Melt Separation Research Articles

A New Method of Tungsten Extraction by Liquid Cathode Molten Salt Electrolysis-Zinc Melt Separation

A New Method of Tungsten Extraction by Liquid Cathode Molten Salt Electrolysis-Zinc Melt Separation

Fe, Zn, and Mg stable isotope systematics of acapulcoite lodranite clan meteorites

AbstractThe processes of planetary accretion and differentiation, whereby an unsorted mass of primitive solar system material evolves into a body composed of a silicate mantle and metallic core, remain poorly understood. Mass‐dependent variations of the isotope ratios of non‐traditional stable isotope systems in meteorites are known to record events in the nebula and planetary evolution processes. Partial melting and melt separation, evaporation and condensation, diffusion, and thermal equilibration between minerals at the parent body (PB) scale can be recorded in the isotopic signatures of meteorites. In this context, the acapulcoite–lodranite meteorite clan (ALC), which represents the products of thermal metamorphism and low‐degree partial melting of a primitive asteroid, is an attractive target to study the processes of early planetary differentiation. Here, we present a comprehensive data set of mass‐dependent Fe, Zn, and Mg isotope ratio variations in bulk ALC species, their separated silicate and metal phases, and in handpicked mineral fractions. These non‐traditional stable isotope ratios are governed by mass‐dependent isotope fractionation and provide a state‐of‐the‐art perspective on the evolution of the ALC PB, which is complementary to interpretations based on the petrology, trace element composition, and isotope geochemistry of the ALC. None of the isotopic signatures of ALC species show convincing co‐variation with the oxygen isotope ratios, which are considered to record nebular processes occurring prior to the PB formation. Iron isotopic compositions of ALC metal and silicate phases broadly fall on the isotherms within the temperature ranges predicted by pyroxene thermometry. The isotope ratios of Mg in ALC meteorites and their silicate minerals are within the range of chondritic meteorites, with only accessory spinel group minerals having significantly different compositions. Overall, the Mg and Fe isotopic signatures of the ALC species analyzed are in line with their formation as products of high‐degree thermal metamorphism and low‐degree partial melting of primitive precursors. The δ66/64Zn values of the ALC meteorites demonstrate a range of ~3.5‰ and the Zn is overall isotopically heavier than in chondrites. The superchondritic Zn isotopic signatures have possibly resulted from evaporative Zn losses, as observed for other meteorite parent bodies. This is unlikely to be the result of PB differentiation processes, as the Zn isotope ratio data show no covariation with the proxies of partial melting, such as the mass fractions of the platinum group and rare earth elements.

Trace element geochemistry of carbonatites and associated alkaline rocks of Mundwara Igneous complex, Sirohi district, Rajasthan, India

Carbonatites are widely recognized for their potential to host significant deposits of rare earth elements (REEs) and other rare metals. These igneous rocks, characterized by their high carbonate mineral content, are often rich in REEs, niobium, tantalum, and other valuable elements. This makes carbonatites key targets for mining and exploration. Carbonatites are believed to form from either primary carbonate magma derived directly from the mantle or from secondary melts. These secondary melts can originate from carbonated silicate magmas through liquid immiscibility or from the residual melts resulting from the fractional crystallization of silicate magmas. The coexistence of carbonatites and alkaline silicate rocks in most complexes, their coeval emplacement in many, and overlapping initial 87Sr/86Sr ratios supports the theory of their cogenesis. In this study, we aim to investigate the trace element geochemistry of carbonatites and coeval alkaline silicate rocks from the Mundwara Igneous Complex, Sirohi district, Rajasthan in India. Our trace element data indicate that the carbonatites and alkaline silicate rocks in this complex are products of fractional crystallization from two separate parental melts, formed through liquid immiscibility of a carbonated alkaline silicate magma.

