Types Of Inclusions Research Articles

Optimization of Inclusion and Microstructure of As‐Cast Nonquenched and Tempered Steel F38MnVS with Trace Ce

Various techniques, such as optical microscopy, high‐temperature confocal laser scanning microscopy, scanning electron microscopy, electron backscatter diffraction, and thermodynamic calculations, are employed to analyze the optimization mechanism of Ce on the inclusions and microstructures in F38MnVS as‐cast samples. The results show that the addition of Ce inhibits MnS precipitation at the grain boundaries and significantly reduces the diameters and aspect ratios of the inclusions. After Ce treatment, a new type of composite inclusion appears in the steel. The modification of the inclusions by Ce promotes the optimization of the as‐cast microstructure during solidification, which mainly exhibits austenite grain refinement and polygonal ferrite formation in the grains. Based on the misfit degree theory, the refinement of the austenite grains is because of the nucleation of austenite grains facilitated by Ce2O2S and CeAlO3. The increased nucleation of the intragranular polygonal ferrite is mainly attributed to Ce2O2S, Ce2S3, CeAlO3, and VC, which can promote the nucleation of α‐Fe. Simultaneously, the addition of Ce reduces the phase transition temperature, increases the driving force of the phase transition, and increases the nucleation rate. This study's results can provide a reference for the application of Ce treatment in the preparation of nonquenched tempered steel for automobiles.

Effect of lanthanum on inclusions and solidification structure of alloy 800H

Alloy 800H is commonly used in high temperatures and corrosive environments due to its exceptional strength and resistance to high temperatures, but the ingots are prone to longitudinal cracking during the hot working process because of its coarse solidification structure. Based on the heterogeneous nucleation effect of rare earth inclusions, a strategy is proposed to refine the solidification structure of alloy 800H by La treatment to solve the crack problem. In this study, four kinds of alloy 800H ingots (0, 120, 260 and 470 ppm La) were prepared to investigate the effect of La on the solidification structure. After adding La, the types of inclusion were changed, and the modification path of inclusions was Al2O3 (0 ppm La) → LaAlO3 (120 ppm La) → LaAlO3·La2O2S and La2O2S (260 ppm La) → La2O2S and La2O3 (470 ppm La). After adding La, the inclusion morphology tended to be more spherical and the average size smaller. The lattice misfit calculation indicated that La-containing inclusions can serve as heterogeneous nucleation cores, and the number of effective heterogeneous nucleation also increased with La content increased. The columnar to equiaxed transition occurred early with La treatment, the ratio of the equiaxed zone increased from 2.1% to 36.5%, and the average equiaxed grain size decreased from 2.56 to 0.43 μm with La content increased from 0 to 470 ppm. The solidification structure of alloy 800H was significantly refined by adding La, and can thus provide a new strategy to solve the crack problem.

Validated kinetic modelling of ladle furnace process for predicting inclusions in API steel grade

A kinetic model of ladle furnace (LF) process is developed in C++ format using the FactSage database and ChemApp subroutines. The model considers all the process parameters such as ferroalloy and slag dissolution, wire additions, electrical arcing, steel/slag reactions, reoxidation due to slag eye opening, heat exchange between metal/slag, and refractory dissolution. Further, a correlation for inclusion removal rate was developed as a function of argon flow rate, using discrete phase method (DPM) in Computational Fluid dynamics (CFD). Lollypop samples from steel bath and slag samples were collected from the plant for API steel grade for chemical analysis and inclusion characterisation. At LF_in, the inclusions found were mostly alumina spinel with very low amount of Mg (∼3%), followed by spinel at intermediate stage having ∼15 wt. % of Mg and after Ca treatment, inclusions transformed into CaS and Calcium Aluminate type of inclusions. Overall inclusion weight fraction varied from 136 ppm at LF_in to 93 ppm at LF_out. The model calculations were found to give very good prediction for steel and slag chemistry, and inclusion global composition as compared to the plant results. Predicted temperature was found with an accuracy of ± 5 oC, while the calculated inclusion weight fraction was having an accuracy of ±12 ppm.

