOR]

CM chondrites are samples from primitive water‐rich asteroids that formed early in the solar system; many record evidence for silicate rock–liquid water interaction. Many CM chondrites also exhibit well‐developed fine‐grained rims (FGRs) that surround major components, including chondrules and refractory inclusions. Previous studies have shown that Aguas Zarcas, a CM2 chondrite fall recovered in 2019, is a breccia consisting of several lithologies. Here, we present a study of Aguas Zarcas using optical microscopy, scanning electron microscopy, and electron probe microanalysis, focusing on brecciation and aqueous alteration on the parent body. We observed two lithologies within our sample, separated by a distinct textural and chemical boundary. The first lithology has a higher chondrule abundance ("chondrule‐rich") and significantly larger FGRs compared to the second lithology ("chondrule‐poor"), even for similarly sized chondrules. We observed clear compositional differences between the two lithologies and more multilayered FGRs in the chondrule‐rich lithology. We determined that the chondrule‐rich lithology is less altered (petrologic type 2.7–2.8) and displays larger FGRs to chondrule ratios compared to the more altered chondrule‐poor lithology (petrologic type 2.5–2.6). These observations are contrary to previous models that predict aqueous alteration as a cause of FGR formation in the parent body. Our observed differences in Mg and Fe distribution in the lithology matrices alongside variable FGR thickness suggest distinct formation environments. We propose that the Aguas Zarcas parent body was subjected to several minor and major brecciation events that mixed different materials with variable degrees of aqueous alteration together, in agreement with previous studies. [ABSTRACT FROM AUTHOR]

We carried out a petrological, mineralogical, and geochemical study of fragmental and regolith breccia clasts separated from two Chang'e‐5 (CE‐5) soil samples, CE5C0000YJYX03501GP and CE5C0400, which provide an opportunity to investigate the compositional change of regolith at the landing site through time. Fragmental breccia CE‐5‐B3 contains a diverse range of basaltic clasts and basaltic mineral fragments, and some rare Mg‐suite‐like minerals. Regolith breccias CE‐5‐B006, CE‐5‐B007, CE‐5‐B010‐08, CE‐5‐B010‐09, CE‐5‐B011‐07, and CE‐5‐B016‐03 contain mare basaltic fragments, mare vitrophyric clasts, rare Mg‐rich fragments possibly derived from the Mg‐suite rocks, and impact‐derived glass spherules. Pb‐isotope data obtained for baddeleyite grains found both inside some of the basaltic clasts identified in breccia fragments and in the breccia matrices yield Pb/Pb dates similar to the 2 Ga crystallization age of the CE‐5 basalt fragments, extracted directly from the soil sample. Seventy‐four Pb isotope analyses of Ca‐phosphate grains also indicate that the majority of these grains have Pb/Pb dates of 2 Ga, suggesting that they originate from the CE‐5 basalts. In addition, a Pb–Pb isochron drawn through analyses of four Ca‐phosphates in breccia CE5‐B006 yielded an intercept corresponding to a date of 3871 ± 46 Ma, which is the best possible estimate of the formation age of these four grains. Electron probe microanalysis shows that the breccias contain components similar to CE‐5 mare basalt fragments extracted directly from the soil sample, implying that the fragmental and regolith breccia fragments are mostly composed of material sourced from the underlying basalts. The general absence of impact melt breccia clasts, along with the general lack of Fe–Ni metal and absence of added meteoritic debris all suggest that the regolith at the CE‐5 landing site is immature and dominated by material mixed together by small local impact cratering events. Trace element analyses show that the glass beads in the regolith breccias have a Th abundance of 4.06–5.28 μg g−1. This is similar to the Th content of the regolith above the Em4 unit at the landing site as measured from orbit, as well as the estimated bulk Th content of CE‐5 basalts, suggesting that Th of the local regolith is predominantly sourced from the underlying mare basalts, without significant Th addition from Th‐rich exotic clasts sourced from evolved lunar lithologies. [ABSTRACT FROM AUTHOR]