Pulsatile extractions of Lower Cretaceous silicic volcanic plumbing system beneath the Baiyunzhang and Lianhuashan basins, eastern Guangdong: silicic magma evolution and related mineralization

Highly differentiated magmas are closely related to the formation of tin deposits. The Lianhuashan Basin and Baiyunzhang Basin, surrounded by multiple coeval tin deposits, developed various types of volcanic and subvolcanic rocks. The diagenetic connections between different types of rocks within the two basins provide new insight into the evolution of the silicic magma systems and the impact of highly differentiated magmas on tin mineralization. Both basins have consistent zircon U–Pb ages (143–138 Ma) and similar whole-rock Nd isotopes ( ε Nd ( t ) = −5.7 to −3.4) and zircon Hf–O isotope ranges ( ε Hf ( t ) = −9.0 to −2.5; δ 18 O = 5.1–7.9), suggesting that both basins originate from the same deep-level magma reservoir, followed by different degrees of crystal differentiation and several episodes of crystal–melt separation in their respective shallow-level magma reservoirs. The multiple pulses of magma extraction eventually produced different volcanic rocks (granite porphyry and rhyolite porphyry), whereas the remaining crystal mush consolidated in situ to form quartz monzonite porphyry. Further studies show that the tectonic regime changed from a compressive to an extensional environment at c . 140 Ma. Consequently, mantle-derived magmas with low oxygen fugacity injected shallow magma reservoirs that were able to evolve to a high degree of differentiation through multiple recharge, thus favouring the formation of the Sn deposit.

Influence of sequential melting and sintering process on morphology development and performance properties of ultra‐high molecular weight polyethylene/low‐density polyethylene blends

AbstractBlending ultra‐high molecular weight polyethylene (UHMWPE) with a low molecular weight polyolefin is a well‐established technique to improve its processability. The binary blends of UHMWPE and low‐density polyethylene (LDPE) were prepared with varying LDPE content (10%, 20%, 30%, 40%, and 50% by wt.) leading to the formation of a single polymer composite system (SPCS) as melting and sintering followed preferential stages during mixing. Interestingly, the sequence of either “melting followed by sintering” or “simultaneous sintering and melting” depends on the LDPE content in the blend, resulting in unique blend morphology. Separate melting peaks for the blend's constituents were observed in thermal characterization, showing the blend's immiscibility, while intermediate peaks showed moderate miscibility in the melt state. Due to the high entanglement density, UHMWPE retained a solid‐like structure and showed an intense viscous nature even above the melting point in rheological characterization. Typically, the UHMWPE samples are fabricated by boundary fusion between particles called sintering. At LDPE content higher than 30 wt.%, the sea island structure was visible in morphological analysis, and the preexisting cavities reduced the tensile modulus by 54% in the blend, along with decreased elongation at failure (250%–100%). Similarly, the flexural modulus was reduced by 34.7% in the blends, along with the decreased flexural strength. Interestingly, the decrease in performance properties occurred in two steps over the range of LDPE content. Thus, it was clear that 30 wt.% of LDPE in the UHMWPE/LDPE blend represented the critical concentration for controlling melting and sintering sequence to develop specified morphology and performance properties. These blends have the potential for biomedical application as well as for the development of foam products, which is the further scope of the present study.

The Role of Latent Heat Buffering in the Generation of High-Silica Rhyolites

Abstract The physical process of crystal-melt separation is responsible for the accumulation of small to very large volumes (>100 km3) of eruptible rhyolitic melt in the shallow crust. Granitic intrusions, although providing a terminal, time-integrated image of melt segregation processes, host an unmatched record of the physical properties controlling mechanisms and rates of interstitial melt extraction from a crystal-rich source. We applied mass balance calculations and thermodynamic modeling simulations to an extensive bulk rock geochemistry dataset (>150 samples) collected in a Permian upper-crustal granitoid intrusion of the Italian Southern Alps. Textural and geochemical evidence indicate that this intrusion constituted a single, zoned magma body, with a crystal-rich base and a thick (~2 km), high-silica cap (75–77 wt% SiO₂). The large compositional variability of the crystal-rich materials suggests variable degrees of melt extraction efficiency and corresponding terminal porosities. Specifically, the loosely bimodal distribution of porosity values (φ) indicates that at least two distinct melt segregation mechanisms were operating in this system, which produced both high (0.65–0.45) and low terminal porosities (0.45–0.25) in the crystal-rich, cumulate materials. Modeling of latent heat budget shows that coexistence of cumulate products with differing terminal porosity signature can be explained by melt segregation processes taking place at different depths across a thick, interconnected magmatic reservoir with an initial homogenous water content (~4 wt% H2O). Deep in the mush column, low water activities (aH₂O < 0.5) promoted thermal buffering of cooling magma at high crystallinities, enabling residual melt extraction by percolation through a crystalline framework accompanied by compaction. Instead, at shallower depths, high water activities (aH₂O > 0.5) ensured prolonged magma residence at porosities that promoted crystal melt separation via hindered settling. Distinct melt extraction processes, acting synchronously but at different depths in vertically extensive silicic mush columns, can account for the large volumes of residual, haplogranitic melt mobilized during the relatively short lifespan of upper crustal magma reservoirs (~105 years).