Characterization and 3D Reconstruction of the Crushing Behavior of SiO2–CaO–Al2O3–MgO Complex Inclusions in Spring Steel with High Basicity Slag Treatment

This article mainly studies the element content, phase composition, and fragmentation mechanism of SiO2–CaO–Al2O3–MgO composite inclusions that cause fatigue fracture of spring steel. The study found that the SiO2–CaO–Al2O3–MgO composite inclusions in the wire rod are not a homogeneous phase. According to the electron microscopy energy spectrum analysis results, although the SiO2–CaO–Al2O3–MgO composite inclusion is in the low‐melting‐point area of the phase diagram according to the component content ratio. However, field‐emission transmission electron microscopy analysis reveals that this type of composite inclusions includes MgAl2O4, CaAl2Si2O8, CaSiO3, MgSiO3, and a small amount of CaS. The Zeiss Crossbeam 550 electron microscope is used to conduct a three‐dimensional reconstruction analysis of this type of composite inclusions, which once again verified that the composition of this type of inclusions includes calcium silicate, MgAl2O4, MgO, and other phases. It is also found that there is a certain gap between the inclusions and the matrix, and the gap between the inclusions with high‐melting‐points such as MgAl2O4 and MgO and the matrix is more obvious. During the rolling process of SiO2–CaO–Al2O3–MgO composite inclusions, due to differences in hardness and deformation rate between different phases, the rolling process is deformed and fragmented for extended periods.

Effect of Ti–Mg–Ce Complex Deoxidation on the Inclusions and Mechanical Properties of S355 Steel

Oxide metallurgy technology not only refines the microstructure but also modifies the type, density, and size of inclusions. This study examines the impact of Ti–Mg–Ce composite deoxidation on the inclusions and mechanical properties of S355 steel used for heavy‐duty H‐beams. Compared to base alloy, Ti–Mg–Ce‐added alloy features a higher presence of inclusions such as MgO, TiN (containing Ce), TiOx, and TiS, except for SiO2, Al2O3, MnS, and MnO. Following Ti–Mg–Ce composite deoxidation, the number density of inclusions increases by 16.4%, and the equivalent diameter, length, and width of the inclusions decrease by 41.0%, 41.2%, and 37.9%, respectively. The length of large‐angle grain boundaries in the same area increases by 20%, and the average grain size reduces by 12.5%, resulting in an enhancement of yield strength by 23.6 MPa, tensile strength by 37 MPa, total elongation by 2.1%, and impact energy by 92 J. By employing Ti–Mg–Ce composite deoxidation to optimize inclusions and microstructure, the strength, plasticity, and toughness of the experimental steel are significantly improved.

Inverse problems of the wave equation for media with mixed but separated heterogeneous parts

In this article, the inverse problems for the wave equation in a medium in which multiple types of cavities and inclusion exist in a mixture are considered. From the point of view of the indicator function of the enclosure method, there are two types of heterogeneous parts: “minus group” and “plus group.” For example, cavities with the Dirichlet boundary condition belong to the minus group, while inclusions with smaller propagation velocity belong to the plus group. The heterogeneous part of the minus group gives a negative sign to the indicator function, and the heterogeneous part of the plus group gives a positive sign. In general, the presence of many types of heterogeneous parts causes cancelation of the sign of the indicator function. Such cases are referred to as “mixed cases.” Here, we consider the case that the shortest length obtained from the indicator function is attained only by heterogeneous parts of the same group. This case is called the “mixed but separated case,” and it is shown that the method of elliptic estimates developed by Ikehata works well. We also show that the case of a two‐layered background medium with a flat layer can be considered in the same way as the case of a homogeneous background medium.

On the formation of oxide inclusions in the high nitrogen chromium-manganese steel produced by the Wire and Arc Additive Manufacturing

