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The thermal state of a magma reservoir controls its physical and rheological properties: at storage temperatures close to the liquidus, magmas are dominated by melt and therefore mobile, while at lower temperatures, magmas are stored as a rheologically locked crystal network with interstitial melt (crystal mush). Throughout the lifetime of a magmatic system, temperature fluctuations drive transitions between mush-dominated and melt-dominated conditions. For example, magma underplating or magma recharge into a crystal mush supplies heat, leading to mush disaggregation and an increase in melt fraction via crystal resorption, before subsequent cooling reinstates a crystal mush via crystal accumulation and recrystallisation. Here, we examine the textural effects of such temperature-driven mush reprocessing cycles on the crystal cargo. We conducted high-P-T resorption experiments during which we nucleated, grew, resorbed, and recrystallised plagioclase crystals in a rhyolitic melt, imposing temperature fluctuations typical for plumbing systems in intermediate arc volcanoes (20–40 °C). The experiments reproduce common resorption textures and show that plagioclase dissolution irreversibly reduces 3D crystal aspect ratios, leading to more equant shapes. Comparison of our experimental results with morphologies of resorbed and unresorbed plagioclase crystals from Mount St. Helens (MSH) (USA) reveals a consistent trend in natural rocks: unresorbed plagioclase crystals (found in MSH dacite, basalt and quenched magmatic inclusions [QMIs]) have tabular shapes, while plagioclase crystals with one or more resorption horizons (found in MSH dacite, QMIs, and mush inclusions) show more equant shapes. Plagioclase crystals showing pervasive resorption (found in the dacite and mush inclusions) have even lower aspect ratios. We therefore suggest that crystal mush maturation results in progressively more equant crystal shapes: the shapes of plagioclase crystals in a magma reservoir will become less tabular every time they are remobilised and resorbed. This has implications for magma rheology and, ultimately, eruptibility, as crystal shape controls the maximum packing fraction and permeability of a crystal mush. We hypothesise that a mature mush with more equant crystals due to multiple resorption–recrystallisation events will be more readily remobilised than an immature mush comprising unresorbed, tabular crystals. This implies that volcanic behaviour and pre-eruptive magmatic timescales may vary systematically during thermal maturation of a crustal magmatic system, with large eruptions due to rapid wholesale remobilisation of mushy reservoirs being more likely in thermally mature systems. [ABSTRACT FROM AUTHOR]

This study assessed the influence of sediment and water redistribution in host sediments on peperite formation by examining the peperites at the boundary between Cretaceous lacustrine sedimentary successions and intruding dikes (D1 and D2). The peperite zones occur along the dike margins and consist of fluidal juvenile fragments, classified as Type A and Type B perperite zones based on lateral extent of the peperite zones. Type A peperite zone, the dominant type, exhibites a narrow distribution (<20 cm), whereas Type B peperite zone sporadically occurs along D1 with a wider width (<1 m). Type B peperite zone is laterally linked with clastic dikes. These dikes containi fluidal shaped dike fragments with jigsaw-fit textures, indicating syn-magmatic fluidization and the resultant formation of the clastic dike via heat transfer. During dike emplacement, the interaction between the host sediments and the intruding magma formed Type A along the margins. Simultaneously, the clastic dikes, composed of fluidized sediments and water, supplied additional water and sediments, enhancing magma-host sediment intermingling and leading to the wide lateral extent of Type B. Our findings demonstrate that sediment and water redistribution via syn-magmatic fluidization is crucial in peperite formation, influencing the initial processes of phreatomagmatic volcanism. [ABSTRACT FROM AUTHOR]

Observing in‐conduit physical mechanism underlying the switching of eruptive activity between the craters of multi‐vent volcanoes could contribute to hazard assessment at these complex volcanic edifices. We performed monitoring of mass density changes beneath two active craters of Sakurajima volcano in Kyushu, Japan between September 2018 and July 2023 with cosmic‐ray muography. From December 2022, the mass density decreased beneath Minamidake crater and increased beneath Showa crater in accordance with a switch of eruptive activity from Minamidake crater to Showa crater. Plug formation and convective magma degassing processes have been observed with muography in accordance with the deformation of the surface of volcanic edifice measured by Interferometric Synthetic Aperture Radar. We found a moderate inverse correlation with a Pearson's coefficient of −0.52 between the mass densities observed beneath the two active craters throughout the entire period. The inverse correlation of mass densities indicates a magmatic gas flux dynamics which characterizes a branched conduit structure. Muography thus reveals the shallow magmatic processes during switching of eruptive activity between the craters of multi‐vent volcanoes and allows to infer to the conduit structure. Plain Language Summary: Observing the changing of structure and amount of materials in the upper plumbing systems of active volcanoes can contribute to the visualization the ongoing volcanic phenomena and assessing of related hazards. For instance, the increase in mass density indicates the uprise of deep volcanic materials in the conduit that may result in the onset of eruption. We measured the directional dependent yield of naturally occurring cosmic‐ray muon particles across the active Sakurajima volcano in Kyushu, Japan. We utilized muography to visualize the changes in mass density structure beneath the erupting craters over time. The captured muon images revealed that the mass densities varied inversely underneath the Minamidake and Showa craters throughout the measurement period. The observed inverse correlation between the mass densities indicates a branched linkage between the conduits of the two active craters. Key Points: Muography is utilized for visualizing and monitoring the mass density changes beneath the active craters of Sakurajima volcano, Kyushu, JapanInverse correlation is found between the mass densities observed beneath the two active cratersA branched linkage between the conduits of active craters inferred from the changes of eruptive activity and mass densities [ABSTRACT FROM AUTHOR]

The variety of Moufang loops is axiomatized by any one of four well known (equivalent) identities. We prove that this axiomatic harmony holds in a broader setting by obtaining two alternate, generalized versions of the (traditional) definition of a Moufang loop using four “local” identities, each derived from one of the four “global” Moufang identities, one for loops, the other for magmas with the right or left inverse property. [ABSTRACT FROM AUTHOR]

