Pressure Melting Research Articles

A modified Steinberg–Cochran–Guinan model applicable to solid–liquid mixed zone along the principle Hugoniot

A constitutive model is vital for describing the deviatoric stresses of metallic materials under intense impact loading. Although the classical Steinberg–Cochran–Guinan (SCG) model has been widely regarded as an acceptable scheme, it does not clearly describe the coupling effect of the strain hardening and temperature softening at high temperatures and pressures, especially for the solid–liquid mixed phase. In this work, a modified SCG (MSCG) model is proposed based on an idealized assumption that the shear modulus and yield strength are equal to zero at the complete melting temperature and pressure. The temperature-dependent shear modulus model is then introduced in the MSCG model. The proposed model avoids the over-temperature softening effect by discarding the linear temperature term. More importantly, the pressure–temperature coupling factor (k) is employed in the pressure term, and the k adjusts the coupling effect of the strain hardening and temperature softening. In addition, the asymmetric relation in the MSCG model indicates that the temperature softening effect is more dominant than the strain hardening effect during the whole shock loading process. Moreover, the MSCG model is compared with the SCG model, Li and Chen's SCG model, and available data; the comparison verified the ability of the model to reproduce the shear moduli and yield strengths of Al, Be, Cu, and W in the solid–liquid mixed phase.

First demonstration of high current canted-cosine-theta coils with Bi-2212 Rutherford cables

Future high energy physics colliders could benefit from accelerator magnets based on high-temperature superconductors, which may reach magnetic fields of up to 45 T at 4.2 K, twice the field limit of the two Nb-based superconductors. Bi2Sr2CaCu2O8-x (Bi-2212) is the only high-T c cuprate material available as a twisted, multifilamentary and isotropic round wire. However, it has been hitherto unclear how an accelerator magnet can be fabricated from Bi-2212 round wires and whether high field quality can be achieved. This paper reports on the first demonstration of high current Bi-2212 coils using Rutherford cable based on a canted-cosine-theta (CCT) design and an overpressure processing heat treatment. Two Bi-2212 CCT coils, BIN5a and BIN5b, were made from a nine-strand Rutherford cable. Their electromagnetic design is identical, but they were fabricated differently: both coils underwent heat treatment in their aluminum–bronze mandrels, but unlike BIN5a that was impregnated with epoxy in its reaction mandrel, the conductor of BIN5b was transferred to a 3D printed Accura Bluestone mandrel after the heat treatment, a process attempted here for the first time, and was not impregnated. BIN5a reached a peak current of 4.1 kA with a self-field of 1.34 T in the bore. This corresponds to a wire engineering current density (J e) of 912 A mm−2, which is two times that of BIN2-IL, a previous Bi-2212 CCT coil fabricated at LBNL, which used a six-around-one cable processed with the conventional 1 bar pressure melt processing. On the other hand, BIN5b reached 3.1 kA. The coils exhibited no quench training. All the quenches were thermal runaways that occurred at the same location. In addition, we report on the field quality and ramp-dependent hysteresis measurements taken during the test of BIN5a at 4.2 K. Overall, our results demonstrate that the CCT technology is a route that should be further investigated for making high field, potentially quench training free dipole magnets with Bi-2212 cables.

Again About the "Magmatic" Nature of Topaz Crystals From Chamber Pegmatites of Volyn (Ukrainian Shield)