Oxide inclusions significantly impeded the mechanical properties of the Wire and Arc Additive Manufacturing (WAAM) made high nitrogen Cr–Mn austenite stainless steels (HNSs). This paper focused on the inclusions' component, crystallization characteristics and formation mechanism. Results revealed that there are two types of inclusions: the round-shape nano-size inclusion (Type-I) and the micron-size island-shape inclusion (Type-II). The Type-I inclusion usually consists of the MnO particle or the combination of the MnO, Si-oxides and precipitations (MnS or Cr2N). Most of the Type-I oxide inclusion is located in the range between 300 nm and 700 nm,the number of Type-I oxide inclusion takes the main part of 69.7%.With higher content, smaller size and more even distributions, the isolated Type-I oxide inclusions would be beneficial to the mechanical properties owing to the Orowan strengthening mechanism. The Type-II inclusion is mostly composed of the MnO matrix and the coherent chromite spinel (MnCr2O4). In general, the larger the size, the more serious the negative impact on mechanical properties. And there was a strong negative correlation between the size and quantity of type II oxide inclusions. After heat treatment, abundant phase transformations occurred in the Type-II inclusions and some harmful phases (Sigma, MnS et cl.) were often found in or around the inclusions with specific orientation relationships. During deposition, the unstable droplet transformation and the trapped residual slag were the main causes for the inclusions in the molten pool.

Multistage fluid mixing events induced Sn polymetallic super-enrichment at Dulong in Yunnan Province, South China

Dulong Sn polymetallic deposit is a world-class skarn tin deposit situated at the Youjiang basin with a reserve of 0.4 Mt Sn at 0.56 %, 5.0 Mt Zn at 5.12 %, together with 7 kt In. The deposit predominantly occurs within the Neoproterozoic Xinzhaiyan Formation and is controlled by NS-trending faults. Based on elaborate field and petrographic observations, the Dulong Sn polymetallic deposit was divided into four mineralization stages: stage 1 (prograde stage), stage 2 (retrograde stage), stage 3 (quartz-sulfide stage) and stage 4 (carbonate stage). Tin mineralization primarily occurs as cassiterite during stage 2, with additional cassiterite-stannite formation noted in stage 3. Analysis of fluid inclusions across these stages reveals the evolutionary history of the mineralizing fluids and the precipitation mechanisms at Dulong. During stage 1, diopside hosts both daughter-bearing multiphase inclusions and vapor-rich inclusions. The daughter-bearing multiphase inclusions exhibit homogenization temperatures ranging from 510 to 574 °C and salinities between 44.7 and 49.6 wt% NaCl equiv., whereas the vapor-rich inclusions display homogenization temperatures of 573–586 °C and salinities from 2.9 to 4.0 wt% NaCl equiv., indicating a boiling fluid process. Cassiterite (stage 2) features primarily liquid-rich two-phase inclusions, with homogenization temperatures of 351–410 °C and salinities of 6.3–9.6 wt% NaCl equiv. These inclusions document the mixing of magmatic fluid with meteoric water, which is likely the principal mechanism driving initial tin mineralization. Similarly, the same type of inclusions is also recorded in cassiterite of stage 3. The homogenization temperature of the inclusions in cassiterite is 290–334 °C and the salinities of the inclusions is 3.4–8.4 wt% NaCl equiv. Comparatively, the temperature continued to decrease in stage 3, indicating that fluid mixing may have persisted during this stage which could also explain the occurrence of cassiterite and stannite in this stage. In addition, redox reaction where CO2 and/or As (III) serve as oxidants may also be another mechanism to exact cassiterite from ore-forming fluid. Our Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) data suggests that cassiterite of the Dulong deposit involves a variety of complex substitutional mechanism. Due to the differing geochemical properties of the elements and variations in their concentrations, there is an indication that two phases distinct mineralizing fluids may have been present. The varying geochemical properties and concentrations of elements such as Nb, Ta, Zr, Fe, In, and Ga align with microthermometric results, indicating a reduction in magmatic hydrothermal fluid contribution and/or a transition from high to low temperatures in the hydrothermal system. This variation is also likely attributable to fluid mixing processes.

Formation of the Lianhuashan Cu deposit in the southern Great Xing’an Range, NE China: Constraints from fluid inclusions, whole-rock geochemistry, zircon U–Pb geochronology, and H–O–S–Pb isotopes

