Composition Of Inclusions Research Articles

Исследование циклической трещиностойкости стали литых несущих деталей грузовых вагонов

Purpose: Carrying out complex experimental studies of cyclic crack resistance of molten steel which is used for load-bearing parts of freight wagon running systems with kinetic diagram building for fatigue failure. Methods: Method of mechanical testing of molten steel samples under cyclic loading conditions was applied, the method makes it possible to obtain quantitative estimates of stuff ability to resist fatigue failure on the stage of fatigue crack development (testing on cyclic crack resistance). To study the surface of fatigue failure, relief micrographic analysis was used. To study molten steel elemental composition and the mechanisms of fatigue crack development, X-ray micro-spectral analysis was used on fatigue failure various stages. Results: The results of the research of cyclic crack resistance of 20 GL molten steel, which is used for load-bearing parts of freight cars, are presented. Fatigue failure kinetic diagram has been built, detailed micrographic analysis of fatigue failure surface has been carried out and elemental composition of non-metallic inclusions has been studied. Practical significance: Based on the research results, it is possible to assess the performance of 20 GL steel with cracks and to predict survivability. The results obtained make it possible to improve the methods of resource projection of molten bearing parts for freight wagon running systems in order to increase their operational reliability. The research results are used by enterprises - manufacturers of molten parts to control technology stability and to improve product quality.

Analysis of Ancient Slag Inclusion-Metal Systems as a Method to Disclose Processing Thermo-chemical Parameters: The Case Study of a Medieval Lombard Steel Bar from Northern Italy

An archaeometallurgical characterization of a VI to VII century Lombard steel bar from Ponte di Val Gabbia I site (northern Italy) was performed to reconstruct its manufacturing process and extract processing thermochemical parameters (i.e., temperature and oxygen chemical potential) from the slag inclusion-metal systems. Metallographic observations by optical microscopy and Vickers microhardness measurements indicated that the steel bar was forged from a heterogeneous steel lump, most probably an iron bloom, which was cooled in the air after the forging process. The chemical composition of non-metallic inclusions was determined by scanning electron microscopy coupled with X-ray dispersive spectroscopy. A multivariate statistical analysis of the smelting-derived non-metallic inclusions chemistry allowed to conclude that the steel bar was obtained by the direct or bloomery method. Under the hypothesis of local near-equilibrium conditions for the slag inclusion-metal systems, a thermodynamic-based strategy was adopted to estimate the firing conditions in the bloomery furnace in terms of both temperature and oxygen chemical potential of the reducing gas atmosphere. In particular, the computed temperatures are in the range of 1003 °C to 1171 °C, whereas the values of oxygen chemical potential vary between − 447.47 and − 385.79 kJ/mol.

Re-evaluation of equilibrium relationships involving U6+/U4+ and Fe3+/Fe2+ in hydrothermal fluids and their implications for U mineralization

Uranium (U) and iron (Fe) are generally considered to have contrasting aqueous geochemical behavior, with U dissolution being favored in oxidizing fluids as oxidized U (U6+) and Fe in reducing fluids as reduced Fe (Fe2+) species. However, high concentrations of both U and Fe have been reported for the ore fluids of uranium deposits, suggesting that the two elements can be co-transported in the same fluid. In this study, geochemical modeling, based on recent thermodynamic and experimental data for U and Fe species and fluid inclusion compositions from two types of hydrothermal U deposits (volcanic-related and unconformity-related), was conducted to investigate the nature and conditions of UFe co-transportation. The results of the modeling indicate that high concentrations of U (>10, up to >100 ppm) and Fe (>1000 ppm) can be dissolved in acidic aqueous fluids (pH < ∼3.3) of moderate to high chlorinity (∼ 55 to 250 g/L Cl), for a wide range of logfO2 above and below the magnetite-hematite (MH) buffer (from ∼ MH-5 to MH + 30), at temperatures from 150 to 250 °C. There are four different combinations of dominant dissolved U and Fe species depending on the pH and redox conditions: U6+ and Fe3+ species (UO2Cl20 and FeCl30) at relatively high fO2, U4+ and Fe2+ species (UCl40 and FeCl42−) at relatively low fO2, and U6+ and Fe2+ species (UO2Cl20 and FeCl42−) or U4+ and Fe3+ species (UCl40 and FeCl30) at intermediate fO2 conditions. Because the most important U mineral in hydrothermal uranium deposits is uraninite (UO2), in which U is present as U4+, a necessary condition for U mineralization is that U is either transported as U4+ species or, if transported as U6+ species, precipitation of uraninite is induced by a reducing agent. The recognition that U6+ and Fe2+ species can be co-transported in the same fluid indicates that uraninite can be precipitated without the need to invoke a reducing agent external to the ore fluid. The driver of uranium mineralization in this case is an increase in pH due to fluid-rock interaction that leads to the alteration of the rocks by clay minerals and associated coupled sorption-reduction. These findings provide for a more extensive range of conditions for U transport and deposition than previously imagined and require that interpretation of the conditions of uranium mineralization consider both oxygen fugacity and pH. This study underscores the potential for uranium deposits to occur in geological settings where reducing agents are either absent or insufficiently abundant to account for the observed mineralization, and the possibility for the transport of U in environments that might otherwise be considered unfavorable.

