Glass Composition Research Articles

Evaluation of fracture resistance of composite resin and glass ionomer in beveled versus non beveled class II restorations in primary molars: In vitro comparative study

Introduction: The high viscosity Bulk-Fill composite (Tetric N ceram) and high viscosity glass ionomer cement (Equia Forte GIC) are the most used materials in class II cavities of primary molars. They have the advantages of being placed in a single layer of 4mm and therefore allow better ergonomics and speed of use. Until now, we find failures of restorations at the level of class II cavities of temporary teeth and many authors have tested the role of the bevel in improving the mechanical strength of restorations. Objectives: The objectives of this study are: to test the role of the bevel in improving the fracture resistance of Bulk Fill composite restorations versus GIC of class II restorations in primary molars, and to test which material has better resistance to fracture. Methods: One hundred temporary extracted molars are collected and randomly divided into four groups: Group I (non-beveled) and II (beveled) filled with Equia forte. Group III (non-beveled) and IV (beveled) filled with Bulk Fill Ivoclar Tetric N Ceram. The specimens were subjected to thermocycling from 5 to 55° for 10000 cycles. After artificial aging, an axial loading at a speed of 1 mm/min was applied until the specimens fractured. Results: The statistical analysis reveals the following: an average of 442.2 N for group I and 498.80 N for group II. Thus, no statistical difference was observed between the groups restored with Equia Forte (p-value>0.05). Whereas, the resistance to fracture for groups III (901.80N) and IV (2438.33N) with a p-value<0.001 so there is significant difference between the two groups. Conclusions: The bevel improves the fracture resistance of the BulkFilll Ivoclar restorations. Whereas, it does not influence the fracture resistance of the Equia Forte group. Bulk Fill Ivoclar Tetric N ceram has better resistance to fracture than Equia Forte GIC restorations.

Magneto-optic properties of highly Dy3+-doped GeO2-B2O3 glasses for NIR optical applications

Recent progress in the development of optical communication and high power laser systems in the near-infrared (NIR) region (1.5 to 2.0 μm) increased the demand for magneto-optic (MO) devices employing MO materials. These MO materials are required with lower optical absorption coefficients and higher Verdet constants at spectral range of interest. In this study, two series of highly Dy3+-doped GeO2–B2O3 glasses with and without P2O5 were fabricated using a simple melt-quenching technique. The glasses were characterized through various techniques (Raman, UV–VIS-NIR, and DTA) for the evaluation of characteristic properties with respect to the Dy2O3 concentration and glass composition. Faraday rotation measurement was carried out at 1550 nm to quantify the Verdet constant of the glasses. The Verdet constant values were found to increase linearly with increasing Dy3+ concentration for both the glass systems. The increase in Dy3+ concentration and, consequently, the number of unpaired electrons, leads to an increase in the Verdet constant. The GeO2-B2O3 glass doped with 30 mol% of Dy2O3 exhibited the highest Verdet constant of −5.36 rad/(T⋅m) at 1550 nm. The glasses exhibited a good optical transparency (>70 %) in the region covering from 400 to 2400 nm. The thermo-physical, optical, and polarizability properties of both glass systems were also investigated. The results indicate that the highly Dy3+-doped glasses are attractive for magneto-optics at 1550 nm.

An Experimental Investigations on Design and Weight Optimization for a Light Motor Vehicle (LMV) Drive Shaft Using a Composite Material Aluminum and Glass Fiber (Al + GF)

Aluminum is primarily used in Metal Composites because of its lighter weight and higher strength. Glass fibers are wound around an aluminum shaft to create the composite. ANSYS results determine the relative amounts of aluminum and Eglass fiber in each shaft. The purpose of this study is to use a torsion test to evaluate the mechanical performance of a composite shaft composed of aluminum and glass fiber. The results are carefully examined for different combinations of glass fiber layers and aluminum layers. When the weight proportion of aluminum in the composite increases, the mechanical properties of the composites improve.