The timing and duration of volatile generation from crystallizing magma reservoirs and fluid release across the magmatic‐hydrothermal interface depend on complex coupled interactions controlled by non‐linear, dynamic properties of magmas, rocks and fluids. Understanding these mechanisms is essential to explain the rare formation of economic porphyry copper deposits. For this study, we further developed a coupled numerical model that can simultaneously resolve magma and hydrothermal flow by introducing a description of fluid transport within the magma reservoir and volatile release to the host rock. Our simulations use realistic magma properties derived from published experimental and modeling studies and cover different magma compositions and water contents. We show that magma convection at melt‐dominated states leads to homogenization, which delays fluid release and promotes a rapid evolution toward a mush state. The onset of magmatic volatile release can be near‐explosive with a tube‐flow outburst event lasting <100 years for high initial water contents of >3.5 wt% H2O that could result in the formation of hydrothermal breccias and vein stockworks or trigger eruptions. This event can be followed by sustained fluid release at moderate rates by volatile flushing caused by magma convection. Subsequent fluid release from concentric tube rings by radial cooling of non‐convecting magma mush with a volume of ∼100 km3 at ∼5 km depth is limited to remaining water contents of ∼3.1 wt% H2O and lasts 50–100 kyr. Ore formation from hydrous magmas may thus involve distinct phases of volatile release. Plain Language Summary: High‐temperature fluids are expelled from water‐bearing magma bodies as they cool in the subsurface. These fluids can lead to the formation of ore deposits and geothermal resources and even trigger volcanic eruptions. In this study, we investigate how fluids are transported within a coupled magmatic‐hydrothermal system and how the magma composition, including the initial amount of water, and magma convection can affect the process of subsurface fluid flow. Using insights from experimental and numerical studies, we designed computer simulations to investigate the formation of porphyry copper deposits. We find that magma convection plays a critical role in the initial stage of cooling, creating a uniform mixture of magma and volatiles that stays in suspension during an "incubation" period. During cooling, magmas with high water contents exhibit near‐explosive outgassing events that can be both precursors to volcanic eruptions or a pre‐ore stage. Subsequently, as convection ceases, the magma body undergoes a transition from homogeneous uniform to radial cooling with more gradual fluid release over 50–100 kyr, leading to metal enrichment in porphyry copper deposits. Key Points: Coupled simulations of magma convection, crystallization, degassing and hydrothermal fluid flow reveal distinct stages of volatile releaseAfter a magma incubation phase with bubble suspension, hydrous magmas can experience a near‐explosive tube‐flow outburst from magma mushAfter crystal lock‐up, shifting from uniform to radial cooling leads to continuous outgassing, potentially forming porphyry Cu deposits [ABSTRACT FROM AUTHOR]

The processing of hundreds of Synthetic Aperture Radar (SAR) images acquired by two satellite systems: Sentinel‐1 and COSMO‐SkyMed reveals a decade of ground deformation for a ∼0.5 km diameter area around the summit crater of the only active carbonatitic volcano on Earth: Ol Doinyo Lengai in Tanzania. Further decomposing ascending and descending orbits when the appropriate SAR data sets overlap allow us to interpret the imaged deformation as ground subsidence with a significant rate of ∼3.6 cm/yr for the pixels located just north of the summit crater. Using geodetic modeling and inverting the highest spatial resolution COSMO‐SkyMed data set, we show that the mechanism explaining this subsidence is most likely a deflating very shallow (≤1 km depth below the summit crater at the 95% confidence level) magma reservoir, consistent with geochemical‐petrological and seismo‐acoustic studies. Plain Language Summary: We used data from two satellite systems, Sentinel‐1 and Cosmo‐SkyMed, to study Ol Doinyo Lengai, the only active carbonatitic volcano on Earth located in Tanzania. We analyzed hundreds of radar satellite images over a decade to understand changes in the ground deformation. By separating data from different orbits of the satellites and comparing them, we found that the ground at the volcano's summit was sinking at a rate of approximately 3.6 cm per year. Through simple geodetic modeling, we concluded that this sinking was likely caused by a shallow deflating magma reservoir, less than one km deep below the summit. This conclusion aligns with other scientific studies focusing on the volcano's petrology and geophysics. Key Points: InSAR time series show a ∼0.5 km diameter subsiding area around the summit crater at Ol Doinyo LengaiThe subsidence is likely due to a deflating shallow magma reservoir (point‐source)The modeled reservoir is less than 1 km deep below the summit crater, consistent with geophysical and geochemical studies [ABSTRACT FROM AUTHOR]

My paper (Suzuki 2003) produced some computer routines in Magma (Bosma et al. J Symb Comp 24:235–265, 1997) for the numerical invariants of Fano 3-folds, and used them in particular to determine the maximum value f = 19 of the Fano index. As a byproduct of the research, extensive data associated with all possible sets of singular points of Fano 3-folds with Fano indices greater than or equal to 2 was obtained. Collaborative research with Gavin Brown developed an improved version of the Magma program. The data discussed above was added to the Graded Ring Data Base (Brown et al. 2015) at the University of Kent. Subsequently, GRDB, now located to the University of Warwick, recently modified its interface to accommodate additional conditions, facilitating a more refined selection of Fano manifolds. In this context, we focus on the inequality known as the Bogomolov stability bound. We present a list of candidates for Fano 3-folds that do not satisfy these conditions and propose the conjecture that they do not exist.This result has been independently obtained in Liu and Liu (2023). [ABSTRACT FROM AUTHOR]

The Archean–Proterozoic transition in the Earth's history is marked by significant changes in the mantle dynamics and temperature regimes. A notable consequence is the disappearance of Al-depleted komatiites in the Late Archean and an almost complete absence of Archean-typical peridotitic komatiites since the Proterozoic. This work presents a study of the 2.41 Ga komatiitic basalts from the Vetrenyi Belt, dating back to the early Proterozoic. Unique data on the compositions of olivine and chromite, as well as on the crystallization temperatures based on Al-in-olivine geothermometry for komatiitic basalts from the Vetrenyi Belt are provided. The temperatures of the earliest stages of crystallization were approximately 1240 ± 25°C, which indicates the occurrence of water in the melt and is consistent with measured water contents of 0.4 ± 0.2 wt % H2O in the melt inclusions. However, during crystallization, the komatiitic basalt melt underwent degassing, resulting in mass crystallization of the system and a temperature rise by ~20°C due to the release of the latent heat of crystallization. The degassing of water from the melt suggests crystallization under surface conditions. [ABSTRACT FROM AUTHOR]