Various aspects of the genesis of primary fluid inclusions (0.01-1.0 sometimes up to 2 mm) with a large number of mineral inclusions in topaz crystals from chamber pegmatites of Volyn were analyzed. The data could be interpreted in two fundamentally different ways. The first argues for crystals grown in a magmatic melt; the second for an aqueous solution, with a density close to critical. The essence of the discrepancy is the reliability of the identification of the nature of mineral phases in the primary inclusions, if they are crystals captured during growth (xenogenic) or daughter crystals from the fluid. The xenogenic origin of the phases is indicated by the following observations: 1) The location of the mineral inclusions on the growing faces of the topaz crystals depends on the orientation of the crystal’s axis [001] relative to the horizontal plane. It determines the faces on which small mineral phases could be deposited from an aqueous suspension during the growth of topaz crystals. The studied crystals are dominated by individuals in which the mineral inclusions are located on the growing faces {011}, {021}, (001) (and others) of the crystal head. During growth, they were approximately in an upright position. 2) The filling of primary fluid inclusions is not constant. The volume of mineral phases in the inclusions varies from 40 to 95%, often 70-75%, the rest of the volume is gas and aqueous solution. Liquid-gas (liquids ˂ 40%) inclusions without or with < 5% solid phases are very rare. In addition, the ratio between the volumes of different mineral phases in the inclusions is not constant. 3) Light rims (Becke lines) around the inclusions record a change in the refractive indices (caused by a different chemical composition) of topaz when inclusions are acquiring the equilibrium form of the negative crystal. 4) The xenogenic nature of the mineral phases of the primary fluid inclusions in topaz is indirectly confirmed by the value of the fluid pressure (260-300 MPa)of the magmatic melt (determined by the method of homogenization of these inclusions), as it denies the possibility of chamber pegmatite formation at depths of 9-11 km. Thus, the peculiar mineral inclusions were deposited on the face of growing topaz crystals of small mineral phases from a turbid aqueous suspension, which boiled violently. We conclude that topaz crystals in chamber pegmatites of Volyn grew in aqueous solution at a temperature of 380-415ºС and a pressure of 30-40 MPa.

Variations of Source Composition and Melting Degrees of Olivine-Phyric Rocks from Kamchatsky Mys: Results of Geochemical Modeling of Trace Element Contents in Melts

We conducted the geochemical modeling of trace element contents for primary melts of olivine-phyric rocks from Kamchatsky Mys. This modeling reveals substantial chemical heterogeneity of their source while the average source composition is close to the enriched DMM (E-DMM). The average estimation of the melting degree is in the range from 9.1 ± 3.8% for the model of modal batch melting to 15.4 ± 5.2% for the model of accumulated fractional melting, which is slightly higher than the estimation for primitive mid-ocean ridge basalt (MORB) glasses (7.4 ± 2.2% and 12.5 ± 3.8% respectively). It is in a good agreement with high melting degrees estimated earlier for other rocks of the Kamchatsky Mys ophiolites. Low pressure of mantle melting caused by the elevated speed of decompression relative to the average MORB could explain elevated melting degrees estimated for Kamhcatsky Mys ophiolites as well as their characteristic Sr-anomalies and sulfide saturation on the earliest stages of magmatic evolution.

Microstructure and magnetic properties of Mn-Al-C permanent magnets produced by various techniques

Bulk Mn52Al46C2 in τ-phase was prepared by vacuum induction melting and used as precursor for the production bulk permanent magnets by suction casting and hot-extrusion. Part of the precursor alloy was mechanically milled into a τ-phase powder and used as precursor for production of samples by electron beam melting, hot-compaction and high pressure torsion processes. The microstructure and magnetic properties of all samples were investigated and correlated. It was found that the mechanical deformation enhances coercivity, up to 0.58 T, while the absence of this strain is beneficial for magnetization. Among the observed techniques, hot extrusion and high pressure torsion have shown promising possibilities to further develop Mn-Al-C as permanent magnets. However, it should be taken into account the challenges related to design a proper processing window for hot extrusion and the limitation of HPT regarding the absence of texture.