Scalable fabrication of multifunctional polylactic acid fibrous membranes with enhanced superhydrophobicity and radiative cooling performance

The disadvantages of traditional bio-based materials melt centrifugal spinning, such as low efficiency, long cycle and poor performance, limit its industrialization process. Herein, a scalable strategy was proposed for the fast and scale fabrication of bio-based melt centrifugal spinning fiber. The polymer melt was continuously transported to the high-speed rotating centrifugal disk, where it was rapidly conveyed and separated. The separated melt was then drawn and cooled by the synergistic supergravity and high-pressure cyclone field, resulting in formatting a nonwoven fabric by self-bonding alone with a diameter of ∼3 μm. Compared to conventional white CVC fabrics, the fabricated polylactic acid fibrous membranes demonstrated exceptional biocompatibility (cell viability of 98.7%), radiative cooling properties and favorable emissivity (94.1%), which can reduce the covered object temperature by 4.6 °C during hot summer. Furthermore, the water vapor transmission rate, moisture regain, water absorption, and boiling water shrinkage rate of PP20/8-F are 39.98 g m−2 h−1, 2.31%, 2.09%, and 8.11%, respectively, meeting the comfort requirements of wearable fabrics. The robust superhydrophobicity with a water contact angle of 153 ± 1° provides excellent antifouling and self-cleaning properties. This novel bio-based material melt centrifugal spinning method provides a viable strategy for the industrial preparation of high-performance and functionalized fibrous.

Silicate melt immiscibility as the cause of large-scale rare-metal mineralization in a peralkaline granite system: The case of the Baerzhe deposit in NE China

The Early Cretaceous peralkaline Baerzhe pluton hosts a potentially large REE-Nb-Zr-Be deposit in inner Mongolia, northeastern China. The mechanism responsible for the extreme enrichment of rare metals and rare earth elements in the pluton is still ambiguous. This study presents new evidence for silicate melt immiscibility as the key mechanism at Baerzhe using amphibole-group minerals from spherulite granite, which contains spherulites with abundant REE- and HFSE-bearing minerals. The spherulite from the transsolvus granite is composed of two distinct zones, i.e., a dark-colored core consisting of arfvedsonite aggregates and a light-colored rim consisting mostly of quartz and feldspar, rare amphibole, and abundant HFSE- and REE-bearing minerals. Four types of amphibole (AmpI, Amp-IIa, Amp-IIb and Amp-III) from the transsolvus granite and one type (Amp-IV) from the subsolvus granite are recognized, and all of them are magmatic fluoro-arfvedsonite. The earliest phase consists of euhedral inclusions of Amp-I within quartz or feldspar. They show an enrichment in HREEs relative to LREEs and a depletion in medium REEs, consistent with the REE pattern controlled by the mineral lattice. This implies that Amp-I likely formed in an initial homogeneous mel relatively depleted in REEs; thus, the mineral structure played a dominant role in REE partitioning. Compared with other types of amphiboles, Amp-IIa and Amp-IIb from the spherulite phase display the highest REE contents, with flat LREEs and MREEs and a slight upward HREE pattern. Combined with the significant accumulation of REE- and HFSE-bearing minerals in the rim zone, differences in REE patterns among different amphibole types imply that the spherulite crystallized in a volatile-rich silicate melt and was probably the product of silicate melt immiscibility. Interstitial Amp-III with lower REE contents from the matrix phase crystallized in the separate volatile-poor silicate melt. The Amp-IV from the subsolvus granite has the lowest CaO content, with strong depletion in LREEs relative to HREEs, suggesting a more evolved melt composition. It is concluded that silicate melt immiscibility may serve as an important key mechanism that occurred in the early stage of magmatic evolution, resulting in the enrichment of REEs and HFSEs, which played a critical role in the formation of large to giant ore deposits such as the Baerzhe deposit.

