Natural Glasses Research Articles

Scanning probe microscopy in mineralogical studies: about origin of the observed roughness of natural silica-rich glasses

We have studied different mineralogical objects: natural glasses of impact (tektites, impactites) and volcanic (obsidians) origin, using atomic force microscopy, X-ray microanalysis, infrared and Raman spectroscopy. The spectroscopy showed the difference in the structure and chemical composition of the glasses of different origin. The analysis of the dependence of nanoscale heterogeneity of the glasses, revealed by the atomic force microscopy, on their structural and chemical features was carried out.

SICAK CAM ÜFLEME TEKNİĞİNDE ODUN KÜLÜ KULLANIMININ ESTETİK İFADE OLANAKLARININ ARAŞTIRILMASI

Glass has passed some important phases throughout history. The development process that began with the discovery of glass in about 3500 years ago has enabled glass to spread to wider masses with the discovery of hot glass blowing. Later, the use of glassware became widespread with the development of crystal glass and the beginning of low cost glass production. The most important turning point is the movement of the studio glass, which was about 100 years ago. Glass is a material used for decorative purposes from ancient civilizations to day-to-day. Nature has spontaneously produced glassware and the natural glass called obsidian has been used in the construction of various tools since ancient times. With the development of technology, the production of glass industry has started and at the same time, with the development of studio glassware, hot glass forming has made itself a technique in glass arts. In this study, the effect of wood ash on hot glass formation was investigated in order to investigate surface effects in hot glass technique. According to the results obtained, it has been shown that wood ash, which has many advantages such as having very fine particles, high avaliability and high reactivity, can be used in hot glass technique as a eco-friendly decoration material.

Generation of shock lamellae and melting in rocks by lightning‐induced shock waves and electrical heating

AbstractThe very rapid energy release from impact events, such as those resulting from lightning strikes or meteorites, can drive a variety of physical and chemical processes which alter rocks and result in the formation of natural glasses (i.e., fulgurites and tektites). Fulgurite is the vitrified soil, sand, or rock resulting from lightning strikes. A thunderbolt is associated with air temperatures of up to 105 K, which can heat rocks to >2000 K within tens of microseconds. The rapid fusing and subsequent quenching of the surface of the rock leaves a distinctive, thin, garbled coating composed of a glassy to fine‐grained porous material. Previous studies on rock fulgurites found planar deformation features in quartz crystals within the target rock substrate, evidence of strong shock waves during fulgurite formation. In this paper, we simulated the shock pressure and temperature caused by an idealized lightning impact on rocks and compared the model results with observations on rock fulgurites from the literature. Our model results indicate that a lightning strike can cause >7 GPa pressure on the rock surface, generate a layer of fulgurite (of radius ∼9 cm), and leave a burned region (of radius ∼11 cm). The fulgurites found on rock surfaces share many features with sand fulgurites, but their spatial distribution is completely different, as sand fulgurites are hollow tube structures. Our study on rock fulgurites provides an indirect constraint on the energy of a lightning event and also demonstrates that the presence of shock features in rocks cannot be taken as unequivocal evidence for impact events.

Studies for understanding effects of additions on the strength of cement concrete

The paper analyzes the effects of different types of additions introduced in concrete mix on the compressive strength. The current studies show that additions contribute to improve some characteristics of concrete and to reduce the cement dosage, so it can obtain concretes which are cheaper and friendlier with environment. In the experimental mixes were introduced: crushed natural aggregates, slag aggregates, silica fume, fly ash, chopped tire, polystyrene granule, glass fibers and metallic fibers. The experimental values of compressive strengths were compared for two concrete grades (C20/25 and C25/30). The study shown that near the well-known possibilities of improving mechanical strengths of cement concrete by increasing cement dosage and strength, by using crushed aggregates and by reducing the water/cement ratio, there are other methods in which less cement is used by replacing it with different wastes or by adding fiber.