Atomization mechanism and powder morphology in laminar flow gas atomization

Metal powders prepared by laminar flow gas atomization have the advantages of small particle size and narrow particle size distribution. At present, the research on laminar flow gas atomization mainly focuses on the influence of process parameters on atomization and powder characteristics, but the atomization mechanism of laminar flow gas atomization is still not clear. In this work, the atomization gas flow, primary and secondary breakup mechanism, and particle morphology of the laminar flow gas atomization process are systematically investigated through numerical simulation and experimental analysis. The characteristics of single-phase atomization gas flow through the De Laval nozzle are studied using the standard <i>k-ε</i> turbulence model. The flow field structure shows a “necklace”-like structure with an expansion wave cluster of oblique shock. The primary and secondary atomization mechanism are investigated using the coupled level-set and volume-of-fluid model, which is validated by solidified fragments and powders after the atomization experiment, and results of the numerical simulation also provide some important advices for the application and specific process of laminar gas atomization technology. The studies indicate that the melts at the periphery of the liquid column are mainly peeled off by filaments or ligaments, which exhibits the small dimension and pressurized melt atomization characteristics. The secondary atomization is mainly based on the disintegration of spherical droplets in the mode of Rayleigh-Taylor instability deformation and sheet-thinning breakup. The simulation results also show that increasing the gas pressure and melt superheat can effectively reduce the probability of irregular powders to occur. The AlSi10Mg powders are obtained under a pressure of 2.0 MPa in the experiment on gas atomization, and the properties of the powders are analyzed. The results show that the powders have good sphericity and flowability, and the proportion of hollow powders is very low. In addition, the mean particle size of the AlSi10Mg powders is 54.3 μm, and the yield of fine powders reaches 48.7%, which is greatly improved compared with the traditional gas atomization processes. Moreover, about 90% of the powders have particle sizes in a range of 30–100 μm, which indicates that a narrow particle size distribution can be obtained by the laminar gas atomization technology.

Molecular dynamics simulations of shock melting in single crystal Al and Cu along the principle Hugoniot

Shock melting in single crystal Al and Cu along the principle Hugoniot was investigated through molecular dynamics simulations. First, the GRAY equation of state (EOS) was employed to reproduce the melting curve, which aimed at obtaining the Simon melting equation. The accuracy and validity of Simon melting curve are evaluated by the first-order derivative of melting temperature with respect to pressure at zero pressure, initial and complete melting temperatures and pressures, which are in good agreement with the available data. Next, the specific melting volume and latent heat calculated by the Clausius-Clapeyron equation present a descending and ascending trend as pressure increases, respectively. Then it is assumed that the liquid fraction is a power law function of pressure, whose nonlinear increasing is featured by the symmetry. More importantly, the expression of second-order derivative of melting temperature with respect to pressure is deduced by the Clausius-Clapeyron relation and Simon melting equation, respectively. Specifically for the Clausius-Clapeyron relation, its application to solid-liquid phase transformation for Al and Cu is quite effective and the result of the second-order derivative at zero pressure is reasonably compatible with that calculated from the Simon melting equation, which manifests that this two methods can be verified mutually. Moreover, it further discusses that the change characteristics of Simon melting equation by virtue of its first- and second-order derivatives.

Heat capacities and thermal conductivities of palladium and titanium melts and correlation between thermal diffusivity and density of states for transition metals in a liquid state

The normal spectral emissivities at 807 and 940 nm, heat capacities at constant pressure and thermal conductivities of Pd and Ti melts were measured using an electromagnetic levitation technique in a static magnetic field. The static magnetic field suppresses the surface oscillation, translational motion, and convection flow on electromagnetically levitated samples. The convections in the levitated Pd and Ti melts were suppressed sufficiently for thermal conductivity measurement by the static magnetic field. The emissivities and heat capacities of Pd and Ti melts showed no temperature dependence within the experimental temperature region. The thermal conductivity of Pd melt was constant within experimental temperature region, on the other hand, the thermal conductivity of Ti melt increased with increasing temperature. The measured emissivity and thermal conductivity were compared with values evaluated by a free electron model such as Drude model and Wiedemann-Franz law. Based on the results, the correlation between density of states (DOS) at Fermi energy and thermal diffusivities for transition metals was discussed.

Effects of Native AlN Particles on Heterogeneous Nucleation in an Al-3Fe Alloy

The naturally formed inclusions in an Al-3Fe alloy were investigated using a pressurized melt filtration technique. Naturally formed AlN particles with a rodlike morphology and a size distribution between 200 nm and 4 µm coexist with the native Al2O3 particles in the Al-3Fe alloy. These native AlN particles were investigated with scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). A well-defined orientation relationship (OR) between AlN and α-Al was found from the AlN particle embedded in α-Al. A tilt angle of 5.8 deg was observed between {111}α-Al and {0001}AlN at the α-Al/AlN interface. The atomic matching for the α-Al/AlN interface was investigated by considering interfacial segregation on the AlN particles. The heterogeneous nucleation potency of the native AlN particles was investigated. Although these native AlN particles can nucleate the α-Al, the contribution is very small. This contribution reveals the heterogeneous nucleation of α-Al on the native AlN particles and the competitive relationship between the native Al2O3 and AlN as the nucleation substrates. The surface modification of the native AlN in Al alloys containing multiple alloy elements and the corresponding effects on the heterogeneous nucleation were preliminarily investigated.