The medium-sized Lianhuashan Cu sulfide deposit is located in the southern Xing’an Range of Inner Mongolia, NE China. The zoned massive sulfide vein ores are hosted mainly in the Permian Dashizhai Formation, and the ore veins are controlled by NW–NNW-trending structures. The ore-forming process comprises four stages: arsenopyrite–quartz (I); chalcopyrite–pyrite–quartz (II); pyrite–chalcopyrite–sphalerite–galena–quartz (III); and ore-barren sulfide–quartz–carbonate (IV). Three types of fluid inclusions (FIs), namely vapor-rich two-phase (LV-type), liquid-rich two-phase (VL-type), and daughter mineral-bearing three-phase (SL-type), are distinguished. Stage I, II and III contain all types of FIs (LV-, VL-, and SL-type), with homogenization temperatures (Th) of 268–462°C, 230–382°C and 180–340°C and salinities of 3.4–52.3, 3.4–44.5 and 3.7–39.9 wt% NaCl eqv., respectively, whereas stage IV has only VL-type FIs, with Th = 152–232°C and salinity = 3.4–7.9 wt%. Fluid geochemical data show that the Lianhuashan ore fluids were of medium–high temperature (236–382 °C), high-salinity (31.5–44.5 wt%), and relatively oxidizing conditions, typical of a NaCl-H2O system. The microthermometric and H–O isotope data (δ18OH2O = − 9.0 to 6.1 ‰; δD = − 149.0 to − 99.0 ‰) indicate that the ore fluids were initially magmatic with later meteoric water incursion. The sulfide S (δ34S = − 2.9–3.8 ‰) and Pb (206Pb/204Pb = 17.954 − 18.492, 207Pb/204Pb = 15.427 − 15.739, 208Pb/ 204Pb = 37.815 − 38.357) isotopes support that the metals were magmatic-derived. Fluid boiling, cooling, and meteoric water mixing were likely the main ore precipitation mechanism at Lianhuashan.We suggest that Cu minerals at Lianhuashan were precipitated with boiling at ∼ 1km depth. For the ore-forming granodiorite porphyry (zircon U-Pb age: 252.8 ± 1.8 Ma), geochemical data indicate that the primary magma was formed by partial melting of the thickened or delaminated lower crust. Integrating the available age, geological, and geochemical evidence, we suggest that mineralization at Lianhuashan is spatial–temporal and genetically associated with the granodiorite porphyry, and was formed in a volcanic arc setting after the Paleo-Asian Ocean closure.

METALLOGRAPHIC ANALYSIS OF NON-METALLIC INCLUSIONS IN SEMI-KILLED STEEL (GRADE 25G2S) DEOXIDIZED WITH A COMPLEX ALLOY Fe-Si-Mn-Al

This study presents a metallographic analysis of non-metallic inclusions in steel samples obtained from six different heats of the oxygen converter shop at JSC «Qarmet» and under laboratory conditions at the Karaganda Industrial University. The investigation focused on semi-killed steel samples deoxidized using traditional technology under industrial conditions and with a complex alloy containing Fe-Si-Mn-Al under laboratory conditions, aiming to identify the types and assess the level of contamination by non-metallic inclusions. The results revealed the presence of various types of non-metallic inclusions, such as corundum, chromite spinel, chromium oxides, as well as titanium nitrides and carbonitrides. The degree of contamination by non-metallic inclusions ranged from 2 to 3 points. The analysis showed that the use of a complex Fe-Si-Mn-Al alloy instead of traditional deoxidizers can affect the quantitative and qualitative composition of non-metallic inclusions. It was established that the complex alloy promotes the formation of more stable inclusion phases, which can positively impact the mechanical properties of the steel. It was also found that different production technologies and the use of deoxidizers can significantly influence the quantity and types of non-metallic inclusions, requiring further study and optimization of technological processes. Therefore, the results of this study can be valuable for metallurgical enterprises in selecting optimal steel deoxidation methods and improving steel quality, as well as for further scientific research in the fields of metallurgy and materials science.