A Thermodynamic Model to Predict the Composition of Inclusions in Al‐Killed Ca‐Treated Steels

Based on the principle of minimum Gibbs free energy, a thermodynamic model is established to predict the composition of inclusions in the Al‐killed steel during the calcium treatment process. The Wagner model combined with coexistence theory is applied to calculate the Gibbs free energy of the steel‐inclusion system. The composition evolution of inclusions is accurately predicted through the current thermodynamic model which is widely applied to predict the modification of inclusions by the calcium treatment process with different contents of total oxygen (T.O), total sulfur (T.S), and total calcium (T.Ca) in the molten steel. Alumina inclusions can be modified to liquid calcium aluminate inclusions with appropriate T.Ca contents. Solid CaS or CaO inclusions can be formed as a result of the excessive calcium addition to molten steel, while the insufficient calcium addition can hardly modify alumina inclusions to liquid ones. The effect of the T.O and T.S contents on the liquid window is also discussed. The relationship between the value of T.S/T.O in the molten steel and the composition of inclusions is also studied. Based on the established thermodynamic model, a software for the precise control of inclusions is also developed to guide the calcium treatment operation timely in the accrual refining process.

Inclusion analysis in a dual-phase automotive strip steel

ABSTRACT A holistic assessment of inclusions present within a cold rolled DP800 steel was performed. The assessment comprised a variety of methods including optical microscopy and image processing, alongside quantitative, statistical analysis. The ‘statistics of extreme values’ approach was applied, utilising outputs from microstructural analysis. A qualitative analysis followed via the use of SEM and EDS to determine the morphologies and compositions of inclusions within the material. This has allowed for cross-coil examination; identifying the variation in behaviour of inclusions through the width of a cold rolled strip, which can be correlated with slab solidification as well as final product performance. This understanding is also critical in informing sample extraction for microstructural characterisation and mechanical property assessments. The research has provided an accelerated methodology of inclusion analysis that can be applied to DP800 effectively, allowing for manufacture-microstructure relationships to be determined.

Effect of Bismuth and Telluride on the Inclusions of Sulfur Free-Cutting Steel

The development of free-cutting steel is inseparable from the development of environmentally friendly alloy elements and the control of inclusions shape. Alloying elements can affect the composition, morphology, size, and distribution of inclusion, which are the main factors affecting the machinability of free-cutting steel. This study selected sulfur free-cutting steel with different chemical compositions as the research object to examine the effects of bismuth and bismuth tellurium on sulfur-containing free-cutting steel through electrolytic corrosion experiments, metallographic microscopy, scanning electron microscopy, energy spectrum, and electron backscattering analyzer. The results showed that the microstructures of free-cutting-steel containing sulfur, free-cutting steel containing sulfur bismuth, and free-cutting steel containing sulfur bismuth tellurium are composed of ferrite, pearlite, and inclusions. The inclusions in sulfur-containing free-cutting steel are chain, cluster, and a few dotted MnS. The inclusions in sulfur-bismuth free-cutting steel are point and a few dotted MnS. After the addition of Te, the number of dotted inclusions is reduced, while the number of chain and cluster inclusions is increased. Most of the inclusions in bismuth-containing free-cutting steel are flake inclusions, and the class II MnS change into class III MnS, which is beneficial for improving the free-cutting property of steel and to reduce anisotropy. With the addition of Te, MnS of other shapes, such as heart, water drop, butterfly, etc. of a length–width ratio of less than 4 also appeared as MnS and MnTe complex inclusions, and the fusiform manganese sulfide accounted for most of the steel. Both Bi and Te had modification effects on MnS.