Research gemology and mineralogy characteristics of Tektite in North region of Da Lat City

Tektite in northern of Da Lat city is a kind of natural glass, formed from meteorite collisions with Earth, have basic elements Si, Al, Fe, Mg. Typical shapes inclued debris, drops, oval, dumbbell, flat sphere, flat mace, short prism with external shape characterized by holes covering the surface. Typical color is black, sometimes brownish green at thin edges. The average density is about 1.45 g/cm3, a refractive index of about 1.50, with prolonged gas and the inclusion of carbonate, lechatelierite characteristic of natural glass. Tektite in Northern Dalat is proven to have a planetary origin that fits the hypothesis that they are formed by meteorite impacts. Tektite in the area can be used in jewelry.

Mechanical energy dissipation in natural ceramic composites.

Ceramics and glasses, in their monolithic forms, typically exhibit low fracture toughness values, but rigid natural marine ceramic and glass composites have shown remarkable resistance to mechanical failure. This has been observed in load-extension behavior by recognizing that the total area under the curve, notably the part beyond the yield point, often conveys substantial capacity to carry mechanical load. The mechanisms underlying the latter observations are proposed as defining factors for toughness that provide resistance to failure, or capability to dissipate energy, rather than fracture toughness. Such behavior is exhibited in the spicules of glass sponges and in mollusk shells. There are a number of similarities in the manner in which energy dissipation takes place in both sponges and mollusks. It was observed that crack diversion, a new form of crack bridging, creation of new surface area, and other important energy-dissipating mechanisms occur and aid in "toughening". Crack tolerance, key to energy dissipation in these natural composite materials, is assisted by promoting energy distribution over large volumes of loaded specimens by minor components of organic constituents that also serve important roles as adhesives. Viscoelastic deformation was a notable characteristic of the organic component. Some of these energy-dissipating modes and characteristics were found to be quite different from the toughening mechanisms that are utilized for more conventional structural composites. Complementary to those mechanisms found in rigid natural ceramic/organic composites, layered architectures and very thin organic layers played major roles in energy dissipation in these structures. It has been demonstrated in rigid natural marine composites that not only architecture, but also the mechanical behavior of the individual constituents, the nature of the interfaces, and interfacial bonding play important roles in energy dissipation. Additionally, the controlling effects of thin organic layers have been observed in other natural ceramic composite structures, such as teeth and bones, indicating that a variety of similar energy dissipating mechanisms in natural ceramic composites may operate as means to resist failure.

Mechanical Property Analysis on Sandwich Structured Hybrid Composite Made from Natural Fibre, Glass Fibre and Ceramic Fibre Wool Reinforced with Epoxy Resin

Natural fibre composites find wide range of applications and usage in the automobile and manufacturing industries. They find lack in desired properties, which are required for present applications. In current scenario, many developments in composite materials involve the synthesis of Hybrid composite materials to overcome some of the lacking properties. In this present investigation, two sandwich structured hybrid composite materials have been made by reinforcing Aloe Vera-Ceramic Fibre Wool-Glass fibre with Epoxy resin matrix and Sisal fibre-Ceramic Fibre Wool-Glass fibre with Epoxy resin matrix and its mechanical properties such as Tensile, Flexural and Impact are tested and analyzed. The test results from the two samples are compared and the results show that sisal fibre reinforced hybrid composite has better mechanical properties than aloe vera reinforced hybrid composite.

The Suburban Church: Modernism and Community in Postwar America

In The Suburban Church Gretchen Buggeln weaves a fascinating story of the rise of the modern church-building movement in the upper Midwest, viewed as the “cradle of modern church architecture” (p. 17). The book provides a rich and detailed study of the intricate dynamics of designing and building hundreds of mid-twentieth-century Protestant churches. Buggeln investigates the complex processes of collaboration and compromise among creative architects, pastors, church-building committees, and congregations within the wider contexts of family growth and the emergence of automobile-enabled suburbs. How were these churches to be distinctive, practical, and attractive to the growing suburban population in an increasingly secular world? Momentum was created through local, national, and even international meetings, where important discussions concerned the relationship among religious belief, architectural form, and visual attractiveness. Architects provided distinctive designs for dignified, economical, beautiful, and functional sanctuaries, as well as rooms that fit the multiple roles of the suburban church. These churches broke from the restrictions of tradition and were rational and simple solutions to form and design, with architectural structure, materials, and simplified ornament honestly expressed, often using natural wood, brick, and glass to humanize the elegant spaces.