Synthesis and Characterization of Polyester Derived from Renewable Source and its Application as Tackifiers Resins in Hot Melt Pressure Sensitive Adhesives (HMPSA)

AbstractGlycerol esters are synthesized from rosin of Elliottii type by different methodologies and characterized in relation to the most relevant properties that define their quality for use in adhesive formulations. The produced esters have different properties due to the different synthesis recipes, mainly in relation to the percentage of glycerol and the type of additive used in the esterification. However, all cases showed great potential to be used as tackifiers resins in hot melt pressure sensitive adhesives (HMPSA).

Slab-controlled progressive evolution of the Kudi back-arc ophiolite in response to the rollback of the Proto-Tethys oceanic slab, in Western Kunlun, NW Tibetan Plateau

Slab-derived components can significantly diversify subduction-related magmatism, for example, fore-arc ophiolites evolving from normal mid-ocean ridge basalts to fore-arc basalts and then to boninites. Here we show a progressive evolution of back-arc ophiolites controlled by slab-derived components but different from fore-arc ophiolites through studying the Kudi back-arc ophiolite in Western Kunlun, NW Tibetan Plateau. Our results reveal that the Kudi ophiolite was formed at 516–512 Ma in a back-arc setting in response to the rollback of the Proto-Tethys oceanic slab. The back-arc setting is supported by geochemistry of basalts (e.g., low Th/Nb and V/Ti ratios), low melting pressure (<10 kbar) revealed by amphibole geobarometer and low δ11B values (−19.1 to −8.1‰) of the mantle units. In such a scenario, the early-stage depleted Kudi basalts are characterized by depletions in light rare earth elements and enrichments in fluid-mobile elements, probably resulting from decompression melting of the primary back-arc mantle slightly modified by slab-derived fluids. Subsequently, partial melting of the back-arc mantle enriched by progressive addition of slab-derived sediments resulted in the formation of residual harzburgites and corresponding primary magmas that evolved into dunites, gabbros, quartz diorites and enriched pillow lavas. Additionally, both the residual harzburgites and cumulated dunites experienced minor impregnation of melts, without significant interstitial melt-crystal reactions. Compared with the early-stage depleted Kudi basalts, the late-stage enriched pillow lavas are characterized by enrichments in light rare earth elements and depletions in high field strength elements, typical arc affinities, confirming the addition of slab-derived sediments. Compared with typical fore-arc ophiolitic series, it is possible that there is a progressive evolution in back-arc basins in which a “new” enriched mantle source (corresponding arc basalts) modified by slab-derived sediments displaces an “old” depleted mantle source (corresponding basalts characterized by enrichments in fluid-mobile elements) modified by slab-derived fluids.

Mathematical modelling of supercritical fluid extraction of liquid lanoline from raw wool. Solubility and mass transfer rate parameters

A new mathematical model is presented for the supercritical fluid extraction of lanoline from wool using near-critical ethanol-modified CO2, using our previous experimental data. The model is intended to account for the extraction of lanoline at conditions well above its melting point (60–80 °C) and pressures up to 150 bar. The model parameters are a Henry-type fluid-to-liquid partition coefficient for lanoline, K = Cg/CL, and a fluid-side mass-transfer coefficient, kG. For Re ∼1, K is independent of velocity and wool packing density, but increases with pressure (K = 4 − 15 × 10−4). kG is found to be independent of temperature; it increases with velocity, decreases with pressure, and increases with wool packing density. The values found are kG = 5.66 × 10-6 m/s (70 bar) and kG = 1.51 × 10-6 m/s (150 bar).