Modification of Rare Earth Ce on Inclusions in W350 Non-Oriented Silicon Steel

In this paper, the effect of rare earth Ce content on the morphology, composition, type and size distribution of inclusions in W350 non-oriented silicon steel was investigated by means of ICP-MS (inductively coupled plasma mass spectrometry), SEM/EDS (scanning electron microscope-energy Dispersive Spectrometer), and ASPEX (automated SEM/EDS inclusion analysis). The results showed that with the increase of Ce content in the steel, the modification sequence of inclusions was CeAlO3→Ce2O2S→CexSy. The type and size distribution of inclusions in the steel obviously changed with the difference in added Ce content. When the added Ce content in the steel was 10 ppm, 14 ppm, 20 ppm and 30 ppm respectively, the rare earth inclusions were mainly CeAlO3-Ce2O2S. Furthermore, when the added Ce content increased to 60 ppm, the rare earth inclusions were mainly Ce2O2S with a small amount of CeAlO3 contained in part inclusions. When the added Ce content increased continually to 95 ppm, the rare earth inclusions were mainly CexSy-Ce2O2S. The critical Ce content for the conversion between CeAlO3 and Ce2O2S was 41 ppm. To ensure that inclusions transform from CeAlO3 to Ce2O2S, the Ce content in the steel should be greater than 41 ppm. Under the current experimental conditions, it was found that when the Ce content was 20 ppm, the number density and proportion of inclusions in the steel were lower, and their average size was larger. When the added Ce content increased to 95 ppm, the number density of inclusions in the steel significantly increased, which deteriorated the steel cleanliness.

Deformation and mineralizing fluid circulation of gold-silver-bearing quartz veins in the Yushishan gold deposit, Altyn Mountain, northwestern China

Understanding the coupled process of deformed microstructure and fluid evolution of ore veins therefore provides insight into processes that influence mineralization distribution and its mechanism. Gold is often developed in quartz veins in many gold deposits. This paper presents detailed evidence for solid deformation, hydrothermal fluid, and mineralization in a fault-controlled gold-silver-bearing quartz vein from the Yushishan gold deposit, Altyn Mountain, NW China. Macro-and microstructure combined quartz crystal preferred orientation (CPO) unravel the ductile–brittle transition deformation of quartz veins formed at the deep crustal level ca. 9 ∼ 13 km and the deformation temperature ranging between 180 ∼ 381 °C. The homogenization temperatures and salinities of fluid inclusions change slightly, while the trapping pressure of fluid inclusions has a large fluctuation of ca. 125 ∼ 275Mpa. HO isotopes and the composition of fluid inclusions decipher the source of ore-forming fluid mainly related to the regional magmatic-metamorphic event. Combined with the fluid immiscibility that is evidenced by different types of fluid inclusion coexistence characteristics and the pH increase induced by CO2 degassing in an inhomogeneous fluid system, it is suggested that an obvious fluid overpressure and rapid decompression occur during Au deposition from the quartz vein. The seismically fractured opening and healing of rocks during ductile–brittle deformation controls the formation of the mineralization and fluid circulation. There has positive feedback between the fluid overpressure evolution, strain localization and mineralization through time. The channelized and circulated fluid flow triggered extensive veining, mineral growth, and connections with fluid reservoirs.