Understanding the Hydrocarbon Accumulation Process in Deep–ultradeep Oil and Gas Reservoirs in Complex Structural Areas—The Qixia Formation in the Shuangyushi Structure in Northwestern Sichuan Basin, China

Deep-ultradeep oil and gas reservoirs in complex structural areas have typically undergone multistage tectonic processes that have a considerable influence on the hydrocarbon composition, isotopic composition, and other geochemical characteristics of petroleum. By assessing the charging period of hydrocarbon accumulation during a particular age we can determin these changes. We studied the characteristics of fluid inclusions developed in the dolomite reservoir in the Middle Permian Qixia Formation in the Shuangyushi structure of the northwestern Sichuan Basin using methods such as inclusion petrography, microbeam fluorescence fluorescence spectroscopy, and inclusion homogenization temperature. Furthermore, the main peak wavelength of the fluorescence spectrum, red–green ratio/chromatic parameter, Q650/500, as well as the chromatic parameter corresponding to emission flux at 535 nm (QF535) and their correlations with the homogenization temperature distribution, were used to identify the charging period of hydrocarbons in the Qixia Formation. The results show that different types of fluid inclusions were developed in the Qixia Formation. The fluorescence of hydrocarbon inclusions is mainly blue, with a small amount of yellow–green and orange–yellow. The max of orange–yellow, yellow–green, and blue fluorescence of the hydrocarbon inclusions range between 562 ∼ 579 nm, 497 ∼ 548 nm, and 447 ∼ 497 nm, respectively. The distribution of the homogenization temperatures during the same period ranges from 100 °C to 110 °C, from 120 °C to 140 °C, and from 160 °C to 170 °C, respectively. By combining the burial and thermal evolution histories of the Qixia Formation, we concluded that the Qixia Formation has experienced three stages of oil and gas charging, with the time of 204, 185 and 158 Ma. This method is of great significance to determine the date and duration of oil and gas accumulation, and provides technical support for the recovery of ultra-deep hydrocarbon accumulations in complex structural areas.

PECULIARITIES OF CRACK FORMATION IN HETEROPHASE INCLUSIONS OF THE “EUTECTICS OF INCLUSION − MATRIX” TYPE

Purpose. The goal of the work was to study the peculiarities of crack nucleation in heterophase inclusions of the “eutectic inclusion − matrix” type during steel deformation. Methods. The research was carried out after deformation of samples from steels 08Yu, 12GS, 08kp, 09G2S, NB-57, 08GSYUTF in the temperature range of 20…1 200 °C with the speed of movement of grips 1 680 mm/min. The research methods were used − petrography, micro-X-ray spectral analysis (Cameca MS-4, Nanolab-7), optical microscopy (Neophot-21). Results. It is established that the variety of phases that make up heterophase inclusions of the type “eutectic of inclusion − matrix” leads to their different behavior under conditions of plastic deformation. It is shown that the nucleation of brittle or viscous microcracks occurs along the internal interfacial boundaries between the metal matrix and the second phase of the eutectic. It is determined that the nature of cracks is determined by the level of plasticity of the inclusion phases and the deformation temperature. It is shown that the critical degrees of deformation of the samples, at the achievement of which there were noticeable microcracks along the internal interfacial boundaries, depend on the temperature and nature of the phases of inclusions “eutectic of inclusion − matrix”. It is established that the values of critical degrees of deformation determine the level of cohesive strength of the internal interfacial boundaries in heterophase inclusions “inclusion − matrix eutectic”. Scientific novelty. Peculiarities of microcracking nucleation in heterophase inclusions of the “inclusion − matrix eutectic” type have been established. It is shown that the nature of microcracks formed along the interfacial boundaries depends on the temperature, level of plasticity and conditions of combination of brittle and plastic phases in inclusions of the “eutectic of inclusion − matrix” type, as well as on the deformation temperature. It is shown that the critical degrees of deformation of steels, when microcracks occurred along the inner interfacial boundaries, determine the cohesive strength of these boundaries and depend on the temperature and nature of the phases of inclusions such as “inclusion − matrix eutectic”. Practical significance. The use of the results obtained will make it possible to develop technologies for producing steels with regulated types of heterophase nonmetallic inclusions, which will significantly increase their technological and operational characteristics, as well as prevent the formation of various kinds of defects during the processing of steels by pressure and the operation of products.