Sound speed and attenuation in water-saturated granular materials at MHz frequencies

Sound speed and attenuation measurements are reported for water-saturated granular materials (natural sand and glass beads) at frequencies of 1.0 to 1.8 MHz. Median grain diameters were 0.219 to 0.497 mm, corresponding to kd>1, i.e., the scattering regime. The measurements were made for different thicknesses of sediment resting on a reflective surface using a monostatic geometry. The attenuation estimates compare well with previously reported experimental results and to the predictions of multiple scattering theory. The sound speed estimates exhibit the negative dispersion predicted by theory, but compared to previous measurements are biased low by 100 m/s to 200 m/s. It is argued that this bias is due to microbubbles in concentrations of O(10) ppm by volume.

Phase petrology reveals shallow magma storage prior to large explosive silicic eruptions at Hekla volcano, Iceland

Understanding the conditions that culminate in explosive eruptions of silicic magma is of great importance for volcanic hazard assessment and crisis mitigation. However, geological records of active volcanoes typically show a wide range of eruptive behavior and magnitude, which can vary dramatically for individual eruptive centers. In order to evaluate possible future scenarios of eruption precursors, magmatic system variables for different eruption types need to be constrained. Here we use petrological experiments and microanalysis of crystals to clarify the P–T–x state under which rhyodacitic melts accumulated prior to the H3 eruption; the largest Holocene Plinian eruption of Hekla volcano in Iceland. Cobalt-buffered, H2O-saturated phase equilibrium experiments reproduce the natural H3 pumice phenocryst assemblage (pl>fa+cpx>ilm+mt>ap+zrc) and glass chemistry, at 850±15°C and PH2O of 130 to 175 MPa, implying shallow crustal magma storage between 5 and 6.6 km. The systematics of FeO and anorthite (CaAl2Si2O8) content in plagioclase reveal that thermal gradients were more important than compositional mixing or mingling within this magma reservoir. As these petrological findings indicate magma storage much shallower than is currently thought of Hekla's mafic system, we use the constrained storage depth in combination with deformation modeling to forecast permissible surface uplift patterns that could stem from pre-eruptive magma intrusion. Using forward modeling of surface deformation above various magma storage architectures, we show that vertical surface displacements caused by silicic magma accumulation at ∼6 km depth would be narrower than those observed in recent mafic events, which are fed from a lower crustal storage zone. Our results show how petrological reconstruction of magmatic system variables can help link signs of pre-eruptive geophysical unrest to magmatic processes occurring in reservoirs at shallow depths. This will enhance our abilities to couple deformation measurements (e.g. InSAR and GPS) to petrological studies to better constrain potential precursors to volcanic eruptions.

Quantification of bulk form and angularity of particle with correlation of shear strength and packing density in sands

The study presents the quantification of shape parameters in sands. Natural sands, crushed sands, and glass beads are subjected to 2D microscopic and 3D X-ray computed tomographic imaging. Parameters of sphericity, elongation and slenderness are selected for analyzing the bulk forms and roundness is selected to quantify the angularity. Relationship among 2D shape parameters confirms that sphericity, elongation and slenderness are independent with roundness. Critical state friction angles are obtained by a direct shear test and void ratio ranges are measured as well. Both sphericity and roundness denote the strong linearity with void ratio range (emax−emin) bounded 0.15 and critical state friction angle (ϕcs) delineated by 20° at the unity, emphasizing that readily computable sphericity is sufficient to estimate properties of sands even without roundness. The multiple 2D projections of 3D images and their correlation for different orientation support that either bulk form or angularity in 2D images are acceptable enough to establish correlations between shape parameters and properties in sands. It implies that 2D quantification of particle shape is rational and can be used to approximate soil properties without conducting the laboratory experiments.