A Possible Natural and Inexpensive Substitute for Lapis Lazuli in the Frederick II Era: The Finding of Haüyne in Blue Lead-Tin Glazed Pottery from Melfi Castle (Italy)

The blue color of glass and ceramic glazes produced in Apulia and Basilicata (Southern Italy) between the 13th and 14th centuries and connected to the Norman-Swabian Emperor Frederick II, has been, for a long time, under archaeometric investigation. On the one hand, it has usually been associated with lapis lazuli, due to the finding of the polysulphide blue chromophores typical of lazurite. Moreover, the observation that the mineral haüyne, which belongs to the sodalite group as well as lazurite, can be blue and/or can gain a blue color after heating, due to the same chromophores, has caused this automatic attribution to be questioned, and also considering that the mineral is characteristic of the rock haüynophyre of Melfi (Potenza, Southern Italy), a location of interest for glass and pottery findings. In this paper, for the first time, several haüyne crystals were found in the blue glaze of a ceramic dish found at Melfi Castle, leading to the hypothesis that, in this case, the local haüyne-bearing source could have been used as the coloring raw material. The discovery was possible thanks to SEM-EDS and Raman analyses that, respectively, highlighted the typical numerous presence of very fine sulphur-based inclusions in the crystals and the characteristic Raman signal of blue haüyne. This study was also focused on the composition of the crystals inclusions, aided by SEM-EDS and Raman maps, since the original very fine pyrrhotite was transformed into Cu and Pb phases (copper sulphates, copper sulphides, and lead oxide) due to reactions with cations that had mobilized from the glaze, while the migration of Si from the glass allowed the transformation of the rim of the haüyne, a silica-undersaturated mineral, into a corona of small euhedral and neomorphic Pb-rich feldspars, a silica-saturated phase.

Ore-forming materials and fluids and ore-controlling factors of the Liaoshang gold deposit in Jiaodong Peninsula, NE China

The Jiaodong Peninsula is the most important gold province in China, and the Liaoshang gold deposit represents a major recent prospecting breakthrough in Jiaodong.Based on detailed metallographic and microstructural observations, and He-Ar-Pb isotope compositions of fluid inclusions from main-ore-stage pyrite were presented, as well as the CO isotope compositions of main-ore-stage dolomite. Fluid inclusions from the pyrite have 3He = 1.18 – 8.69 × 10-14 cm3STP/g, 4He = 1.21 – 3.24 × 10-7 cm3STP/g, and 3He/4He = 0.12 – 0.81 Ra, and the ore-forming fluid was mainly crustal-sourced with mantle fluid input. The fluid inclusions have 40Ar = 5.42 – 1.87 × 10-7 cm3STP/g, 40Ar/36Ar = 328.5 – 511.3, close to saturated meteoric water 40Ar/36Ar value. It is speculated that the crustal-sourced ore fluid may have had meteoric water input in the mineralization. The main-ore-stage dolomite contains δ13C = -2.9 to −4.4 ‰ and δ18OV-SMOW = 10.5 to 11.3 ‰. It is speculated that the carbon was mainly deep magmatic fluid- or magma-sourced. The pyrite has 206Pb/204Pb = 17.244 – 17.416, 207Pb/204Pb = 15.448 – 15.462, 208Pb/204Pb = 37.824 – 37.950, and 206Pb/207Pb = 1.116 – 1.125, indicating that the ore-forming materials were derived from a crust-mantle-mixed source, which we considered to be the Linglong granite and the Jiaodong (or Jingshan) Group wallrocks. We conclude that the ore-forming fluids and materials at Liaoshang have multiple and complex sources, and that the Mesozoic tectono-magmatic activities have a clear control on the formation and distribution of the Liaoshang gold orebodies..

The obscuring effect of magma recharge on the connection of volcanic-plutonic rocks

