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Abstract Understanding carbon dioxide emissions variability in volcanic regions is vital for detecting instabilities in the subvolcanic plumbing system, crucial for managing both volcanic and environmental risks. While changes in magmatic sources drive these variations, non-magmatic processes can complicate signal interpretation, especially in caldera environments. Here, geothermal systems can sequester CO2 within the bedrock through hydrothermal calcite precipitation, significantly impacting surface-level CO2 emissions. Unfortunately, few studies have explored this phenomenon, examining hydrothermal calcite origins and their effects on carbon balances and temporal gaseous patterns in active volcanic settings. Our study developed a specialized methodology for quantifying CO2 sequestered in hydrothermal calcites within alkaline caldera systems. We focused on analyzing hydrothermal calcite in lithics from volcanic deposits of eruptions of varying ages, Volcanic Explosivity Index (VEI), and eruptive vent locations to enhance the representativeness of the entire caldera bedrock. Unlike core samples from geothermal wells, which are infrequent and limited to specific depths, lithics can be easily collected, offering a comprehensive understanding of CO2 sequestration. Through extensive 3D textural characterization and isotopic investigations on hydrothermal calcite within lithic fragments from selected alkaline volcanic deposits in the Campi Flegrei caldera, our findings emphasized the significant influence of calcite sinks on the overall CO2 budget released by volcanoes throughout their evolution.

Imaging the intra-sediment magma chamber in the Damavand region, northern Iran, is beyond the resolution of the local seismic observations. Gravity anomalies can precisely image the lateral extension of magma reservoir. In order to provide vertical extension of magma chamber, we apply inversion of magnetic data with a higher sensitivity to shallow structure in comparison to gravity data. More importantly, knowledge of magma chamber’s density allows prediction of its mechanical behaviour including the potential of eruption. As Damavand is estimated to be an active volcano, it is important to revisit the physical properties of the magma chamber to be able to evaluate the potential of eruption. Here, we apply the sparse norm inversion of Bouguer gravity anomaly and magnetic data to model the uppermost crust beneath Damavand volcano. Qualitative analysis of the Bouguer anomaly shows that the power of the spectrum remains almost unchanged by upward continuation using heights greater than 4 km. Thus, we conclude that the 4-km upward continued Bouguer anomaly represents the regional gravitational effects free from very shallow effects. Inversion of magnetic anomaly, interestingly, shows a susceptibility structure, with susceptibility contrast of up to ~ +0.025 SI, in the same place as density anomaly. This study proposes a 10-km wide magma chamber beneath Damavand from depth ~3 km to depth ~12 km. The resulted density structure is comparable with the obtained values from derived densities (using thermodynamic mineral phase equilibrium) based on geochemical data and those from conversion of seismic velocity to density. According to the geochemical data analysis, the lava is andesitic which is categorized among dense crustal rocks (2.8 g/cm3). But, our modeling results shows a density contrast of maximum + 0.25 g/cm3 between the magma chamber and the surrounding sedimentary rocks (with density of 2.45 g/cm3) above 5 km. Therefore, we can conclude that the shallow magma chamber, composed of dense andesite, is relatively warm and probably not completely consolidated. The high temperature of magma chamber appears to be neutralized by the impact of high density of andesite (naturally dense rocks) to result in moderate negative anomaly in tomography (i.e., ∆Vs=~ -2 %). Magma chamber’s temperature might exceed 750-800 ºC which is still beyond the solidus-liquid transition temperature of 1100 ºC. Therefore, we can conclude that the magma is no liquid and is partially consolidated.

Understanding carbon dioxide emissions variability in volcanic regions is vital for detecting instabilities in the subvolcanic plumbing system, crucial for managing both volcanic and environmental risks. While changes in magmatic sources drive these variations, non-magmatic processes can complicate signal interpretation, especially in caldera environments. Here, geothermal systems can sequester CO2 within the bedrock through hydrothermal calcite precipitation, significantly impacting surface-level CO2 emissions. Unfortunately, few studies have explored this phenomenon, examining hydrothermal calcite origins and their effects on carbon balances and temporal gaseous patterns in active volcanic settings. Our study developed a specialized methodology for quantifying CO2 sequestered in hydrothermal calcites within alkaline caldera systems. We focused on analyzing hydrothermal calcite in lithics from volcanic deposits of eruptions of varying ages, Volcanic Explosivity Index (VEI), and eruptive vent locations to enhance the representativeness of the entire caldera bedrock. Unlike core samples from geothermal wells, which are infrequent and limited to specific depths, lithics can be easily collected, offering a comprehensive understanding of CO2 sequestration. Through extensive 3D textural characterization and isotopic investigations on hydrothermal calcite within lithic fragments from selected alkaline volcanic deposits in the Campi Flegrei caldera, our findings emphasized the significant influence of calcite sinks on the overall CO2 budget released by volcanoes throughout their evolution. [ABSTRACT FROM AUTHOR]

Imaging the intra-sediment magma chamber in the Damavand region, northern Iran, is beyond the resolution of the local seismic observations. Gravity anomalies can precisely image the lateral extension of magma reservoir. In order to provide vertical extension of the magma chamber, we apply the inversion of magnetic data with a higher sensitivity to shallow structure in comparison to the gravity data. More importantly, the knowledge of the magma chamber’s density allows the prediction of its mechanical behaviour, including the potential of eruption. As Damavand is estimated to be an active volcano, it is important to revisit the physical properties of the magma chamber to be able to evaluate the potential of eruption. Here, we apply the sparse norm inversion of the Bouguer gravity anomaly and magnetic data to model the uppermost crust beneath the Damavand volcano. The qualitative analysis of the Bouguer anomaly shows that the power of the spectrum remains almost unchanged by upward continuation using heights greater than 4 km. Thus, we conclude that the 4-km upward continued Bouguer anomaly represents the regional gravitational effects free from very shallow effects. The inversion of the magnetic anomaly, interestingly, shows a susceptibility structure, with susceptibility contrast of up to ~ +0.025 SI, in the same place as the density anomaly. This study proposes a 10- km wide magma chamber beneath Damavand from depth ~3 km to depth ~12 km. The resulting density structure is comparable with the obtained values from derived densities (using the thermodynamic mineral phase equilibrium) based on geochemical data and those from the conversion of seismic velocity to density. According to the geochemical data analysis, the lava is andesitic which is categorized among dense crustal rocks (2.8 g/cm³ ). But our modelling results shows a density contrast of maximum + 0.25 g/cm³ between the magma chamber and the surrounding sedimentary rocks (with a density of 2.45 g/cm³ ) above 5 km. Therefore, we can conclude that the shallow magma chamber, composed of dense andesite, is relatively warm and probably not completely consolidated. The high temperature of the magma chamber appears to be neutralized by the impact of the high density of andesite (naturally dense rocks) to result in a moderate negative anomaly in tomography (i.e., ∆Vs=~ -2 %). The magma chamber’s temperature might exceed 750-800 ºC which is still beyond the solidus-liquid transition temperature of 1100 ºC. Therefore, we can conclude that the magma is no liquid and is partially consolidated. [ABSTRACT FROM AUTHOR]

During the last 10 kyr, significant subsidence and uplift occurred on Mayotte Island in the Comoros archipelago (Indian Ocean), but the role of volcanic processes in Holocene vertical movements has been neglected in the research so far. Here, we show that an abrupt subsidence of 6–10 m occurred between 9.4 and 10 kyr ago, followed by an uplift of the same amplitude at a rate of 9 mm/yr from 8.1 to 7 kyr ago. A comparison of the relative sea level of Mayotte and a reference sea level curve for the global ocean has been conducted using a modeling approach. This shows that an increasing and decreasing pressure at depth, equivalent to the process caused by a deep magma reservoir (50–70 km), was responsible for ~6–10 m subsidence and 6–10 m uplift, whereas loading by new volcanic edifices caused subsidence during the last few thousand years. Surface movements and deep pressure variations may be caused by pulses from the deep mantle, related to superplume activity, but uncertainties and unknowns about these phenomena are still present and further studies are needed. A better understanding of the volcano-tectonic cycle may improve assessments of volcanic hazards. [ABSTRACT FROM AUTHOR]