Early Triassic S-Type Granitoids in the Qinzhou Bay Area, South China: Petrogenesis and Tectonic Implications

The influence of the paleo-Tethys or paleo-Pacific oceanic plate subduction on Early Triassic South China has long been debated. We have studied the zircon U-Th-Hf isotopes, trace elements, and whole-rock geochemistry of Early Triassic peraluminous granitoids in the Qinzhou Bay area, South China Block. LA–ICP–MS zircon U–Pb dating has revealed the Jiuzhou granodiorites and Dasi-Taima granite porphyries formed between 248.32 ± 0.98 and 246.6 ± 1.1 Ma. These rocks are characterized by high K2O and Al2O3, and low MgO, CaO, and P2O5 contents with A/CNK = 1.06–1.17, showing high-K calc-alkaline S-type affinities. The Early Triassic intrusive rocks and adjacent silicic volcanic rocks in the Qinzhou Bay area were found to be comagmatic and derived from a common magma pool, detached in an undifferentiated melt instead of indicating remarkable crystal—melt separation. Although the analyzed granitoids have highly enriched zircon Hf isotopic compositions (εHf(t) = −23.9 to −7.8), they cannot originate solely from metasedimentary protoliths. Source discrimination indicators have revealed enriched lithospheric mantle-derived magma was also an endmember component of the S-type silicic magma, which provided a heat source for the crustal anatectic melting as well. We inferred the studied Early Triassic granitoids formed under the paleo-Tethys tectonic regime before the collision of South China and Indochina blocks, as the oceanic plate subduction would have created an extensional setting which further caused the mantle-derived upwelling and volcanic eruption.

The origin, conditions and mechanism for the formation of alpine-type hyperbasites of the Lesser Caucasus

The problem of hyperbasites origin is one of the widely discussed topics in geology. This is because they often appear when no expected. Their development does not correspond to the general regularities of the geological complexes’ development. Therefore, when problematic instances of hyperbasites appear, discussion is inevitable. This is due to the imperfections of existing concepts, which are not without flaws. The essence of this concept lies in the fact that during the rotation of the Earth around its axis, geodynamic forces are formed. The hyperbasites complex by its nature belongs to deep igneous formations formed at the initial stage of development of volcano-plutonic processes, where the composition of magmatic products was not subject to decomposition. In general, the origin of igneous rocks is associated with deep anomalous processes, which were formed under the influence of geodynamic forces, where decompression of mantle matter occurs, causing a catastrophic increase in the volume of mantle matter, as well as the associated development of volcanoplutonic processes. Hyperbasites are formed both in divergent and convergent zones of the Earth’s crust. The main factor for their formation is high pressure – deep thermodynamic conditions, where there are no favorable thermodynamic conditions for the complete separation of magmatic melts by composition. The emergence of hypermafic rocks on the surface is associated with geotectonic or denudation processes. Denudation processes can expose only those hypermafic formations that are located at the site of formation. These zones include ancient platforms, sheets, terranes, etc., which were cut by deep erosion processes. As for those hyperbasic formations that are classified as alpinotype hyperbasites, they were moved to the structure of the Alps-Himalayan folded zone from the basement with a collision with subsequent geotectonic processes, where they formed in the bed of the Paleotethys Ocean, both in the process of divergence and convergence. The noted pattern of formation and the mechanism of formation of alpine-type hyperbasites clearly corresponds to the patterns of development of geodynamic forces in the face of the Earth, also with natural laws, which are the main factors in the evolution of the Earth’s crust. From the standpoint of KDEZK, the origin, mechanism of formation, as well as the form of distribution of alpinotype hypermafic rocks of the Lesser Caucasus occurred in the Paleotethys bed, under different thermodynamic conditions and at depths. Further, as a result of the collision, it participated in the formation of folded zones of the Lesser Caucasus. Within the Lesser Caucasus, two genetic types of hypermafic rocks are exposed. Some of them correspond to the convergent zone of the Tethys paleocean, while others correspond to divergent zones. In terms of ore content, the most promising are those hypermafic rocks that are genetically related to convergent zones.