We present a new set of reference materials, the ND70‐series, for in situ measurement of volatile elements (H2O, CO2, S, Cl, F) in silicate glass of basaltic composition. The materials were synthesised in piston cylinders at pressures of 1 to 1.5 GPa under volatile‐undersaturated conditions. They span mass fractions from 0 to 6% m/m H2O, from 0 to 1.6% m/m CO2 and from 0 to 1% m/m S, Cl and F. The materials were characterised by elastic recoil detection analysis for H2O, by nuclear reaction analysis for CO2, by elemental analyser for CO2, by Fourier transform infrared spectroscopy for H2O and CO2, by secondary ion mass spectrometry for H2O, CO2, S, Cl and F, and by electron probe microanalysis for CO2, S, Cl and major elements. Comparison between expected and measured volatile amounts across techniques and institutions is excellent. It was found however that SIMS measurements of CO2 mass fractions using either Cs+ or O− primary beams are strongly affected by the glass H2O content. Reference materials have been made available to users at ion probe facilities in the US, Europe and Japan. Remaining reference materials are preserved at the Smithsonian National Museum of Natural History where they are freely available on loan to any researcher. [ABSTRACT FROM AUTHOR]

The new mineral calcioveatchite, ideally SrCaB11O16(OH)5·H2O, is a Ca-Sr-ordered analogue of veatchite. It was found at the Nepskoe potassium salt deposit, Irkutsk Oblast, Siberia, Russia in halite-sylvite and sylvite-carnallite rocks, with boracite, hilgardite, kurgantaite, hydroboracite, volkovskite, veatchite, anhydrite, magnesite, and quartz. Calcioveatchite forms prismatic or tabular crystals up to 1 × 1.5 × 3 mm3 and crystal clusters up to 3 mm across. It is transparent and colourless with vitreous lustre. Calcioveatchite is brittle, cleavage is perfect on {010}, the Mohs' hardness is ca 2, Dmeas is 2.58(1), and Dcalc is 2.567 g cm−3. Calcioveatchite is optically biaxial (+), α = 1.543(2), β = 1.550(5), γ = 1.626(2), 2Vmeas = 30(10)°, and 2Vcalc = 35°. The average chemical composition (wt.%, electron microprobe, H2O calculated by stoichiometry) is: CaO 7.05, SrO 20.70, B2O3 61.96, H2O 10.22, and total 99.93. The empirical formula, calculated based on 22 O apfu = O16(OH)5(H2O) pfu, is Sr1.23Ca0.78B10.99O16(OH)5·H2O. Calcioveatchite is monoclinic, space group P21, a = 6.7030(3), b = 20.6438(9), c = 6.6056(3) Å, β = 119.153(7)°, V = 798.26(8) Å3, and Z = 2. Polytype: 1M. The strongest reflections of the powder XRD pattern [d,Å(I,%)(hkl)] are: 10.35(100)(020), 5.633(12)(110), 5.092(10)(120), 3.447(14)(060), 3.362(13)(101, 051), 3.309(38)(–102), 2.862(10)(012), and 2.585(19)(080). The crystal structure was solved based on single-crystal XRD data, R1 = 0.0420. Calcioveatchite (calcioveatchite-1M) is an isostructural analogue of veatchite-1M with the 11-fold cation polyhedron occupied mainly by Sr [Sr0.902(8)Ca0.098(8)] whereas the 10-fold polyhedron is Ca dominant [Ca0.686(7)Sr0.314(7)]. The chemical composition of veatchite from five localities in Russia (Nepskoe), Kazakhstan (Shoktybay and Chelkar in the North Caspian Region), and the USA (Tick Canyon and Billie Mine in California) was studied, and it is shown to exist in nature as a continuous, almost complete isomorphous series which extends from Ca-free veatchite, Sr2B11O16(OH)5·H2O, to calcioveatchite with the composition Sr1.14Ca0.87B10.99O16(OH)5·H2O. [ABSTRACT FROM AUTHOR]