Sapas Mons is a large shield volcano in Atla Regio on Venus. Its summit region is partially encircled by a system of pits and extensional faults (graben). The existence and configuration of this system have been attributed to stresses generated above the margin of a magma chamber spanning the region beneath the summit. The proposed stress‐generating mechanism includes either withdrawal of magma from or solidification of magma within such a chamber (Keddie & Head, 1994, https://doi.org/10.1007/bf00644896). To explore these hypotheses, we calculate Finite Element Method models of stresses and deformations resulting from magma chamber depressurization beneath a Sapas Mons‐sized edifice with axisymmetric geometry. For a range of magma chamber depths and vertical thicknesses, we determine the minimum under pressure that produces a stress state predicting failure in circumferential normal mode at the observed position of the graben system. We also determine maximum under pressure under two conditions: (1) no failure (thrust fault mode) predicted at the summit, and (2) predicted failure (thrust fault mode) limited to within 10 km of the summit. We find that successful models require sill‐like chamber geometry with vertical thicknesses <1.5 km (diameter to thickness aspect ratios >66:1), and chamber depth <8 km beneath the summit. Calculated reductions in chamber volume are comparable to volumes of late‐stage eruptive units mapped at Sapas Mons, favoring the magma withdrawal hypothesis for graben system formation. Evidence that unit 5 of Keddie and Head (1994, https://doi.org/10.1007/bf00644896) overlapped in time with, but largely postdated, the graben forming event renders it the most likely destination for magma removed from the chamber. Plain Language Summary: Sapas Mons is a large volcanic mountain on Venus, with lava flows that extend outwards for 100s of kilometers. Its distinctive summit region is partially encircled by a narrow ring of faults, which are most prominent on the east side. It has been proposed that a very wide but short chamber full of molten rock (magma) exists beneath the center of Sapas Mons, and that the faulting occurs when the top of the chamber moves downward, which can happen in two ways: (1) magma cools and solidifies within the chamber or (2) the magma leaves the chamber, presumably to erupt at the surface in lava flows. We calculated computer models of the process by which the magma chamber would contract in order to figure out the conditions under which the observed faults could happen (and also under which other types of faults, not seen, are avoided). The chambers must be less than 8 km below the summit and thinner than 1.5 km tall. We determined that the volume lost by the chamber is about the same as that estimated for a specific group of lava flows near the summit, a finding that favors scenario 2 above. Key Points: Sapas Mons volcano on Venus exhibits a partial ring of extensional faults that results from depressurization of an oblate magma chamberNumerical models of magma chamber deflation require extremely oblate chambers at shallow depths to explain observed fault patternsModeled chamber volume changes are comparable to volumes of the youngest mapped volcanic units, pointing to a magma withdrawal mechanism [ABSTRACT FROM AUTHOR]

During the last 10 kyr, significant subsidence and uplift occurred on Mayotte Island in the Comoros archipelago (Indian Ocean), but the role of volcanic processes in Holocene vertical movements has been neglected in the research so far. Here, we show that an abrupt subsidence of 6–10 m occurred between 9.4 and 10 kyr ago, followed by an uplift of the same amplitude at a rate of 9 mm/yr from 8.1 to 7 kyr ago. A comparison of the relative sea level of Mayotte and a reference sea level curve for the global ocean has been conducted using a modeling approach. This shows that an increasing and decreasing pressure at depth, equivalent to the process caused by a deep magma reservoir (50–70 km), was responsible for ~6–10 m subsidence and 6–10 m uplift, whereas loading by new volcanic edifices caused subsidence during the last few thousand years. Surface movements and deep pressure variations may be caused by pulses from the deep mantle, related to superplume activity, but uncertainties and unknowns about these phenomena are still present and further studies are needed. A better understanding of the volcano-tectonic cycle may improve assessments of volcanic hazards.

In this study, we present an artificial neural network (ANN)-based approach for travel-time tomography of a volcanic edifice under sparse-ray coverage. We employ ray tracing to simulate the propagation of seismic waves through the heterogeneous medium of a volcanic edifice, and an inverse modeling algorithm that uses an ANN to estimate the velocity structure from the “observed” travel-time data. The performance of the approach is evaluated through a 2-dimensional numerical study that simulates i) an active source seismic experiment with a few (explosive) sources placed on one side of the edifice and a dense line of receivers placed on the other side, and ii) earthquakes located inside the edifice with receivers placed on both sides of the edifice. The results are compared with those obtained from conventional damped linear inversion. The average Root Mean Square Error (RMSE) between the input and output models is approximately 0.03 km/s for the ANN inversions, whereas it is about 0.4 km/s for the linear inversions, demonstrating that the ANN-based approach outperforms the classical approach, particularly in situations with sparse ray coverage. Our study emphasizes the advantages of employing a relatively simple ANN architecture in conjunction with second-order optimizers to minimize the loss function. Compared to using first-order optimizers, our ANN architecture shows a ∼25% reduction in RMSE. The ANN-based approach is computationally efficient. We observed that even though the ANN is trained based on completely random velocity models, it is still capable of resolving previously unseen anomalous structures within the edifice with about 5% anomalous discrepancies, making it a potentially valuable tool for the detection of low velocity anomalies related to magmatic intrusions or mush.

The gravity and gradient anomalies contain valuable information about the underground geological structures at various depths. Deep and shallow buried source bodies are able to be identified through multi-scale field separation processes, and visual comprehensions of geological structures can be obtained via 3D density inversion techniques. In this study, we propose an improved 3D imaging strategy based on gravitational field separation using the preferential continuation filter. This strategy incorporates the relationship between spectral features and buried depths of source bodies, allowing for a one-step transformation from planar gravity and full-tensor gradient field observations to a 3D density structure in the wave-number domain. Synthetic tests validate the effectiveness and robustness of the gravity and gradient imaging approaches, highlighting their advantages in high vertical resolution and low computational requirements. Nonetheless, it should be noted that the imaging effects of horizontal gradients Γ x x and Γ y y are unsatisfactory due to their weak noise resistance. Thus, they are not suitable for real data applications. The other imaging approaches are further applied to recover the subsurface 3D density structure beneath the Weishan cone in Wudalianchi Volcanic Field, Northeastern China. Our results provide insights into the possible location and shape of the low-density magma chamber. Also, the potential presence of partial melts is inferred and supported from a gravity perspective. The primary advantage of these approaches is their ability to generate a reasonable geological model in scenarios with limited prior information and physical property constraints. As a result, they have significant practical value in the field of applied geophysics, including mineral exploration and volcanology studies. [ABSTRACT FROM AUTHOR]

According to the 'trapped liquid' paradigm, whole-rock chemical compositions of cumulate rocks in layered intrusions can be represented as closed-system multicomponent mixtures of the cumulus phases and the liquids from which they crystallised. Alternative open-system models for cumulate solidification assert that intercumulus liquid is continuously mobile as a result of compaction of crystal mushes. In the closed-system models, all excluded elements, i.e. those incompatible in the cumulus phases, should be correlated with one another, whereas in open systems the more incompatible elements should be decoupled from the more compatible ones and correlations should be poor. These alternative hypotheses are tested using a database of >63 000 whole-rock analyses of mostly ultramafic cumulates from a single package of layers across the entire width of the Mirabela layered intrusion, a 2.5-km-wide by >2-km-thick intrusion with Great Dyke-like stratigraphy. Variably compatible elements Al, Na, Ti and P are found to show strong correlations with one other in olivine-pyroxene cumulates across the spectrum from mesocumulate to orthocumulate rocks, where drill-core sample intervals are composited over 3 m; weaker correlations are found over 1-m sample intervals. The closed-system trapped liquid model is robust for this suite of rocks at the scale of 3-m lengths of drill core (~1 kg of sample). Furthermore, a very smooth and symmetrical variation is observed from dominantly ad- to mesocumulate rocks in the geometrical centre of the intrusion towards orthocumulates at both margins, attributable to increase in cooling rate towards the margins. The most adcumulate rocks are gabbronorites at the base of the mafic sequence in the centre of the intrusion. There is no corresponding decrease in layer thickness towards the centre that would be predicted by a compaction model. The only incompatible element showing partial decoupling is K, which appears to have been mobile at a very late stage, probably in an aqueous fluid phase. There is no evidence for mobilisation of platinum group elements or other chalcophile elements by this fluid despite the presence of disseminated sulfide throughout the sampled interval. [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]