Needle Penetration Studies on the Dynamics during Internal Short Circuits in Automotive Lithium-Ion Cells: Measurement of Internal Temperature and Short Circuit Current

Lithium-ion batteries (LIBs) have been widely applied in consumer electronic devices and electric vehicles for energy storage. Especially for the battery electric vehicles (BEVs), it is desirable to increase the volumetric energy density of LIB cells due to the limitation of a further volumetric expansion of the battery pack, which amounts to currently 220-400 L depending on the size of the BEV [1]. As an example, the capacity of the Li-ion battery pack in BMW i3s has been improved from 60 Ah over 94 Ah to 120 Ah over the course of a few years. Along with this trend of increasing energy density, however, the reactivity of the cells is increasing. Therefore, the potential safety issues are becoming more important. Between 2015 and 2018, a total of 15 fire incidents of BEVs were reported in Europe. In 2019, 113 fire incidents took place only within China [2]. Considering the decision by the European Union to ban the sale of new petrol and diesel vehicles from 2035, this concern with regards to the safety of LIBs would be growing progressively with the accelerated switch to BEVs.One of the main causes for a thermal runaway is an internal short circuit (ISC) [1,3]. Under many different abuse scenarios, ISC appears to trigger the thermal runaway (TR); (i) mechanical abuse (deformation of separator leading to ISC),(ii) electrical abuse (separator pierced by dendrite resulting to ISC) or iii) thermal abuse (shrinkage or melting of separator causing ISC) [1]. Nail penetration tests have been widely used to reproduce ISCs. Only the temperature on the cell surface and the cell voltage are measured in a conventional nail penetration test. However, there is also a challenge to understand the internal dynamics in a Li-ion cell in which an ISC takes place [4]. This study introduces an advanced needle penetration test that enables the measurement of both the internal temperature and the ISC current.As seen in Figure 1 (a), the amount of ISC current can be measured indirectly by replenishing the lost cell capacity from ISC with a power supply that is set to constant voltage mode (in this case, 4.2 V) and connected to the cell via a shunt. Additionally, the internal temperature can be measured using a thermocouple which is embedded in a specially crafted probe. The needle penetrates Li-ion cells with a slow penetration speed of 0.01 mm/s to understand the effect of piercing individual layers on the ISC with regard to electrical and thermal behaviour.Figure 1 (b) presents the ISC current and the internal temperature measured using this method. In the unstable ISC current signal, sharp periodical peaks are detectable. It is assumed that the ISC current is constantly increasing by several layer-to-layer shorts adding up and that its periodically decreasing profile originates from the increasing contact resistance by cell layers melting or being ruptured. Since thermal energy emerges from the ISC current, the internal temperature fluctuates dynamically corresponding to the ISC current profile, while surface temperature signals do not show any changes. This advanced needle penetration test offers the great research possibility to understand the internal dynamics of ISC that has been barely studied and to determine the internal onset cell temperature for TR.[1] X. Feng et al Energy Storage Mater., 10, 246 (2018).[2] Y.S. Duh et al J. Energy Storage, 41, 102888 (2021).[3] D.P. Finegan et al J. Electrochem. Soc., 164 , A3285 (2017).[4] S. Huang et al J. Electrochem. Soc., 167, 90526 (2020). Figure 1

Thermoporometry of mesoporous carbons: Application of octamethylcyclotetrasiloxane as probe liquid for small mesopores