The ultramafic rock located on the northern slope of Lüliang Mountain in the northwestern region of North Qaidam Orogen is altered to serpentinite. The occurrence of disseminated chromite within the serpentinite holds significant implications for understanding the petrogenesis of the protolith. This work provides strong evidence of a distinct zonal texture in the chromite found in the ultramafic rock, using petrographic microstructure and electron probe composition analysis. The core of the chromite is characterized by high contents of Cr#, with enrichment in Fe3+# (Fe3+/(Cr + Al + Fe3+)) and depletion in Al2O3 and TiO2. The Cr2O3 content ranges from 51.64% to 53.72%, while the Cr# values range from 0.80 to 0.84. The FeO content varies from 24.9% to 27.8%, while the Fe2O3 content ranges from 5.19% to 8.74%. The Al2O3 content ranges from 6.70% to 9.20%, and the TiO2 content is below the detection limit (<0.1%). Furthermore, the rocks exhibit Mg# values ranging from 0.13 to 0.25 and Fe3+# values ranging from 0.07 to 0.12. The mineral chemistry of the chromite core in the ultramafic rock suggests it to be from an ophiolite. This ophiolite originated from the fore-arc deficit asthenosphere in a supra-subduction zone. The estimated average crystallization temperature and pressure of the chromite are 1306.02 °C and 3.41 GPa, respectively. These values suggest that the chromite formed at a depth of approximately 110 km, which is comparable to that of the asthenosphere. The chromite grains are surrounded by thick rims composed of Cr-rich magnetite characterized by enrichment in Fe3+# contents and depletions in Cr2O3, Al2O3, TiO2, and Cr#. The FeO content ranges from 28.25% to 31.15%, while the Fe2O3 content ranges from 44.94% to 68.92%. The Cr2O3 content ranges from 0.18% to 23.59%, and the Al2O3 and TiO2 contents are below the detection limit (<0.1%). Moreover, the rim of the Cr-rich magnetite exhibits Cr# values ranging from 0.90 to 1.00, Mg# values ranging from 0.01 to 0.06, and Fe3+# values ranging from 0.64 to 1.00, indicating late-stage alteration processes. The LA-ICP-MS zircon U-Pb dating of the ultramafic rock yielded an age of 480.6 ± 2.4 Ma (MSWD = 0.46, n = 18), representing the crystallization age of the ultramafic rock. This evidence suggests that the host rock of chromite is an ultramafic cumulate, which is part of the ophiolite suite. It originated from the fore-arc deficit asthenosphere in a supra-subduction zone during the northward subduction of the North Qaidam Ocean in the Ordovician period. Furthermore, clear evidence of Fe-hydrothermal alteration during the post-uplift-denudation stage is observed. [ABSTRACT FROM AUTHOR]

This manuscript presents the results from the synthesis and characterization of a slag analogue with a nominal composition of 17 wt% LiMnO2 and 83 wt% Ca2SiO4 encountering fairly high cooling rates in order to study the evolution of Mn-species. The Mn species was also simulated from 1223 K to 1773 K using a thermodynamic model, assuming a homogeneous melt. The micro-composition including the Mn species of the solidified slag was determined experimentally, and was used as basis for molecular dynamics (MD) simulation. The MD simulation provides information on structure and viscosity at high temperatures, which are otherwise difficult to access. These parameters significantly influence oxidation state of redox-active elements and the solidified product. The micro-composition analyzed by electron probe micro analysis (EPMA) and synchrotron-based micro-X-ray fluorescence (micro-XRF) showed that Mn-rich and Ca-Si-rich phases are separated. While the Mn-O phases did not contain noticeable Ca, the Ca2SiO4 phase had incorporated 0.6 wt% of Mn. The slag solidified into round-shaped and droplet-shaped grains of a Li-Mn-oxide, some Mn3O4 and Ca2SiO4. The powder X-ray diffraction (PXRD) confirmed the formation of larnite; the identity of the Li-Mn-oxide, however, remained inconclusive. The Mn oxidation state (OS) was identified using synchrotron-based micro-X-ray absorption near edge spectroscopy (micro-XANES). The Mn-O grains matched well with Li-Mn-oxides and a Mn OS: +3, e.g., LiMn3+O2. Small areas matching hausmannite (Mn2+Mn23+O4) were also identified. The OS of Mn in the silicate phase could not be identified. For comparison, a slowly cooled slag analogue with similar composition, but higher Si content, was also subjected to micro-XANES. The slowly cooled slag formed long Mn-rich needles in a matrix of large calcium silicate crystals. The Mn-rich crystals matched well with the XANES spectrum of a Mn3+ Li-oxide like LiMn3+O2. At the rim of the needles, the Mn-spectra matched well the hausmannite (Mn2+Mn23+O4) reference. In the silicate phases, Mn had an OS: +2, unambiguously. The melt structure at different temperatures of two compositions, i.e., LiMn3+O2 and Ca2SiO4, was simulated using molecular dynamics (MD). They serve as model compositions, assuming a heterogeneous melt. The results show significant different degrees of polymerization and viscosity. Information from MD simulations can support the identification of potentially different oxygen permeability and with that prediction of oxidation states. The bulk composition was identified by inductively coupled plasma optical emission spectrometry (ICP-OES), bulk structure by PXRD and bulk species by lab-XANES. The synchrotron micro analysis including micro-XRD were performed at the microfocus beamline I18 at the Diamond Light Source. Pure reference compounds were prepared and characterized with the same multi-modal approach. [ABSTRACT FROM AUTHOR]