The Asal–Ghoubbet Rift area comprises basaltic rocks with similar compositions that were formed by volcanic eruptions. To gain insight into the magmatic processes of these volcanic formations, we investigated the mineral chemistry of plagioclase macrocrysts and microcrysts found in the basaltic rocks by using an electron probe micro-analyzer (EPMA). These basaltic rocks contain olivine, pyroxene, euhedral plagioclase macrocrysts, and euhedral to subhedral plagioclase microcrysts. These plagioclase macrocrysts reach up to 4 cm in length in the form of giant crystals as plagioclase ultraphyric basalts (PUBs). They have a mineral composition varying from bytownite to labradorite with anorthite content ranging from An53 to An86. Also, the microcrysts of all these volcanic rocks are characterized by labradorite and andesine compositions with An22–80. According to the calculated plagioclase thermobarometry, the crystallization temperature of the plagioclase macrocrysts and microcrysts is 1082 to 1216 °C and 1072 to 1203 °C, respectively, and the pressure is 3.92 to 14.51 kbar for the macrocrysts and 2.99 to 14.84 kbar for the microcrysts. Based on these thermobarometry results for the plagioclases, we conclude that the volcanic formations located in the Asal–Ghoubbet area would have come from different eruptions from a single magmatic chamber. [ABSTRACT FROM AUTHOR]

Owing to their abundance and relative availability on Earth's seafloor, mid‐ocean ridge basalts (MORBs) have a well‐defined chemical element budget, reflected by the low standard deviation associated with typical normal MORB (N‐MORB) composition. However, the exact mechanisms leading to magma differentiation and MORB generation remain debated, which hinders our ability to evaluate MORB parental magma composition. In this study, we leverage the predictive power of the BDD21 numerical framework to obtain a representative trace element budget of parental MORB magma and assess its ability to fractionate into the N‐MORB composition. Utilizing revised parameterizations for mineralogy, melting, and partitioning, we couple BDD21 with numerical simulations of a MOR system driven by seafloor spreading in which we track the evolution of partial melting, mineral modal abundances, and concentrations of incompatible elements. Parental magma compositions are determined once simulations reach a steady state, and magma chamber replenishment models are employed to predict the trace element budget of the erupted liquid. We explore a range of geophysical and geochemical parameters to evaluate their effect on computed trace element concentrations. Previous magma chamber replenishment models are extended to account for multiple crystallization events and melt‐crystal interaction. Modeling outcomes suggest that petrologically constrained fractionation of parental magma compositions obtained through BDD21 yields glass compositions compatible with the N‐MORB budget. Nevertheless, our results show a systematic underestimation of Sr concentration, indicating the presence of recycled oceanic crust in the MORB source region. Plain Language Summary: Beneath Earth's oceans, tectonic plates spread apart at mid‐ocean ridges, generating volcanic regions whose magmatic output forms Earth's oceanic crust. The rocks composing the oceanic crust represent the solidification of magma produced by partially melting deeper mantle rocks. Accordingly, they carry a message about the nature of Earth's interior. To decipher this message, scientists recover rock samples from the seabed and analyze their composition to infer the nature of that otherwise inaccessible deep layer. Unfortunately, the chemical inventories obtained for these rocks reveal that significant processing of the magma occurs as it ascends toward the surface. Therefore, the relationship between crustal rocks and their deep parental counterparts is indirect. Here, we address this complexity using a two‐step process. First, we simulate the generation and composition of partial melts derived from mantle peridotites (archetypal upper‐mantle rocks) using a mid‐ocean ridge numerical model. Second, we employ models of magma chamber processes to account for the expected magmatic evolution of the generated liquid. By optimizing and extending existing magma chamber models, we obtain an accurate representation of rock compositions sampled from Earth's seabed. Our findings provide a new opportunity to decipher the nature of Earth's interior. Key Points: Refined the BDD21 peridotite melting and melt chemistry framework to reproduce geochemical observations of the mid‐ocean ridge systemImproved calibration of peridotite melting parameterization revises solidus and yields appropriate crustal thickness for mid‐ocean ridgesDepleted mantle compositions underestimate Sr concentration in basalts, requiring a prevalent contribution from recycled oceanic crust [ABSTRACT FROM AUTHOR]

Abstract We investigated magma storage conditions prior to the 2011 and 2018 eruptions at Kirishima Shinmoe-dake volcano in Japan based on the relationship between geodetic volume change of magma chamber and erupted magma volume. We derived an analytical expression for the ratio of the erupted magma volume to the geodetic volume change (“volume ratio”), which was formulated as a function of parameters related to the magma storage conditions. This expression shows that the volume ratio is strongly dependent on the effective compressibility of the magma chamber, which in turn depends on the rigidity of surrounding host rocks and shape of the chamber. For the Shinmoe-dake eruptions, the magnitude of the volume change (i.e., deflation) of a spherical magma chamber associated with lava effusion was estimated based on geodetic observations. The erupted magma volume was estimated from a SAR image analysis of the lava accumulation inside the summit crater. Based on these observations, we estimated that the volume ratio in 2011 and 2018 was 2.69 and 2.33, respectively. Substituting the estimated volume ratio into the analytical expression revealed that the observed geodetic data and volume ratio can be explained only when the magma chamber, which was assumed to be spherical, is filled with bubble-free magma. This result suggests that efficient gas segregation from the chamber occurred prior to the eruptions. Our results indicate that combining multi-observation data based on the volume ratio provides valuable information about the magma storage process, such as the behavior of the gas phase in the magma chamber. Graphical Abstract

Abstract Owing to their abundance and relative availability on Earth's seafloor, mid‐ocean ridge basalts (MORBs) have a well‐defined chemical element budget, reflected by the low standard deviation associated with typical normal MORB (N‐MORB) composition. However, the exact mechanisms leading to magma differentiation and MORB generation remain debated, which hinders our ability to evaluate MORB parental magma composition. In this study, we leverage the predictive power of the BDD21 numerical framework to obtain a representative trace element budget of parental MORB magma and assess its ability to fractionate into the N‐MORB composition. Utilizing revised parameterizations for mineralogy, melting, and partitioning, we couple BDD21 with numerical simulations of a MOR system driven by seafloor spreading in which we track the evolution of partial melting, mineral modal abundances, and concentrations of incompatible elements. Parental magma compositions are determined once simulations reach a steady state, and magma chamber replenishment models are employed to predict the trace element budget of the erupted liquid. We explore a range of geophysical and geochemical parameters to evaluate their effect on computed trace element concentrations. Previous magma chamber replenishment models are extended to account for multiple crystallization events and melt‐crystal interaction. Modeling outcomes suggest that petrologically constrained fractionation of parental magma compositions obtained through BDD21 yields glass compositions compatible with the N‐MORB budget. Nevertheless, our results show a systematic underestimation of Sr concentration, indicating the presence of recycled oceanic crust in the MORB source region.

A model for the formation of intrusions of the collision stage of 525–490 Ma and a model of magmatism of the transtensional shear stage of 465–440 Ma within the Mugur-Chinchilig and Erzin-Naryn blocks of Western Sangilen (Tuva) have been developed to describe the process of crust-mantle interaction. Model experiments confirm petrological data on the presence of multi-level chambers during the formation of the Pravotarlashkinsky and Bashkymugur massifs. The proposed model describes the migration of mantle magmas above the head of the mantle plume at the collision stage and assumes the rise of magmas along a permeable tectonic zone in the mantle lithosphere and crust at the transtensional-shear stage. The modeling results allow us to establish that material from the magma chamber can reach depths of the upper crust in the volume ratio of gabbroids to diorites from 1 : 2 to 3 : 4 and additionally introduce about 5 % of the volume fraction of lower crustal material.The physical parameters of the primary magmas (viscosity, solidus and liquidus temperatures, degree of melting depending on temperature and composition, change in density) were calculated taking into account the real geochemical characteristics of igneous rocks from the polyphase massifs of Western Sangilen.