Study on rheological properties of in-mold co-injection self-reinforced polymer melt

The injection molding filling process is a complicated non-steady-state, non-isothermal non-Newtonian fluid flow process and heat transfer process. With the development of polymer melt pressure, temperature, shear rate and other physical quantities during the mold filling process will affect the melt rheological properties. This research combines the injection molding visualization device and analysis method to collect real-time online parameters of the co-injection self-reinforced parts in the mold under different molding conditions. The distribution and change data provide an effective means for better characterizing the rheological properties of the polymer in the mold and the theoretical analysis of the mold filling rheology. This article starts with the basic equations of viscous fluid mechanics, draws on the establishment of the mathematical model of the filling process of the conventional injection molding, corrects and resets the basic assumptions and boundary conditions, and establishes a flow that can reflect the melt flow at the slender scale. The basic equation of scale effect is made in the process, and it is substituted into the simulation software for simulation analysis. The results show that there is no deviation in the overall structure of the model, but the parameters in the model should be variable factors that change with the change of the melt molding parameters. Therefore, we made a second correction to the variable parameters of the in-mold co-injection self-reinforced cross-scale viscosity model. Although there is a certain difference (12.62%) between the viscosity results obtained after the simulation and the measured values, it is compared with the conventional model deviation value of the model (101.25%) has been better improved, which can better achieve the purpose of simulation prediction.

Overview and outcomes of the OECD/NEA benchmark study of the accident at the Fukushima Daiichi NPS (BSAF), phase 2 – Results of severe accident analyses for unit 2

This is the second paper in a series of 3 in which results of severe accident analyses for Unit 2 of Fukushima Daiichi are presented, gained in phase 2 of the OECD/NEA project “Benchmark Study of the Accident at the Fukushima Daiichi Nuclear Power Plant (BSAF)”. Nine organizations of six countries (CNL Canada; CRIEPI, IAE, JAEA and NRA Japan; IRSN France; KAERI Korea; NRC/DOE/SNL U.S. and VTT Finland) submitted results of their calculated severe accident scenarios for Unit 2 of Fukushima Daiichi using different severe accident codes (ASTEC, MAAP, MELCOR, SAMPSON, THALES-KICHE).The present paper describes the findings of the comparison of the participants’ results for Unit 2 against each other and against plant data, the evaluation of the accident progression and the final status inside the reactors. Special focus is on reactor pressure vessel status, melt release and fission product behavior and release. Unit 2 specific aspects will be highlighted and points of consensus as well as remaining uncertainties and data needs will be summarized.

Temperature-pressure-composition model for melt viscosity in the Di-An-Ab system

A model for the viscosity (η) of melts in the system CaMgSi2O6-CaAl2Si2O8-NaAlSi3O8 (Di-An-Ab) based on data compiled from the literature is presented. The model is calibrated on 560 measurements of melt viscosity at 1 atm pressure on 40 individual melt compositions and 303 measurements obtained at high pressure on 18 melt compositions. The model is continuous and accounts for variations in melt composition (X), temperature (T) and pressure (P). At ambient pressure, the model spans 15 orders of magnitude of η, a T range of 933–2450 K, and reproduces the dataset well (RMSE = 0.26 log units). The high-P model is calibrated over a T range of 970–2470 K and pressures of 50 MPa to 13 GPa for viscosities of 10−1 to 1014.5 Pa s and reproduces the high-pressure dataset to within (larger) experimental uncertainties (RMSE = 0.35 log units). Used in conjunction with chemical proxies for melt structural organization (i.e. SM and NBO/T), the model illustrates the strong coupling between viscosity and changes in melt polymerization as a function of X and P. Di-An-Ab melts with SM values >25.34 have positive pressure coefficients and show a minimal to strong increase in viscosity with pressure. Model values of glass transition temperatures (Tg) (i.e. η ~ 1012 Pa s) range between 930 K and 1130 K at 1 atm; Tg values for highly polymerized melts are depressed by as much as 150 K at 5 GPa at elevated pressures but are higher for more depolymerized melts and higher P. Melt fragility (m) is only weakly affected by increased P as expressed by a slight decrease in m for the most fragile melts versus a slight increase for the least fragile melts. Activation energies (Ea) increase with rising P for depolymerized melts and decrease with rising P for polymerized melts with the crossover at SM = 25.34. Ea values increase at low T for all P conditions and the effects of P are most pronounced at lower T. Lastly, a comparison of the liquidus surface topology for the ternary system to the corresponding isokoms of viscosity shows the relative effects of composition and temperature on melt viscosity at liquidus conditions to be highly varied.