Surface treatments on commercial glasses: durable impact on the retention of lead, barium and boron

Glass durability is one of the properties that can be affected by surface treatments such as coatings or chemical attacks. These treatments can be used to reduce the quantities of potentially toxic elements contained in glass that may be released in solution. Five surface treatments were selected: three different coatings (SnO2, TiO2, SiO2) and two acidic attacks (SO2 dealkalization and acid polishing). These treatments were performed on five glass compositions (soda-lime, borosilicate, barium silicate, opal, and lead crystal). Their effects on alteration rates and mechanisms were investigated through a single protocol (acetic acid 4%, 70 °C) simulating accelerated aging conditions for containers of beverages or food. The data collected over 1.3 years showed significant reduction of lead leaching with all treatments except acid polishing. The best reduction factor was obtained with SO2 dealkalization, which also demonstrated beneficial effects towards the retention of Ba by reducing the diffusion of alkalis.

Structural, elastic and gamma-ray attenuation properties of potassium borate glasses doped with BaO, Bi2O3, or Pb3O4: A comparative assessment

This study investigates the effect of substituting boron oxide (B2O3) with heavy metal oxides (HEMOs) on the structural, mechanical, and gamma-ray shielding properties of potassium borate (KB) glass systems. The glass compositions analyzed include 80B2O3–20K2O and 65B2O3–20K2O-15HEMO (where, HEMO = BaO, Bi2O3, or Pb3O4). All samples were prepared using the melt-quenching method, and their amorphous nature was confirmed through X-ray diffraction (XRD). Fourier-transform infrared spectroscopy (FTIR) had revealed BO3, BO4, and BiO6 groups beside the B–O–B linkages. The density increased with the addition of HEMOs, following the order: Pb3O4 (KB4) > Bi2O3 (KB3) > BaO (KB2) > and pure KB (KB1). This trend was also observed in the molar volume (Vₘ) and oxygen molar volume (Vₒ), while the oxygen packing density (Pρ) decreased. Mechanical properties assessed using the Makishima-Mackenzie model indicated that KB3 exhibited the highest elastic modulus (Yₘ) and Poisson's ratio (μ). The microhardness (Hₘ) followed the sequence KB2 > KB3 > KB4 > KB1, attributed to the higher bonding energy in KB2. Gamma-ray shielding parameters, including mass attenuation coefficients (MAC), were calculated using Phy-X and XCOM software for photon energies between 0.2835 MeV and 1.333 MeV. KB4 (Pb3O4) showed superior shielding performance with the highest linear attenuation coefficient (LAC) and the lowest half-value layer (HVL) and mean free path (MFP). Despite KB4's high density, KB3 (Bi2O3) is suggested as a more suitable candidate for radiation shielding applications due to its balanced combination of mechanical strength and γ-ray attenuation efficiency.

Electrochemical performance study of AlF₃-containing lithium phosphate glass electrolytes

This study aims to enhance the performance of Li₂O-P₂O₅-based lithium phosphate glass electrolytes for all-solid-state lithium batteries by incorporating aluminum fluoride (AlF₃). Initially, Li₂O-P₂O₅ glass was melted, followed by the addition of stoichiometric AlF₃, and remelted to achieve an optimized composition of 10AlF₃⋅50Li₂O⋅40P₂O₅. By adjusting the melting temperatures and the ratios of raw materials, we explored different synthesis procedures and obtained the lithium fluoro-phosphate glass electrolytes and systematically investigated their physicochemical properties and electrochemical performance. Its physicochemical properties include the glass composition, NMR spectra, and glass transition temperature. Symmetrical cell tests conducted at high current densities demonstrated that the incorporation of AlF₃ significantly enhanced the stability of the interface with lithium metal, maintaining excellent cycling performance. Furthermore, the doping with AlF₃ did not reduce the ionic conductivity of the original Li₂O-P₂O₅-based glass electrolyte, and the activation energy remained unchangeable.

Chemical durability of optical temperature sensors made of tellurite glass: Effect of the alumina concentration

Tellurite glass is an amorphous material commonly doped with rare earth ions for the development of optical temperature sensors. Considering the intrinsic properties of glasses, it is expected that these sensors could be used in acidic environments and withstand temperature changes. However, this has not been fully demonstrated since most of the literature is limited to demonstrate the sensor operation under normal conditions. Additionally, there is a lack of information regarding the chemical durability of these glasses and methods to improve it. In this work, a special tellurite glass composition was proposed for the development of optical temperature sensor. The effect of the alumina concentration on the structure, chemical durability and emission properties of the glasses was evaluated. Chemical durability was assessed by monitoring the weight loss of glass samples after immersion in hydrochloric acid solutions at room temperature, vegetable oil or air at 150 °C. The results indicate that the addition of alumina increases the chemical durability of the glass and improves its emission properties. It was found that the average temperature estimated by the optical sensor had a relative error of 1.3 % due to the degradation of the glass caused by remaining immersed in a 1 N HCl solution for 60 days.