Olivine is the most abundant mineral in mantle peridotite and a typical inclusion in diamonds, providing essential evidence for the characterization of the diamondiferous lithospheric mantle. Three olivine inclusions in diamonds (OlDia) from Liaoning in the North China Craton (NCC) were exposed for in situ measurements, and the compositional data of 62 other OlDia from Liaoning were collected based on previous reports. The enrichment of TiO2 (>0.1 wt.%) with high Cr# (>50; Cr# = 100Cr/(Cr + Al) by atom) was revealed, despite the predominance of depleted TiO2 contents and high Mg# (92.8–93.2; Mg# =100Mg/(Mg + Fe) by atom) for OlDia. Silica fluid accompanying olivine still trapped in the host diamond was recognized using Raman spectroscopy. Three thermometers were applied to the OlDia, based on the data from Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) and Electron Probe Micro-Analysis (EPMA), and a temperature range (TLA and TEPMA) of 1080–1380 °C was yielded. With respect to the TLA, Al-in-olivine thermometers were preferred, although there was a smaller deviation between TEPMA and TLA when using the Cr-in-olivine thermometer. The results of these thermometers show a high correlation with TEPMA, enabling their application based on EPMA data. Projections onto 39–42 mW/m2 model geotherms underline a diamondiferous base of the lithospheric mantle beneath the NCC. The lithospheric mantle is characterized by refractory and depleted sections, where enrichment metasomatism may have occurred at the lower roots (161–178 km). [ABSTRACT FROM AUTHOR]

The Sub-Antarctic South Atlantic Ocean has been inferred to have undergone a complex tectonic history involving dismemberment and plume-ridge interaction. Here we report new in situ major (electron probe microanalysis, EPMA), trace element (laser ablation–inductively coupled plasma–mass spectrometry, LA-ICP-MS), and Sr isotopic (laser ablation–multicollector–inductively coupled plasma–mass spectrometry, LA-MC-ICP-MS) compositions for minerals (olivine, clinopyroxene, and plagioclase) from the Northeast Georgia Rise (NGR; Sites 698 and 699), Islas Orcadas Rise (IOR; Site 701), and Meteor Rise (MR; Site 703) volcanic samples in the Sub-Antarctic South Atlantic Ocean. Plagioclases and clinopyroxenes from Sites 698, 699, and 703 are characterized by similar incompatible element patterns and Sr isotopic characteristics, suggesting that they are likely to have originated from a cogenetic mantle source. The plagioclases and clinopyroxenes exhibit an oscillatory, reverse, and normal zoning texture, and display clear evidence of Sr isotopic disequilibrium, suggesting dynamic and open fractional-crystallization processes as well as extensive mixing of compositionally distinct magmas. Rims and groundmass of plagioclase exhibit much more highly radiogenic Sr isotopes than their cores, likely indicating the involvement of both continental lithospheric and recycled oceanic crust. The in situ geochemical and isotopic compositions of these minerals exhibit the features of both the oceanic-island basalt–type TristanGough mantle plume track and the normal mid-oceanic-ridge basalt–type Mid-Atlantic spreading ridge (MAR) and Agulhas spreading ridge (AR) track. We speculate that the NGR, IOR, and MR were formed from the same mantle source with volcanic flow of the Tristan-Gough mantle plume. Subsequently, tectonic movement along the MAR and AR separated the originally combined MR-IORNGR, resulting in the incursion of depleted asthenospheric mantle and the contamination contributions of continental and recycled oceanic crust components. [ABSTRACT FROM AUTHOR]