This article reports a protocol on the application of Amp-TB2 (single-amphibole thermobarometry) based on detailed electron-microprobe analyses performed on homogeneous natural standards and synthetic glasses, and amphibole crystals (mostly phenocrysts) of volcanic products erupted by the Bezymianny volcano during its activity through time. The application of this protocol is facilitated by a new version of the model (Amp-TB2.1.xlsx) including an equation to identify heterogeneous domains (disequilibrium; not suitable for thermobarometric constraints) and homogenous (equilibrium) zones within amphibole crystals, which can be used to quantify the physicochemical parameters (i.e., pressure, P; temperature, T; volatile content in the melt, H2Omelt; oxygen fugacity, fO2) of "steady-state" magmatic crystallization. Application examples of the protocol, showing detailed core–rim microprobe data and physicochemical parameter variations in representative amphibole phenocrysts of the Bezymianny are also reported. The depth (and P) estimated by Amp-TB2.1 for this volcano are compared to seismic tomography results. Amp-TB2.1 results mainly show (1) that the Bezymianny is characterized by a very dynamic feeding system where the magma is stored at shallow crustal levels before recent activity periods characterized by climatic events and (2) that the pre-eruptive depth of magma storage generally increases with the age of the investigated products. [ABSTRACT FROM AUTHOR]

Melt percolation through partially molten "mushy" regions of the crust underpins models for magma migration, accumulation, and processes that prime systems for eruption. Knowledge of the hydraulic properties of magma mush, specifically permeability, is required for accurate predictions of melt migration rates and accumulation timescales. Previous studies, validated for cuboidal crystal analogs, show that crystal shape exerts a first‐order control on the permeability, and is tested here for anisometric natural crystal shapes using X‐ray CT 3D data sets of magma mush analogs made from packed confectionary particles arranged randomly. We use a lattice‐Boltzmann fluid flow simulation tool to determine the permeability of the analogue melt phase network between the packed particles. We find excellent agreement with our data sets to within ∼0.1 log units, when the specific surface area is measured. To extend this to more typical cases where the specific surface area is unknown, we use the shape and size of the objects determined in both 3D and 2D to estimate the specific surface area assuming a cuboid approximation. These approximate solutions give good results to within ∼0.5 log units of the measured permeability and offer a method by which permeability could be estimated from a thin section of a cumulate or pluton sample. Our shape‐sensitive approach is more accurate than existing models for permeability of magma mush, most approximating natural crystal shapes to spheres. We therefore propose that these could be implemented in dynamic magma mush models for melt movement in the crust to produce more accurate flux predictions. Plain Language Summary: Magma chambers in the Earth are "mushy," meaning that liquid magma is trapped in between solid crystals. In many cases, the liquid magma must escape before an eruption occurs. For the liquid magma to escape, it must move through the tight spaces between the solid crystals, which occurs at a speed dictated by the "permeability" of the crystal framework. Here, we use fudge and sugar crystals as a proxy for the solid crystals in these magma chambers, and we use simulations to observe how the fluid between the fudge and sugar moves. The key advance here is that we show how the complicated shape of fudge and sugar crystals changes the speed at which the fluid is able to move. Key Points: Crystal shape exerts a first order control on magma mush permeabilityThe specific surface area of magmatic crystals is the relevant metric to predict the permeability, across all crystal shapesMagma mush permeability can be calculated from crystal size measurements made on a 2D thin section, via a 2D‐to‐3D conversion [ABSTRACT FROM AUTHOR]

The gravity and gradient anomalies contain valuable information about the underground geological structures at various depths. Deep and shallow buried source bodies are able to be identified through multi-scale field separation processes, and visual comprehensions of geological structures can be obtained via 3D density inversion techniques. In this study, we propose an improved 3D imaging strategy based on gravitational field separation using the preferential continuation filter. This strategy incorporates the relationship between spectral features and buried depths of source bodies, allowing for a one-step transformation from planar gravity and full-tensor gradient field observations to a 3D density structure in the wave-number domain. Synthetic tests validate the effectiveness and robustness of the gravity and gradient imaging approaches, highlighting their advantages in high vertical resolution and low computational requirements. Nonetheless, it should be noted that the imaging effects of horizontal gradients Γxx and Γyy are unsatisfactory due to their weak noise resistance. Thus, they are not suitable for real data applications. The other imaging approaches are further applied to recover the subsurface 3D density structure beneath the Weishan cone in Wudalianchi Volcanic Field, Northeastern China. Our results provide insights into the possible location and shape of the low-density magma chamber. Also, the potential presence of partial melts is inferred and supported from a gravity perspective. The primary advantage of these approaches is their ability to generate a reasonable geological model in scenarios with limited prior information and physical property constraints. As a result, they have significant practical value in the field of applied geophysics, including mineral exploration and volcanology studies.

The processes driving the evolution of crystal mushes are often documented in complex systems where crystallization, assimilation, magma replenishment and mixing occur concurrently and are generally overprinted by compaction and deformation. Documenting the characteristics of an undisturbed crystal mush is thus of upmost importance; it highlights the initial conditions with which complex crystal mush processes proceed. We here present the structure and composition of an oceanic crystal mush through detailed petro‐structural and chemical study of metre‐scale intrusions from the Mid‐Atlantic Ridge. Textures, bulk‐rock and mineral compositions indicate closed‐system crystallization of primitive melts, undisturbed by dissolution–precipitation reactions and subsequent deformation. These frozen crystal mushes record the simplest possible evolution of small‐scale intrusions and can be used as a baseline to pinpoint the impact of crystal mush processes on the evolution of complex systems. Any divergence from this reference results from processes occurring concomitantly to the progressive closure of the magmatic system. [ABSTRACT FROM AUTHOR]

We investigated magma storage conditions prior to the 2011 and 2018 eruptions at Kirishima Shinmoe-dake volcano in Japan based on the relationship between geodetic volume change of magma chamber and erupted magma volume. We derived an analytical expression for the ratio of the erupted magma volume to the geodetic volume change ("volume ratio"), which was formulated as a function of parameters related to the magma storage conditions. This expression shows that the volume ratio is strongly dependent on the effective compressibility of the magma chamber, which in turn depends on the rigidity of surrounding host rocks and shape of the chamber. For the Shinmoe-dake eruptions, the magnitude of the volume change (i.e., deflation) of a spherical magma chamber associated with lava effusion was estimated based on geodetic observations. The erupted magma volume was estimated from a SAR image analysis of the lava accumulation inside the summit crater. Based on these observations, we estimated that the volume ratio in 2011 and 2018 was 2.69 and 2.33, respectively. Substituting the estimated volume ratio into the analytical expression revealed that the observed geodetic data and volume ratio can be explained only when the magma chamber, which was assumed to be spherical, is filled with bubble-free magma. This result suggests that efficient gas segregation from the chamber occurred prior to the eruptions. Our results indicate that combining multi-observation data based on the volume ratio provides valuable information about the magma storage process, such as the behavior of the gas phase in the magma chamber. [ABSTRACT FROM AUTHOR]

Slamet Volcano (3,432 m) is the highest volcano in Central Java, Indonesia, with a weak explosive type of eruption compared to other active volcanoes. Designing the magma chamber model may help reveal the characteristics of Slamet Volcano. The modelling uses the gravimetric satellite data from GGMplus, which is best in spatial resolution compared to other satellite data, i.e. 220 m. Data processing begins with Bouguer correction and terrain correction and has resulted in complete Bouguer anomalies data, with values ranging from 11.068 – 117.451 mGal. Further, residual Bouguer anomalies data were obtained after data reduction to the horizontal surface and removal of regional anomalies data, to obtain values ranging from -67.569 – 38.808 mGal. The residual anomaly contour map shows the lowest anomalous value is under the volcanic cone at positions of 109.21967° E and 7.24281° S which is estimated to be the location of the magma chamber of Slamet Volcano. However, the inversion modeling resulting from the residual Bouguer anomalies data shows that the magma chamber of Slamet Volcano can be observed clearly at positions of 109.22053° E and 7.24719° S. The location of the magma chamber is not perfectly vertical under the volcanic cone but has a slight slope. The obtained model of the magma chamber has a relatively small volume and shallow depth, i.e. about 1 – 4 km. The obtained physical parameters of the magma chamber impact the characteristics of the eruption of Slamet Volcano which tend to be weak explosive.

