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Conclusion: We have identified the rhyolitic samples from the HT geothermal drillhole KT-8 in the Tianzhen area, northeastern Datong Basin. Such rock consists of phenocryst grain of quartz, perthite, and biotite with minor volcanic glass. The geothermometer of ternary-feldspar yields the crystallized temperatures ranging from 600 to 800 °C with average value of 700 °C, representing the crystallized temperature of rhyolitic magma. According to major and trace element characteristics as well as Sr-Nd isotope, such magma likely derived from partial melting of Archean gneissic complexes that was triggered by the segregation of mantle-derived basalts in the studying area. The magmatic evolution is important link between deeply magmatic source and shallow volcanic activity. Combined with tectonic background and geothermal investigation, the rhyolite and its surrounding gneissic complexes would be as the source and reservoir for the HT geothermal system in the Tianzhen area, respectively. The final publication is available at Springer via https://doi.org/10.1007/s12583-024-0035-y. [ABSTRACT FROM AUTHOR]

We have obtained the first data on the chemical composition of the eruptive materials from the explosive eruption of Bezymianny volcano on April 7, 2023. Our unique collection includes freshly sampled pumice lapilli from the eruption and juvenile blocks from pyroclastic flows. We have identified interesting patterns in both macro components and specific chalcophile elements, such as copper. The rocks we studied belong to medium-K two-pyroxene basaltic andesite (55.5‒57 wt % SiO2), with mafic enclaves characterized by a slightly more primitive composition (53.7 wt % SiO2). According to mineral geothermometry data, the phenocrysts of basaltic andesite crystallized at temperatures in the range from 940 to 960°C, while the formation of phenocryst rims and microlites occurred at 980°C, which corresponds to conditions immediately before the eruption. The composition of volcanic glass allows us to estimate the pressure at which the magma reached the last equilibrium with crystallizing phases before eruption (0.5‒0.6 kbar). Based on these findings, we have formulated hypotheses about the potential evolution of the shallow magma chamber of Bezymianny volcano during the period from 2017 to 2023. [ABSTRACT FROM AUTHOR]

Reliable reconstructions of tephrostratigraphy and emplacement mechanisms of Early to Middle Miocene volcaniclastic deposits across the Alpine-Mediterranean region may yield important clues as to the nature, spread, volume, magnitude and frequency of large silicic eruptions of the Carpathian-Pannonian Region. Here we report on a sequence of Middle Miocene volcaniclastic deposits intercalated with lacustrine strata from the Livno-Tomislavgrad Basin, part of the Dinaride Lake System. We applied a multi-proxy approach to elucidate their source, decipher their emplacement mechanism, and evaluate their basin-scale and regional correlativity. New high-precision zircon geochronology (~ 14.32 Ma) reveals their simultaneity with numerous volcaniclastic deposits (and their alteration products) widely spread across the Alpine-Mediterranean region. Additionally, their correlativity is confirmed at the scale of the Livno-Tomislavgrad Basin, based on similar lithostratigraphy, mineralogy and volcanic glass geochemistry. Newly obtained zircon Hf isotope data imply that Livno-Tomislavgrad Basin distal volcaniclastic deposits and ~ 14.36 Ma Harsány ignimbrite of the Carpathian-Pannonian Region had shared a parental eruptive center. However, different volcanic glass geochemistry, bolstered by the high-precision geochronology, suggests distinct eruption events, implying more frequent explosive volcanism of the Carpathian-Pannonian Region during Middle Miocene than previously recognized. We suggest that the ~ 14.32 Ma fine fallout tephra, deposited in the distal basin in the Dinarides (> 400 km from the source), was likely re-mobilized by water-driven hillside erosion from the extensive paleo-relief, and further transported via land-derived gravity flows. Upon entering the lake, the gravity flows likely transformed into subaqueous sediment density flows. These deposited ~ 1 to 7-m-thick overall graded volcaniclastic turbidites, thinning away from the presumed source of tephra re-mobilization. Although over-thickened, the ~ 14.32 Ma Livno-Tomislavgrad Basin volcaniclastic deposits can still serve as a reliable tephro- and tectono-stratigraphic markers due to their rapid mode of accumulation. Schematic illustration of the formation of studied ~14.32 Ma volcaniclastic successions of the SE Livno-Tomislavgrad Basin, Dinaride Lake System [ABSTRACT FROM AUTHOR]

This paper explores the strategies implemented by hunter-gatherer groups in Southern Patagonia during the Late Holocene in relation to the circulation of goods and information. Previous archaeological investigations have revealed important changes in human mobility and land-use patterns during this period, associated with increasingly dry environmental conditions. In this context, we undertake a broad spatial scale analysis of the circulation of goods and information through the integrated examination of two lines of evidence: rock art and lithic raw materials. Specifically, we consider the distribution of engravings and black obsidian artefacts assigned to the Late Holocene. The former can offer certain insights into the circulation of information, and the latter are indicative of the circulation of goods. Our analysis suggests that during this period different strategies were developed by hunter-gatherer groups to face the changing environment. Several implications concerning social interaction and the movement of people during this period in Southern Patagonia are discussed. [ABSTRACT FROM AUTHOR]

Background: Sphincter-preserving techniques like autologous compound platelet-rich fibrin foam have gained popularity, offering potential for better functional outcomes in anal fistula treatment. The present study aimed to evaluate the efficacy and safety of Obsidian RFT®. Methods: The study conducted a retrospective analysis from January 2018 to December 2022 on patients who received anal fistula closure with Obsidian RTF® at the Department of General Surgery, Medical University of Vienna. Clinical diagnosis, complemented by radiographic imaging, was employed to confirm inconclusive cases. Demographic and fistula characteristics and postoperative data were collected from electronic records following STROCSS criteria. Results: Fifteen patients received Obsidian RFT® treatment for anal fistulas. We found no intra- and postoperative complications. The median hospital stay was 3 days. After a median follow-up of 32 months, a closure rate of 53.3% was detected. Non-significant differences were observed in various variables, yet trends emerged, indicating associations between abscess presence and non-healing fistulas. A distinct age threshold (≥ 42.7 years) served as an indicator for an inability to achieve anal fistula cure. Conclusion: Obsidian RFT® represents a safe, minimally invasive operative procedure. Approximately half the patients experienced healing, with better outcome in a younger population. Trial Registration: Ethical Approval number Medical University of Vienna (#1258/2018). This study was registered retrospectively in ClinicalTrials.gov (NCT06136325). [ABSTRACT FROM AUTHOR]

Clay-type Li deposits are poised to play a pivotal role in addressing the surging global demand for Li. The McDermitt clay-type Li deposit, located in Nevada, is the largest Li deposit in the United States, with Li hosted by a clay-rich sequence of smectite-dominated intervals and illite-dominated intervals, respectively. However, the occurrence of Li and the genesis of Li-bearing minerals within smectite-dominated intervals have not been thoroughly investigated in previous research. Here, we studied the mineralogy, the in-situ Li distribution, and the bonding environments of Li within the smectite intervals using a combination of instrumental techniques including scanning electron microscope, transmission electron microscope, time-of-flight secondary ion mass spectrometry, and nuclear magnetic resonance. Our results indicate that the smectite exhibits low crystallinity characteristics of lacustrine clay authigenesis and is commonly found to fill the interstices among volcanic minerals or envelop them; Li is mainly hosted by Mg-smectite rather than the volcanic minerals. Within the tuffaceous sediment samples, the volcanic glass has undergone a transformation, resulting in its complete disappearance and alteration into clay minerals. Owing to the octahedral sites of Mg-smectite bounded in Li, it is referred to be hectorite. We interpret that the hectorite's precipitation occurs in a high saline-alkaline water environment, a result of McDermitt tuff dissolution. This conclusion can be supported by the coexistence of spherulitic calcite and hectorite. Overall, this study confirms hectorite as the main Li-bearing mineral and increases the understanding of the genetic model of hectorite formation in intracontinental caldera basins. [ABSTRACT FROM AUTHOR]