Immediate and delayed shear bond strength evaluation between root canal sealers and restorative materials: an experimental study

BackgroundSeveral calcium silicate-based sealers have recently emerged in endodontics. This study aimed to compare the immediate and delayed shear bond strength between the bioceramic and calcium hydroxide-based sealers and different resin-based restorative materials.MethodsOne hundred and twenty specimens with a 3-mm depth and a 3-mm diameter were prepared. They were evenly divided into two groups, the bioceramic sealer and calcium hydroxide-based sealer groups. Each primary group was subdivided into two subgroups based on the restorative material used; i.e., the flowable resin composite and resin-modified glass ionomer subgroups. Moreover, each subgroup was further divided into the restoration process’s timing: either immediately post-sealing or delayed after setting the sealers for seven days. The mode of failure was assessed by stereomicroscopic examination.ResultsThe highest shear bond strength was found when the bioceramic sealer was used and restored with the flowable resin composite. The strengths were 8.45 (1.17) and 6.67 (1.60) megapascals (MPa) in the immediate and delayed restoration groups, respectively. In contrast, the lowest strength, 2.91 (1.22) MPa, was recorded when calcium hydroxide-based sealer was employed and restored after allowing the sealer to set completely with resin-modified glass ionomer. Notably, there were no cohesive fractures within the tested restorative materials. All observed fractures occurred within the sealer materials, at the interface of the sealer and restorative material, or in combination. Moreover, the most common failure was a mixed failure.ConclusionsWhen flowable resin composite was used immediately before complete setting, bioceramic sealers showed a higher bond strength than calcium hydroxide-based sealers.

Role of in-situ electrical stimulation on early-stage mineralization and in-vitro osteogenesis of electroactive bioactive glass composites

Bioactive glass (BAG) has emerged as an effective bone graft substitute due to its diverse qualities of biocompatibility, bioactivity, osteoblast adhesion and enhanced revascularization. However, inferior osteogenic capacity of BAG compared to autologous bone grafts continues to limiting it's wide-spread clinical applications towards repairing of bone fractures and healing. In this study, we have fabricated BAG composites with 0.5 to 2 wt% bismuth ferrite (BF, a multiferroic material) with an aim to generate in-situ electrical charges pertinent to early-stage bone regeneration thus mimicking nature bone, which is a piezoelectric material. The fabricated BAG composites were characterised in terms of microstructures, phase analysis, remanent polarization, wettability and subsequently evaluated for in vitro cell proliferation and osteogenesis with and without magnetic field exposure (200 mT, 30 min./day). Pre-osteoblast cells from mice (MC3T3-E1) seeded on these composites exhibited excellent cell growth without any cytotoxicity, which is further supported by FITC/DAPI staining and a live/dead assay. The results of Alizarin Red S assay and increased levels of Alkaline Phosphatase (ALP) activity, at 21 days of culture, suggest that the BAG-BF composites promote in vitro osteogenic differentiation of pre-osteoblast cells. The enhanced osteogenesis of BAG-BF composites was also confirmed through qRT-PCR analysis, which showed rapid upregulation of osteoblastogenic specific genes namely RunX-2, Collagen-1, Bone Sialo Protein, and ALP after 21 days. Additionally, the osteogenic differentiation was assessed by the Western Blot technique, which revealed significantly higher band intensity of osteogenic markers in BAG-1.5 BF and BAG-2 BF composites than pure BAG. These findings clearly demonstrate that in-situ electrical stimulation and osteoconductive capacity of BF reinforced BAG composites have positive impact on osteoblast cell development, bone formation, and healing.