Abstract The current debate on volcanic-plutonic connection is centered on whether efficient liquid-crystal segregation dominates the evolution of a mushy reservoir to produce evolved, crystal-poor rhyolite and cumulate leftover. However, magma recharge may remarkably influence the evolution of a mushy reservoir and obscure the evidence of liquid-crystal segregation. This complexity poses a challenge to exploring the connection of volcanic-plutonic rocks. This study investigates the Qinzhou Bay granitic complex (~250–248 Ma) from South China, which contains crystal-poor (&amp;lt;19 vol%) peraluminous rhyolites and subsequent crystal-rich (28–54 vol%) porphyries. Although the rhyolite and porphyry units have a close spatio-temporal link, they do not share a fractionation trend and similar whole-rock Sr-Nd-O isotopic compositions; thus, a direct connection is not evidenced. We further present textural analyses, mineral and melt inclusion compositions, thermobarometry (the combination of Ti-in-zircon thermometer and Ti-in-quartz thermobarometer), and thermodynamic modeling to examine the alternative interpretations, i.e., the two units may have intrinsically independent origins or the connection of the two units has been obscured. For the rhyolite unit, thermobarometric results reveal a polybaric storage system consisting of middle (&amp;gt;600 ± 80 MPa) and upper (~150 ± 40 and ~60 ± 20 MPa) crustal reservoirs. Variations in quartz Fe content and chlorine-rich, metaluminous melt inclusions suggest that magma hybridization with less-evolved metaluminous magmas occurred at both crustal levels. In particular, the elevated Fe contents in the quartz population that crystallized at the shallowest level (~60 ± 20 MPa) suggest that recharge magmas were directly injected into the shallowest reservoir. Deviation of the whole-rock composition from the liquid evolution trend recorded in melt inclusions suggests a combined effect of magma mixing and crystal-melt segregation processes in upper crustal reservoirs. Thermodynamic modeling and mass balance calculations suggest that the whole-rock composition of the rhyolite could be reproduced by mixing between regionally exposed dacites and segregated melts at crystallinities of 50–60% (using parental magma represented by the least-evolved melt inclusion). For the porphyry unit, thermobarometric results reveal magma storage at middle (more than 450 ± 40 to 550 ± 40 MPa) and upper (110 ± 20 to 140 ± 20 MPa) crustal levels. The small-scale oscillatory zonation of plagioclase, the pervasive resorption of quartz and alkali feldspar, and the presence of peraluminous microgranular enclaves in the porphyries suggest a recharge event of metasediment-sourced magmas, triggering reactivation and convection of the reservoir. Autoclastic and overgrowth textures of quartz, plagioclase, and alkali feldspar phenocrysts and development of columnar jointing suggest that the reactivated porphyritic magmas ascended and emplaced at ultrashallow levels (~30 ± 10 MPa). Because of the similar storage pressures, the porphyries may represent remobilized cumulates of rhyolitic magmas, whereas the texture and geochemistry of the cumulate-liquid pair were modified, a key factor rendering a cryptic connection between the rhyolite and porphyry. Alternatively, the plumbing systems feeding the rhyolite and porphyry units are horizontally independent or vertically discrete, but this circumstance is inconsistent with the same evolution trend of quartz Fe and Al contents of the rhyolite and porphyry. Our study highlights that whole-rock composition may record blended information of complex processes, and caution should be taken when whole-rock composition is used to extract information of a single process. Multi-method constraints are required to evaluate the influence of recharge processes on the modification of liquid-cumulate records, and big data analysis on the basis of geochemistry should be conducted with caution to avoid biased understanding.

Analysis of the evolution law of oxide inclusions in U75V heavy rail steel during the LF–RH refining process

Abstract The number density, size and composition of inclusions in U75V heavy rail steel during ladle furnace (LF)–RH refining process were studied by an Aztec-Feature inclusion automatic software which equipped with a field emission microscope. The results showed that the MnO–SiO2–Al2O3-type inclusions were the main inclusions at LF start. The MnO–SiO2–Al2O3-type inclusions were transformed into the CaO–SiO2–Al2O3-type inclusions during the LF refining process because of the Ca and Al elements which were brought by ferroalloy. At the RH start stage, the main inclusions were CaO–SiO2–Al2O3-type inclusions with low melting temperature and CaO–MgO–Al2O3-type inclusions with high melting temperature in the sample. And, the CaO–MgO–Al2O3-type inclusions were obviously removed during RH vacuum treatment. The average compositions of CaO–SiO2–Al2O3-type inclusions had no obvious change from RH vacuum holding for 15 min, RH vacuum break to RH soft blowing.