Fluid inclusions and H–O isotopes of the super-large Nanyangtian tungsten deposit in southeastern Yunnan, southwestern China

The Nanyangtian deposit is a super-large reduced skarn tungsten deposit located in the Laojunshan WSn polymetallic ore province in southeastern Yunnan (SW China). The deposit is represented by three flat-lying mineralized zones formed vertically by the replacement of limestone or minor calcareous schist. The tungsten orebodies are mainly stratiform, lenticular, and vein types, hosted in the Paleoproterozoic Nanyangtian Formation. Three mineral formation stages have been identified based on the mineral assemblages and vein crosscutting relationships (pre-, syn-, and post-ore). The Nanyangtian is a calcic skarn deposit, dominated by a grossular-diopside-tremolite-actinolite assemblage. Scheelite, pyrrhotite, pyrite, and chalcopyrite are the main ore minerals. Detailed petrographic observations show three types of fluid inclusions (FIs) in various hydrothermal minerals: liquid-rich two-phase (type-I), gas-rich two-phase (type-II), daughter mineral-bearing three-phase (type-III). Their homogenization temperatures (193–298 °C) and salinities (1.2–9.3 wt% NaCl eq.) indicate that the Nanyangtian ore-forming fluids were of medium to low temperature and low salinity compared to the statistical data from representative skarn tungsten deposits in South China. Laser Raman microprobe analysis of the FIs shows that the inclusions are dominated by H2O with minor CH4 and N2. The δD values (relative to Vienna-Standard Mean Ocean Water, VSMOW) of fluid inclusions and calculated δ18Owater values (relative to VSMOW) of the fluids in equilibrium with hydrothermal minerals are −105 to −69 ‰ and − 1.9 to 7.6 ‰, respectively. These oxygen–hydrogen isotopic compositions indicate that the ore-forming fluids were magmatic-derived, which may have metasomatized the Nanyangtian Formation carbonaceous calcareous rocks along interlayer structures to form the prograde skarn minerals. Then the fluids mixed with meteoric water migrated along faults to form the retrograde skarn and tungsten ore. Mixing of magmatic fluid with meteoric water is likely the main factor for the ore precipitation at Nanyangtian.

Is Governance Aligned with Rhetoric? Exploring the Board Composition of Leading Transnational NGOs

Transnational NGOs (TNGOs) often claim to speak and act on behalf of diverse communities, yet many are governed by boards that may not reflect the sector’s rhetorical commitments to inclusive governance. This apparent gap between rhetoric and practice has led to growing pressure for leading TNGOs to engage in governance reforms. This exploratory article evaluates the composition of the boards of 25 leading TNGOs in the United States with a combined 395 board members to assess the extent to which this rhetoric is associated with board composition. A latent class analysis of board member data measuring demographic, competency, and cognitive background indicators identifies a distinction between “inclusive” and “traditional” board types. We find that the inclusive board type is associated with rhetorical commitments to diversity, equity, and inclusion, whereas the traditional board type is not. We conclude with recommendations for research to inform TNGO governance reforms.

Prion protein pathology in Ubiquilin 2 models of ALS

Mutations in UBQLN2 cause ALS and frontotemporal dementia (FTD). The pathological signature in UBQLN2 cases is deposition of highly unusual types of inclusions in the brain and spinal cord that stain positive for UBQLN2. However, what role these inclusions play in pathogenesis remains unclear. Here we show cellular prion protein (PrPC) is found in UBQLN2 inclusions in both mouse and human neuronal induced pluripotent (IPSC) models of UBQLN2 mutations, evidenced by the presence of aggregated forms of PrPC with UBQLN2 inclusions. Turnover studies indicated that the P497H UBQLN2 mutation slows PrPC protein degradation and leads to mislocalization of PrPC in the cytoplasm. Immunoprecipitation studies indicated UBQLN2 and PrPC bind together in a complex. The abnormalities in PrPC caused by UBQLN2 mutations may be relevant in disease pathogenesis.

Investigating the broom-like inclusions in type Ib diamond single crystal synthesized by high pressure high temperature

The exceptional properties of diamonds enable diverse applications. However, the applications are significantly hindered by its inclusions. In this study, a specific type of inclusion, broom-like inclusions, has been investigated. The broom-like inclusions in diamonds were synthesized through various high-pressure high-temperature (HPHT) experiments. The synthesis methods were optimized by adjusting the metal catalyst composition, synthesis temperature, Mg(OH)2 content, and nitrogen getter (Ti). The broom-like inclusion morphology and composition were physically characterized and analyzed using various methods. Optical microscopy and SEM were utilized to characterize the morphology and shape of the inclusions, while Raman spectroscopy and Fourier Transform Infrared Spectroscopy were employed to analyze the influence of the defects on the properties of diamonds and investigate the composition of the broom-like inclusions. Gaseous inclusions emerged as crucial for broom-like inclusion formation. They probably originated from residual gases like H2 and CH4. The investigation of broom-like inclusions within diamond crystals has led to the development of various synthetic methods for producing inclusion-free crystals. The findings of this study offer valuable insights into the nature and origin of these inclusions in diamonds, as well as provide strategies to mitigate their formation during production.