The Asal–Ghoubbet Rift area comprises basaltic rocks with similar compositions that were formed by volcanic eruptions. To gain insight into the magmatic processes of these volcanic formations, we investigated the mineral chemistry of plagioclase macrocrysts and microcrysts found in the basaltic rocks by using an electron probe micro-analyzer (EPMA). These basaltic rocks contain olivine, pyroxene, euhedral plagioclase macrocrysts, and euhedral to subhedral plagioclase microcrysts. These plagioclase macrocrysts reach up to 4 cm in length in the form of giant crystals as plagioclase ultraphyric basalts (PUBs). They have a mineral composition varying from bytownite to labradorite with anorthite content ranging from An53 to An86. Also, the microcrysts of all these volcanic rocks are characterized by labradorite and andesine compositions with An22–80. According to the calculated plagioclase thermobarometry, the crystallization temperature of the plagioclase macrocrysts and microcrysts is 1082 to 1216 °C and 1072 to 1203 °C, respectively, and the pressure is 3.92 to 14.51 kbar for the macrocrysts and 2.99 to 14.84 kbar for the microcrysts. Based on these thermobarometry results for the plagioclases, we conclude that the volcanic formations located in the Asal–Ghoubbet area would have come from different eruptions from a single magmatic chamber.

This paper reports the results of seismic, electromagnetic, and gravity surveys, as well as seismicity data in the lithosphere at depth for the active volcanoes in the Avacha–Koryaksky group which is part of the East Kamchatka volcanic belt. We have developed an integrated geophysical model for the crust and lithospheric mantle in the area of study. The resulting distribution of crustal geophysical inhomogeneities, in particular, beneath Avacha Volcano, was used to study the main features of intracrustal fluid saturation and of pathways as channels for deeper fluids to rise to the upper crust. The integrated model assumes that the stresses that arise at boundaries of zones with different conditions of defluidization constitute one of the factors to produce seismicity beneath the active volcanoes. We also incorporate data from regional seismic tomography to deal with a general scheme for deep processes in the lithosphere and the system that supplies magma to the volcanoes. It is assumed that active volcanoes, in particular, Avacha, are connected to the asthenospheric layer of the lithosphere mantle at a depth of about 70–120 km, whence fluids/melts are coming into the magma chamber in the lower crust with subsequent formation of a peripheral chamber in the upper crust beneath the volcanic cone due to the heat supplied by the lower crustal source. [ABSTRACT FROM AUTHOR]

The Tabar-Lihir-Tanga-Feni (TLTF) island chain in northeastern Papua New Guinea formed by tectonic and alkaline to shoshonitic magmatic activity since the Pliocene. Several volcanic centers are Cu Au mineralized including the world-class Ladolam Au deposit and Conical Seamount south of Lihir. The latter has been recognized as a juvenile analogue to the Ladolam deposit located on-shore. Whereas the mineralization at Conical Seamount is reasonably well studied, the specific magmatic processes that promote epithermal mineralization at this seamount but not at others are poorly understood. Here, we present new petrological and geochemical data from Conical Seamount, and compare them with those from the barren (unmineralized) Edison, Tubaf and New World seamounts nearby. We focus on whole rock compositions and major and trace element analysis of melt inclusions and minerals including clinopyroxene, sulfide and magnetite. We combine our observations with modelled constraints on mantle source composition and partial melting as well as magma evolution. A first-stage melting leaves a residual mantle source enriched in Au. Second-stage melting of a previously subduction-metasomatized mantle generally promotes the transfer and concentration of metals and volatiles in the ascending melts. These magmas are unlikely to control ore formation as all seamounts show evidence for similar mantle sources and parental melt composition. However, the presence of a shallow crustal magma chamber is unique to Conical Seamount. It is characterized by frequent melt replenishments and extensive magma fractionation leading to sulfide and magmatic volatile saturation. These specific magma chamber processes lead to the pre-enrichment of the magma in chalcophile elements including Au, while sulfide saturation coeval with magmatic volatile exsolution provide the way for an effective Au transfer from the magmatic to the epithermal system. • Alkaline magmas of the TLTF island chain result from a subduction-modified mantle source and two-stage partial melting. • The role of mantle source and parental melt composition for high Cu-Au mineral potentials is important but limited. • A shallow crustal magma reservoir is key for epithermal ore formation. [ABSTRACT FROM AUTHOR]

• The study delineates the heat contribution of the deep and shallow magma chambers beneath Mt. Changbai. • The study investigated the thermal energy transfer induced by shallow hydrothermal circulation in the Mt. Changbai area. • The study evaluates hydrothermal and hot dry rock geothermal resources in the Mt. Changbai area. Mount Changbai is an active volcano in Northeast China that has erupted several times since the Miocene. Investigating the potential high–temperature geothermal reservoirs associated with magma chambers under the volcano has a significant meaning for clean energy development and utilization. Through a geological field survey combined with drilling data and collected geophysical data, including seismic and magnetotelluric data, of the Mt. Changbai area, we constructed a geological model extending from the upper mantle to the surface. Based on the geological model, we performed thermal simulations to understand the evolution of temperature profiles under Mt. Changbai since the Miocene (∼25 Ma). The results were compared with temperature measurements from geothermal drilling and hot springs for validation. We found that: (1) The total temperature increase can reach ∼263 °C at –6 km (absolute depth) under the Mt. Changbai volcano. While the temperature increase has reached ∼224 °C since the shallow magma chamber appeared at ∼1.5 Ma, which accounts for >80 % of the total temperature increase. (2) Surface cold–water infiltration caused the decrease of subsurface temperature. However, the water can result in local accumulation of heat with a temperature increase up to 44 °C. (3) Both hydrothermal and hot dry rock geothermal resources are abundant in the Mt. Changbai area. Sedimentary strata of the Meso–Neoproterozoic and above that have good porosity and permeability, forming hydrothermal reservoirs. The temperature can reach 150 °C at a depth of 3 km under the Tianchi crater and are transferred to the surface by water through faults. While, metamorphic rock of the Archean–Paleoproterozoic and intrusive rock of the Mesozoic can form hot dry rock geothermal reservoirs with a temperature of 200–400 °C at a depth of 4–7 km under the Tianchi crater and surrounding areas. [ABSTRACT FROM AUTHOR]

This article reports a protocol on the application of Amp-TB2 (single-amphibole thermobarometry) based on detailed electron-microprobe analyses performed on homogeneous natural standards and synthetic glasses, and amphibole crystals (mostly phenocrysts) of volcanic products erupted by the Bezymianny volcano during its activity through time. The application of this protocol is facilitated by a new version of the model (Amp-TB2.1.xlsx) including an equation to identify heterogeneous domains (disequilibrium; not suitable for thermobarometric constraints) and homogenous (equilibrium) zones within amphibole crystals, which can be used to quantify the physicochemical parameters (i.e., pressure, P; temperature, T; volatile content in the melt, H2Omelt; oxygen fugacity, fO2) of “steady-state” magmatic crystallization. Application examples of the protocol, showing detailed core–rim microprobe data and physicochemical parameter variations in representative amphibole phenocrysts of the Bezymianny are also reported. The depth (and P) estimated by Amp-TB2.1 for this volcano are compared to seismic tomography results. Amp-TB2.1 results mainly show (1) that the Bezymianny is characterized by a very dynamic feeding system where the magma is stored at shallow crustal levels before recent activity periods characterized by climatic events and (2) that the pre-eruptive depth of magma storage generally increases with the age of the investigated products.