We investigated Late Permian Li-rich claystones with up to 1.05 wt% Li2O (average: 0.45 wt% Li2O) in the Pingguo area in Guangxi, southwest China. Our results show that cookeite (chlorite group) is the dominant Li-bearing mineral. Cookeite is intercalated with authigenic illite and detrital kaolinite, which suggests that cookeite formed during burial diagenesis from pre-existing Li-rich kaolinite in the original clay assemblage. The Li-rich claystones were mainly sourced from felsic volcanic rocks of the Emeishan large igneous province (LIP), and the Li-rich kaolinite was likely produced by weathering of felsic volcanic materials (i.e., pyroclastic rocks, tephras, and volcanic glass) deposited on a Permian carbonate platform. We propose that the abundance of precursor kaolinite and its Li content control the degree of Li enrichment in this new potential Li resource. [ABSTRACT FROM AUTHOR]

This research investigated the physicochemical properties and pozzolanic reactivity of mechanochemically and thermally treated clay, marl, and obsidian as supplementary cementitious materials (SCMs). The results suggest that the mechanochemical treatment of clay and marl resulted in delamination, dehydroxylation, and amorphisation of the mineral components (including calcite); while for obsidian, the main effect was particle size reduction. Among all samples prepared, the mechanochemically treated obsidian exhibited the best performance as a SCM and achieved marginally higher strength performance at 20% cement replacement compared with the CEM I cement mortar (with on SCM). The thermally activated clay and marl exhibited highest pozzolanic reactivity than the mechanochemically treated counterparts owning to the formation of free lime from calcination of calcite. However, the mechanochemically treated clay and marl were still able to achieve over 80% of the strength activity index and performed much better than the untreated materials. These results indicate that mechanochemical treatment can effectively improve the pozzolanic reactivity of clay minerals that contain calcite up to 68% without directly emitting process CO2 to the environment (calcination of carbonates), which can be an alternative activation route to the high-temperature calcination-treatment method. [ABSTRACT FROM AUTHOR]

Data from our original database, which includes more than 2 600 000 analyses for 75 elements of mineral-hosted melt inclusions and quench glasses in volcanic rocks, are generalized to calculate the mean concentrations of major, volatile, ore, and trace elements in magmatic melts from the following dominant geodynamic environments: (I) spreading zones of oceanic plates (mid-oceanic ridges), (II) environments affected by mantle plumes in oceanic plates (oceanic islands and lava plateaus), (III, IV) environments related to subduction processes (III is zones of arc magmatism on the oceanic crust, and IV is zones of magmatism in active continental margins in which magma-generating processes involve the continental crust), (V) environments of continental rifts and areas with continental hotspots, and (VI) environments of backarc spreading. A histogram of SiO2 distribution in natural magmatic melts shows a bimodal distribution: one of the maxima falls onto SiO2 concentrations of 50–52 wt % and the other onto 72–76 wt %. The most widely spread melts contain 62–66 wt % SiO2. Mean temperatures and pressures are calculated for each of the environments. The normalized multielemental patterns presented for environments I through VI show the ratios of the mean concentrations of elements in magmatic melts of mafic, intermediate, and felsic composition to the concentrations in the primitive mantle. Mean ratios of incompatible, trace, and volatile components (H2O/Ce, K2O/Cl, Nb/U, Ba/Rb, Ce/Pb, etc.) are evaluated for the melts of each of the environments. The variations in these ratios are calculated, and it is demonstrated that the ratios of incompatible elements are mostly statistically significantly different in the different environments. The differences are particularly significant between the ratios of the most differently incompatible elements (e.g., Nb/Yb) and some ratios involving volatile components (e.g., K2O/H2O). [ABSTRACT FROM AUTHOR]

Chemical anomalies in polar ice core records are frequently linked to volcanism; however, without the presence of (crypto)tephra particles, links to specific eruptions remain speculative. Correlating tephras yields estimates of eruption timing and potential source volcano, offers refinement of ice core chronologies, and provides insights into volcanic impacts. Here, we report on sparse rhyolitic glass shards detected in the Roosevelt Island Climate Evolution (RICE) ice core (West Antarctica), attributed to the 1.8 ka Taupō eruption (New Zealand)—one of the largest and most energetic Holocene eruptions globally. Six shards of a distinctive geochemical composition, identical within analytical uncertainties to proximal Taupō glass, are accompanied by a single shard indistinguishable from glass of the ~25.5 ka Ōruanui supereruption, also from Taupō volcano. This double fingerprint uniquely identifies the source volcano and helps link the shards to the climactic phase of the Taupō eruption. The englacial Taupō-derived glass shards coincide with a particle spike and conductivity anomaly at 278.84 m core depth, along with trachytic glass from a local Antarctic eruption of Mt. Melbourne. The assessed age of the sampled ice is 230 ± 19 CE (95% confidence), confirming that the published radiocarbon wiggle-match date of 232 ± 10 CE (2 SD) for the Taupō eruption is robust. [ABSTRACT FROM AUTHOR]

The mineralogical and structural properties of the analcime-bearing rocks from Milići (Bosnia and Herzegovina) have been investigated in this work. The analyzed tuff samples, enriched in natural analcime, were characterized through microscopic, DTA/TGA, SEM, and X-ray powder diffraction analysis. The mineralogical composition of the analcime-bearing rocks consists of analcime, quartz, feldspars, mica, carbonates, volcanic glass, zircon, apatite, rutile, and plant fossils. Quantitative XRD analysis shows that the most abundant mineral is analcime. The representative composite sample of analcime-bearing rocks was refined on tetragonal (I41/acd) unit-cell parameters. Tetragonal unit-cell parameters of analcime yielded the best refinement agreement factors (a = 13.7097 (3), c = 13.6953 (4) Å, V = 2571.32 (5) Ǻ3 – Rw = 14.2, Rp = 12.2, Rexp = 8.7, DW stat. = 1.1, GofF = 1.6). The quantitative amounts of main minerals obtained using the Rietveld method yielded before the following results (wt %): analcime 48.79% (RB = 5.99, RF = 5.95), sanidine 29.20% (RB = 2.55, RF = 2.31), biotite 15.99% (RB = 6.56, RF = 3.94), quartz 6.02% (RB = 4.86, RF = 4.63). [ABSTRACT FROM AUTHOR]

We quantified the redox state of magma recorded in volcanic glass particles from an ash-forming eruption at Bromo volcano, Indonesia, to obtain insights into its degassing process. An ash sample was collected by real-time sampling from the ash-forming eruption on 24 March 2011. The ash sample contains juvenile glass particles with a brown-colored, transparent appearance. Detailed observations of texture under a field-emission–electron probe micro analyzer show that the brown glasses lack nanoscale crystals in their groundmass. The compositions of groundmass glass (trachy-andesite) and phenocrysts in the brown glass particles indicate a pre-eruptive magma temperature of 1060 ± 20 °C. The Fe3+/ΣFe ratios of the brown glasses were determined to be 0.15–0.24 using synchrotron-based Fe–K edge micro X-ray absorption near-edge structure spectroscopy. From the chemical composition, temperature, and Fe3+/ΣFe data, the oxygen fugacity of the magma is estimated to be in the range of 10−10.3 to 10−8.9, yielding a redox state of ΔQFM = 0.57 ± 0.70. The redox state of magma estimated from the brown glasses is more reduced than that of volcanic gas emitted during the open-vent degassing phase (~ 700 °C and ΔQFM of 1.8). The low temperature and oxidized condition of the volcanic gas can be explained by closed-system cooling from 1060 to 700 °C in the gas phase after outgassing, suggesting that the magma head was located deeper during the open-vent degassing phase than during the ash-forming eruption. The comparison between the redox states of volcanic glass and gas reported in this study gives valuable insights into the degassing process driving volcanic activity. [ABSTRACT FROM AUTHOR]