The mesoporosity of carbons can be determined using traditional methods such as gas physisorption or mercury intrusion, as well as by an alternative technique, thermoporometry (TPM). TPM focuses on determining porosity in the wet state. If water is used as probe liquid, the mesopores larger than 10 nm are hard to evaluate due to the overlapping of pore and bulk melting peaks. To overcome this problem, octamethylcyclotetrasiloxane (OMCTS) is used. Due to the fact that OMCTS undergoes solid-solid phase change in the same temperature range as melting in small mesopores, its use for mesopores below 10 nm is problematic. Thus, the applicability of OMCTS as a probe liquid for TPM characterization of small mesopores was tested in this work. The separation of melting in small pores from solid-solid transition was elaborated by several approaches like changes of heating rate, implementation of prefreezing step, deconvolution of experimental DSC records with the use of basic kinetic equation as underlying functions). It was found that the prefreezing step and a measurement of pure OMCTS under the same conditions as expected for TPM measurement is useful since the solid-solid transition depends on the measurement conditions. The usefulness of the suggested measurement conditions and deconvolution method was successfully demonstrated on carbonaceous samples with exclusively small mesopores (5 nm), as well as carbons containing both small and large mesopores. The results indicate that this approach enables the investigation of the entire mesoporous range and makes OMCTS a more versatile probe liquid for TPM.

Copper-Bearing Magnetite and Delafossite in Copper Smelter Slags

The cooling paths and kinetics in the system Cu-Fe-O are investigated by the empirical micro- and nanoscale analysis of slags from the flash furnace smelter at Olympic Dam, South Australia. We aim to constrain the exsolution mechanism of delafossite (Cu1+Fe3+O2) from a spinel solid solution (magnetite, Fe3O4) and understand why cuprospinel (CuFe2O4) is never observed, even though, as a species isostructural with magnetite, it might be expected to form. Flash furnace slags produced in the direct-to-blister copper smelter at Olympic Dam contain four Cu-bearing phases: Cu-bearing magnetite, delafossite, metallic copper, and cuprite. Delafossite coexists with magnetite as rims and lamellar exsolutions, as well as bladed aggregates, associated with cuprite within Si-rich glass. The empirical compositions of magnetite and rim delafossite are (Fe2+6.89Cu2+0.86Co0.13Mg0.15Si0.02)8.05 (Fe3+15.52Al0.41Ti0.01Cr0.01)15.95O32, and (Cu1+0.993Co0.002Mg0.002)0.997(Fe3+0.957Al0.027Ti0.005Si0.004)0.993O2, respectively. The measured Cu content of magnetite represents a combination of a solid solution (~6 mol.% cuprospinel endmember) and exsolved delafossite lamellae. Atomic-resolution high-angle annular dark field scanning transmission electron microscope (HAADF STEM) imaging shows epitaxial relationships between delafossite lamellae and host magnetite. Defects promoting the formation of copper nanoparticles towards the lamellae margins suggest rapid kinetics. Dynamic crystallization under locally induced stress in a supercooled system (glass) is recognized from misorientation lamellae in delafossite formed outside magnetite grains. The observations are concordant with crystallization during the cooling of molten slag from 1300 °C to <1080 °C. Melt separation through an immiscibility gap below the solvus in the system Cu-Fe-O is invoked to form the two distinct delafossite associations: (i) melt-1 from which magnetite + delafossite form; and (ii) melt-2 from which delafossite + cuprite form. Such a path also corroborates the published data explaining the lack of cuprospinel as a discrete phase in the slag. Delafossite rims form on magnetite at a peritectic temperature of ~1150 °C via a reaction between the magnetite and copper incorporated in the oxide/Si-rich melt. The confirmation of such a reaction is supported by the observed misfit orientation (~10°) between the rim delafossite and magnetite. HAADF STEM imaging represents a hitherto underutilized tool for understanding pyrometallurgical processes, and offers a direct visualization of phase relationships at the smallest scale that can complement both experimental approaches and theoretical studies based on thermodynamic modelling.

Paleoproterozoic Variolitic Lavas from the Onega Basin, Fennoscandian Shield: Mineralogy, Geochemistry and Origin

The Yalguba Ridge volcanic rocks form part of the Middle Paleoproterozoic (ca. 1.97 Ga) volcano-sedimentary sequence within the Karelian Craton in the Fennoscandian Shield. Yalguba variolitic textures are known worldwide and have been previously considered to originate from liquid immiscibility. The present study reveals two new variolite types recognized in the Yalguba sequence: (1) Variolites with unzoned varioles have distinct chemical and mineralogical compositions of varioles and matrix that support an origin by liquid immiscibility. They were recognized in quenched zones of pillows, so it might be assumed that melt separation caused by liquid immiscibility occurred before magma emplacement. The difference from the previously described variolites lies in the variole microtexture and might be caused by the various cooling conditions. (2) Spherulitic variolites have varioles composed of andesine–oligoclase spherulites embedded in the cryptocrystalline matrix with oligoclase–anorthoclase composition, thus the variole and matrix have similar chemical and mineralogical composition. The mineralogical and textural features of these variolites suggest that the spherulites have a primary magmatic origin due to the rapid cooling of superheated magma. The variety of variolitic textures in the Yalguba section might be caused by the different H2O saturation of parental magma and cooling conditions.