Ferro-chloro-winchite in Northwest Africa (NWA) 998 apatite-hosted melt inclusion: New insights into the nakhlite parent melt

Melt inclusions are of major significance because they can constrain the volatile abundances in magmas. Here, we report the discovery of the first melt inclusion in a martian apatite containing the first chloro-amphibole reported in Northwest Africa (NWA) 998, a sample that crystallized early from the nakhlite-source. The amphibole is also the first sodic-calcic amphibole in a nakhlite, identified as ferro-chloro-winchite (4.75 wt% Cl) by FIB-TEM. The melt inclusion is present in a euhedral, cumulus apatite grain (Cl/F = 2.11) and is surrounded by a shell of voids. Evidence indicates that the melt inclusion remained as a closed system although syn- and post-entrapment processes may have modified the chemical composition of the original trapped melt. The inclusion also contains Fe-rich, Ca-poor pyroxene and a residual silicate melt consisting of pyroxene and interstitial K-rich glass. Additionally, Cl-enriched apatite is present within the boundaries of the melt inclusion. This apatite could result from cracking of host-apatite during contraction of the melt inclusion glass or represent daughter apatite crystallizing on the walls of the inclusion. Given that Cl-enrichments are found in the host apatite outside the melt inclusion, it is inferred that a later, fluid alteration event locally modified the composition of the apatite in and/or around the melt inclusion. The calculated bulk composition of the melt inclusion is generally consistent with previous work in other nakhlites. Prior to this study, Cl-rich amphiboles have only been found within olivine- and pyroxene-hosted melt inclusions in the later-formed nakhlites. The present study thus demonstrates that (i) the nakhlites record magmatic mixing with a Cl-rich exogenous component that is absent within olivine-hosted melt inclusions in the chassignites, (ii) Cl-rich amphiboles were able to crystallize from the earliest nakhlite parent melt, and (iii) the presence of a Cl-rich fluid was not required to stabilize chloro-amphiboles. We also conclude that magmatic martian amphiboles likely stabilized at lower pressures (and temperatures) than terrestrial amphiboles due to their higher Cl contents.

Origin of nitrogen on Mars: First in situ N isotope analyses of martian meteorites

Martian meteorites are key for assessing the isotopic characteristics of nitrogen in different martian reservoirs (i.e., mantle, crust, and atmosphere), and, ultimately, for constraining the source(s) of nitrogen trapped during the earliest stages of planetary accretion in the terrestrial planet-forming region. In this study, we analysed, for the first time, the nitrogen content and isotopic composition of glassy melt inclusions of Chassigny and of the mesostasis of five nakhlites (MIL 03346, Nakhla, NWA 6148, NWA 998, and Y 000593) by in situ secondary ion mass spectrometry. The nitrogen content of Chassigny melt inclusions, corrected for olivine overgrowth on the inclusion walls, varies from 4 ± 1 to 860 ± 45 ppm N, and the majority of δ15N values range from –35 ± 41 to +73 ± 36‰. The estimated nitrogen isotopic signature of the primitive melt, prior to degassing of N2 or NH3, is 0 ± 32‰. The mesostasis of nakhlites contains 2.7 ± 0.2 to 943 ± 156 ppm N, with δ15N values from –30 ± 37 to +348 ± 43‰. Whereas degassing of N2 or NH3 can explain the lowest nitrogen isotopic ratios measured in the nakhlite mesostasis, the 15N-enriched isotopic composition (δ15N > 150‰) of four nakhlites (MIL 03346, Nakhla, NWA 6148, and Y 000593) likely results from interaction of the mesostasis melt with the martian atmosphere during ejection. The δ15N values (+25 ± 42 and +77 ± 19‰) of two melt inclusions in Y 000593 are comparable to those of Chassigny, further confirming that these meteorites likely sample a common volatile reservoir in the martian interior. Overall, the new results indicate that the chassignite-nakhlite reservoir did not inherit nitrogen from the solar nebula but, instead, from chondritic-like materials. These findings further confirm that planetary bodies in the inner solar system accreted (isotopically) chondritic nitrogen during the first few million years of solar system history.