Structure–property relations of sodium iron phosphate nuclear waste glasses: Effects of iron redox ratio and glass composition

Structure–property relations of sodium iron phosphate nuclear waste glasses: Effects of iron redox ratio and glass composition

Determination of the Optimum Architecture of Additively Manufactured Magnetic Bioactive Glass Scaffolds for Bone Tissue Engineering and Drug-Delivery Applications.

For better bone regeneration, precise control over the architecture of the scaffolds is necessary. Because the shape of the pore may affect the bone regeneration, therefore, additive manufacturing has been used in this study to fabricate magnetic bioactive glass (MBG) scaffolds with three different architectures, namely, grid, gyroid, and Schwarz D surface with 15 × 15 × 15 mm3 dimensions and 70% porosity. These scaffolds have been fabricated using an in-house-developed material-extrusion-based additive manufacturing system. The composition of bioactive glass was selected as 45% SiO2, 20% Na2O, 23% CaO, 6% P2O5, 2.5% B2O3, 1% ZnO, 2% MgO, and 0.5% CaF2 (wt %), and additionally 0.4 wt % of iron carbide nanoparticles were incorporated. Afterward, MBG powder was mixed with a 25% (w/v) Pluronic F-127 solution to prepare a slurry for fabricating scaffolds at 23% relative humidity. The morphological characterization using microcomputed tomography revealed the appropriate pore size distribution and interconnectivity of the scaffolds. The compressive strengths of the fabricated grid, gyroid, and Schwarz D scaffolds were found to be 14.01 ± 1.01, 10.78 ± 1.5, and 12.57 ± 1.2 MPa, respectively. The in vitro study was done by immersing the MBG scaffolds in simulated body fluid for 1, 3, 7, and 14 days. Darcy's law, which describes the flow through porous media, was used to evaluate the permeability of the scaffolds. Furthermore, an anticancer drug (Mitomycin C) was loaded onto these scaffolds, wherein these scaffolds depicted good release behavior. Overall, gyroid-structured scaffolds were found to be the most suitable among the three scaffolds considered in this study for bone tissue engineering and drug-delivery applications.

A New Approach Toward Extreme Thermal Stability of Femtosecond Laser Induced Modifications in Glasses

AbstractImprinting thermally stable transformations by femtosecond laser in glass would benefit the development of optical sensors dedicated to harsh environments including combustors, nuclear reactors, aircraft engines, or metal/ceramic manufacturing processes. While glass brings undeniable assets over refractory crystalline materials like shaping ability (e.g., optical fiber form), one key challenge is to prevent the erasure of induced transformations at high temperatures and for long periods. In this article, the role of glass composition and viscosity to achieve modifications stable at high temperatures is first reviewed, providing a comprehensive roadmap for engineers in optics and photonics. While silica appears to be the candidate of choice, it is revealed that binary aluminosilicates can compete and sometimes surpass it. The hypothesis is formulated and investigated that a hybrid glass‐crystalline nano‐structuring can imprint ultra‐stable modifications inside glass. Laser‐induced modifications in Al2O3‐SiO2 and ZrO2‐Al2O3‐SiO2 glasses reveal a partial crystallization, shaped into a lamellar structure and orientable with laser light polarization. These birefringent structures can withstand temperatures up to 1300 °C for 30 minutes. Even after erasure, a positive index contrast persists, up to 1650 °C for binary 60Al2O3‐40SiO2 (mol%). This is the first observation of this kind of persisting index contrast, paving the way to ultra‐stable glass‐based optical waveguiding.

Spatial and temporal mush heterogeneity during eruptions recorded in clinopyroxene from the 2021 paroxysms at Mt. Etna, Italy