Formation of N–С–О–Н molecules and complexes in the basalt–basaltic andesite melts at 1.5 Gpa and 1400°C in the presence of liquid iron alloys

The contents and speciation of nitrogen, carbon, and hydrogen were determined in basalt–basaltic andesite melts in equilibrium with liquid Fe alloys at 1.5 Gpa, 1400°C, and oxygen fugacity (fO2) 1.4–1.9 log units below that of the Fe–FeO buffer (ΔlogfO2(IW) =–1.4 …–1.9). Experiments were carried out on a piston- cylinder type apparatus using welded Pt capsules in the presence of excess С (graphite). Starting mixture consisted of natural ferrobasaltic glass and silicon nitride (Si3N4) as nitrogen source in the system. Experimental quench products representing glasses with spherical inclusions of iron alloy were analyzed using electron microprobe, Raman, and IR spectroscopy. With increase of Si3N4 in the starting mixture and, respectively, decrease of fO2, silicate melt forming during experiments became depleted in FeO and enriched in SiO2. It was established that the nitrogen content in the glasses increases from 0.13 to 0.44 wt % with decrease of ΔlogfO2(IW) from–1.4 to–1.9, whereas C content in the first approximation remains constant within 1.18–1.13 wt %, while the total water content (ОН– + Н2О) determined by IR spectroscopy decreases from 4.91 to 1.20 wt %. The N (0.13–0.48 wt %) and C (0.75–2.26 wt %) contents determined in the Fe alloy show no clear correlation with fO2. The IR and Raman spectroscopic study of the glasses indicates the formation of molecules and complexes with bonds N–H (NH3, NH2−, NH2+, NH4+), Н–О (Н2О, OH–), С–Н (СН4) as well as N2 and Н2 molecules in silicate melts. IR spectra also reveal the presence of complexes with С=О, С–N bonds and СО2 molecules. Obtained data are compared with results of previous studies on the solubility and speciation of N, С, and Н in the model FeO–Na2O–SiO2–Al2O3 melts in equilibrium with liquid iron alloys at 1.5 GPa (1400°C) and 4 GPa (1550°C) (Kadik et al., 2011, 2015).

A new set of standards for in–situ measurement of bromine abundances in natural silicate glasses: Application to SR-XRF, LA-ICP-MS and SIMS techniques

Measuring the low bromine abundances in Earth's materials remains an important challenge in order to constrain the geodynamical cycle of this element. Suitable standard materials are therefore required to establish reliable analytical methods to quantify Br abundances. In this study we characterise 21 Br-doped glasses synthesized from natural volcanic rocks of mafic to silicic compositions, in order to produce a new set of standards for Br analyses using various techniques. The nominal Br contents (amounts of Br loaded in the experimental samples) of 15 of 21 glasses were confirmed within 20% by instrumental neutron activation analysis (INAA). Using this new set of standards, we compare three micro-analytical approaches to measure Br contents in silicate glasses: synchrotron X-ray fluorescence (SR-XRF), laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS), and secondary ion mass spectrometry (SIMS). With SR-XRF, the Br contents of the standard glasses were determined with the highest accuracy (<10% for Br≥10ppm; >25% for Br≤5ppm), and high precision (<10% for Br contents >10ppm; 20–30% for Br≤10ppm). The detection limit was estimated to be <1ppm Br. All those factors combined with a high spatial resolution (5×5μm for the presented measurements), means that SR-XRF is well suited to determine the low Br abundance in natural volcanic glasses (crystal-hosted melt inclusions or matrix glasses of crystallized samples). At its current stage of development, the LA-ICP-MS method allows the measurement of hundreds to thousands ppm Br in silicate glasses with a precision and accuracy generally within 20%. The Br detection limit of this method has not been estimated but its low spatial resolution (90μm) currently prevents its use to characterise natural volcanic glasses, however it is fully appropriate to analyse super liquidus or sparsely phyric, Br-rich experimental charges. Our study shows that SIMS appears to be a promising technique to measure the low Br contents of natural volcanic glasses. Its spatial resolution is relatively good (~15μm) and, similarly to SR-XRF, the detection limit is estimated to be ≤1ppm. Using our new set of standards, the Br contents of two MPI-DING reference glasses containing ≤1.2ppm of Br were reproduced with precision <5% and accuracy <20%. Moreover, SIMS presents the advantage of being a more accessible instrument than SR-XRF and data processing is more straightforward.