The Ora Ignimbrite (~275 Ma) is a crystal-rich (~40%), heterogeneous, supereruption-sized (~1300 km3) rhyolite in northern Italy and the final eruptive product of the Athesian Volcanic Group (289–274 Ma), the largest Permian volcanic district in Europe. Two key outcrops, an intracaldera vitrophyre and an outflow vitrophyre, contain well-preserved, glass-bearing juvenile material. We investigate at what scale heterogeneities existed in the Ora magmatic system by studying the geochemical and petrological characteristics of crystal-rich (20–50%) and crystal-poor (<20%) fiamme from the Ora vitrophyres, allowing us to reconstruct critical aspects of Ora's magmatic architecture and pre-eruptive history and granting us further insight into the storage and dynamic processes that occur in large, crystal-rich, silicic systems. Textural analysis of fiamme reveals four types: the intracaldera vitrophyre has very coarse-grained crystal-rich (VCCR) and fine-grained crystal-poor (I-FCP) fiamme, while the outflow vitrophyre has coarse-grained crystal-rich (CCR) and fine-grained crystal-poor (O-FCP) fiamme. The diversity of crystal-poor (I-FCP & O-FCP) fiamme glass trace-element compositions suggests that multiple small crystal-poor magma bodies were dispersed throughout the Ora magmatic system. Compositionally and texturally distinct glass types in single O-FCP fiamme preserve evidence of variable degrees of magma mixing and record different mingling to eruption timescales, revealing that the Ora magmatic system experienced multiple silicic recharge events. In the crystal-rich (VCCR & CCR) fiamme, high crystal contents (VCCR: 40–50%; CCR: 20–40%), large crystals (max grain size: VCCR: 4–10 mm; CCR: 3–4 mm), and interlocking growth textures suggest that these fiamme contain parcels of disaggregated magma mush. High-silica rhyolite glass compositions (77.2–78.3 wt.% SiO2) and extremely depleted Sr (VCCR: <20; CCR: <5 ppm) and Ba (VCCR: <70; CCR: <20 ppm) glass trace-element concentrations indicate that the crystal-rich fiamme glasses represent highly fractionated melts. Crystal-rich fiamme glass trace-element compositions also form discrete, tightly clustered populations, suggesting that multiple crystal-rich, melt-dominated magma bodies existed prior to eruption. We propose that the coexistence of large-scale heterogeneity (e.g. deposit-scale and outcrop-scale) with small-scale homogeneity observed in crystal-rich fiamme is resolved by a model in which at least two separate magma reservoirs, each containing multiple melt-dominant magma bodies, erupted to form the Ora Ignimbrite. [ABSTRACT FROM AUTHOR]

A generalized construction procedure for algebraic number systems is hereby presented. This procedure offers an efficient representation and computation method for complex numbers, quaternions, and other algebraic structures. The construction method is then illustrated across a range of examples. In particular, the novel developments reported herein provide a generalized form of the Cayley–Dickson construction through involutive dimagmas, thereby allowing for the treatment of more general spaces other than vector spaces, which underlie the associated algebra structure. [ABSTRACT FROM AUTHOR]

This study provides new constraints on the causes of the chemical and isotopic variability in the central Victorian, Devonian, silicic, magmatic rocks and relates these to crustal architecture in the region. Synthesising present and previous work, it is concluded that the Selwyn Block, which forms the main source region for the Devonian silicic magmas (granitic and silicic volcanic rocks), is heterogeneous in three dimensions, on scales of 1 km and less. The sources of both the I- and S-type magmas were formed in Paleoproterozoic to Mesoproterozoic times, in the distal back-arc region of an Andean-type margin, in a basin that was extending and deepening eastward with time. The prominent rock types are high-grade metamorphosed greywackes, potassic andesites and dacites, with smaller volumes of pelitic rocks. The metasediment-dominated source rocks generally lie at deeper levels and reached higher metamorphic grades than the sources of the I-type magmas. This means that the I-type magmas were generally at lower temperatures and were also more hydrous than the S-type magmas. Heat for the metamorphism and partial melting of the source rocks of the silicic magmas was advected into the crust by mantle-derived magmas. These probably formed an underplate, to drive the regional metamorphism, but numerous, scattered, sill-like mafic bodies caused local contact anatexis and silicic magma production. Along with the emplacement of mafic magma bodies, the ascent of the silicic magmas to the upper crust rendered the deeper parts of the Selwyn Block denser and more mafic. The largely unexposed Selwyn Block, which forms the crustal basement in central Victoria, is heterogeneous in three dimensions, on scales of 1 km and less. The sources of the Devonian I- and S-type silicic magmas here formed in the Paleoproterozoic to Mesoproterozoic distal back-arc of an Andean-type margin. The metasedimentary S-type source rocks lie at deeper levels and reached higher metamorphic grades than the sources of the I-type magmas. Heat for the metamorphism and partial melting was advected by both underplating and numerous sill-like mafic bodies scattered throughout the deep crust. [ABSTRACT FROM AUTHOR]

We review empirical data and theoretical relationships to derive equations which relate the upper boundary of maximum earthquake magnitude to the volume of fluids injected by pumping water and supercritical СО2, as well as to magmatic activity preceding volcanic eruptions. The equations can be used to predict triggered seismicity occurring during the extraction of shale gas and oil, to develop systems for extraction of geothermal energy and for burial of supercritical СО2, as well as to assess the volumes of magma injected before eruptions of volcanoes. [ABSTRACT FROM AUTHOR]

Abstract The processing of hundreds of Synthetic Aperture Radar (SAR) images acquired by two satellite systems: Sentinel‐1 and COSMO‐SkyMed reveals a decade of ground deformation for a ∼0.5 km diameter area around the summit crater of the only active carbonatitic volcano on Earth: Ol Doinyo Lengai in Tanzania. Further decomposing ascending and descending orbits when the appropriate SAR data sets overlap allow us to interpret the imaged deformation as ground subsidence with a significant rate of ∼3.6 cm/yr for the pixels located just north of the summit crater. Using geodetic modeling and inverting the highest spatial resolution COSMO‐SkyMed data set, we show that the mechanism explaining this subsidence is most likely a deflating very shallow (≤1 km depth below the summit crater at the 95% confidence level) magma reservoir, consistent with geochemical‐petrological and seismo‐acoustic studies.

Abstract This short report introduces one of the ways to quickly and accurately aim melt inclusions in phenocryst using NanoSIMS. Graphical Abstract

Currently, our ability to interpret the mechanics of magma mingling and mixing is limited by an incomplete understanding of the modes of mixing across all melt fractions and compositions. Here, we present numerical simulations of the emplacement of crystal-free magma in crystal-rich reservoirs employing a computational fluid dynamics and discrete element method (CFD–DEM). We performed two runs corresponding to the emplacement of basalt into two end-member types of magmas mush (basaltic and dacitic). We found that the intruded volumes have similar shapes and are surrounded by a halo where the crystal volume fraction of the mush is lower. The dynamics of intruded melt are, however, different. Importantly, the mingling of the intruded and host materials starts after emplacement and consists in the incorporation of mush material into the intruded magma. Our findings imply that purely thermo-mechanical processes controlled by grain-scale dynamics are sufficient to explain fundamental aspects of recharge.