Characterization of microstructures and perlitic textures may be carried out by combining volcanological and glass technical concepts, with supporting evidence from image analysis. These methods enable investigation of the mechanisms of protracted fracture formation, propagation, and characterization of fracture networks in silica-rich volcanic glass. Here we present analyses of rhyolitic lava and ignimbrites from different locations and geological ages. Our results allow characterization of the relationship between primary sublinear quench fractures and secondary rounded perlitic fractures, which together form a three-dimensional fracture network. Completely hydrated samples from the pre-Cenozoic show no variations in volatile fluid content within fractured glass but do show differential depletion in alkali contents, suggesting significant fluid-mediated alteration. In contrast, younger samples are incompletely hydrated and may demonstrate a connection between alkali mobility and rock hydration. Formation of primary fractures and a first generation of secondary fractures is caused by thermal shock close to the glass transition temperature. Formation and propagation of subsequent fracture generations is related to intrinsic stresses induced by the continued hydration of volcanic glass. We find that the pore space in rhyolitic rocks is not only influenced by fracture porosity or initial vitric porosity but may increase or decrease during post-emplacement, low-temperature alteration processes. [ABSTRACT FROM AUTHOR]

This study aims to explore the potential of µ-Raman and µ-XRF spectroscopy for discriminating between various obsidian sources found in northwest Iran and to trace the provenance of prehistoric artifacts discovered at archaeological sites close to these sources. The study utilized excitation lasers of 532 and 785 nm to analyze obsidian samples from different sources, including Tajaraq (Miyaneh) associated with the Bozqush volcanic mountain range and Ghizilja (Bostan Abad) and Ideloo (Sarab) linked to the Sabalan volcanic mountain range. Principal component analysis (PCA) and hierarchical clustering (HCA) were utilized to analyze the data. Archaeological sites that were examined in the study were Kultepe Asbfrooshan of the Chalcolithic and Kura-Araxes cultures and Tepe Emam Chay of the Bronze and Iron Ages. Micro X-ray fluorescence (µ-XRF) was used to check the viability of the Raman use in discriminating the sources of obsidian. Results indicate that Raman spectroscopy is an effective method for differentiating sources of obsidian and confirming the origins of ancient tools from Ideloo. These findings suggest that local obsidian sources had limited usage, and it is crucial to explore and identify other possible sources of obsidian to comprehend ancient obsidian trade networks fully. The paper establishes the significance of using Raman spectroscopy in determining the provenance of obsidian artifacts and the complexities involved in the geoprocessing and trade of obsidian. A more comprehensive investigation of potential sources in the region can help unravel the trade dynamics of ancient Iran. [ABSTRACT FROM AUTHOR]

Semitransparent gray color obsidian samples (bulk and powder) were irradiated at room temperature by Co60 radiation source with the γ-photon average energy of 1.25 MeV and different doses from 5 to ~500 kGy. It is known that γ-irradiation influences the optical properties of glass materials depending on the composition as well as on the presence of defects in the glass matrix. Analysis of obsidian samples was carried out by absorption and reflection spectroscopy in the UV, visible, and IR ranges, as well as by EPR measurements for characterization of semitransparent gray color obsidian depending on the γ-irradiation of different doses. The difference in transmittance spectra between the pristine sample and those irradiated with different doses made it possible to distinguish three absorption bands at 368, 386, and 442 nm, which are responsible for Fe3+ ions in different environments. The content of hydroxyl OH groups, determined from the absorption in the band at ~4500 cm–1, does not change in the range of used doses. The EPR measurements showed three signals with g-factors of ~6.0, ~4.2, and ~2.0 characteristic for Fe3+ ions, the intensities of which increase with increasing irradiation doses. Obsidian turned out to be resistant to the formation of NBOHC paramagnetic defects in the region of the indicated doses of γ-irradiation. [ABSTRACT FROM AUTHOR]

Drinking water with a high natural concentration of fluoride (F−) has serious consequences for the health of the rural population in the state of Guanajuato, Mexico, where the water contains levels of F− that are not allowed by national and international regulations (1.5 mg/L). This health problem is very common in multiple states throughout Mexico where drinking water is generally extracted from aquifers that are hosted in fractured volcanic rocks of the Tertiary. These aquifers show similar geological characteristics: deep basins that formed as a result of felsic eruptive events and the extensional deformation of the Basin and Range and are now filled with unconsolidated sediments. In this study, we assessed the occurrence of F in volcanic rocks collected at 11 sampling sites along the Sierra de Codornices in Guanajuato (ranging between 0.01299 and 0.146 wt%, average 0.039 wt%, and SD = 0.039 wt%; n = 10), a region where both rural and urban communities consume drinking water with a high F− content (up to 7.1 (mg/L). The F content is dispersed in volcanic rocks, and the highest levels are present in felsic rocks. The statistical and hydrogeochemical results of a sampling campaign of 32 wells in the Juventino Rosas (JR) and Villagran (Vill) municipalities in 2019 suggest that F− mobilization in groundwater is the product of silicate weathering and the dissolution of volcanic glass, alkaline desorption in the surfaces of F-containing minerals, and possibly ion exchange of minerals and clays or deep fluids enriched with F−, in addition to the precipitation of carbonates that decrease the Ca2+ concentration in groundwater. All of these processes can be accelerated by groundwater geothermal characteristics within the study area. The hydrogeochemical, fluoride exposure risk, and fluoride pollution index (FPI) results, as well as the epidemiological survey, indicate that teenagers and older adults from Praderas de la Venta are at risk of exposure to F− due to the high concentrations ingested over a long period, the toxicity of the element, and its ability to accumulate in the bones. Extended exposure to elevated levels increases the risk. This work allows us to observe how the populations of JR and Vill can be exposed to high F− contents in drinking water due to the geological characteristics of the region. [ABSTRACT FROM AUTHOR]

Disposal of waste material is causing environmental issues all around the world. Waste glass and tin can are two such products that impose detrimental effects on the environment. One feasible approach is to utilize these discarded materials as constituents of concrete. This study investigates the performance of concrete prepared with glass waste as fine aggregate (GWA) and tin can fiber (TCF) in terms of workability, fresh density, compressive, and splitting tensile strength as desired concrete properties. An Artificial Neural Network (ANN) approach has been adopted for developing predictive models to simulate the impact of these waste materials on concrete properties. Experimental findings demonstrate that the worability of concrete mix decreases with increasing GWA and TCF contents in the mix. Increasing TCF percentages results in an increase in fresh density of concrete; however, a declining pattern in fresh density has been observed with increasing GWA percentage in the concrete mix. Compressive strength at all curing ages shows positive trends till 20% GWA and 1% TCF incorporation in concrete. Similar pattern has been observed for splitting tensile strength up to 10% GWA and 0.5% TCF. Constructed models are feasible for prediction of the desired concrete properties as verified by various statistical parameters. Sensitivity analysis reports that TCF has a greater influence on concrete properties than GWA. [ABSTRACT FROM AUTHOR]

Nanometer-sized crystals (nanolites) play an important role in controlling eruptions by affecting the viscosity of magmas and inducing bubble nucleation. We present detailed microscopic and nanoscopic petrographic analyses of nanolite-bearing and nanolite-free pumice from the 2021 eruption of Fukutoku-Oka-no-Ba, Japan. The nanolite mineral assemblage includes biotite, which is absent from the phenocryst mineral assemblage, and magnetite and clinopyroxene, which are observed as phenocrysts. The boundary between the nanolite-bearing brown glass and nanolite-free colorless glass is either sharp or gradational, and the sharp boundaries also appear sharp under the transmitted electron microscope. X-ray absorption fine structure (XAFS) analysis of the volcanic glass revealed that the nanolite-free colorless glass records an oxygen fugacity of QFM + 0.98 (log units), whereas the nanolite-bearing brown glass records a higher apparent oxygen fugacity (~ QFM + 2). Thermodynamic modelling using MELTS indicates that higher oxygen fugacities increase the liquidus temperature and thus induced the crystallization of magnetite nanolites. The hydrous nanolite mineral assemblage and glass oxygen fugacity estimates suggest that an oxidizing fluid supplied by a hot mafic magma induced nanolite crystallization in the magma reservoir, before the magma fragmentation. The oxidation-induced nanolite crystallization then enhanced heterogeneous bubble nucleation, resulting in convection in the magma reservoir and triggering the eruption. [ABSTRACT FROM AUTHOR]