H2O-Controlled Eruptive Filtering on the Bimodality of Continental Volcanism Across Tectonic Settings

Abstract The contemporary basaltic and rhyolitic volcanism with a dearth of intermediate compositions creates a compositional gap (‘Daly gap’), which is known to be pronounced in continental rifts/hotspots but absent in continental arcs. The intrinsic mechanism(s) producing the Daly gap remain poorly understood. Similar bimodal spectra recorded in melt inclusions from continental rifts/hotspots and arcs suggest that similar processes modulate the bulk composition of erupted magmas. A compiled data set of melt inclusion composition, phenocryst fraction, pre-eruptive temperature and melt H2O content enables precise calculations of melt viscosities and bulk magma viscosities for &amp;gt;100 eruptions of global volcanoes in various tectonic settings. Analyses of the data set suggest lower viscosities of rhyolitic melts in arcs than in rifts/hotspots (~104.5 ± 0.2 versus ~105.5 ± 0.2 Pa·s, respectively), at comparable temperatures, because of ~1.5 wt % higher melt H2O contents in arcs. Combining numerical constraints on ascent dynamics and data set observations, our study defines an eruption threshold of ~106.0 ± 0.3 Pa·s at the base of a volcanic conduit rooted in the subvolcanic reservoir. The lower viscosities of rhyolitic melts in arcs facilitate stirring/re-homogenization of upper crustal reservoirs upon recharge and accommodation of more phenocrysts in erupted products, leading to the common appearance of crystal-rich (30–50%) andesites and dacites (with rhyolitic interstitial melts) with mixing signatures in magmatic provinces of continental arcs. In contrast, the lower mixing efficiency and eruptibility of the more viscous magmas present in continental rifts/hotspots lead to preferential eruption of crystal-poor (&amp;lt;~30%) rhyolites, enhancing compositional bimodality in the erupted records. This H2O-controlled eruptive filter modulates the presence versus absence of the Daly gap and is key to the distinct differentiation patterns across tectonic settings.

Diamonds reveal subducted slab harzburgite in the lower mantle

AbstractCharacterizing compositional heterogeneity in Earth’s lower mantle is critical to understanding its dynamics. Three low-nitrogen diamonds from Koffiefontein (South Africa), containing inclusion assemblages of ferropericlase ± orthopyroxene ± magnesite, constrain diamond formation in an Mg-rich lower-mantle environment. Ferropericlase inclusions have Mg# 82.7–88.5 and orthopyroxene inclusions (retrogressed bridgmanite) have Mg# 95.0–95.1 and mantle-like δ18O of +5.6‰ ± 0.2‰. Magnesite included in one diamond implicates carbonated fluids in diamond formation. High Mg# and low Ca, Al, and Na of the assemblage indicate a melt-depleted meta-harzburgitic environment, in contrast to more fertile compositions expected for primitive lower mantle. Extremely low Ca in orthopyroxene inclusions may reflect a combination of melt depletion and low equilibration temperatures at the time of trapping. Inclusion compositions implicate subducted oceanic slab meta-harzburgite as the host for diamond growth. Mantle-like δ18O of the orthopyroxene inclusions indicates unaltered oceanic lithosphere. Similar melt-depleted characteristics in lower-mantle inclusion assemblages worldwide support that meta-harzburgite is the dominant host of lower-mantle diamonds.

Enhanced Mechanical Properties of CLAM by Zirconium Alloying and Thermo-Mechanical Processing

In this study, we present the effects of 0.004~0.098 wt% Zr and thermo-mechanical processing (TMP) on the microstructure and mechanical properties of the China RAFM steel, CLAM, as a feasibility study for improving mechanical properties. The inclusions in ingots were characterized using optical microscope (OM) and scanning electron microscope (SEM), which could be classified as fine simple particles and large complex particles. The complexity of the alloy’s inclusion composition increases with the increasing Zr concentration. The higher the Zr content, the more complex the composition of inclusions in the alloy. The average diameter of inclusions in 0.004Zr steel was the smallest, which was 0.79 μm and the volume fraction was 0.018%. The highest yield strength, tensile strength, elongation, and impact energy of 0.004Zr alloy at room temperature were 548.3 MPa, 679.4 MPa, 25.7%, and 253.9 J. The structure of the TMPed steels was all tempered martensite. With the increase in tempering temperature, the yield and tensile strength of the experimental steel gradually decreased, while the elongation and impact energy gradually increased. The 0.004ZrD and 0.004ZrH alloys had the best yield strength and impact energy, which were 597.9 and 611.8 MPa and 225.9 and 243.3 J, respectively. In addition, the alloys showed good thermal stability during the aging at 600 °C for 1500 h. It was discovered that TMP is a simple and practical industrial technique that could successfully enhance the mechanical properties of CLAM steel without sacrificing impact toughness.