This study assessed the influence of sediment and water redistribution in host sediments on peperite formation by examining the peperites at the boundary between Cretaceous lacustrine sedimentary successions and intruding dikes (D1 and D2). The peperite zones occur along the dike margins and consist of fluidal juvenile fragments, classified as Type A and Type B perperite zones based on lateral extent of the peperite zones. Type A peperite zone, the dominant type, exhibites a narrow distribution (

Determining the volume and timing of magmatism during rifting and breakup is challenging due to the similar density and seismic velocity of inherited continental crust, magmatic additions and serpentinized mantle; and the difficulty of dating magmatic additions. Here rules of thumb to estimate these are proposed based on the characteristics of the top basement and Moho on seismically imaged margins. A simple kinematic model is used to generate first‐order crustal shapes of margins as a function of magma volume and timing of emplacement, which are successfully compared to a representative number of rifted margins. It appears that 'magma‐rich margins' require melt emplacement in advance of crustal thinning but not necessarily enhanced melt volume, while margins with exhumed mantle require a delay in melt emplacement but not necessarily a low magmatic volume. An alternative classification for the magma‐poor/magma‐rich dichotomy is proposed to better represent the crustal shape variability of rifted margins. [ABSTRACT FROM AUTHOR]

The Ijero-Ekiti tourmaline-bearing pegmatite was investigated, using geological, geochemical, and geophysical methods to characterize its geological evolution and evaluate its mineralisation potential. Petrographical studies revealed a typical granitic mineralogical composition of quartz, feldspar, and muscovite, with tourmaline as accessory minerals. Geochemical data on whole rock analysis showed high and moderate enrichments in SiO2 (av. 71.65 wt. %) and Al2O3 (av. 14.71 wt. %) respectively, while mean values for the other major oxides ranged between 0.01 and 3.63 wt. %. Results also showed that K2O (av. 3.63 wt. %) and Na2O (av. 3.52 wt. %) concentrations were comparable to average Upper Continental values. The relatively high aluminum and alkaline compositions could be attributed to pneumatolytic crystallization from the pegmatitic melt. Aluminum Saturation Index (ASI) [Al/(Ca+Na+K)] indicated peraluminous character. Ranges of some trace elements (Cs, 1.5 - 705.6 ppm; Be, 0.5 - 12 ppm; Sn, 2.0 - 34 ppm; Ta, 1.0 - 14) support a Lithium-Cesium-Tantalum (LCT) type rare-elements pegmatites for the pegmatites of the study. The spider and K/Rb vs K/Cs plots portrayed fractionation trends suggestive of potential mineralisation. The vertical electric sounding data showed that pegmatites underlie the lateritic zone and represent the anomalous layer characterized by high resistivity values ranging from 1086 to 9489 Ohm-m with the surface to a maximum depth of 20.8m which is suspected to be a mineralised zone. Some of these pegmatites are highly tourmalinated, suggesting that they emanate from highly mineralised magma and are believed to represent late-stage pneumatolytic fluids derived from acidic magma bodies through magmatogenic processes. [ABSTRACT FROM AUTHOR]

Many sub-Neptune exoplanets have been believed to be composed of a thick hydrogen-dominated atmosphere and a high-temperature heavier-element-dominant core. From an assumption that there is no chemical reaction between hydrogen and silicates/metals at the atmosphere-interior boundary, the cores of sub-Neptunes have been modeled with molten silicates and metals (magma) in previous studies. In large sub-Neptunes, pressure at the atmosphere-magma boundary can reach tens of gigapascals where hydrogen is a dense liquid. A recent experiment showed that hydrogen can induce the reduction of Fe2+ in (Mg,Fe)O to Fe0 metal at the pressure-temperature conditions relevant to the atmosphere-interior boundary. However, it is unclear whether Mg, one of the abundant heavy elements in the planetary interiors, remains oxidized or can be reduced by H. Our experiments in the laser-heated diamond-anvil cell found that heating of MgO + Fe to 3,500 to 4,900 K (close to or above their melting temperatures) in an H medium leads to the formation of Mg2FeH6 and H2O at 8 to 13 GPa. At 26 to 29 GPa, the behavior of the system changes, and Mg-H in an H fluid and H2O were detected with separate FeHx. The observations indicate the dissociation of the Mg-O bond by H and subsequent production of hydride and water. Therefore, the atmosphere-magma interaction can lead to a fundamentally different mineralogy for sub-Neptune exoplanets compared with rocky planets. The change in the chemical reaction at the higher pressures can also affect the size demographics (i.e., "radius cliff") and the atmosphere chemistry of sub-Neptune exoplanets. [ABSTRACT FROM AUTHOR]

Inclusions of the mineral-forming media in quartz of the Vysokogorskoe deposit are studied in detail. The compositions of the melts correspond to peraluminous potassium granites of normal alkalinity, depleted in rare alkalis, F, and Cl. The water content in the melts reached 7–9 wt %; CO2 and CH4 were also important in mineralizing fluids. Quartz crystallized at 620–650°C. Assemblages of four types have been identified as primary fluid inclusions: (1) inclusions of carbonate or sulfate aqueous solutions coexisting with melt inclusions, (2) low-density vapor-dominated primarily magmatic inclusions, (3) presumably postmagmatic low-salinity aqueous and vapor-dominated inclusions, and (4) multiphase fluid inclusions associated with vapor-dominated ones also formed at the postmagmatic stage. Daughter pyrosmalite–(Fe) and hibbingite, which was found for the first time in inclusions from quartz of the Vysokogorskoe deposit, made it possible to characterize the solutions as high-salinity chloride Na/K and Fe2+. Presumably, those solutions may have been the most efficient in Sn transport during the formation of fluid–explosive breccias and vein mineralization of the Vysokogorskoe deposit. The magma chamber itself most likely served as a heat source and, to a large extent, a source of aqueous fluid for the hydrothermal system of the deposit. [ABSTRACT FROM AUTHOR]

The relationship between strong earthquakes and powerful volcanism in subduction zones are discussed. It is shown that abnormally strong earthquakes or a group of strong earthquakes and powerful volcanic events or volcanic activation of large areas can be considered as an interconnected geodynamic pair. At high level of horizontal compression, magma-conducting faults are clamped and volcanism in the upper part of the crust is hindered. Mega-earthquakes or a series of strong earthquakes reduce the level of the horizontal compression in the crust of the island arc (continent active margin), which creates favorable conditions for the resumption of volcanic activity. For major faults, located along the strike of subduction zones, upward movement of magma during volcanic eruptions or intracrustal magmatism leads to an increase in the stresses of horizontal compression in the surrounding rocks up to the pressure level of rising magma. As a result, the stress state of horizontal compression is restored in the crust and, thus, the cycle is closed. The state in which earthquakes are an effective mechanism for reducing stresses occurs once again. [ABSTRACT FROM AUTHOR]