Investigations On Mechanical Properties Of Glass And Sugarcane Fiber Polymer Matrix Composites

Most of the developing countries are very rich in agricultural and natural fibres. It has got a very large percentage of production of rice husk, jute, stalk, baggase and coconut fibre in India. All these natural fibers have excellent physical and mechanical properties and can be utilized more effectively in the development of composite materials for various industrial applications. The present study deals with the effects of natural fibers on some mechanical properties of the Epoxy composites. This research was carried out by reinforcing the matrix (Epoxy) resin with natural fibre (cane sugar fibers) and glass fiber. The natural fibers were exposed to chemical treatment before reinforcement. The hybrid composites reinforced with chopped glass and cane sugar fibers were produced using hand layup method. Each sample was fabricated with different 10, 20, and 30 percent by volume of sugar cane fiber. After preparation of composite material, the mechanical properties like flexural and impact strength were studied. Cane sugar fibre composites were found to have the higher values of flexural strength (490.77 MPa) and impact strength 93.92 KJ/m2) than chopped glass fiber composites (flexural strength 93.19 MPa and impact strength (23.92 KJ/m2). It was found that the addition of natural fibers (cane sugar) along with chopped glass fibers improve the mechanical properties of hybrid composites.

In situ measurement of ferric iron in lunar glass beads using Fe-XAS

Through use of a new X-ray Absorption Spectroscopy (XAS) calibration for Fe3+ analysis in silicate glasses, the first direct measurements of ferric iron in natural lunar picritic glasses are presented. Lunar glass beads from the Apollo sample collection contain up to 60.0% Fe3+. No correlation with melt chemical properties, such as Mg# or weight % TiO2, or physical properties, such as bead diameter, was observed. Fe3+/ΣFe is negatively correlated with NBO/T. These elevated Fe3+/ΣFe values reflect eruption and post-eruption oxidation due to magmatic degassing of H or OH. Glass beads observed to be zoned to lower Fe3+/ΣFe rims may represent a subsequent reduction in the lunar vacuum prior to cooling through the glass transition temperature.▪

Developing methodologies for source attribution: glass phase separation in Trinitite using NF3

Abstract This study details thermal reactions between glasses, common minerals, and Trinitite post-detonation material with the fluorinating agent nitrogen trifluoride (NF3). The ultimate goal of our investigation is to develop a relatively rapid method for the effective separation of bomb components from complex matrices resulting from a nuclear explosion. Trinitite samples, silicate minerals (quartz; plagioclase and microcline), amorphous SiO2, calcite, a natural glass (obsidian), and two synthetic glasses were characterized extensively before and after the fluorination to fully understand the effects of the NF3 thermal treatment. Samples were reacted with NF3 using a combined thermogravimetric (TG) differential thermal analysis (DTA) unit, as well as in a stainless steel bomb reactor connected to a fluorination line. Subsequent to the NF3 treatment, samples were imaged by scanning electron microscopy in order to document changes in grain size and morphology. Energy dispersive spectroscopy was performed to determine changes in major element abundances. Results demonstrate that rates of reaction are dependent on grain size, temperature, pressure, and time of fluorination. All mineral samples experienced mass loss during fluorination. Specifically, amorphous SiO2 (~90% mass loss) experienced the most while calcite experienced the least (~18%). Major element analysis reveals that mass loss is attributable to the volatilization of silica (SiO2) in Si-bearing phases, or sample decomposition in calcite due to fluorination. Results for fluorinated samples of Trinitite demonstrate that mass loss occurs at different rates for each sample, but each sample experienced an expected large decrease in Si content (resulting from volatilization of SiF4). Hence, the concentration of metals in the residual material increased due to the volatilization of Si. These results validate that this thermal-fluorination technique allows the separation of silica from minerals (i.e. naturally occurring crystalline materials) and glasses (i.e. amorphous materials), leaving behind non-volatile fluorinated species and refractory phases. The results from our investigation clearly indicate that the NF3 treatment of nuclear materials is a technique that provides effective separation of bomb components from complex matrices (e.g. post-detonation samples), which will aid with rapid and accurate source attribution.