Arc volcanoes are underlain by complex systems of molten‐rock reservoirs ranging from melt‐poor mush zones to melt‐rich magma chambers. Petrological and satellite data indicate that eruptible magma chambers form in the topmost few kilometres of the crust. However, very few chambers have ever been definitively located, suggesting that most are too short‐lived or too small to be imaged, which has direct implications for hazard assessment and modeling of magma differentiation. Here we use a high‐resolution technology based on inverting full seismic waveforms to image a small, high‐melt‐fraction magma chamber that was not detected with standard seismic tomography. The melt reservoir extends from ∼2 to at least 4 km below sea level (b.s.l.) at Kolumbo—a submarine volcano near Santorini, Greece. The chamber coincides with the termination point of the recent earthquake swarms and may be a missing link between a deeper melt reservoir and the high‐temperature hydrothermal system venting at the crater floor. The chamber poses a serious hazard as it could produce a highly explosive, tsunamigenic eruption in the near future. Our results suggest that similar reservoirs (relatively small but high‐melt‐fraction) may have gone undetected at other active volcanoes, challenging the existing eruption forecasts and reactive‐flow models of magma differentiation. Plain Language Summary: Arc volcanoes, which mark the curved boundaries between converging tectonic plates, host the most explosive events on Earth. The associated hazard depends on how much mobile magma is currently present shallow beneath a volcano. Standard tomographic methods used so far have relatively low resolution and give a blurred picture of only the largest molten‐rock bodies. In particular, they struggle to distinguish between mobile magma and melt spread between tightly packed mineral grains. This study, a first in volcanology, combines a next‐generation tomographic method with extraordinarily dense seafloor recordings of controlled marine sound sources. This state‐of‐the‐art experiment at Kolumbo volcano, offshore of Santorini allowed us to detect a body of mobile magma which has been growing at an average rate of 4 × 106 m3 per year since the last eruption in 1650 CE. This rate is large enough to counteract the effect of cooling and crystallization. Our results show that Kolumbo poses a serious threat and deserves a real‐time monitoring facility. Despite the excellent data coverage, the small magma body was missed by standard tomography. This suggests that applying next‐generation imaging methods to already‐well‐studied volcanoes may lead to similar discoveries. We envision that small‐volume, high‐melt‐fraction reservoirs may be more widespread than previously thought. Key Points: A shallow, very strong negative Vp anomaly imaged under the explosive, submarine Kolumbo volcano, Greece, using full‐waveform inversionThe high‐fidelity image and petrologic data indicate the anomaly is a small (∼0.6‐km wide, ∼2‐km deep), magma chamber with ∼42% of meltThe chamber was missed by travel‐time tomography indicating similar reservoirs may have gone undetected at other volcanoes [ABSTRACT FROM AUTHOR]

Abstract Arc volcanoes are underlain by complex systems of molten‐rock reservoirs ranging from melt‐poor mush zones to melt‐rich magma chambers. Petrological and satellite data indicate that eruptible magma chambers form in the topmost few kilometres of the crust. However, very few chambers have ever been definitively located, suggesting that most are too short‐lived or too small to be imaged, which has direct implications for hazard assessment and modeling of magma differentiation. Here we use a high‐resolution technology based on inverting full seismic waveforms to image a small, high‐melt‐fraction magma chamber that was not detected with standard seismic tomography. The melt reservoir extends from ∼2 to at least 4 km below sea level (b.s.l.) at Kolumbo—a submarine volcano near Santorini, Greece. The chamber coincides with the termination point of the recent earthquake swarms and may be a missing link between a deeper melt reservoir and the high‐temperature hydrothermal system venting at the crater floor. The chamber poses a serious hazard as it could produce a highly explosive, tsunamigenic eruption in the near future. Our results suggest that similar reservoirs (relatively small but high‐melt‐fraction) may have gone undetected at other active volcanoes, challenging the existing eruption forecasts and reactive‐flow models of magma differentiation.

High-temperature melting and crystallization experiments were carried out at pressures from 1 atm to 196 MPa and under H2O-saturated conditions on the basaltic andesite melt of the Izu-Oshima 1986B eruption (i.e., the BM melt), using a 1-atmosphere fO2-controlled furnace and an internally heated pressure vessel. These data were used to constrain the H2O-saturated plagioclase liquidus (HSPL) of the melt. The fO2 conditions were controlled by a mixed H2-CO2 gas at the Ni-NiO (NNO) buffer for the 1 atm experiments, but were not controlled for the high-pressure experiments. Plagioclase is the liquidus phase at 1 atm, whereas early saturation of Fe-Ti oxide above the plagioclase liquidus occurred in the high-pressure experiments due to the elevated fO2 conditions. The HSPL temperature decreases from 1172 ± 8°C to 1030 ± 20°C as the pressure increases from 1 atm to 196 MPa. A combination of previously proposed models for the plagioclase liquidus and melt H2O-solubility can predict the experimentally determined HSPL temperatures, even if oxidation-induced magnetite crystallization occurs. Using these models and the previously reported pre-eruptive temperature of ∼1100 ± 30°C, we estimate the pre-eruptive pressure conditions of the BM melt to be 42-32+48 MPa, which corresponds to depths of 1.9-1.4+1.9 km. The estimated depth is consistent with that of the shallow active dikes previously identified from geophysical studies, suggesting that the BM melt was derived from a small, shallow magma chamber formed in the shallow dike region. [ABSTRACT FROM AUTHOR]

Crustal magmatic systems likely consist of magmatic reservoirs dominated by crystal mush. Recent studies suggest that the physical processes occurring in crystal mush could alter the response of magmatic reservoirs during volcanic unrest. Here, we present a magma chamber deformation model that incorporates two new aspects in crystal mush: heat and exsolved gas. The model is based on earlier studies by Liao et al. (2021, https://doi.org/10.1029/2020JB019395) with additional processes including thermal‐mechanical coupling, dependence of material properties on gas content, and temperature evolution following an injection of hotter magma. The post‐injection time‐dependent evolution of the system can be grouped into three periods, which are dominated by poroelastic diffusion (short term), viscoelastic relaxation (mid term), and thermal equilibration (long term). All three time‐regimes are strongly affected by gas distribution, which alters the relative compressibility of the crystal‐rich and crystal‐poor regions in the chamber. The contribution of thermal evolution emerges during the mid‐term evolution. The time‐dependent evolution of the system highlights the intrinsic ability of a gas‐bearing mushy magma chamber to generate non‐monotonic time series of stresses, deformation, and magma transport. Plain Language Summary: The processes that occur in magmatic reservoirs and their surrounding crustal rocks can modulate the triggering, duration, and style of volcanic eruptions. Although magmatic reservoirs are typically modeled as cavities filled with fluid magma, geophysical and petrological observations have long suggested that they likely contain crystal mush, an ensemble of solid crystals and fluid (gas/melt) that reside in interstitial pore spaces. Some recent studies show that a mushy magma chamber could behave differently than a fluid‐filled chamber, leading to different interpretation of observations such as ground deformation. Here, we extend these studies to incorporate two new aspects that are typical for crustal magmatic systems: gas phase (in the form of disconnected gas bubbles) and nonuniform temperature. The incorporation of these two new aspects allows for more processes that can be examined quantitatively, and a more realistic depiction of crustal magmatic reservoirs. We find that when gas and heat distribute unevenly, a simple magma injection event could result in complex time‐dependent changes in pressure, stress, and magma flows in the chamber. Key Points: A physics‐based model explores the influence of gas and heat in the a magma chamber containing crystal mush upon magma injectionThe non‐uniform distributions of gas and heat cause non‐monotonic time evolution of deformation, crustal stresses, and magma transportPoroelastic diffusion, viscous relaxation, and thermal equilibration lead to three time regimes in the post‐injection evolution [ABSTRACT FROM AUTHOR]

The Gardar Province of south Greenland is defined by the products of alkaline igneous magmatism during the Mesoproterozoic. The most laterally extensive Gardar intrusions are a series of giant dyke complexes best exposed on the Tuttutooq archipelago. We present new field observations and a geological map of north-east Tuttutooq island that provide fresh insights into the temporal evolution of the Younger giant dyke complex and two associated ultramafic lamprophyres. Our data demonstrate that distinctive crystallisation regimes occurred in different sectors of the dyke complex, leading to the formation of marginal gabbros and ovoid pod-like domains displaying lamination, modal layering and/or more evolved differentiates. We infer that at least two pulses of magma contributed to the formation of the Younger giant dyke complex. In addition, the relative ages of two ultramafic lamprophyre diatremes are constrained and attributed to two distinct phases of rifting in the Gardar Province.