Genesis and fluid evolution of the Hatu orogenic gold deposit in the West Junggar, Western China

The West Junggar in Xinjiang, western China, represents a significant gold mineralization belt hosting over 200 gold deposits, with the Hatu gold deposit being the largest among them. In this study, ore geology and fluid inclusion assemblages of quartz samples from the Hatu gold deposit were investigated in an effort to clarify the mineralization process and its relationship with the geodynamic settings. The mineralization process is delineated into early (pyrite-albite-quartz veins), middle-a (quartz-ankerite veins), middle-b (quartz-ankerite-sulfide-native gold veins), and late (quartz-calcite veins) stages. The early stage veins suggest a compressional setting while the middle-a and middle-b stage veins suggest a tensional shear setting. The late stage veins are typically filled fissures cutting through earlier veins. Scanning electron microscope-cathodoluminescence (SEM-CL) reveals that early stage quartz (Q1) exhibits concentric CL-oscillatory growth zoning, while middle-a stage quartz (Q2a) displays unidirectional zoning and ranges from CL-bright to CL-dark, middle-b stage quartz (Q2b) is CL-bright and weakly zoned, and late-stage euhedral quartz (Q3) shows sector zoning transitioning from CL-gray to CL-dark. Quartz that formed in these stages developed three types of fluid inclusions: pure CO2 (PC-type), CO2–H2O (C-type), and H2O–NaCl (W-type). The early stage quartz contains C- and W-type fluid inclusions homogenizing at 309–345 °C, while the late stage quartz contains only W-type fluid inclusions with homogenization temperatures of 164–229 °C. Microthermometry of fluid inclusion indicated the evolutionary of the metallogenic fluid from a high-temperature, CO2-rich, and minor CH4 metamorphic fluid to a low-temperature, CO2-poor meteoric fluid. From the early to middle-a stages, fluid boiling caused the unloading of ore-forming elements whereas fluid mixing led to the precipitation of polymetallic sulfides and gold in the middle-b stage. Trapping pressures in the middle-b stage were estimated using C-type inclusions, illustrating that gold mineralization took placed at depth of 8.0 km. We propose classifying the Hatu gold deposit as an orogenic deposit, originating from the collisional orogenesis between the Yili-Kazakhstan and Siberian continents in the Late Carboniferous.

Heteromeric amyloid filaments of ANXA11 and TDP-43 in FTLD-TDP type C

Neurodegenerative diseases are characterized by the abnormal filamentous assembly of specific proteins in the central nervous system1. Human genetic studies have established a causal role for protein assembly in neurodegeneration2. However, the underlying molecular mechanisms remain largely unknown, which is limiting progress in developing clinical tools for these diseases. Recent advances in cryo-electron microscopy have enabled the structures of the protein filaments to be determined from the brains of patients1. All neurodegenerative diseases studied to date have been characterized by the self-assembly of proteins in homomeric amyloid filaments, including that of TAR DNA-binding protein 43 (TDP-43) in amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with TDP-43 inclusions (FTLD-TDP) types A and B3,4. Here we used cryo-electron microscopy to determine filament structures from the brains of individuals with FTLD-TDP type C, one of the most common forms of sporadic FTLD-TDP. Unexpectedly, the structures revealed that a second protein, annexin A11 (ANXA11), co-assembles with TDP-43 in heteromeric amyloid filaments. The ordered filament fold is formed by TDP-43 residues G282/G284–N345 and ANXA11 residues L39–Y74 from their respective low-complexity domains. Regions of TDP-43 and ANXA11 that were previously implicated in protein–protein interactions form an extensive hydrophobic interface at the centre of the filament fold. Immunoblots of the filaments revealed that the majority of ANXA11 exists as an approximately 22 kDa N-terminal fragment lacking the annexin core domain. Immunohistochemistry of brain sections showed the colocalization of ANXA11 and TDP-43 in inclusions, redefining the histopathology of FTLD-TDP type C. This work establishes a central role for ANXA11 in FTLD-TDP type C. The unprecedented formation of heteromeric amyloid filaments in the human brain revises our understanding of amyloid assembly and may be of significance for the pathogenesis of neurodegenerative diseases.