Long-term stability of hydrogen isotope ratios in hydrated volcanic glass

The advancement of conceptual and numerical geodynamic models necessitates quantitative, orogen-scale paleoelevation data. Felsic volcanic glasses, which record the hydrogen isotope compositions (δD) of meteoric water shortly after deposition, provide several advantages as a paleoelevation proxy. Questions remain, however, about the reliability of this relatively new proxy, including the effect of hydrofluoric (HF) acid abrasion in the preparation of glass shards for hydrogen isotope analysis and the stability of hydrogen isotope ratios in hydrated glass shards over geologic time (106–107years). HF acid abrasion of natural ancient glass shards results in systematic shifts in glass δD values away from modern water δD values. To evaluate the effectiveness of HF acid abrasion, we treated 70–150μm glass shards separated from various natural tephras with deuterium-labeled water (DLW; δD=+18,205‰) for up to 400days. For all glasses, this treatment resulted in elevated δD values in comparison to untreated samples. HF acid abrasion after DLW exposure, however, removed this effect and restored glass shards to their original untreated δD values in samples older than 104years. HF acid abrasion removes hydrous alteration precipitates at the glass surface without measurably changing the δD values of the underlying hydrated glass, regardless of abrasion duration or glass composition. Additionally, 45–34Ma glasses record δD values that directly reflect their depositional environments as determined by stratigraphy: glasses from tuffs deposited in demonstrably evaporative lacustrine environments have relatively high δD values compared to glasses from contemporaneous tuffs deposited in nearby fluvial environments, which have much lower δD values. The preservation of δD values that systematically vary with original depositional environment, despite >30Myr of post-hydration exposure to the same meteoric water, indicates that these volcanic glasses resisted measurable H isotope exchange on geologic timescales. This research supports the use of natural felsic glass separates for paleoaltimetry, and demonstrates the necessity of HF acid abrasion and glass shard isolation in sample preparation methods.

Much More Than a Glass: The Complex Magnetic and Microstructural Properties of Obsidian

Obsidian is a natural volcanic glass in which nanocrystalline and microcrystalline phases can coexist with the glassy one. In this paper, magnetic properties of Monte Arci obsidians are investigated by an experimental approach commonly applied to synthetic nanostructured materials and rarely to natural ones, and correlated with the mineralogical composition and microstructure. Among the different crystalline phases, the iron-containing components are found to be responsible for a great variety of magnetic behaviors, including paramagnetism, antiferromagnetism, ferromagnetism, and superparamagnetism. The combined use of powder X-ray diffraction (PXRD), 57Fe Mossbauer spectroscopy, DC magnetometry, and transmission electron microscopy (TEM/HRTEM) provides new insights in the Monte Arci obsidian: (i) the presence of magnetite nanoparticles spread into the glassy matrix; (ii) the presence of an antiferromagnetic phase responsible for a discontinuity at about 45 K; (iii) exchange bias phenomena, for the first ...

The origin of nelsonite constrained by melting experiment and melt inclusions in apatite: The Damiao anorthosite complex, North China Craton