In this study, waste glass obtained from a discarded green glass bottle and unexploited natural red soil (RS) were prepared to get glass–ceramic foams. Red soil is an earthy material, which is used as a foaming agent. A mixture of starting powders containing different mass fractions (5–16 wt.%) of RS with particle size smaller than 20 μm was uniaxially pressed (at 30 MPa), and the obtained compacts were fired at different temperatures (750–850 °C) and holding time (30–120 min). Furthermore, the influences of temperature, holding time, and natural rock additions on the structure, type, and size of pores, besides physical and mechanical properties of the processed foamed glass–ceramic samples, were investigated. The results show that the optimum foaming temperature was found to be 800 °C leading to a maximum value of porosity as high as 90%, while the bulk density and compressive strength reached the values 0.26–0.75 g·cm−3 and 1.2–6.1 MPa, respectively. Based on the present data, the obtained glass–ceramic allowed the preparation of different porosity types. Therefore, they provide practical value for specific applications where thermal insulation is desired. [ABSTRACT FROM AUTHOR]

Identifying the microstructural characteristics of volcanic ash particles is key in developing our understanding of their production, transport and impact. Volcanic glass in ash clouds can damage aircraft engines, surfaces and coatings, and if inhaled cause harm to humans and animals on which they depend. We present results of 3D imaging of volcanic glass particles from two Icelandic volcanoes together with two samples of experimentally vesiculated volcanic glass. True colour 3D images were obtained using an Olympus LEXT 3D laser scanning confocal microscope. The images enabled examination of bubble structure, fracture patterns, and shape morphology characteristics of grains. For the two simulated fragments, the bubbles had a median long axis lengths of 13.2 and 37.0 μm. For the material from Grimsvötn and Eyjafjallajökul volcanic eruptions, the median long axis length was 25.2 μm and 23.1 μm, respectively. Laser confocal microscopy-based 3D imaging of volcanic glass fragments provides a rapid, non-destructive way to assess 3D particle geometry and quantify internal artefacts responsible for their formation. [ABSTRACT FROM AUTHOR]

Explosive volcanism produces myriad hazards from pyroclastic flows to widespread ejecta dispersal. Effusive eruptions can emit noxious, damaging gases and extensive lava flows. A single eruption of silicic magma can produce both types of activity, sometimes concurrently. Understanding what drives such eruptions, their transitions in styles, and associated hazards requires detailed observations of eruptions and analysis of resulting products. The physical and geochemical characteristics of pyroclasts serve as snapshots of final conduit processes before their egress. Here, we examine the explosive phase of the 640 CE rhyolitic eruption of Newberry Volcano (OR, USA), which began with sub-Plinian pyroclastic fallout and terminated with the effusion of the Big Obsidian Flow. To better understand shallow conduit dynamics, we combine previous work on the geochemistry and textures of obsidian pyroclasts with our detailed physical and textural analyses of > 2000 pumices from 37 layers pulled from 4 pits along the dispersal axis. We analyze the density, mass, and volume distribution of ash and lapilli layers and also examine external the texture of the latter. As with the rhyolitic eruptions of Volcán Chaitén in 2008 and Cordón Caulle in 2011–2012 (both in Chile), we find transitory Vulcanian pulses to be the link between the initial Subplinian phase and subsequent effusive activity. We also concur with recent studies that the syn-eruptive formation of obsidian by ash agglomeration and sintering along the conduit edges above the fragmentation level modulates eruptive style, ultimately leading to the subaerial effusion of rhyolitic lava. [ABSTRACT FROM AUTHOR]

Floods in 1997 and 2010 exposed the Frýdek and Frýdlant formations of the Subsilesian Unit in the Ostravice River bed near Frýdek-Místek. In the sedimentary sequence of upper Campanian to Maastrichtian marls and paraconglomerates, clasts of strongly altered basic volcanic rock were found, accompanied by carbonate concretions and layers. Rare apatite, biotite, and a Cr-rich spinel subgroup mineral are the only relatively well-preserved primary minerals in the clasts. The matrix contains buddingtonite, albite, sanidine, kaolinite, illite-muscovite, a mineral of the smectite group, and possibly also a mixed structure mineral of the chlorite-smectite type. Laths of buddingtonite, identified by powder X-ray diffraction and wavelength-dispersive X-ray spectrometry, are not homogenous. Their compositions range from Bd41 to Bd59 molar component, with Kfs ranging between 26 and 35 mol%, Nafs between 5 and 27 mol%, and Ca-feldspar between 1 and 4 mol%. The matrix is irregularly dolomitized. Carbonates are also present in pseudomorphs after idiomorphic olivine and in fill of amygdaloidal cavities. These carbonates reveal complicated alteration rock history, having cores of magnesite passing into almost pure siderite outer parts. Calcite is always the youngest and most homogenous carbonate, probably connected with a different geological event. Accompanying carbonate concretions are composed of three dolomitic phases with quartz, calcite, and muscovite. We can conclude that buddingtonite originates in alteration of primary feldspar and/or volcanic glass during the catagenetic breakdown of kerogen in the sediment, surrounded by clayey sediments rich in decomposing organic matter. Volcanic clasts have similar texture and supposed pre-alteration phase composition as the rocks of teschenite association, namely monchiquites to picrites. However, the source of volcanic clast within the sediments remains unclear. [ABSTRACT FROM AUTHOR]

The emplacement behaviors and the associated hazards of silicic lavas remain poorly understood because detailed real-time observations have only been made during a few modern eruptions. Therefore, we rely on older well-preserved glassy rhyolites like Banco Bonito and the VC-1 Rhyolite from the Valles caldera, New Mexico to constrain the emplacement behaviors of silicic lavas. Continuous whole cores, collected from both units during drilling in 1984 by the Continental Scientific Drilling Program, provide the unique opportunity to assess the rheological evolution of the interior of obsidian lavas. Banco Bonito is a large (0.9 km3; up to 150 m thick) obsidian lava coulée. The VC-1 Rhyolite is a relatively thin (~ 20 m) obsidian rhyolite that is not exposed at the surface and has an unclear emplacement history. Evidence for the emplacement dynamics of these two units is preserved as trends in volatile content and thermal history through the thicknesses of the rhyolite obsidians. We acquired 46 glassy samples from the VC-1 drill core through the entire thicknesses of both Banco Bonito and the VC-1 Rhyolite. We measured Archimedean densities, glass water concentrations using Fourier transform infrared spectroscopy (FTIR), and natural cooling rates using relaxation geospeedometry as a function of depth for both rhyolite obsidians. Systematic trends in both datasets provide evidence of the emplacement style of Banco Bonito and the VC-1 Rhyolite in the vicinity of the VC-1 drill hole. Total water contents range from 0.03 ± 0.01 up to 6.93 ± 1.09 wt. % for Banco Bonito, and range from 0.24 ± 0.06 to 1.08 ± 0.05 wt. % for the VC-1 Rhyolite. Both rhyolite obsidians display evidence of having been partially rehydrated. Cooling rates are fastest near the top and bottom of Banco Bonito (up to tens of °C s−1) and are slowest in the center of the flow (< 1 °C year−1). The VC-1 Rhyolite has fast cooling near the bottom of the flow (tens of °C s−1), but top and interior of the flow cooled slowly (< 1 °C year−1). We find that Banco Bonito was likely emplaced in an exogenous or "tank-tread" style because primary magmatic water (OH−) concentrations are at or below predicted solubility values for a given depth and eruption temperature, and measured cooling rates resemble values predicted by a conductive cooling model of a single flow unit. We estimate an emplacement timescale for Banco Bonito of < 3 months by combining a conductive cooling model, estimated glass transition temperatures using dissolved OH− concentrations, and a crustal thickness relationship used on active flows. We conclude that the VC-1 Rhyolite was likely emplaced as a lava that has been partially eroded based on stratigraphic evidence and the absence of fast cooling near the current top of the unit. [ABSTRACT FROM AUTHOR]