Textural and compositional zoning of volcanic minerals archives pre-eruptive magma processes. Crystals erupted simultaneously may be sampled from different regions of the plumbing system and hence record variable histories due to complex magma dynamics. In addition, crystals erupted throughout the course of an eruption may record temporal variations in the plumbing system. To resolve mush variability on both spatial and temporal scales, we investigate clinopyroxene erupted during a series of paroxysmal episodes between February–April 2021 at Mt. Etna, Italy. Using a combination of high-resolution geochemical techniques, we observe that Cr enrichments in clinopyroxene mantle zones, grown upon eruption-triggering mafic rejuvenation, exhibit both temporal and spatial (sample-scale) variability. Temporal variability correlates with changes in glass compositions, attesting to the ability of clinopyroxene to track magma maficity throughout an eruption. Spatial variability, indicated by the scatter of Cr concentrations, is greatest for the first event and lowest for the final paroxysm. In conjunction with core textures, degree of sector enrichment and thermobarometry, our data suggest that the onset of the paroxysms was preceded by the remobilisation of a mid-crustal clinopyroxene mush (534 ± 46 MPa) by hot, mafic magma causing variable resorption of mush-derived crystal cores. Towards the end of the eruption, waning magma supply led to less efficient mush remobolisation and mixing, resulting in homogenous crystal populations. Our results highlight that clinopyroxene Cr contents and sector enrichment can be used to track mafic rejuvenation and magma evolution throughout eruptions, while also reflecting spatial heterogeneities within the plumbing system.

Supercontinuum generation from silver nano species embedded sodium antimony zinc borate glass matrices

Abstract Glass composites that contain metal nanostructures exhibit improved nonlinear properties and ultrafast responses due to their inherent local field effects. In this work, we synthesized glass matrices embedded with diverse silver nano species through the ion exchange method and investigated the generation of supercontinuum from these composites. The formation of silver nano species and their volume fraction were analyzed using the XPS analysis, and their contribution towards supercontinuum broadening was studied. The size of a nanoparticle influences the electron–electron scattering and the frequency of acoustic breathing rate, which influences the extent of supercontinuum broadening. The result indicates the possibility of tuning the nonlinear response of glass nanocomposites by varying the volume fraction of Ag+ and Ag°.

Computational study of γ-ray and fast neutron shielding efficacy of (70–x)B2O3 – 5TeO2 – 20SrO – 5ZnO – (x)Bi2O3 glass systems using Phy-X/PSD, XCOM and GEANT-4

Abstract This study investigated the LAC, MAC, half-value thickness, tenth-value thickness, mean free path, Zeff, Neff, FNRCS, EBF, and EABF of a glass composition (70-x)B2O3 – 5TeO2 – 20SrO – 5ZnO – (x)Bi2O3, with x ranging from 0 to 15 mol%. Sample S5 showed the lowest HVT, TVT, and MFP and the highest MAC, LAC, Zeff, and Neff across 300 keV–15 MeV, indicating enhanced γ-ray shielding with higher Bi2O3 content in narrow-beam applications. However, EBF and EABF decreased with Bi2O3 at 0.5 and 1 MeV, but increased at 10 MeV, indicating improved shielding only at low and intermediate energies in broad-beam scenarios. Sample S4 exhibited the highest FNRCS and best neutron shielding efficiency. The comparison of our results with the literature revealed that S5 and S4 are, respectively, even more superior, in shielding γ radiation and neutrons than some of the glass materials that have been recently investigated in the literature. Therefore, in γ-ray shielding applications, incorporating Bi2O3 into the glass matrix is advisable primarily for narrow-beam conditions, and for broad-beam scenarios at intermediate energies, but not at high energies in broad-beam contexts.

Geopolymers made using organic bases. Part III: Cast magnesium, yttrium, and zinc aluminosilicate and silicate ceramics

AbstractIt was shown in Part II of this series of articles that geopolymers synthesized with organic bases could be used as precursors to mullite and mullite + glass composites. A natural next step is to determine whether it is possible to synthesize materials outside the Al2O3·SiO2 and alkali oxide·Al2O3·SiO2 phase systems. Hence, the focus of this study was the use of geopolymer‐like processing to make preceramic bodies with magnesium, yttrium, and zinc aluminosilicate and silicate compositions. These preceramics were successfully fired into monolithic bodies of cordierite, mixed yttrium and aluminum silicates, yttrium disilicate, and willemite. The synthesis of these preceramics employed a guanidine silicate solution, a synthetic oxide powder, and in some cases metakaolin to reach the oxide composition of the ceramic. All solidified within 3 days at 20°C or 50°C, depending on the composition. For the first time, this study showed that Y2O3 and ZnO can react with silicate solutions to give some Y‐O‐Si and Zn‐O‐Si bonding analogous to Al‐O‐Si bonding in geopolymers. These results suggest that other silicate compositions may be possible, such as with the rare earth oxides, which might be valuable to process like a geopolymer rather than by traditional ceramic processing. However, the ceramics made here were generally porous due to the expansion of gases within the sample that were trapped by a viscous liquid phase during firing.