Models for the nelsonite formation are currently highly contentious, with liquid immiscibility and fractional crystallization as frequently proposed formation mechanisms. The nelsonites in the Damiao massif anorthosite complex in the North China Craton are revisited here together with experimental evidence for the existence of silica-free CaO-FeO-Fe2O3-TiO2-P2O5 immiscible nelsonitic liquids. Our results of differential scanning calorimetry (DSC) and internally heated pressure vessel (IHPV) demonstrate that nelsonite with the composition of one-third apatite and two-thirds Fe-Ti oxides by weight 1) completely melts well above 1450°C at dry condition, which is in good agreement with numerous experimental studies of the CaO-P2O5-FexO system for metallurgical purposes; 2) does not melt at the temperature up to 1200°C with presence of considerable amount of volatiles, e.g., fluorine and water. Therefore, the composition of the nelsonite cannot be molten at temperatures relevant for crystallization of the Damiao magma. A review of experimental studies of liquid immiscibility and analyses of natural immiscible glasses show that all the liquids on the Fe- and P-rich side of the miscibility gap have at least 20wt.% of aluminosilicate components.Analyses of apatite-hosted melt inclusions from Damiao nelsonite provide further constraints on the nelsonite formation. The inclusions range from ~3 to 200μm in diameter. They are ubiquitous and meet all the morphological criteria of primary melt inclusions crystallized into assemblages of daughter minerals. Almost all assemblages contain vermiculite and/or chlorite, and some contain biotite, amphibole and Fe-Ti oxide. Melt compositions of individual inclusions has been estimated based on modal proportions and mineral compositions of daughter phases. The inclusions show large variations in SiO2 (20.8–50.2wt.%) and FeOt (13.4–32.8wt.%). With a few exceptions, the inclusions are very low in CaO (<1.5wt.%) and high in Al2O3 (10.0–21.2wt.%). The low total values indicate very hydrated nature of the melt inclusions. The melt inclusions were also re-heated at 1200°C by IHPV. Glasses from partly to fully homogenized melt inclusions show similar compositional characteristics as the bulk compositions from the crystallized melt inclusions but incorporated excessive melting of the host apatite. It appears that the cumulus apatite crystallized from hydrated late-stage immiscible Fe-rich melt formed by liquid immiscibility occurred in the relatively early stage, i.e. prior to the arrival of aqueous fluid phase. We propose that the inclusions at Damiao record a trend of late-stage melt evolution, which have been through silicate liquid immiscibility but most likely have been strongly affected by separation of a magmatic fluid phase and loss of alkali and Ca silicate components from the melt into the fluid.

Magma mixing induced by particle settling.

A time series of experiments at high temperature have been performed to investigate the influence of particle settling on magma mixing. A natural rhyolite glass was held above a natural basalt glass in a platinum crucible. After melting of the glasses at superliquidus temperatures, a platinum sphere was placed on the upper surface of the rhyolitic melt and sank into the experimental column (rhyolitic melt above basaltic melt). Upon falling through the rhyolitic–basaltic melt interface, the Pt sphere entrained a filament of rhyolitic melt in its further fall. The quenched products of the experiments were imaged using X-ray microCT methods. The images of our time series of experiments document the formation of a rhyolite filament as it is entrained into the underlying basalt by the falling platinum sphere. When the Pt particle reached the bottom of the crucible, the entrained rhyolitic filament started to ascend buoyantly up to the initial rhyolitic–basaltic interface. This generated a significant thickness increase of a comingled “melange” layer at the interface due to “liquid rope coiling” and piling up of the filament. As a consequence, the basalt/rhyolite interface was greatly enlarged and diffusive hybridisation greatly accelerated. Further, bubbles, originating at the interface, are observed to have risen into the overlying rhyolite dragging basalt filaments with them. Upon crossing the basalt/rhyolite interface, the bubbles have non-spherical shapes as they adapt to the differing surface tensions of basaltic and rhyolitic melts. Major element profiles, measured across the rhyolite filaments, exhibit asymmetrical shapes from the rhyolite into the basalt. Na and Ti reveal uphill diffusion from the rhyolite towards the interface in the filament cross sections. These results reveal the potential qualitative complexity of the mingling process between rhyolitic and basaltic magmas in the presence of sinking crystals. They imply that crystal-rich magma mingling may be expected to be accelerated with respect to crystal-poor systems. We urge the further fluid dynamic analysis of these phenomena, obtainable for the first time using detailed tomographic imaging.Electronic supplementary materialThe online version of this article (doi:10.1007/s00410-016-1305-1) contains supplementary material, which is available to authorized users.