For any set X we let F (X) denote the complex vector space of functions f : X → C . Let X = S be a magma, and let V be a subspace of F (S) , which is invariant under left or right translations. It is known for an abelian group S that if p 1 χ 1 , ⋯ , p n χ n ∈ F (S) are nonzero exponential polynomials with distinct exponentials χ 1 , ⋯ , χ n then p 1 χ 1 + ⋯ + p n χ n ∈ V ⇒ p 1 χ 1 , ⋯ , p n χ n ∈ V and χ 1 , ⋯ , χ n ∈ V . We extend this to magmas. Our results imply that any exponential polynomial solution f ∈ F (S) of f (x y) = f (x) χ (y) + χ (x) f (y) where χ ∈ F (S) is an exponential, has the form f = a χ where a ∈ F (S) is additive, even when χ has zeros. [ABSTRACT FROM AUTHOR]

Lake Taupō (Taupō-nui-a-Tia) infills the composite caldera above an active rhyolitic magmatic system in the central Taupō Volcanic Zone (TVZ). Ground deformation is a key unrest indicator at Taupō volcano. We present a spreadsheet tool, TaupōInflate, to calculate and plot ground deformation from magmatic inflation at depth beneath Taupō caldera. Examples show detection limits for inflating magma bodies and their ascent through the crust beneath Lake Taupō. Source locations where it is challenging to detect even substantial volumes of inflating magma bodies are as large as 20 km3, with volume changes up to 0.01 km3, owing to the restricted station placement around the lake, although a dike propagating from shallow crustal depths towards the surface is likely to be detectable. For a magma overpressure of 10 MPa, the sizes of detectable inflating bodies at depths of 5–8 km using the present monitoring system are larger than the volumes of many past eruptions, illustrating the importance of future improvements to the geodetic network. We discuss the potential for future equipment installation, including lakebed instrumentation that would require approval of local iwi Ngāti Tūwharetoa through the Tūwharetoa Māori Trust Board who oversee the health and wellbeing of Lake Taupō. [ABSTRACT FROM AUTHOR]

The composition of fluid from carbonate- and chlorine-bearing pelite has been studied at 5.5 GPa, 850–1030 °C and at 7.8 GPa, 940–1090 °C using the diamond trap method. The run products include a residue composed of an eclogitic assemblage (garnet, coesite, clinopyroxene, and kyanite ± phengite and accessory pyrite/pyrrhotite, rutile, and zircon) and fluid solutes captured in the trap. The new data show that the pelite-derived supercritical fluid, with nearly equal amounts of solutes and H2O + CO2 [at the weight ratio H2O/(H2O + CO2) from 0.8 to 0.9], is stable at the applied P–T conditions. At higher temperatures, the amount of solutes in the supercritical fluid increases only slightly, apparently, due to the presence CO2 and 0.4–0.5 wt% Cl in the fluid. The reconstructed supercritical fluid composition includes components decreasing in the series SiO2 > Al2O3 > K2O > Na2O ≈ CaO ≈ MgO ≈ FeO. At 7.8 GPa, phengite becomes unstable, and K2O in the supercritical fluid increases from 3 to 8 wt% (on hydrous basis) while Al2O3 decreases from 8 to 5–6 wt%. Among the elements that fractionated into the fluid, B, Sr, Rb and P, as well as K at 7.8 GPa and 1090 °C, are the least compatible. The fluid-residue Sr partition coefficient varies from 4 to 10 and is notably lower at higher temperatures. Thus, supercritical fluids can form in carbonate- and chlorine-bearing sediments under subduction back arc-conditions, in cases of fluid-fluxing of the slab. Such supercritical fluids penetrating into the mantle together with H2O and CO2 can transport large amounts of major elements, B, Sr, Rb and P. The formation of potassium-rich silicic supercritical fluids is possible during subduction of pelite to ~ 250 km depths. They can be important agents in metasomatism of lithospheric mantle, with its composition reconstructed from data on micro-inclusions from fibrous diamond. [ABSTRACT FROM AUTHOR]

3D analysis of the magma transport and accumulation mechanism in the structure and basement of the Klyuchevskoy volcano preceding 11 eruptions in 2003-2021 has been performed. Using the Frac-Digger method and seismological data from the Kamchatka Branch Federal Research Center United Geophysical Survey Russia Academy of Sciences it has been shown that magma transport from the deep crustal magma chamber (−30 km) is carried out in the vertical fracturing (dykes) mode to the peripheral shallow magma chamber (+1 km). The feeding dykes orientation corresponds to geomechanical conditions of radial or N-NNE extension. This is followed by inclined dykes and sills of various orientations from the peripheral magmatic chamber. Magma accumulation in the peripheral magmatic chamber in the form of sills (in the horizontal fracturing mode at elevations of +0,3 to +2,3 km) contributes to the efficiency of magma degassing and heat exchange with meteoric waters, and to the formation of a high-pressure vapour-gas reservoir with subsequent venting of the volcano channel and its eruption. Three-dimensional analysis of the distribution of flank eruptions of the Klyuchevskoy volcano in 1932-2021 (16 cinder cones) shows their association with two main low-inclined structural surfaces. Changes in the drainage level of the magmatic system are reflected in the volumes and geochemical history of the 1932-2021 flank eruption products.

This short report introduces one of the ways to quickly and accurately aim melt inclusions in phenocryst using NanoSIMS. [ABSTRACT FROM AUTHOR]

Magnetotelluric data were collected on and around the Mount Meager volcanic complex, an active volcanic complex with eruptions ∼2400 and ∼24 300 years ago. Three-dimensional inversion was used to create an electrical resistivity model to a depth of >20 km. The model is characterized by high resistivity (>100 Ωm) in the upper 6–7 km, implying relatively dry, unaltered rock. Within this resistive layer, localized conductors are observed in the upper 2 km beneath Pylon Peak and Fish Creek, corresponding to low-permeability, clay-rich layers, acting as caprocks to geothermal fluids below. Beneath the resistive upper crust, there is a large conductor at ∼5–15 km below sea level with an average resistivity of ∼3 Ωm. Laboratory experiments of melt resistivity and petrological data from erupted volcanic rocks were used to interpret the model. The magma body (deep conductor) is inferred to have a minimum volume of ∼2 × 1012 m3 comprising ∼18–32% dacitic-to-trachydacitic melt with ∼6–8 wt.% H2O at a temperature of ∼800–900 °C. This is below the melt fraction of an eruptible magma body. Resolution tests suggest it might be regional in extent, not localized beneath Mount Meager. There are fluid pathways from the northern part of the magma body, up toward Mount Meager and nearby fumaroles. This model is a significant advancement from its predecessors, created 20–40 years ago, providing the first deep 3D image of this volcanic system. Along with other geophysical and geological models of the Garibaldi Geothermal Energy Project, it will reduce the exploration risk associated with geothermal energy development. [ABSTRACT FROM AUTHOR]

A generalized construction procedure for algebraic number systems is hereby presented. This procedure offers an efficient representation and computation method for complex numbers, quaternions, and other algebraic structures. The construction method is then illustrated across a range of examples. In particular, the novel developments reported herein provide a generalized form of the Cayley–Dickson construction through involutive dimagmas, thereby allowing for the treatment of more general spaces other than vector spaces, which underlie the associated algebra structure.