A new set of iron-uranium phosphate glasses containing (1–20) UO2.67. (10–20) Fe2O3. (55–68) P2O5 (mass/%) were melted adequately. They were tested for glassy matrices to immobilize hazardous wastes such as radioactive ones. Likewise, new compositions had uranium oxide replaced with Bi2O3. Differential Thermal Analysis (DTA), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), and dilatometry measurements allowed us to study the thermal properties. TGA runs on phosphate glasses containing Fe and U oxides indicated that on heating the glasses, up to TS (dilatometric softening point), the Fe2+ ions oxidized irreversibly to Fe3+ ions which can increase the thermal stability of the glasses by delaying (or even avoiding) crystallization. The densification behavior, applied to pressed powder pellets of ground glasses, from controlled heating rate (CHR) runs (Δl/lo versus T/K), shows relative sample length change versus temperature during heating, provided further thermal data like densification details as well as definition of ranges of creep stability. Various DTA, DSC methods allowed estimating the activation energy for crystallization of these kind of glasses. In addition, separate crystallization treatments for a particular composition provided samples suitable to study the shape and content of crystals with the Scanning Electron Microscope (SEM)/Energy-Dispersive X-ray Spectroscopy (EDS) technique. Thus, a new family of iron-phosphate glasses having Na2O, Al2O3 added (RR6—RR62—RR63) is presented and discussed here and compared to various glasses (like PFeOx and PFeUOx) previously developed at the Bariloche Atomic Center, Argentina (CAB) for radioactive waste immobilization. Activation energies depicted roughly similar values for viscous flow densification of glasses melted with controlled amounts of UO2 for the earlier compositions as well as for the new formulations. [ABSTRACT FROM AUTHOR]

Large silicic eruptions can be preceded by small eruptions of different styles and volumes. The Holocene Llao Rock, Cleetwood, and climactic eruptions of Mt. Mazama, OR, USA, were sourced from the same magma and followed this pattern. The Llao Rock and Cleetwood eruptions are both relatively small, have pyroclasts with microlites and a wide range of vesicularities, and each consisted of an explosive phase followed by an effusive phase. The climactic eruption had no effusive phase and created highly vesicular pyroclasts with no microlites. We analyzed microlite crystallization using phase equilibria and decompression experiments. Comparing the results to the pyroclasts from the Llao Rock and Cleetwood eruptions, we find that the differences between the small and climactic eruptions are likely caused by different magma ascent dynamics. Our experiments show that plagioclase and pyroxene microlites crystallize only during decompressions that are most likely too slow to result in explosive eruptions. The Llao Rock magma likely stalled at shallow depths before continuing fast ascent, which allowed for microlite crystallization that might have also caused explosive eruptions. The Cleetwood magma likely took two separate ascent paths, a majority fraction that ascended quickly from high pressure without stalling and a minority fraction that stalled at shallow depths before continuing ascent along with the majority fraction. These ascent dynamics of the Llao Rock and Cleetwood magmas led to the creation of obsidian pyroclasts from sidewall sintering of fragmented majority-fraction ash. The climactic magma did not stall at shallow depths and instead ascended from depth quickly to the surface, creating the conditions necessary for caldera collapse. [ABSTRACT FROM AUTHOR]

Mineralogical, geochemical, and isotopic studies of the Fe–Mn crust collected in the Jan Mayen vent field area have been carried out for the first time. The crust (about 3 cm thick) has a distinct microstratified structure, sharp contact with the underlying volcanic substrate, and colloform Fe and Mn oxyhydroxides at its bottom. The crust is composed mainly of Mn oxyhydroxides: birnessite and buserite with an impurity of volcanic glass. As follows from the layer-by-layer study of the crust, the Mn content increases by 3–10 times from bottom to top, whereas Fe and REE decrease in the same direction. The samples are marked by a positive Eu anomaly (Eu/EuNASC 1.08–1.41). Ce/CeNASC is 0.89 ± 0.05. 87Sr/86Sr in the crust's lower and middle layers is within 0.70621–0.70713, while εNd reaches 5.6–6.2. These parameters are 0.70740 and –0.1, respectively, in the uppermost layer of the crust. The REE composition, positive Eu anomaly, high εNd values, and low 87Sr/86Sr ratios in the crust are indicative of the fact that the ore material mainly originated from hydrothermal solutions. Changes in the Sr and Nd isotope characteristics and REE composition in the crust layers are due to a decrease in the hydrothermal material contribution as the crust grew at a high crust deposition velocity in the Jan Mayen vent field area. [ABSTRACT FROM AUTHOR]

Silicate glasses are durable materials in our daily life, but corrosion rate accelerates under alkaline aqueous environment. Such situation has raised concerns, for example, in nuclear waste disposal where vitrified wastes encounter to alkaline leachate from surrounding concrete materials. Here we report volcanic glass example surviving with a hyperalkaline groundwater (pH > 11) and high flow rate for about 4000 years. The tiny glass fragments were extracted from the volcanic ash layer sandwiched between ultramafic sediments using microanalytical techniques. Sharp elemental distributions at the glass surface, where amorphous-like smectite precursors and crystalline smectites coexist, suggest the corrosion by an interface-coupled dissolution–precipitation mechanism rather than inter-diffusion. The corrosion rate was maintained at, the minimum, 2.5 orders of magnitude less than the rate observed for fresh glass, even in the presence of Fe and Mg that might have consumed Si through the silicate precipitation. [ABSTRACT FROM AUTHOR]

The Early Jurassic Butcher Ridge Igneous Complex (BRIC) in the Transantarctic Mountains contains abundant and variably hydrated silicic glass which has the potential to preserve a rich paleoclimate record. Here we present Fourier Transform Infrared Spectroscopic data that indicates BRIC glasses contain up to ~8 wt.% molecular water (H2Om), and low (<0.8 wt.%) hydroxyl (OH) component, interpreted as evidence for secondary hydration by meteoric water. BRIC glasses contain the most depleted hydrogen isotopes yet measured in terrestrial rocks, down to δD = −325 ‰. In situ 40Ar/39Ar geochronology of hydrated glasses with ultra-depleted δD values yield ages from 105 Ma to 72 Ma with a peak at c. 91.4 Ma. Combined, these data suggest hydration of BRIC glasses by polar glacial ice and melt water during the Late Cretaceous, contradicting paleoclimate reconstructions of this period that suggest Antarctica was ice-free and part of a global hot greenhouse. Analysis of volcanic glass from the Transantarctic Mountains suggests that 90 Million years ago glaciation was widespread in Antarctica, a period in Earth's history when the continent was considered to be ice-free and part of a global greenhouse. [ABSTRACT FROM AUTHOR]

Widely held assumptions about static societies during the early-middle Holocene (c. 10,000–3300 BP) in the Willaumez Peninsula, Papua New Guinea are challenged by a hypothetical reconstruction of social negotiations that we propose were embedded within the manufacture of large obsidian stemmed tools that circulated as cultural valuables. Made by skilled knappers, these artefacts were manufactured in stages (quarrying, preform production, shaping, hafting, and re-hafting) often segregated in discrete and possibly restricted locations. The successful completion of a large obsidian stemmed tool may have required effective management to negotiate multiple social networks, thereby enhancing the status of those who directed the process. Social connections forged and re-inforced to support the production process may also have been enhanced by ritual practices. Through the social links created and strengthened by the process of its crafting and the subsequent ceremonies and exchanges in which it circulated, a stemmed tool contributed to a vibrant social life that persisted over several millennia. [ABSTRACT FROM AUTHOR]

The lunar volcanic glasses and Mg-suite rocks represent the early enigmatic episodes of lunar magmatism. Due to the gravitational instability of the Fe–Ti enriched (± KREEP) layer, which is formed at the later stage of fractional crystallization, a post-magma-ocean cumulate overturn occurred contemporaneously or near-contemporaneously with the lunar magma ocean (LMO) solidification. The radioactive elements within the KREEP layer were transferred downward and provided continuous energy for the partial melting of the Moon's interior. The melt from the Moon's interior and those from decompression melting, in turn, provide source magma for the origin of lunar volcanic glasses and Mg-suite. However, experimental and theoretical studies on the formation process of lunar volcanic glasses and Mg-suite show that the origin of their parental magma is poorly constrained, which largely depends on the initial depth and composition of the LMO. This review examines the mineralogy, petrogenesis, and distribution of lunar volcanic glasses and Mg-suite. Combining with existing models, we constrain the degree, distribution, and timescale of lunar mantle overturn and explore their relationship with later stages of LMO differentiation. We propose an updated chemical composition of the lunar interior, which provides a useful reference for estimating the bulk composition and early differentiation of the Moon and the early Earth. [ABSTRACT FROM AUTHOR]