• LASS-ICPMS depth profiling of zircon reveals geochemical evolution trends. • Zircon tracks titanite saturation and co-crystallization. • An empirical solution to a TiO 2 and T by tandem Ti-in-Zrn and Zr-in-Ttn thermometry. • Titanite saturates at low a TiO 2 (0.4–0.5) and low T (700–715 °C). • Zircon rims crystallize at low temperatures (625–700 °C). Upper-crustal granitoids are a late-stage product of crustal differentiation. This last stage in the evolution has been proposed to be the key interval that governs volcanic eruptions, ore formation, and fluid migration. Though numerous techniques have been employed to understand the evolution of late-stage felsic magmas, there remains little agreement regarding their crystallization histories. Here we use laser ablation depth profiling of zircon trace elements to probe the thermochemical evolution of well-characterized granitoid rocks from the Tuolumne Intrusive Suite (CA, USA). In combination with titanite trace-element data, we can determine the T-X trajectory of the magmatic system during zircon growth at the latest stage of crystallization. Our data also allows for a robust empirical calibration of the widely used Ti-in-zircon thermometer arising from the onset of titanite crystallization captured in zircon rims. These data show that Tuolumne zircon growth occurred at an a TiO 2 of 0.4–0.5, which is lower than many previous estimates. We further model zircon growth up- and down-temperature from titanite saturation, and document extended thermochemical growth records preserved in zircons from these upper-crustal melts. The calculated temperatures are consistent with zircon growth from 775 to 625 °C, indicating that zircon growth occurred over a wide temperature range down to, or potentially below, the water-saturated granite solidus. These findings provide empirically-calibrated values for use in other Ti-in-zircon and Zr-in-titanite temperature calculations, particularly to understand late-stage, low-temperature melts in granitoid systems. [ABSTRACT FROM AUTHOR]

Abstract A magma plumbing system with dual magma chambers beneath active volcanoes is commonly observed through petrological and geophysical measurements. This paper developed a physical model for the dynamics of a dual-magma-chamber system during volcanic eruptions. The model consists of the plumbing system where two elastically deformable magma chambers are connected in series with non-deformable conduits. Based on this model, we obtained an analytical solution that describes temporal changes in pressures at the two chambers accompanied by the eruption. The analytical solution showed that the feature of the chamber pressure changes is mainly controlled by two non-dimensional numbers $$C'$$ C ′ and $$\Omega '$$ Ω ′ . Here, $$C'$$ C ′ is the ratio of the parameter controlling the magnitude of pressure change in the shallower chamber to that in the deeper chamber, and $$\Omega '$$ Ω ′ is the ratio of conduit’s conductivity (inverse of resistivity to magma flow) between the shallower chamber and the surface to that between the chambers. For smaller $$C'$$ C ′ and $$\Omega '$$ Ω ′ , the shallower chamber’s pressure is kept constant during the decrease in the pressure at the deeper chamber in the initial phase of the eruption. This corresponds to a deformation pattern commonly observed in some eruptions, in which the deflation of the deeper chamber was predominant. The estimation of $$C'$$ C ′ and $$\Omega '$$ Ω ′ based on the parameters related to magma properties and geometries of the chambers and the conduits revealed that the smaller $$C'$$ C ′ and $$\Omega '$$ Ω ′ conditions are satisfied under realistic magmatic and geological parameters. This indicates that the magma dynamics in the dual-chamber system generally cause the dominance of the deeper chamber’s deflation.

Abstract The Chalupas Caldera is a rhyolitic volcano located in the Eastern Cordillera to the Southeast of the Cotopaxi Volcano in the Ecuadorian Andes. It is supposedly fed by a huge magmatic chamber below the caldera. For studying the Chalupas magmatic chamber, the tomographic models obtained by a Tarantola-Valette inversion and studied previously in the entire Ecuadorian region were used. The theoretical basis of the tomography method based on a Bayesian solution of the inverse problem is introduced. The process of the inverse problem regularization is obtained by an L-curve scheme to achieve an optimal solution. The seismic tomography images zoomed in the Chalupas region are well correlated with the main geological terranes and faults documented for the basement of Eastern Cordillera. Based on the tomographic images obtained, it can be assumed that there is not a magmatic chamber of considerable magnitude placed close to the surface underneath the Chalupas Caldera, since it does not present seismic and tomographic evidence to be able to assume a possible volcanic eruption before long. Furthermore, the images allow identifying that the seismic and thermal activity is located beneath the Cotopaxi Volcano as a vertical anomaly beneath the Northeast of Cotopaxi Volcano that corresponds to the phreatomagmatic activity observed in 2015.

Towada volcano is an active volcano in northeast Japan, that caused two large caldera‐forming eruptions at 36 ka (episode N) and 15.5 ka (episode L). Petrological analyses and phase equilibrium experiments were performed on silicic endmember rhyolitic pumices from these two eruptions to constrain the pre‐eruptive magma storage conditions. A common mineral assemblage of plagioclase + orthopyroxene + clinopyroxene + magnetite + ilmenite was observed in both eruptions, whereas amphibole (hornblende) was observed only in the episode L pumice. Mineral thermometers presented temperatures of 832–883°C and 802–870°C for the episode N and L pumices, respectively, with an oxygen fugacity of ∼nickel–nickel oxide (NNO) + 1 in log units. The water‐saturation pressures evaluated using the plagioclase‐melt hygrometer were in the range of ∼100–200 MPa. Experiments at 100–350 MPa and 825–900°C under water‐saturated and NNO‐buffered conditions successfully reproduced the mineral assemblages in both pumices, except for magnetite. Further constraints by phase compositions and phase proportions resulted in the preferred storage conditions of 840–850°C and 150–170 MPa for both eruptions. The emergence of hornblende in the episode L magma was likely caused by the higher CaO content compared to the episode N magma and not by the difference in the storage conditions. The storage depths at ∼5–7 km coincide with the depth of the low seismic velocity beneath the present Towada volcano, suggesting possible magma accumulation at the same depths as in the past caldera‐forming eruptions. Plain Language Summary: Experimental constraints on the pre‐eruptive storage conditions of voluminous SiO2‐rich magma are fundamentally important to mitigate the risks of serious future volcanic hazards. Towada volcano is an active volcano located in northeast Japan, that caused two large caldera‐forming eruptions 36 and 15.5 kyr ago. Hornblende is present only in the later eruption, potentially reflecting differences in magma storage conditions and/or bulk compositions. We conducted water‐saturated phase equilibrium experiments on the most SiO2‐rich pumices derived from two caldera‐forming eruptions at Towada volcano to find the pressure and temperature conditions that best explain the mineral assemblage, phase compositions, and phase proportions recorded in the natural pumice. Our preferred pre‐eruptive conditions were 840–850°C and 150–170 MPa for both eruptions under water‐saturated conditions at oxygen fugacity buffered by nickel–nickel oxide. We emphasize the importance of subtle differences in the whole rock compositions to crystallize hornblende in the later eruption. The pre‐eruptive storage depths of 5–7 km coincide with the depth of the low seismic velocity signal beneath the present Towada volcano. This suggests that magma, if present, is stored at the same depth as in the caldera‐forming stage. Key Points: Water‐saturated phase equilibrium experiments successfully reproduced the mineral assemblages in the two magmas, except for magnetitePre‐eruptive depths at 5–7 km for the two magmas coincide with the depth of the low seismic velocity signal beneath the volcanoHornblende crystallization in the later eruption was likely due to the difference in bulk compositions, but not in storage conditions [ABSTRACT FROM AUTHOR]