Shear thinning and brittle failure of silicate melt control the dynamics of volcanic eruptions, but their molecular‐scale origin is still unclear. Here, we conducted tension and compression experiments on silicate melts, using time‐resolved X‐ray diffraction. Our experiments revealed that the intermediate‐range ordering of silicate structures, that is, the ring size formed by the SiO4 tetrahedra, demonstrated elastic and anisotropic dilation under tension and shrinkage under compression in the non‐Newtonian regime. In contrast, there were no significant changes in short‐range ordering, such as Si–O and Si–Si distances. Based on these findings, we inferred that shear thinning observed under high stress originates from the formation of anisotropically deformed large and small rings in silicate structures that are energetically unfavorable and unstable. Brittle failure occurred under high‐stress conditions, in both tension and compression. We propose a stress criterion as a necessary and sufficient condition for magma failure, rather than a strain rate criterion. Plain Language Summary: Explosive volcanic eruptions occur when magma fragments and volcanic gases are released to the surface. However, magma is originally a continuous fluid that behaves like a liquid in the crust. To understand how magma fails during volcanic eruptions, we need to uncover the underlying mechanisms. This challenge was identified over four decades ago, and researchers proposed conducting molecular‐scale experiments on magma deformation to shed light on its complex behavior, including brittle failure. However, this has been difficult to achieve experimentally. In this study, we used powerful X‐ray sources at SPring‐8 in Japan to address this challenge. Our findings reveal that the complex behavior of magma originates from previously unrecognized molecular‐scale elastic and anisotropic deformation. Finally, we propose a criterion for magma failure that can help determine whether an eruption will be explosive. Key Points: Molecular‐scale elastic and anisotropic deformation of the silicate melt was observed under tension (dilation) and compression (shrinkage)Formation of large and small rings by the SiO4 tetrahedra could be the origin of shear thinning and brittle failure in the silicate meltStress condition is "the necessary and sufficient condition" for the magma failure criterion [ABSTRACT FROM AUTHOR]

The relationship between strong earthquakes and powerful volcanism in subduction zones are discussed. It is shown that abnormally strong earthquakes or a group of strong earthquakes and powerful volcanic events or volcanic activation of large areas can be considered as an interconnected geodynamic pair. At high level of horizontal compression, magma-conducting faults are clamped and volcanism in the upper part of the crust is hindered. Mega-earthquakes or a series of strong earthquakes reduce the level of horizontal compression in the crust of the island arc (continent active margin), which creates favorable conditions for the resumption of volcanic activity. For major faults located along the strike of subduction zones, upward movement of magma during volcanic eruptions or intracrustal magmatism leads to an increase in horizontal compression stresses in the surrounding rocks to the pressure level of rising magma. As a result, a horizontal compression stress state is restored in the crust and, thus, the cycle is closed. Once again, a state emerges in which earthquakes are an effective mechanism for reducing stresses.

Volcanic eruptions are driven by bubbles that form when volatile species exsolve from magma. The conditions under which bubbles form depend mainly on magma composition, volatile concentration, presence of crystals, and magma decompression rate. These are all predicated on the mechanism by which volatiles exsolve from the melt to form bubbles. We critically review the known or inferred mechanisms of bubble formation in magmas: homogeneous nucleation, heterogeneous nucleation on crystal surfaces, and spontaneous phase separation (spinodal decomposition). We propose a general approach for calculating bubble nucleation rates as the sum of the contributions from homogeneous and heterogeneous nucleation, suggesting that nucleation may not be limited to a single mechanism prior to eruption. We identify three major challenges in which further experimental, analytical, and theoretical work is required to permit the development of a general model for bubble formation under natural eruption conditions. We review the mechanisms of bubble formation in magma and summarize the conditions under which the various mechanisms are understood to operate. Bubble formation mechanisms may evolve throughout magma ascent as conditions change such that bubbles may form simultaneously and sequentially via more than one mechanism. Contributions from both homogeneous nucleation and heterogeneous nucleation on multiphase crystal phases can be captured via a single equation. Future work should focus on constraining macroscopic surface tension, characterizing the microphysics, and developing a general framework for modeling bubble formation, via all mechanisms, over natural magma ascent pathways. [ABSTRACT FROM AUTHOR]

The magma evolution of Ngebel Volcano, both temporally and spatially, is represented by the characteristics of its lava. Ngebel Volcano, located in East Java, is a Quaternary andesitic stratovolcano. This volcano is part of the Wilis Volcanic Complex. The volcanism stage of Ngebel Volcanic Complex can be divided into the Jeding with andesitic basalt (SiO2 49 - 59%), pyroxene andesite Kemlandingan (SiO2 49 - 59%), Manyutan with hornblende andesite (SiO2 49 - 59%), and Ngebel with dacite (SiO2: 49 - 59%). The variation of major elements combined with petrographic features such as plagioclase, pyroxene, hornblende, quartz, and opaque minerals from basaltic andesite to dacite is interesting. The minerals show that the magma differentiation process of Ngebel Volcanic Complex is the results of fractional crystallization of magma. The purpose of this study is to determine the evolution of magma from volcanic rocks of which stratigraphic positions have been determined. The analytical methodology used is petrographic and geochemical analysis. Detailed temporal evolution shows that magma from the Ngebel Volcanic Complex underwent a differentiation process that changed the magma composition from mafic to more felsic. [ABSTRACT FROM AUTHOR]