We present obsidian sourcing data from Pot Creek Pueblo (LA 260), one of the northernmost Puebloan settlements in the Northern Rio Grande, occupied from at least 1260 ce until ca. 1320 ce when much of the pueblo was burned and the site was depopulated. Although the occupation of Pot Creek Pueblo was short, it occurred during a pivotal period in the Northern Rio Grande. The population of the region increased rapidly at this time, possibly due to an influx of migrants from the Mesa Verde/San Juan area to the west, and locally people living in relatively small villages comprised of pithouses and above-ground unit pueblos begin to coalesce into fewer, but much larger above-ground pueblos. Obsidian-source choices throughout the region may provide insight into how the proposed migration impacted existing resource-procurement patterns. Our data demonstrate that despite the diverse histories of the settlement’s inhabitants, the exchange system supplying obsidian to Pot Creek Pueblo remained stable throughout its occupation. We argue that exchange dynamics of the local community remained the primary means of obtaining obsidian despite potential for new avenues that might have been available through the addition of new community members from outside the region and despite population growth and changing settlement patterns in the broader Northern Rio Grande. [ABSTRACT FROM AUTHOR]

This experimental study aims to contribute to functional analysis research on tools which specifically served to work wood and non-woody plants. They were made of obsidian and other volcanic rocks (basalt, trachyte, and phonolite) characterised by an amorphous matrix and phenocrysts of different number and size. In spite of prior functional analysis research resorting to these raw materials, there remain gaps in our understanding of specific activities. The work thus focused on working different types of wood from the Canary Island as well as on harvesting cereals. It is likewise centred on craftwork, especially regarding certain rarely studied contact materials such as palm leaves and rushes. The results reveal use-wear differences stemming from working woody and non-woody plants with both obsidian and other volcanic rocks. A special attention was given to the identification and description of the different features depending on the raw materials and the characteristics of their knapped surfaces. Identifying the combination of attributes has been essential to attain more accurate diagnostics. There are limits to each of the types of raw materials. The surfaces of obsidian are easier to observe and allow more specific identifications. In turn, the heterogeneous surfaces of volcanic rocks with phenocrysts that require more to time to develop diagnostic traces render use-wear amongst these types of rocks more difficult to observe. It is possible to distinguish longitudinal and transversal actions between woody and non-woody plants on every rock. Actions related to basketry, such us splitting and scraping, are more complicated to identify. The state of the worked plant (dry or fresh) and the time of use are key factors to consider in each case. [ABSTRACT FROM AUTHOR]

This document is a correction notice for an article titled "Increasing obsidian diversity during the Chalcolithic Period at Yeghegis-1 Rockshelter (Armenia) reveals shifts in land use and social networks" published in Scientific Reports. The correction states that Noel Amano was omitted as a corresponding author and provides their contact information. Additionally, an affiliation was omitted for Ricardo Fernandes, and the correct affiliations for all authors are listed. The original article and supplementary information have been corrected. [Extracted from the article]

New obsidian samples (fragments of pebbles and flakes), mixed with ceramic sherds, were found in 10–25 cm cm deep excavations in the Alto Coca Reserve (Napo Province, Ecuador) upon a flat platform on a ridgetop when digging postholes and drainage ditches. Charcoal associated with both obsidian and pottery fragments, attesting to a possible settlement and human pathways (i.e. coluncos), were dated between 1040 and 1210 AD by the AMS radiocarbon (14C) method. Representative samples of obsidian found in the Alto Coca Reserve were analyzed by INAA (major elements) and ICP-OES-MS (trace elements), together with four additional obsidian samples collected from the Sumaco Volcano area, located at the same longitude but ca. 45 km to the south. The Sumaco site (dated by radiocarbon between 1398 and 1451 AD) was preliminary investigated by Santi et al. (in J Archaeol Sci 37:1753–1760. , 2010). Major and trace elements analyses of all the samples closely match with obsidian pebbles collected by Knight et al. (in J Archaeol Sci 38:1069–1079. , 2011) along the Cosanga River and its tributaries, in the eastern piedmont of the Cordillera Real. In particular, they correspond to the secondary fluvial sources of obsidian named “Cosanga A” and “Cosanga B” (as defined by the literature; e.g. Knight et al. in J Archaeol Sci 38:1069–1079. , 2011) most likely deriving from erosional processes of primary sources involving the obsidian-bearing deposits of the Las Caucheras area (5–10 km to the east and north-east of the Cosanga town) where several rhyolite eruptive centers (mostly domes) are related to the youngest activity of the Aliso Volcano. The extensive outcrops of the Andean highlands primary sources of obsidian from the well-known pre-Columbian mines at Sierra de Guamaní, located at the crest of the Eastern Cordillera, are not correlated at all with the investigated samples. The geochemical signatures of the obsidian from the Alto Coca Reserve and Sumaco area therefore support a pre-Columbian exploitation of the secondary fluvial sources of obsidian, along the Cosanga-Quijos Valleys, where obsidian pebbles were collected and brought eastward, towards the Amazonian area. [ABSTRACT FROM AUTHOR]

We present the results of an analysis of the chemical composition for the volcanic glasses discharged by the summit eruption and G.S. Gorshkov flank vent at Klyuchevskoi Volcano in 2020–2021. The data on the chemical and mineral compositions of basaltic andesites produced at the initial stage of the G.S. Gorshkov vent activity are given. The compositional variations of the volcanic glasses from the summit and the subsequent flank eruptions reflect the degree of crystallinity in the tephra particles and the successive change of microlite populations during crystallization of a single parental magma. Comparison of the volcanic glass chemistry from recent eruptions with similar data for the products of the preceding eruptive episodes in 2010 and 2016 shows their complete identity, which indicates a constant composition of the basaltic andesite magma that supplies the present-day volcanic eruptions. [ABSTRACT FROM AUTHOR]

Perlite is an amorphous volcanic glass and an industrial mineral. Because of its relatively low price and density, perlite has a lot of commercial application. Generally, it is used in the horticultural and construction sector. Perlite is a candidate raw material for ceramic products due to its high amorphous phase. Perlite usage in ceramic sanitaryware is investigated with this work. For this purpose, albite was gradually decreased and perlite was added at rates of 3, 5, and 10% to the standard sanitaryware composition instead of albite. All tests and analyses were done under industrial conditions. The compositions were examined based on the rheological and technological properties, chemical analysis, phase analysis, and thermal analysis (thermal expansion coefficient and high-temperature deformation). According to the results, perlite addition increases fired shrinkage, fired strength, and dry shrinkage. Fired strength rose significantly up to 715 kg cm−2. Water absorption values were under 0.02% for all test samples. Besides, the thermal expansion coefficient of the bodies increased up to 10% with perlite addition and then decreased. Thermal expansion coefficient values were determined between 60.1 and 64.9 × 10−7 K−1. High-temperature deformation values decreased up to 10% with perlite addition. The composition which contains 3% perlite showed minimum deformation (− 4.25%) at 1250 °C. As a result, it was determined that the use of perlite would be possible in ceramic sanitaryware compositions. [ABSTRACT FROM AUTHOR]

Volcanic materials can experience up to eleven orders of magnitude of cooling rate (qc) starting from 10–5 K s−1. The glassy component of volcanic material is routinely measured via differential scanning calorimeter (DSC) to obtain qc through the determination of the glass fictive temperature (Tf). Conventional DSC (C-DSC), which has been employed for decades, can only access a relatively small range of qc (from ~ 10–2 to ~ 1 K s−1). Therefore, extrapolations up to six orders of magnitude of C-DSC data are necessary to derive qc of glasses quenched both at extremely low and high qc. Here, we test the reliability of such extrapolations by combining C-DSC with the recently introduced flash calorimetry (F-DSC). F-DSC enables to extend the qc exploration up to 104 K s−1. We use three synthetic glasses as analogs of volcanic melts. We first apply a normalization procedure of heat flow data for both C-DSC and F-DSC to derive Tf as a function of experimental qc, following the "unified area-matching" approach. The obtained Tf–qc relationship shows that Arrhenius models, widely adopted in previous studies, are only valid for qc determination within the calibration range. In contrast, a non-Arrhenius model better captures qc values, especially when a significant extrapolation is required. We, therefore, present a practical "how-to" protocol for estimating qc using DSC. [ABSTRACT FROM AUTHOR]