Repair overlays of modified polymer mortar containing glass powder and composite fibers-reinforced slag: mechanical properties, energy absorption, and adhesion to substrate concrete

This article aims to investigate the mechanical properties and substrate adhesion of the pull-off method in polymer mortars modified with styrene-butadiene resin polymer (SBR) containing glass powder and composite fiber-reinforced slag. Different mix designs were investigated with and without SBR, taking into account different amounts of glass powder and slag separately and in combination, along with the effect of glass, polypropylene, and steel fibers alone and in combination. The flexural performance and energy absorption of beams retrieved with these layers were also assessed. The results revealed significant differences and increases in the substrate adhesion of the restored modified polymer layers containing SBR compared to the polymer-free repair overlays. Furthermore, an improvement was observed in the adhesion performance of the repair overlay using a combination of slag and glass powder and the glass and polypropylene fiber composite. The highest adhesion was related to the modified polymer mortar design containing composite fibers of glass, polypropylene, and steel with 25% replacement of SBR polymer for 10% glass powder, 10% slag, and 5% slag with 5% glass powder. The adhesion was increased by about 3.74, 3.72, and 3.78 times compared to the repair overlay of the control design. Modified polymer mortars had a higher T150D toughness. Moreover, the energy absorption was significantly improved by the presence of SBR polymer. The highest toughness values were found in the beams restored with modified polymer mortars containing polypropylene, glass, and steel composite fibers with an increase of 48.51%–66.42% compared to the samples without polymer as a result of the pozzolans used in this mix.

Advances in and Future Perspectives on High-Power Ceramic Lasers

Advancements in laser glass compositions and manufacturing techniques has allowed the development of a new category of high-energy and high-power laser systems which are being used in various applications, such as for fundamental research, material processing and inertial confinement fusion (ICF) technologies research. A ceramic laser is a remarkable revolution in solid state lasers. It exhibits crystalline properties, high yields, better thermal conductivity, a uniformly broadened emission cross-section, and a higher mechanical constant. Polycrystalline ceramic lasers combine the properties of glasses and crystals, which offer the unique advantages of high thermal stability, excellent optical transparency, and the ability to incorporate active laser ions homogeneously. They are less expensive and have a similar fabrication process to glass lasers. Recent developments in these classes of lasers have led to improvements in their efficiency, beam quality, and wavelength versatility, making them suitable for a broad range of applications, such as scientific research requiring ultra-fast laser pulses, medical procedures like laser surgery and high-precision cutting and welding in industrial manufacturing. The future of ceramic lasers looks promising, with ongoing research focused on enhancing their performance, developing new doping materials and expanding their functional wavelengths. The ongoing progress in high-power ceramic lasers is continuously expanding the limits of laser technology, therefore allowing the development of more powerful and efficient systems for a wide range of advanced and complex applications. In this paper, we review the advances, limitations and future perspectives of ceramic lasers.

Major Holocene cryptotephras layers identified from Jeju Island, Republic of Korea: Implications for regional volcanic eruptions and environmental changes

Cryptotephras recorded in sediments are valuable isochrons with which to reconstruct volcanic eruptive history and synchronize environmental changes across large regions. Here we identify four cryptotephras from Jeju Island, Republic of Korea, that constitute tie-points linking palaeoenvironmental records of tropical to mid-latitude east Asia. A cryptotephra of unknown source with trachytic glass compositions at around 2700 cal a BP (named M263a) can be correlated with the HGY263 recorded in the Huguangyan Maar lake in southern China, and SG14–0433 recorded in Suigetsu lake in central Japan. Another population of glass shards with basaltic andesitic to trachybasaltic composition (named M263b) represents the first cryptotephra record of a Jeju eruption. A rhyolitic cryptotephra at ∼7384 cal a BP (H53) can be correlated with the ∼7.3 ka Kikai-Akahoya eruption (specifically, the K-Ah tephra) from Kikai caldera, southern Kyushu, Japan. The cryptotephra coincides with a marked change in aquatic algae communities in Jeju sediments, possibly signifying a climate response to the eruption. Additionally, cryptotephra layers at ∼6948 cal a BP (H22) in the Hanon Maar Lake and ∼ 1030 cal a BP (M125) in Mulyoungari wetland exhibit similar glass compositions to those of the K-Ah tephra, which suggests they are the product of unknown eruptions from Kikai or a neighboring volcano. Given the widespread distributions of K-Ah and M263a tephra across east Asia, Jeju sediments can be precisely synchronized with those high-resolution sediments from southern China and Japan, providing two Holocene marker horizons for palaeoenvironmental comparisons across east Asia. Our work shows great promise for the improved chronological constraints and inter-site linkages for palaeoenvironmental sequences in the region through the application of tephrochronology.