Geochemical Constraints on Mantle Melting and Magma Genesis at Pohnpei Island, Micronesia

The lithospheric mantle is of paramount importance in controlling the chemical composition of ocean island basalts (OIBs), influencing partial melting and magma evolution processes. To improve the understanding of these processes, the pressure–temperature conditions of mantle melting were investigated, and liquid lines of descent were modelled for OIBs on Pohnpei Island. The studied basaltic samples are alkalic, and can be classified as SiO2-undersaturated or SiO2-saturated series rocks, with the former having higher TiO2 and FeOT contents but with no distinct trace-element composition, suggesting melting of a compositionally homogenous mantle source at varying depths. Both series underwent sequential crystallization of olivine, clinopyroxene, Fe–Ti oxides, and minor plagioclase and alkali feldspar. Early magnetite crystallization resulted from initially high FeOT contents and oxygen fugacity, and late feldspar crystallization was due to initially low Al2O3 contents and alkali enrichment of the evolved magma. The Pohnpei lavas formed at estimated mantle-melting temperatures of 1486–1626 °C (average 1557 ± 43 °C, 1σ), and pressures of 2.9–5.1 GPa (average 3.8 ± 0.7 GPa), with the SiO2-undersaturated series forming at higher melting temperatures and pressures. Trace-element compositions further suggest that garnet rather than spinel was a residual phase in the mantle source during the melting process. Compared with the Hawaiian and Louisville seamount chains, Pohnpei Island underwent much lower degrees of mantle melting at greater depth, possibly due to a thicker lithosphere.

Causes of the Gloss Transition Defect on High-Gloss Injection-Molded Surfaces.

The gloss transition defect of injection-molded surfaces should be mitigated because it creates a poor impression of product quality. Conventional approaches for the suppression of the gloss transition defect employ a trial-and-error approach and additional equipment. The causes of the generation of a low-gloss polymer surface and the surface change during the molding process have not been systematically analyzed. This article proposes the causes of the generation of a low-gloss polymer surface and the occurrence of gloss transition according to the molding condition. The changes in the polymer surface and gloss were analyzed using gloss and topography measurements. The shrinkage of the polymer surface generates a rough topography and low glossiness. Replication to the smooth mold surface compensates for the effect of surface shrinkage and increases the surface gloss. The surface stiffness and melt pressure influence the degree of mold surface replication. The flow front speed and mold temperature are the main factors influencing the surface gloss because they affect the development rate of the melt pressure and the recovery rate of the surface stiffness. Therefore, the mold design and process condition should be optimized to enhance the uniformity of the flow front speed and mold temperature.

Partial melting of a depleted peridotite metasomatized by a MORB-derived hydrous silicate melt – Implications for subduction zone magmatism