A method for obtaining hierarchical BEA, MOR, MFI, MTW, and GIS zeolites and nanocomposites by partial recrystallization of perlite and obsidian in the presence of polyquaternary ammonium salts, which act as structure-directing agents, is proposed. The obtained materials are characterized by a developed specific surface, the presence of Lewis (up to 98 μmol/g) and Bronsted (5-105 μmol/g) acid sites and show catalytic activity in the process of 1,1-diethoxyethane production from acetaldehyde and ethanol. [ABSTRACT FROM AUTHOR]

In this paper, different types of rocks exploited in a quarry located in the Limeira region (São Paulo State, Brazil) were studied to investigate its main petrographic characteristics, physical–mechanical (apparent specific weigh ρa, apparent porosity ηa, water absorption αa and uniaxial compressive strength UCS) and thermoanalytical properties, whose curves of each of the rocks were obtained from thermogravimetry (TG), differential thermal analysis and thermomechanical analysis (TMA). Four main petrographic types were evaluated: an aphanitic rock (APH), a diabase (DIA) and two monzodiorites with distinct granulations designated as MOMM and MONMC. In terms of mineralogical composition APH is the only rock that presents volcanic glass, while for the other rocks the main mineralogy was always associated with plagioclases, clinopyroxenes and opaque minerals. The results of the physical and mechanical characterization indicate the good aptitude of these materials to be used as aggregates in engineering works. The obtained values of apparent porosity (ηa) were less than 1% for all rocks. The value of resistance rates for all samples showed that the APH has the larger value, which is attributed to the grain size of the rock. The TG curves of each of the four samples contain small mass losses between the initial temperature and around 105 °C, which attributed to the water absorption. Besides, the APH sample had a mass loss attributed to the carbonate compound. The TMA curves showed that form DIA and MOMM are similar between them, while the APH differ from both. Further, the MONMC has not presented an appreciable thermal expansion. [ABSTRACT FROM AUTHOR]

The nucleation of crystals in natural obsidian volcanic glass has been studied. It is shown that the main crystalline phase in obsidian volcanic glass is albite Na[AlSi3O8], which is included in the class of feldspars. It is one of the main components of rock-forming minerals of great technical importance in ceramics technology. The fundamental characteristics of homogeneous nucleation of albite such as the steady state nucleation rate Ist, time of unsteady state nucleation τ and activation energy of frictional flow have been determined. The temperature dependence of Ist is obtained. Practical recommendations are presented for the use of obsidian volcanic glass. [ABSTRACT FROM AUTHOR]

The alkali-silica reaction (ASR) is a chemical deterioration of concrete that involves reactive forms of silica. Volcanic glass is one of the potentially reactive forms of silica that can be present in volcanic rocks such as basalts. The aggregates used for concrete purposes from the Azores and Hawaiian Archipelagos are mainly of basic composition (basalts s.l.). In general, there is no report of ASR damaged structures in both archipelagos. However, in order to evaluate the behavior of these rocks regarding ASR and to compare the rocks from the two archipelagos, a set of methodologies were performed on a total of twenty-one volcanic aggregates. Geochemical analysis, total alkali-silica diagram, CIPW norm calculation, and petrographic analysis are some of the methods used for the assessment and analysis of rocks. The study was also complemented by electron probe microanalysis (EPMA) in order to identify the composition of volcanic glass and by X-ray diffractometry (XRD) for the Hawaiian aggregates. The results obtained from the studied aggregates showed that there are some differences between the two archipelagos. The rocks from the Azores are alkaline while the majority of the rocks from Hawaiian Archipelago are tholeiitic. The petrographic study revealed that the analyzed rocks from the Hawaiian Islands contain a higher quantity of interstitial volcanic glass than those from the Azores Archipelago. The EPMA carried out in some samples from the Hawaii showed that the volcanic glass has a composition of silica higher than 65%, value that is considered in the literature as potentially reactive. [ABSTRACT FROM AUTHOR]

The results of study of the intrinsic oxygen fugacity (fO2) of various types of tektites from the European and Australasian scattering fields (moldavites, indochinites, philippinites, and australites) performed by the electrochemical method using an apparatus with two solid electrolytes are reported. The fO2 values of tektite glasses in the temperature range of 800–1050°C studied are between the fO2 of the iron–wustite and wustite–magnetite buffer equilibria. They demonstrate a significantly more reduced character of tektites in comparison with magmatic melts (volcanic glasses) of the crustal and mantle origin. Among the Australasian tektites, the widest fO2 variations are typical of indochinites including more diverse tektite species (Muong-Nong type and splat-forms), which are much closer to the hypothetical parental impact crater than philippinites and australites. At temperatures above that of complete melting (≥1000°C), fO2 for all tektite glasses is significantly higher than the fO2 values that correspond to the equilibrium of the metallic phase of iron with the silicate melt. It is assumed that the presence of microinclusions of metallic iron together with wustite, as well as magnetite and hematite in some tektites, is associated with nonequilibrium processes at different stages of tektite formation. [ABSTRACT FROM AUTHOR]

Dense, glassy pyroclasts found in products of explosive eruptions are commonly employed to investigate volcanic conduit processes through measurement of their volatile inventories. This approach rests upon the tacit assumption that the obsidian clasts are juvenile, that is, genetically related to the erupting magma. Pyroclastic deposits within the Yellowstone-Snake River Plain province almost without exception contain dense, glassy clasts, previously interpreted as hyaloclastite, while other lithologies, including crystallised rhyolite, are extremely rare. We investigate the origin of these dense, glassy clasts from a coupled geochemical and textural perspective combining literature data and case studies from Cougar Point Tuff XIII, Wolverine Creek Tuff, and Mesa Falls Tuff spanning 10 My of silicic volcanism. These results indicate that the trace elemental compositions of the dense glasses mostly overlap with the vesiculated component of each deposit, while being distinct from nearby units, thus indicating that dense glasses are juvenile. Textural complexity of the dense clasts varies across our examples. Cougar Point Tuff XIII contains a remarkable diversity of clast appearances with the same glass composition including obsidian-within-obsidian clasts. Mesa Falls Tuff contains clasts with the same glass compositions but with stark variations in phenocryst content (0 to 45%). Cumulatively, our results support a model where most dense, glassy clasts reflect conduit material that passed through multiple cycles of fracturing and sintering with concurrent mixing of glass and various crystal components. This is in contrast to previous interpretations of these clasts as entrained hyaloclastite and relaxes the requirement for water-magma interaction within the eruptive centres of the Yellowstone-Snake River Plain province. [ABSTRACT FROM AUTHOR]

Secondary alteration minerals like clays accompanied by volcanic activity can provide an important information on eruption cycle. Representative volcanic tuffs and seabed sediments were collected from the Dokdo volcanic island in East Sea, South Korea, to interpret eruption cycle based on clay mineral characteristics and other geochemical proxies (sulfur isotope composition, Si/Al, K/Al, among others). Tuffs are mainly composed of volcanic glass and hydrothermally altered phenocrysts. Secondary minerals such as clay mineral species in volcanic tuffs mostly were identified as smectite comprising dioctahedral sheets, based on expanding to 15.8 Å after treatment with 1 M MgCl2 solution, and 060 reflections near at 1.48 Å. Moreover, the results of infrared bands, based on (Al, Al)–OH (904–912 cm−1), (Al, Fe)–OH (865–877 cm−1), (Fe, Mg)–OH (778–798 cm−1) indicate the presence of dioctahedral sheets in clay mineral structure. Partially, occurrence of kaolinite and relatively low pH values and K/Al ratios at the Eolgulbawi tuff support chemical flexibility of clay mineral species. The δ34S value of Dongdo tuff (H2O–S: 15.3‰) is close to water leached sulfate, whereas Seodo tuff II including pyrite and native sulfur (− 5.5‰) shows a value of H2S-bearing volcanic gases. The similarity of chemical compositions between clay fractions and surrounding volcaniclastic rocks suggests that the smectite formed in low-temperature hydrothermal environments, where alkali elements were supplied under reducing conditions. Clay fractions separated from seabed sediments include diatom frustule with higher SiO2/Al2O3 ratios, and clay minerals contain mineral nitrogen originated from organic-rich seafloor sediments. Moreover, the δ34S values of seabed sediments (1.8‰, 8.4‰) indicate that the different origin of clay mineral species between tuffs and seabed sediments. It can be concluded that the alteration types and clay mineral characteristics are similar to the Surtseyan volcano, generally known as shallow-marine phreatomagmatic eruption and deposits. It further suggests that clay minerals sensitive to environmental change will be useful to interpret the volcanic environment characterized by explosive hydrovolcanic activities that occurred at the time of magma in contact with water before erupting into the atmosphere. [ABSTRACT FROM AUTHOR]