The effect of Nb2O5, CaO/SiO2, and TiO2 on the electrical conductivity of CaO-SiO2-Nb2O5-TiO2-CeO2-CaF2 melt

Electrical conductivity is a very important physical parameter in the process of electrolytic extraction of niobium from molten niobium-enriched slag or preparation of ferroniobium alloy by reduction melting separation in electric arc furnace. The effects of Nb2O5, CaO/SiO2 ratio and TiO2 on the electrical conductivity of CaO-SiO2-Nb2O5-TiO2-CeO2-CaF2 melt were studied by AC four-electrode method. The melt structure was studied by XPS to reveal the change rules of melt conductivity. The results show that the addition of Nb2O5 or increasing the CaO/SiO2 ratio in the melt can depolymerize the melt network structure and effectively improve the melt conductivity, and the activation energy of the conductivity is negatively correlated with the Nb2O5 content and the CaO/SiO2 ratio. With the increase of TiO2 content in the melt, the melt network structure polymerizes, the melt conductivity decreases, and the activation energy of conductivity also showed a decreasing trend.

Trace element and Sr-Nd-Hf-Pb isotope evidence for a multi-magma chamber system beneath the Deccan Volcanic Province, India

With a size of over 500,000 km2, the Deccan Volcanic Province (DVP) covers a large area of the Indian subcontinent. Stratigraphically continuous lava flows piled up to 3000 m record about five million years of volcanic activity. The peak activity of one million years coincides with the migration of the Indian subcontinent across the Réunion plume. Previous studies inferred an isotopic “common signature” for most DVP basalts that is best explained by a mixture of early Réunion plume-related melts and melts from the depleted upper mantle. Further chemical variability of the DVP sequence was explained by the incorporation of material from the lithospheric mantle and continental crust possibly within a single magma chamber system. Yet, indications for a complex crustal magmatic system have also been brought forward by earlier studies and find recently more support in explaining the magmatic plumbing system of the DVP and Large Igneous Provinces in general.This study presents new major and trace element data, including high-precision concentration measurements of high-field strength elements by isotope dilution and Sr-Nd-Hf-Pb isotope compositions for basaltic samples that cover nearly the complete DVP main section. Based on significant variations in Nb/Th (and Th/Ta) over a wide range of MgO concentrations we identified three distinct magma differentiation trends. The distinct differentiation trends result from three types of parental melts that are best explained by different proportions of lower and upper mantle melts indicated by diluted Réunion plume-like trace element and isotope compositions. During their ascent, these separate melts assimilated variable amounts of metasomatized lithospheric mantle and crustal material. Most likely the assimilation occurred before any major differentiation events, thus fixing the Nb/Th (and Th/Ta) of each group regardless of the degree of differentiation. The chemical trends can also be replicated using a statistical numerical approach, confirming that their geochemical signature truly reflects individual differentiation of three distinct parental melts. Field relations require that lavas related to these three unique differentiation trends erupted contemporaneously. This is in contrast to the idea of a gradually evolving single magma chamber system and the concept of a general chemostratigraphy for the DVP main plateau. Rather, our study reveals fast-changing contributions of different mantle reservoirs and provides new insight into the magma-plumbing systems of Large Igneous Provinces that may be more complex.