Mechanical response and failure mechanism of circular inclusion embedded in brittle materials under dynamic impact

Inclusions are prevalent in both natural and synthetic materials. Gaining a comprehensive understanding of their dynamic response and interaction with the surrounding matrix is essential in fundamental mechanics and engineering applications. This study aims to achieve such understanding through theoretical analysis, experimental investigations, and numerical simulations, focusing on the dynamic destruction of inclusions and the underlying mechanisms. Firstly, the circumferential, radial, and shear stresses around elastic heterogeneous inclusions were derived by the wave function expansion and Duhamel integration methods. Subsequently, a set of experiments on sandstone specimens containing three types of inclusions (plaster, epoxy resin, cement) were conducted utilizing the Split Hopkinson Pressure Bar (SHPB) system in conjunction with high-speed photography and Digital Image Correlation (DIC) techniques to obtain the surface deformation of inclusion specimens. Eventually, a series of Finite Element Method (FEM) numerical simulations adopted suitable materials were also carried out to investigate the fracture process of inclusion and matrix under dynamic impact. The results demonstrate that the stress distributions and fracture mode of matrix and inclusion are highly dependent on the physical and mechanical properties of the inclusions and the surrounding matrix, specifically, density ρ, elastic modulus E, Poisson's ratio v, and strength. With an increase in the E and v, there is a reduction in the concentration of circumferential stress, while the radial and shear stresses experience an increase. The experimental and numerical results corroborated the theoretical findings and indicated that the localized dynamic stress concentrations induced by wave scattering around the inclusions directly dominated both local and overall specimen failure. Due to the dissimilarities in elastic parameters and strength between the inclusion and the matrix, the stress state of the inclusion and the interface is not homogeneous. Under dynamic loading, the weaker inclusion experiences tensile cracking at both ends of the loading, and as the mechanical properties (ρ, E, v, and strength) of the inclusion rise, a transition from tensile- hybrid-shear failure occurs within the inclusion. The findings of this study help us understand the dynamic failure mechanisms of dissimilar inclusions in brittle material.

Precious and Base Metal Minerals in Black Sands of the Egyptian Mediterranean Coast: Mineralogical and Geochemical Attributes

This paper investigates the mineralogical and geochemical characteristics, as well as the possible sources, of gold, silver, platinum group elements (PGE), copper, and lead found in the beach sands along Egypt’s Mediterranean coast. Using scanning electron microscopy and electron probe micro-analysis, this study determines the morphology and micro-chemistry of separated grains to assess their economic potential and how various minerals respond to different transport distances. The analysis reveals that gold grains are of high purity (94.11 to 98.55 wt.%; average 96 wt.% Au) and are alloyed with Ag (1.28–2.32 wt.%) and Cu (0.16–3.15 wt.%). Two types of gold grains were identified, indicating differences in transport distances. Variations in morphology, surface features, inclusion types, rims, and chemistry of the native metals, including gold grains, suggest differences in composition, weathering degree, transport distance, deposit types, and host rocks. The average Ag concentration in gold grains (1.86 wt.%) suggests a link to mesothermal or supergene deposits. Most silver, copper, and lead grains are spherical, with some variations in shape. Silver grains have 71.66–95.34 wt.% Ag (avg. 82.67 wt.%). Copper grains have 92.54–98.42 wt.% Cu (avg. 94.22 wt.%). Lead grains contain 74.22–84.45 wt.% Pb (avg. 79.26 wt.%). The identified platinum group minerals (PGM) belong to the Pt–Fe alloys and sperrylite, both of which are PPGE-bearing minerals. These metals likely originate from the weathering of upstream Nile tributaries surrounded by igneous and metamorphic rocks from Ethiopian and Central African regions, with a minor contribution from the Egyptian Eastern Desert Mountains.