The paper summarizes data on germanium and gallium concentrations in natural magmatic melts as follows from analyses of mineral-hosted inclusions and quench glasses in volcanic rocks. Germanium concentrations in melts vary from 0.96 to 17.6 ppm (1472 determinations). The geometric mean germanium concentration in silicate melts is 1.56 ppm, which is quite close to the clarke value. Concentrations of gallium in magmatic melts vary from 0.47 to 495 ppm (8755 determinations). The geometric mean of gallium concentration in silicate melts is 19.0 ppm, which is also close to the clarke value. Germanium concentration in hydrothermal fluids ranges from 0.01 to 930 ppm (405 determinations), and the geometric mean value is 17.0 ppm. Concentrations of gallium in fluids vary from 0.02 to 320 ppm (441 determinations), with a geometric mean of 2.0 ppm. The possible reasons for the differences in germanium and gallium concentrations in natural melts and fluids are discussed. [ABSTRACT FROM AUTHOR]

The process of phosphorus migration from volcanic ash and obsidian to seawater was experimentally studied. For obsidian and ash of the Ksudach, Karymskiy, and Eyjafjallajökull volcanoes, the specific mobilization of phosphorus ranges from 0.3 to 5.0 µg P/g with an average value of ∼1.5 µg P/g. The maximum dissolved mineral phosphorus input into the ocean as a result of the interaction between pyroclastic material from arc volcanism and seawater is 4500–9000 t/yr, which does not exceed 0.3–0.6% of its input from river runoff. [ABSTRACT FROM AUTHOR]

Zeolites are aluminosilicate minerals with multiple channels and cages. They are widely used in industry; further, owing to its increasing demand, the hydrothermal synthesis of zeolites from natural minerals/rocks has attracted great attention. This study aims to discuss the crystal growth mechanisms of zeolites from pumice. Pumice is a widely available porous volcanic glass (mainly consisting of 65–75% SiO2 and 9–20% Al2O3) that can be used in the fabrication of zeolites. In this study, zeolite was formed from pumice via a hydrothermal method with varying alkaline concentrations, reaction times and temperatures, and addition of NaCl. Zeolite Na-P1 was synthesized under conditions of 0.1 or 0.5 M at 150 °C. The feldspar phase (albite) initially occurred, followed by the zeolite phase (zeolite Na-P1). Phillipsite was an unstable intermediate product during this synthesis process. Based on these results, we suggest that the phase transformation sequence follows the order of albite, phillipsite, and zeolite Na-P1. Moreover, it can be speculated that an increase in cation concentration can induce a rapid occurrence of the zeolite phase (zeolite Na-P1). Raman spectrometry analyses provided insights into the formation mechanism of zeolite structures, indicating differences related to the number of sodium ions. Both zeolite Na-P1 and phillipsite are composed of four- and eight-membered rings, and the former is mainly grown with four-membered rings as the main structure. This study provides a low-cost and simple synthetic method for producing zeolite Na-P1 and phillipsite, which can be used as indicator minerals for marine/lake facies and in environmental treatment. [ABSTRACT FROM AUTHOR]

Jabal Al Abyad (2093 m) represents a case study of cone-type monogenetic volcano in Harrat Khaybar, Saudi Arabia., formed in subaerial intracontinental setting. Its formation involved multiple eruption styles including phreatomagmatic eruption of tuff cone truncated by spatter cone of glassy rhyolitic lava flow. The main construction of Jabal Al Abyad is a thick felsic tuff sequence interbedded in part with obsidian rocks. The felsic tuffs range from coarse to fine ash comprising mainly crystal fragments, lithic fragments and vitric shards. The sequence also exhibits changing from massive to stratified lithofacies. The geochemical signatures indicate that Jabal Al Abyad volcanics are rhyolitic peralkaline within plate volcanic rocks related to continental rifting system. Al Abyad volcanics are classified into two groups: A and B of which the former (A) is characterized by relatively higher Ti, Zr, Y, Hf, Th, La, and Ce concentrations. The peralkaline within plate signature, low La/Nb and elevated Nb/Ta ratios (11–17, OIB-like signature) as well as high concentrations of HFSEs (Zr, Y, La, Ce, Rb, Nb, Hf) support the genetic relationship and a heterogeneous mantle origin for the Al Abyad volcanics. The REE and trace element modeling interpretations indicate that a progressive closed-system fractional crystallization of an assemblage dominated by plagioclase and clinopyroxene from the alkaline mafic magma similar to that of St. Helena-SH-35 could produce range of composition from intermediate to acidic ones. [ABSTRACT FROM AUTHOR]

The behavior of iron in the translucent dark-gray obsidian from the Artheni deposit was studied by optical absorption and EPR spectroscopy. The presence of iron in the Fe2+ and Fe3+ states was shown. Transitions in optical spectra and paramagnetic centers in EPR spectra were identified. By the methods of prompt gamma activation analysis (PGAA) and neutron activation analysis (NAA), the content of basic oxides, the amounts of iron, and other elements in the obsidian under study were determined. [ABSTRACT FROM AUTHOR]

Mts. Kalnik and Požeška gora volcaniclastic sequences hold valuable information concerning the Miocene syn-rift evolution of the North Croatian Basin, and the evolution of the Carpathian–Pannonian Region and the Central Paratethys. We present volcanological, high-precision geochronological, and compositional data of volcanic glass to constrain their tephrochronology, magmatic provenance, and timing of the initial Central Paratethys flooding of the North Croatian Basin. Based on CA-ID-TIMS U–Pb zircon ages (18.060 ± 0.023 Ma for Mt. Kalnik and 15.345 ± 0.020 Ma for Mt. Požeška gora) and coeval 40Ar/39Ar sanidine ages (18.14 ± 0.38 Ma and 18.25 ± 0.38 Ma for Mt. Kalnik and 15.34 ± 0.32 Ma and 15.43 ± 0.32 Ma for Mt. Požeška gora), Mt. Kalnik rhyolitic massive ignimbrites and Mt. Požeška gora rhyolitic primary volcaniclastic turbidites are coeval with Carpathian–Pannonian Region Miocene post-collisional silicic volcanism, which was caused by lithospheric thinning of the Pannonian Basin. Their affiliation to Carpathian–Pannonian Region magmatic activity is supported by their subduction-related geochemical signatures. Although Mts. Kalnik and Požeška gora volcaniclastics are coeval with the Bükkalja Volcanic Field Csv-2 rhyolitic ignimbrites, North Alpine Foreland Basin, Styrian Basin, Vienna Basin, and Dinaride Lake System bentonites and volcaniclastic deposits, reliable tephrochronological interpretations based on comparison of volcanic glass geochemical composition are not possible due to a lack of data and/or methodological discrepancies. Our new high-precision geochronology data prove that the initial Middle Miocene (Badenian) marine flooding of parts of the North Croatian Basin occurred at least ~ 0.35 Ma (during the NN4 Zone) before the generally accepted ~ 15 Ma maximum flooding age at the basin scale, calibrating the timing of the onset of the widespread "mid-Langhian" Central Paratethys flooding. [ABSTRACT FROM AUTHOR]