Mantle-crust-interaction and subduction dynamics in Central Cameroon: Evidence from the Pan-African Linté microgranular magmatic enclaves (MMEs) and host syenite

The Central African Fold Belt (CAFB) in Cameroon is characterized by voluminous intrusive rocks hosting microgranular magmatic enclaves (MMEs) whose petrogenesis and tectonic implications remain unclear. Here, we present detailed geochronological and geochemical data of the host rocks and their MMEs from the Linté pluton in central Cameroon. The MMEs are finer-grained than their host syenite and both rocks are composed of alkali feldspar, plagioclase, biotite, amphibole and pyroxenes as main mineral phases. The enclaves show lower Mg#, total alkalis and transition elements contents, and are more HFSEs depleted than the host syenite. Both rocks are characterized by high-K, metaluminous I-type, alkaline to sub-alkaline and magnesian affinities. The Ti-in-zircon thermometer suggests crystallization temperatures of 615–1080 °C and 613–1008 °C for syenites and MMEs, respectively. Their zircon trace element distribution and patterns coupled with whole-rock geochemical features indicate that the Linté intrusive rocks were most likely originated from interaction of mantle-derived magma with crustal material. LA-ICP-MS UPb zircon analyses yield emplacement age of 599 ± 3 Ma and 597 ± 4 Ma for the host syenite and MMEs, respectively, indicating coeval crystallization date. Integrated whole rock geochemistry, UPb dating and Ti-in-zircon thermometry data indicate that the Linté syenite were probably formed from a mantle-derived ultrapotassic alkaline melt with significant crustal contribution, while MMEs are likely derived from a similar but separate melt with more fractionation and crustal contamination. The genesis of the host syenite and MMEs magmas started with break-off of the Congo plate after subduction and collision. This initiated an upwelling thermal pulse and underplating of mafic magma which led to partial melting of the Paleoproterozoic crust of the Central Cameroon.

MoO3 Solubility and Chemical Durability of V2O5-Bearing Borosilicate Glass

In the vitrification of high-level radioactive liquid waste (HLW), the separation of sodium-molybdate melts is a problem because it reduces the chemical durability of the vitrified waste. A glass with both high MoO3 solubility and chemical durability is required for the safe disposal of radioactive waste. In this study, we investigate the effects of vanadium oxide on the phase separation of the molybdenum-rich phase and the water resistance of the resulting glass by phase equilibrium experiments and chemical durability test. Phase equilibrium experiments were performed on SiO2-B2O3-Al2O3-ZnO-CaO-Na2O-LiO2-MoO3 system glasses and on glasses with V2O5 added. The results showed that MoO3 solubility increased when V2O5 was added. The increase in MoO3 solubility in borosilicate melts may be associated with the viscosity-lowering effect of V2O5. Chemical durability tests were performed on borosilicate glass compositions obtained from phase equilibrium experiments. The normalized leaching rates of V2O5-bearing glasses were higher than those of other glasses. This is due to the higher network modifier/network former ratio of the glass tested. The normalized elemental mass loss of glass containing waste components increases with increasing leaching duration. This suggests that the waste component prevents the formation of a gel layer at the reaction front.

3-Dimensional Topology in Materials Science

In this article, we discuss applications of topology to materials science. We explain how topology is used to express the structure and shape of materials. The structure of a multicyclic polymer is described by applying graph theory and the 3-dimensional shape is described by applying knot theory. Polycontinuous patterns of microphase separation of a block copolymer melt can be analyzed by applying the 3-dimensional topology. We also discuss the topological structures of interlocking molecules composed of metal-peptide rings using the concept of polyhedral links.

A high-resolution melt curve toolkit to identify lineage-defining SARS-CoV-2 mutations

The emergence of severe acute respiratory syndrome 2 (SARS-CoV-2) variants of concern (VOCs), with mutations linked to increased transmissibility, vaccine escape and virulence, has necessitated the widespread genomic surveillance of SARS-CoV-2. This has placed a strain on global sequencing capacity, especially in areas lacking the resources for large scale sequencing activities. Here we have developed three separate multiplex high-resolution melting assays to enable the identification of Alpha, Beta, Delta and Omicron VOCs. The assays were evaluated against whole genome sequencing on upper-respiratory swab samples collected during the Alpha, Delta and Omicron [BA.1] waves of the UK pandemic. The sensitivities of the eight individual primer sets were all 100%, and specificity ranged from 94.6 to 100%. The multiplex HRM assays have potential as a tool for high throughput surveillance of SARS-CoV-2 VOCs, particularly in areas with limited genomics facilities.