The Craters of the Moon (COM) Volcanic Field in Idaho is the largest mostly Holocene lava field in the conterminous U.S. and the site of the most recent volcanism in the Yellowstone‐Snake River Plain province. This prominent example of a polygenetic fissure field has produced over 60 eruptions over the past 15,000 years from the Great Rift fissure system. The eight most recent lava flows, known as Period A, were erupted between about 2,500 and 2,000 years ago. In this study, major and trace element and Pb‐Sr‐Nd isotope data were obtained, with several samples collected from each flow from widely spaced locations to evaluate heterogeneity in their source magmas. The results reveal three previously unrecognized compositional groups that may represent separate magma batches, and that assimilation and fractional crystallization (AFC) controlled the evolution of the entire Period A suite. The three oldest flows were periodic withdrawals from a body of highly evolved and poorly homogenized magma, and four later flows represent successive samplings from a stratified body of more primitive magma. These two flow groups are related via variable AFC modeled with Magma Chamber Simulator software, with Neogene rhyolite as a plausible crustal assimilant. A third compositional type that requires a different parent magma and AFC history is represented by a single flow erupted from vents a few km away from the others. The compositional evolution and variability observed in this sequence of flows provide new insights into how magmas are generated, modified, and delivered in such polygenetic fissure systems. Plain Language Summary: The Craters of the Moon Volcanic Field is a prominent example of a long‐lived eruptive fissure system in a continental setting, where lava flows are produced at the Great Rift, a linear zone of fracturing and extending crust on the Snake River Plain in southern Idaho. Craters of the Moon has produced more than 60 eruptions over the past 15,000 years, including young lavas with high‐silica compositions that are relatively uncommon in the region. The eight most recent lava flows, known as Period A, were erupted between about 2,500 and 2,000 years ago. This sequence of flows provides snapshots of the evolving system over time and constrains processes that modify and feed magmas to this type of volcanic system. New chemical and isotope data with higher precision than in previous studies reveal that the flows fall into three compositional groups, likely reflecting separate magma batches with distinct histories of cooling, crystallization, and contamination by wall rock. These results illuminate the processes that deliver and alter magmas in such long‐lived fissure systems. Key Points: Compositions of the eight most recent Craters of the Moon lava flows elucidate magma evolution in this polygenetic fissure systemThis compositional study revealed the flows were fed by three previously unrecognized magma compositions with distinct petrologic historiesThe magmas were heterogenous, stratified, and culminated in the eruption of increasingly less evolved flows [ABSTRACT FROM AUTHOR]

Valles Caldera was formed by large rhyolitic eruptions at ∼1.6 and 1.23 Ma and it hosts post‐caldera rhyolitic deposits as young as ∼69 ka, but the contemporary state of the magmatic system is unclear. Local seismicity beneath Valles Caldera is rare and shear‐velocity (Vs) structure has not been previously imaged. Here, we present the first local Vs tomography beneath Valles Caldera using ambient noise Rayleigh dispersion from a ∼71 km transect of nodal seismographs with mean spacing of ∼750 m. An ∼6 km wide low‐Vs anomaly (Vs < 2.1 km/s) is located at ∼3–10 km depth within the 1.23 Ma caldera's ring fracture. Assuming magma in textural equilibrium, the new tomography suggests that melt fractions up to ∼17%–22% may be present within the upper crustal depth range where previously erupted rhyolites were stored. Plain Language Summary: Silica‐rich magma stored in the shallow crust of the Earth can fuel eruptions that pose significant hazards to society. Valles Caldera was created by a large explosive eruption of silica‐rich magma 1.23 million years ago. Numerous smaller volcanic eruptions occurred following the large eruption event (as young as 69 thousand years ago) and the shallow subsurface at Valles remains hot indicating potential for modern magmatic storage at depth. Seismic shear waves are sensitive to the presence of magma and other variations in crustal structure. However, no local shear wave imaging has been conducted at Valles Caldera. Using new seismic data from densely spaced instruments and a technique known as ambient noise tomography, we produced the first shear velocity image beneath Valles Caldera. A region of significant low shear velocity is present in the upper crust beneath the caldera which we attribute to the presence of silica‐rich magma. These new results on shallow magma storage can contribute to assessing volcanic hazards more accurately near Valles Caldera. Key Points: The Valles Caldera magmatic system was imaged with ambient noise Rayleigh tomography using a dense temporary seismic transectA low‐Vs anomaly, Vs < 2.1 km/s is imaged within the caldera's ring fracture at ∼3–10 km depthThe upper crustal magma reservoir beneath Valles Caldera may contain up to ∼17%–22% rhyolitic melt [ABSTRACT FROM AUTHOR]

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An approach to accelerating a parallel domain decomposition (DD) solver by graphics processing units (GPUs) is investigated. The solver is based on the Balancing Domain Decomposition Method by Constraints (BDDC), which is a nonoverlapping DD technique. Two kinds of local matrices are required by BDDC. First, dense matrices corresponding to local Schur complements of interior unknowns are constructed by the sparse direct solver. These are further used as part of the local saddle-point problems within BDDC. In the next step, the local matrices are copied to GPUs. Repeated multiplications of local vectors with the dense matrix of the Schur complement are performed for each subdomain. In addition, factorizations and backsubstitutions with the dense saddle-point subdomain matrices are also performed on GPUs. Detailed times of main components of the algorithm are measured on a benchmark Poisson problem. The method is also applied to an unsteady problem of incompressible flow, where the Krylov subspace iterations are performed repeatedly in each time step. The results demonstrate the potential of the approach to speed up realistic simulations up to 5 times with a preference towards large subdomains. [ABSTRACT FROM AUTHOR]

Abstract Shear thinning and brittle failure of silicate melt control the dynamics of volcanic eruptions, but their molecular‐scale origin is still unclear. Here, we conducted tension and compression experiments on silicate melts, using time‐resolved X‐ray diffraction. Our experiments revealed that the intermediate‐range ordering of silicate structures, that is, the ring size formed by the SiO4 tetrahedra, demonstrated elastic and anisotropic dilation under tension and shrinkage under compression in the non‐Newtonian regime. In contrast, there were no significant changes in short‐range ordering, such as Si–O and Si–Si distances. Based on these findings, we inferred that shear thinning observed under high stress originates from the formation of anisotropically deformed large and small rings in silicate structures that are energetically unfavorable and unstable. Brittle failure occurred under high‐stress conditions, in both tension and compression. We propose a stress criterion as a necessary and sufficient condition for magma failure, rather than a strain rate criterion.