Recent geodynamic models and geothermometers suggest that slabs in intermediate to hot subduction zone cross the water-saturated basalt solidus, indicating that hydrous silicate melts are important agents of mass transfer from slab to mantle wedge beneath arcs. Yet the effects of basaltic crust-derived hydrous melt fluxing on mantle wedge melting are poorly known. Here we present the melting phase relations of a depleted peridotite + a MORB-derived hydrous silicate melt at a melt:rock mass ratio of 0.1 and 0.05 (3.5 and 1.7 wt.% H2O, respectively) to simulate fluid-present partial melting of a depleted peridotite, which has been metasomatized by a hydrous silicate melt derived from subducting basaltic crust. Experiments were performed at 2–3 GPa and 900–1250 °C in a piston cylinder, using Au and Au75Pd25 capsules. Amphibole (7–10 wt.%) is stable up to 1000 °C at 2 and 3 GPa coexisting with an assemblage dominated by olivine and opx and with minor fractions of cpx and garnet at 3 GPa. The apparent fluid-saturated solidus of our bulk composition is located at 1000–1050 °C, coinciding with the exhaustion of amphibole at 2 and 3 GPa. Amphibole is exhausted between 0 and 5 wt.% melting at 2 and 3 GPa and dominates the melting reactions in this melting interval along with opx, generating SiO2 and Al2O3-rich, and FeO*- and MgO-poor primitive andesites under fluid-saturated conditions. The melting reactions during low-degree, fluid-saturated melting are incongruent, consuming opx and producing olivine + SiO2-rich melts and is observed over a wide range of starting compositions and pressures from this study and others. As extent of melting increases and the free fluid phase is consumed, a spectrum of basaltic andesites to basanites are produced. Comparison of experimental partial melts from this and other hydrous peridotite melting studies with natural primitive arc magmas suggests that melting of peridotites with varying bulk compositions but with 2.5 – 4.2 wt.% H2O can reproduce the major oxide spread and trends of primitive arc magmas globally. From this comparison, it is clear that differences solely in the pressure of hydrous mantle melting, where the partial melts are fluid-under saturated, can account for the first order trends observed in experimental and natural data, with differences in temperature and composition contributing to the compositional spread within these trends. The ubiquity of andesite genesis over a wide range of pressures and bulk compositions during aqueous fluid-saturated melting suggests that the relative rarity of primitive andesitic melt flux through the crust could be related to the fact that such melts are only produced at the base of the mantle wedge where temperatures are relatively low. As fluid-saturated andesitic melts ascend into the hotter core of the mantle wedge, they are likely consumed by higher-degree, fluid-undersaturated melting generating more common hydrous basaltic melts.

Controls of mantle source and condition of melt extraction on generation of the picritic lavas from the Emeishan large igneous province, SW China

Like many continental flood basalt (CFB) provinces in the world, the source mantle compositions and melting conditions for generation of the Emeishan CFB are highly debated. We have carried out an integrated Sr-Nd-O-Mg isotopic study of the Emeishan picritic lavas to evaluate possible effects of mantle heterogeneity on the magma composition. Moreover, we have used PRIMELT3 (Herzberg and Asimow, 2015) to calculate the primary magma compositions and melting conditions for these picritic lavas. Picrites from Maoniuping, Tanglanghe and Wuguijing exhibit depleted Sr-Nd isotopic compositions (87Sr/86Sri = 0.7038–0.7050; εNd = 0.27–3.89), normal mantle-like δ26Mg (−0.27 to −0.2‰) and δ18O (5.0–5.4‰), which can be explained by partial melting of plume materials with negligible contribution of sedimentary carbonates. The Wulongba picrites are characterized by depleted Sr-Nd isotopic compositions (87Sr/86Sri = 0.7041–0.7045; εNd = 2.57–2.85), slightly lower δ26Mg (−0.36 to −0.23‰) and higher δ18O (5.6–5.7‰), which were attributed to involvement of minor sedimentary carbonates (magnesite) in their mantle source. The calculated mantle potential temperatures for the Emeishan picrites range from 1516 to 1596 °C. The initial melting pressures range from 4 to 5 GPa. The final melting pressures for the Wulongba picrites (2–3 GPa) are lower than those for the Tanglanghe, Maoniuping and Wuguijing picrites (>3 GPa). This suggests that the Wulongba picrites were generated in shallower garnet-spinel transition zone of the upper mantle. Picrites from other three localities are entirely generated in garnet stability field of the upper mantle.

Mechanical properties of frozen mixed soils with different coarse-grained contents

For the purpose of investigating the mechanical properties of frozen mixed soils, a series of triaxial compression tests were conducted with the confining pressures ranging from 0.3 to 6.0MPa and coarse-grained contents from 100:0 to 100:80 at the temperature of -6°C. The experimental results indicate that the strength presents an increasing tendency at first and then decreases with increase of confining pressures, whereas appearing to downtrend with increasing coarse-grained contents. And thus the mechanical behaviours are analyzed in detail, including the stress-strain characteristics and strength criterion. Additionally, it is interpreted for the pressure melting phenomenon using the modified Mohr-Coulomb strength criterion. Finally, laboratory investigations demonstrate that different fractions of coarse grains have great influences on the mechanical features of frozen mixed soils.