Dynamic evolution of the transcrustal plumbing system in Large Igneous Provinces: Geochemical and microstructural insights from glomerocrysts and melt inclusions

Abstract The nature of the magma plumbing system of Large Igneous Provinces is still poorly understood. Among these exceptional magmatic events from Earth’s past, the end-Triassic Central Atlantic Magmatic Province (CAMP) and the end-Cretaceous Deccan Traps (Deccan) coincided in time with two of the most catastrophic biotic crises during the Phanerozoic. In order to constrain the architecture of their magma plumbing system, glomerocrysts containing abundant bubble-bearing melt inclusions from basaltic lava flows of both CAMP and Deccan were investigated via in situ geochemical and microstructural analyses. The analysed glomerocrysts, dominated by augitic clinopyroxene crystals, represent fragments of a crystal mush entrained by basaltic magmas before eruption. The analysed melt inclusions, consisting of an intermediate to felsic composition glass and CO2-bearing bubbles, represent relics of interstitial melts and fluids within a porous crystal framework forming the crystal mush. The different volume proportions between bubbles and whole inclusions reveal that melt entrapment occurred after volatile exsolution. The minimum observed bubble/inclusion fraction indicates that the CO2 concentration in CAMP and Deccan melts was at least 0.3 wt.%, consistent with a maximum entrapment pressure of about 0.5 GPa at CO2–H2O fluid-saturated conditions. The MgO-rich composition of host clinopyroxene crystals and whole rocks is in contrast with the SiO2-rich composition of (trachy-) andesitic to rhyolitic glass of melt inclusions, pointing to disequilibrium conditions. Thermodynamic and geochemical modelling shows that fractional crystallization alone cannot explain the evolved composition of glass in melt inclusions starting from their whole rock composition. On one side, the oxygen isotope composition of clinopyroxene crystals in glomerocrysts ranges from + 3.9 (± 0.3) to + 5.8 (± 0.3) ‰ and their sample-averaged oxygen isotope composition spans from + 4.4 (N = 10) to + 5.6 (N = 10) ‰, implying that glomerocrysts crystallized from mafic melts with normal (i.e., mantle-like) to slightly low δ18O values. On the other side, the oxygen isotope composition of glass in melt inclusions ranges from + 5.5 (± 0.4) to + 22.1 (± 0.4) ‰, implying that melt inclusions entrapped intermediate to felsic melts with normal (i.e., mantle-like) to extremely high δ18O values, typical of (meta-) sedimentary rocks. Some melt inclusions are compatible with fractionation from the same mafic melts that crystallized their host mineral phase, but most melt inclusions are compatible with variable degrees of crustal assimilation and partial mixing, potentially followed by minor post-entrapment isotope re-equilibration. In the CAMP, where sedimentary basins are abundant, (meta-) pelites and occasionally granitoids were the most likely assimilants. On the contrary, in the Deccan, where sedimentary basins are rare, granitoids and metapelites were the most likely assimilants. Oxygen isotope compositions of glass in melt inclusions, spanning from mantle-like to crust-dominated signatures, suggest that the CO2 within their coexisting bubbles likely derived partly from the mantle and partly from assimilated crustal materials. The investigated glomerocrysts and their bubble-bearing melt inclusions are relics of a multiphase (i.e., solid + liquid + gas phases) crystal mush revealing a dynamic evolution for the magma plumbing system of both CAMP and Deccan, where crystals, silicate melts and exsolved fluids coexisted and interacted through most of the transcrustal section.