Volcano–Plutonic Complex of the Tumrok Range (Eastern Kamchatka): An Example of the Ural-Alaskan Type Intrusion and Related Volcanic Series

Zoned plutons, composed of dunites, pyroxenites, and gabbroic rocks, have been referred to as the Ural-Alaskan type complexes (UA-complexes) and occur in numerous paleo-arc settings worldwide. Many of these complexes are source rocks for economic placers of platinum-group metals. Thus, it is important to understand how UA-complexes form and the origin and behavior of platinum-group elements (PGEs). It is widely assumed that the UA-complexes result from differentiation of supra-subduction high-Ca high-Mg sub-alkaline magmas. However, there is a lack of direct evidence for the existence and differentiation of such magmas, mainly because cases of UA-complexes being spatially and temporally linked to co-genetic volcanics are unknown. We studied an UA-complex from the Tumrok range (Eastern Kamchatka) where a dunite-clinopyroxenite-gabbro assemblage is spatially and temporary related to high-Ca volcanics (i.e., picrites and basalts). Based on the mineral and chemical composition of the rocks, mineral chemistry, and composition of melt inclusions hosted within rock-forming minerals, we conclude that the intrusive assemblage and the volcanics are co-genetic and share the same parental magma of ankaramitic composition. Furthermore, the compositions of the plutonic rocks are typical of UA-complexes worldwide. Finally, the rocks studied exhibit a full differentiation sequence from olivine-only liquidus in picrites and dunites to eutectic crystallization of diopside or hornblende, plagioclase, and K-Na feldspar in plagio-wehrlites and gabbroic rocks. All these results make the considered volcano–plutonic complex a promising case for petrological studies and modelling of UA-complex formation.

Concentration tensors preserving elastic symmetry of multiphase composites

The micromechanics of composites with multiple phases of different shapes embedded into a matrix phase, typically requires symmetrization strategies for their homogenized elasticity tensors, in particular so if the popular Mori–Tanaka estimate is employed. We here explore the implications of such symmetrization techniques, on the concentrations tensors, i.e. on the relations between macroscopic strains imposed onto a representative volume element of microelastic matter, and the microscopic phase strains developing across the materials’ microstructure. Thereby, we adopt the important idea of Mori and Tanaka to approximate the phase strains by the homogeneous strains inside an Eshelbian inhomogeneity embedded into an infinite matrix, together with the phase strains fulfilling the strain average rule; while we refrain from the identification of the strain in the matrix phase as the auxiliary strain imposed remotely at the infinite matrix of Eshelby’s matrix-inhomogeneity problem. Instead of this identification, we allow for a general multilinear relation between auxiliary strains and RVE-related macroscopic strains, and we express the homogenized stiffness as (i) a function of the conversion tensor quantifying the aforementioned multilinear relation, and (ii) as the symmetrized Mori–Tanaka estimate. In this way, the conversion tensor and all phase concentration tensors can be determined in a way which allows the overall elastic stiffness to remain symmetric. This is illustrated by means of two benchmark examples concerning matrix–inclusion composites hosting both spherical and prolate inclusions, with the matrices being isotropic and transversely isotropic, respectively. These examples benefit from analytical expressions for the Hill tensor governing the underlying matrix-inhomogeneity problems.

Specific features of the microimpurity composition of chrome-spinel inclusions in diamonds from kimberlites of Sakha-Yakutia

Specific features of the microimpurity composition of chrome-spinel inclusions in 323 diamond crystals from eight kimberlite pipes of two diamond-bearing regions of Yakutia were revealed by microprobe analysis. Processed data on their content of the Ni, Zn, V, Mn, and Si impurities are presented. It is shown that chrome-spinels in diamonds from the kimberlite pipes of the different regions are characterized by different contents of the impurity elements. The revealed differences in the composition of chrome spinel inclusions in the diamonds, as well as in the defect-impurity composition of the hosting diamonds, from the different, including neighboring, kimberlite pipes of Yakutia, are evidence of a local heterogeneity in the mantle composition within a certain kimberlite field. These data confirm the opinion of most researchers on heterogeneity of the mantle composition in different regions of the Yakutian diamondiferous province.