Abstract The Craters of the Moon (COM) Volcanic Field in Idaho is the largest mostly Holocene lava field in the conterminous U.S. and the site of the most recent volcanism in the Yellowstone‐Snake River Plain province. This prominent example of a polygenetic fissure field has produced over 60 eruptions over the past 15,000 years from the Great Rift fissure system. The eight most recent lava flows, known as Period A, were erupted between about 2,500 and 2,000 years ago. In this study, major and trace element and Pb‐Sr‐Nd isotope data were obtained, with several samples collected from each flow from widely spaced locations to evaluate heterogeneity in their source magmas. The results reveal three previously unrecognized compositional groups that may represent separate magma batches, and that assimilation and fractional crystallization (AFC) controlled the evolution of the entire Period A suite. The three oldest flows were periodic withdrawals from a body of highly evolved and poorly homogenized magma, and four later flows represent successive samplings from a stratified body of more primitive magma. These two flow groups are related via variable AFC modeled with Magma Chamber Simulator software, with Neogene rhyolite as a plausible crustal assimilant. A third compositional type that requires a different parent magma and AFC history is represented by a single flow erupted from vents a few km away from the others. The compositional evolution and variability observed in this sequence of flows provide new insights into how magmas are generated, modified, and delivered in such polygenetic fissure systems.

Abstract Valles Caldera was formed by large rhyolitic eruptions at ∼1.6 and 1.23 Ma and it hosts post‐caldera rhyolitic deposits as young as ∼69 ka, but the contemporary state of the magmatic system is unclear. Local seismicity beneath Valles Caldera is rare and shear‐velocity (Vs) structure has not been previously imaged. Here, we present the first local Vs tomography beneath Valles Caldera using ambient noise Rayleigh dispersion from a ∼71 km transect of nodal seismographs with mean spacing of ∼750 m. An ∼6 km wide low‐Vs anomaly (Vs

The Dead Sea Fault (DSF) is a crustal‐scale continental transform fault separating the African and the Arabian plates. Neogene to Quaternary volcanic activity is well‐spread in Northern Israel. Yet, the origin of the magmas that fed the eruptions is still unpinned. Our local earthquake tomography depicts velocity distributions typical of rifting settings. At 9 km depth, a prominent high Vp/Vs anomaly marks the presence of cooling melts. We propose that protracted transtension along the DSF caused crustal thinning promoting the emplacement of magmatic bodies. Crustal emplacements of magmas in Northern Israel reconcile multiple observations, including the high geothermal gradient, the prominent magnetic anomalies and the traces of mantle‐derived fluids in the springs across the Sea of Galilee. We provide a compelling evidence for rifting in segments of the DSF and identify the potential source of magmatism that fed part of the volcanic activity of the area. Plain Language Summary: The Dead Sea Fault (DSF) is a deep‐reaching fault separating the African and the Arabian plates. Geologically recent volcanic activity is well‐spread in Northern Israel but the origin of the magmas that fed the eruptions is yet to be found. We propose that protracted extensional motion along the DSF caused crustal thinning facilitating the emplacement of magmatic bodies in the crust. Our local earthquake tomography depicts velocity distributions typical of spreading margins. At 9 km depth, a prominent anomaly marks the presence of cooling melts. Crustal emplacements of magmas in Northern Israel reconcile multiple observations that are normally not common in sedimentary environments. The occurrence of magmas at depth would release fluids that would be compatible with the seismicity that sporadically affects the region. We provide a compelling evidence for rifting in segments of the DSF and identify the potential source of magmatism that fed part of the volcanic activity of the area. Our findings hold major implications for revisiting the natural hazard assessment of the Levant region. Key Points: Magma emplaced along the Dead Sea Fault (DSF)Localized rifting along the segment of the DSFOccurrence of cooling magmas may reconcile several geophysical, geological and geochemical observations in around the Sea of Galilee [ABSTRACT FROM AUTHOR]

Several orogenic/sediment-hosted gold deposits are widely distributed in the Central Belt of Peninsular Malaysia. This study combines U-Pb dating with the isotope composition of lead as well as gold content in ore and magmatic rock-hosted pyrite. It aims to investigate the age of gold mineralization and possibly establish a link between gold mineralization and magmatic intrusion in the district. The results show that the S-type magmatic rocks yield crystallisation ages ranging from 204.1 ± 4.7 Ma to 223 ± 3.2 Ma with low magnetic susceptibility measurements below 3 × 10−3 SI unit. These ages fit within the 200–250 Ma Pb-Pb model age of the Pb isotopic composition of K-feldspars. Pyrite trace element mapping has shown that gold and lead show zoning patterns occurring at the same time in pyrite. The Pb isotope composition of the cores of pyrite grains indicate that the approximate model age of gold mineralization is 200 Ma. This age is close to 197–199 Ma (Early Jurassic), previously determined by K-Ar dating of sericite which was interpreted to be the age of gold mineralization. In this study, gold content varies up to 793 ppb in the analysed magmatic rock-hosted pyrites, indicative of a likely magmatic contribution to gold mineralization. [ABSTRACT FROM AUTHOR]

To illuminate brittle and ductile fracturing of magma, we investigated bubble expansion and fracturing in two contrasting fluids: a Maxwell‐type viscoelastic fluid and a Bingham‐type yield‐strength fluid. Measurements of the complex shear modulus, G′ + iG″ (i is the imaginary unit), under small‐strain oscillation showed that both fluids are elastic (G′ > G″) with similar rigidity. Viscous behavior (G′ < G″) appeared at lower frequency in the Maxwell fluid but at larger strain in the Bingham fluid. When we injected air into the Maxwell fluid, bubbles expanded viscously at low flux, fractured in a brittle manner at high flux, and behaved transitionally at intermediate flux. In contrast, we observed no fracturing in the Bingham fluid. This demonstrates that the G′ > G″ condition is insufficient to infer that brittle fracturing can occur. Brittle fracturing of the Maxwell fluid occurred not at a critical strain rate but under decreasing strain rate and increasing stress. Plain Language Summary: The flow‐to‐fracture transition of magma is an essential process controlling eruption explosivity. This transition has been explained based on the linear Maxwell viscoelastic model: magma can flow slowly but breaks in a brittle manner under rapid deformation. The Bingham model represents another type of fluid‐solid transition: a material flows under a sufficiently large force but behaves elastically below this force. The present study investigates bubble growth and fracture by air injection in Maxwell‐type and Bingham‐type fluids, both having similar elasticity. We demonstrate that brittle fracture occurs in the Maxwell fluid at high air flux but never in the Bingham fluid. Detailed observations of the deformation until brittle fracture reveals a stress increase and strain rate decrease. The fracture onset is not determined by the critical strain rate, contrary to conventional brittle fragmentation criteria widely used in volcanology. These results will help improve brittle‐ductile transition models for complex fluids in volcanic eruptions. Key Points: Rapid air injection generated brittle fracture in a Maxwell fluid but not in a Bingham fluid, although they have similar elasticityThe observation of elasticity in small‐amplitude oscillation tests is not sufficient to infer that the fluid can fractureThe strain rate around a bubble decreased toward fracture, contrary to the conventional critical strain‐rate fracture criterion [ABSTRACT FROM AUTHOR]