In this study, severe cracking occurred during an investigation of the direct hot rolling of industrial electrolytic nickel plates. To determine the cause of hot-rolling cracking, the microstructure phase composition was analyzed through the utilization of various techniques, including optical microscopy, scanning electron microscopy, electron backscattering diffraction, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) and electron probe micro-analysis. The comparative microstructural analysis took place between specimens heat treated in atmospheric and vacuum environments. The characterization and analysis of the hot-rolled plates considered the crack microstructure and fracture morphology. It was shown that holes appeared along the large angular grain boundaries after annealing at 1100 °C for 8 h. Possible reason: In a high-temperature environment, the decomposition of residual additives in the electrolytic nickel releases oxidizing gases, which oxidizes the grain boundaries. The reaction with carbon diffused into the grain boundaries and produced carbon monoxide gas, which induced holes and severely reduced the grain boundary plasticity. The heat treatment time did not need to be very long for severe grain boundary degradation to occur. After severe cavitation, the electrolytic nickel was severely cracked at grain boundaries cracks due to a shear force, and brittle fractures occurred along grains with very low plasticity. [ABSTRACT FROM AUTHOR]

In this study, single crystals of (K1−xNax)NbO3 are grown by the self-flux crystal growth method and their phase transitions are studied using a combination of Raman scattering and impedance spectroscopy. X-ray diffraction shows that single crystals have a perovskite structure with monoclinic symmetry. Single crystal X-ray diffraction shows that single crystals have monoclinic symmetry at room temperature with space group P1211. Electron probe microanalysis shows that single crystals are Na-rich and A-site deficient. Temperature-controlled Raman scattering shows that low temperature monoclinic-monoclinic, monoclinic-tetragonal and tetragonal-cubic phase transitions take place at −20 °C, 220 °C and 440 °C. Dielectric property measurements show that single crystals behave as a normal ferroelectric material. Relative or inverse relative permittivity peaks at ~−10 °C, ~230 °C and ~450 °C with hysteresis correspond to the low temperature monoclinic-monoclinic, monoclinic-tetragonal and tetragonal-cubic phase transitions, respectively, consistent with the Raman scattering results. A conduction mechanism with activation energies of about 0.5–0.7 eV was found in the paraelectric phase. Single crystals show polarization-electric field hysteresis loops of a lossy normal ferroelectric. The combination of Raman scattering and impedance spectroscopy is effective in determining the phase transition temperatures of (K1−xNax)NbO3. [ABSTRACT FROM AUTHOR]

Erionite is the name for a zeolite mineral series originating from diagenesis or hydrothermal alteration of volcanic rocks. The particular erionite "species" is based on the dominant extra-framework cation, erionite-Ca, erionite-K, or erionite Na. Irrespective of the species, erionite can display a fibrous/ asbestiform morphology and has been linked with cases of malignant mesothelioma, a disease typically associated with asbestos exposure. Characterization of new discoveries of erionite is therefore important to assess any potential exposure hazards. This study describes a new asbestiform erionite from vesicles within the Upper Cretaceous Mt. Somers Volcanics Group (MSVG), Canterbury, New Zealand. The erionite is within the Hinds River Dacite, the youngest unit within the MSVG at Gawler Downs, ~100 km west of Christchurch, in the foothills of the Southern Alps. A multi-analytical approach was taken to analyze the sample which included micro-Raman spectroscopy, thermogravimetric analysis, electron microscopy, electron microprobe analysis, and X-ray powder diffraction with the Rietveld method. Results confirmed the mineral as fibrous erionite-K. The chemical composition of the mineral is unique due to the presence of higher levels of Mg. While Fe was also identified, this was due to smectite flakes occurring on the surface of the erionite fibers. According to the World Health Organization (WHO) respirable mineral fiber definition, where length ≥5 μm. width ≤3 μm, and aspect ratio (L/w) ≥3:1, the Gawler Downs erionite fibers are respirable, while the fibers themselves exceed respirable thickness. In addition to morphology. a value for the potential toxicity model was computed to be 2.28 for the Gawler Downs erionite. This is similar to those of other carcinogenic erionites from Karain. Turkey (2.33). and Nevada. U.S.A. (2.28). Taken together. results indicate Gawler Downs erionite represents an environmental hazard. Nevertheless. further investigation is required to determine potential environmental exposure pathways by which erionite may become airborne and assess the actual environmental risk in the Gawler Downs area. [ABSTRACT FROM AUTHOR]