Continental flood basalts intruded and erupted millions of km3 of magma over ∼1–5 Ma. Previous work proposed the presence of large (>105 $ > {\mathrm{10}}^{5}$–106 km3) crustal magma reservoirs to feed these eruptions. However, in Paper I, we illustrated that this model is inconsistent with observations, by combining eruptive rate constraints with geochemical and geophysical observations from the Deccan Traps and other Continental flood basalt provinces (CFBs). Here, we use a new mechanical magma reservoir model to calculate the variation of eruptive fluxes (km3/year) and volumes for different magmatic architectures. We find that a single magma reservoir cannot explain the eruptive rate and duration constraints for CFBs. Using a 1D thermal model and characteristic timescales for magma reservoirs, we conclude that CFB eruptions were likely fed by a number of interconnected small‐medium (∼102–103 km3) magma reservoirs. It is unlikely that each individual magma reservoir participated in every eruption, thus permitting the occasional formation of large xenocrysts (e.g., megacrystic plagioclase). This magmatic architecture permits (a) large volume eruptive episodes with 10–100s of years duration, and (b) relatively short time‐periods separating eruptive episodes (1000s of years) since multiple mechanisms can trigger eruptions (via magma recharge or volatile exsolution, as opposed to long term (105–106 year) accumulation of buoyancy overpressure), and (c) lack of large upper‐crustal intrusive bodies in various geophysical datasets. Our new proposed magmatic architecture has significant implications for the tempo of CFB volatile release (CO2 and SO2), potentially helping explain the pre‐K‐Pg warming associated with Deccan Traps. Plain Language Summary: Continental flood basalts represent some of the largest volcanic events in Earth's history with a significant impact on the terrestrial environment. However, the nature of the magmatic system associated with the eruption of millions of cubic km of basaltic lavas remains an open question. In this study, we developed a set of new mechanical and thermal models to analyze what sized magma chambers can feed the CFB lavas and what is the dominant physical process leading to eruptions. We find that flood basalt lavas were most likely erupted from a set of interconnected medium (∼102–103 km3) sized magma chambers. In addition, eruptions were most likely initiated by magma recharge instead of magma buoyancy associated overpressure. Using these results, we develop a new conceptual model for continental flood basalt volcanism and show that it can help explain the key observational characteristics. Our results also have implications for the CO2 flux from flood basalts and the consequent environmental impact. Key Points: Mechanical magma reservoir model demonstrates that individual continental flood basalt province (CFB) eruptive episodes cannot be fed by a single large crustal magma bodyCFB eruptions are likely fed from a number of small‐medium sized (∼102–103 km3) interconnected magma reservoirsOur new transcrustal magmatic plumbing model explains the primary geophysical and geochemical characteristics for continental flood basalts [ABSTRACT FROM AUTHOR]

We present a 2D thermo‐elastic model of a magma body formation in a granitic crust by injection of rhyolitic or basaltic dikes and sills. Elastic analytical solutions enable the computation of rock displacement in response to magma intrusion and evacuation during volcanic eruptions. Phase diagrams for magma and rocks govern melting/crystallization behavior and temperature evolution in 16 million computational cells. Calculated temperature histories are used to predict zircon crystallization/dissolution, their ages, and isotopic ratios within individual batches of magma and rocks. Incremental dike injection naturally generates magma batches of melt that form kilometer‐wide clusters appearing in different parts of the domain with diverse shapes, horizontal and vertical interconnectivity. The volume of eruptive melt strongly depends on magma influx rates Q, the width of the injection region W, and eruptions. For example, rhyolitic dike injection with Q = 0.125 m3/s with W = 5 km during 100 ka generates ∼50 km3 of eruptive melt while no significant melt forms if W = 10 km. Injection of basaltic dikes into the granitic crust generates comparable amounts of rhyolitic melt from dike‐residual and country rocks. High injection intensities produce magma reservoirs capable of large eruptions, while repetitive eruptions lead to shrinkage of magma bodies. High heat input causes host rock zircons to lose a significant portion of their old cores. Magmatic zircons in the periphery form quickly due to rapid cooling of intruded dikes while in the central part crystals can grow during several hundreds of ka. The model predicts highly heterogeneous O and Hf isotopic ratios recorded in zircons. Plain Language Summary: The formation of large magmatic eruptible bodies beneath active volcanoes or plutons in the Earth's crust involves complicated thermo‐mechanical processes related to magma injection, host rock melting, solid‐melt separation, etc. Revealing enigmas requires joint efforts of geologists, geophysics, and geomechanics. With the development of modern computer architecture and numerical methods, modern models can capture details of these processes with increasing levels of detail. In this paper, we present a new model of magma chamber formation based on the intrusion of dikes and sills in 2D geometry with an extremely high spatial and temporal resolution that can capture individual batches of injected magma. We use temperature‐time histories recorded in more than 10,000 individual batches of magma with zircon crystallization software previously published by us. We are now able to describe in detail magma chamber growth and formation and link it to the history of zircon dissolution and growth. Key Points: A 2D thermo‐elastic model produces vertically extended interconnected magma system in 104 years after basaltic and rhyolitic dike injectionMagma influx rate, the width of injection zone and repetitive eruptions determine the thermal and petrological evolution of a magma chamberZircons record history of magma accretion and crustal melt/intruded magma proportions in their age and O and Hf isotopes [ABSTRACT FROM AUTHOR]

The Isortoq Giant Dykes in the Proterozoic Gardar Province, South Greenland, include the Isortoq South giant dyke and the Isortoq North giant dyke. The fine-grained Fe-Ti-V deposit hosted by the Isortoq South giant dyke, referred to as the Isortoq Fe-Ti-V deposit, is considered a good test site for the use of magnetic susceptibility for the mapping of ore grades. Here, we test this and show that the Fe, Ti and V distribution is controlled by titanomagnetite disseminated throughout fine-grained troctolite. The deposit displays a clear correlation between magnetic susceptibility and Fe, Ti and V grades in bulk samples of consecutive 2 m sections from 11 drill cores, totalling 2671 m in length. We observe that Fe, Ti and V are almost entirely hosted in titanomagnetite, which controls the magnetic susceptibility. Field measurements of the magnetic susceptibility can thus be considered as a reliable exploration tool for this type of mineralisation. We further consider the origins of the deposit by reconnaissance petrography, mineral and bulk rock chemistry of the large mass of aphanitic Fe-rich troctolite in the Isortoq South giant dyke. We suggest that the deposit may represent the base of a basanitic to trachybasaltic magma chamber, in which Fe-rich immiscible melts accumulated, crystallised and fractionated. The processes suggested here may apply to other giant dykes and intrusions of the Gardar Province.

Research subject. The Koytash ore field is located in the potentially productive Au, Ag, W, Mo, Ti, Fe, Cu, Pb, Zn and REE North Nuratau mineralisation zone of Tien Shan. The authors undertook a study of the composition of dikes breaking through the Paleozoic ore-bearing formations, as well as their petro- and ore-generating role in the formation of the Koytash-Ugat sulphide-rare-metal (W, Mo, Fe) specialised mineralisation. Materials and methods. A study of rock and mineral composition was performed at the Institute of Geology and Geophysics named after Kh.M. Abdullaev. The content of petrogenic and rare elements in rocks and sulphides was determined by ICP-MS using an ICPE-9000 mass-spec trometer in the Central Laboratory of the State Committee for Geology of the Republic of Uzbekistan. The chemical analysis of minerals was performed using a Jeol-8800Rh electronic microanalyser at the Institute of Geology and Geophysics named after Kh.M. Abdullaev. The micrographs of transparent sections were obtained using Nikon Optiphot 2 Pol and Polam R-311 microscopes. Results and conclusions. The conducted study showed that, in terms of their structure, the Koytash ore field dike formations can be regarded as lamprophyres. In terms of their chemical composition, these formations are mafic and intermediate rocks of the subalkaline series. It was found that the composition of lamprophyre dikes correlates with the size of the erosion section. Their melanocratic varieties are confined to the southern part of the intrusion (absolute elevations are 1000–1200 m), and leucocratic – to the northern (about 1900 m). This is assumed to be the result of crystallization differentiation of a single initial melt. The dikes of the Koytash ore field lamprophyres break through not only sulphide-rare-metal bodies of the Koytash-Ugat strip, but also skarn and carbonate rocks and, in turn, are broken through by quartz-polymetallic ore-bearing veins, which testifies to their inter-ore character.

Research subject. In this research, volcanoplutonic formations (VPF) in the Baleisky ore node (BON) consisting of intrusions of the Amudzhikan-Shakhtama complex (J2-3) and comagmatic effusions of the Shadaron series (J2-3) were investigated.Methods. Investigations were carried out in the analytical center of the SB RAS Geological (Ulan-Ude). Silicate analysis was performed by the conventional method. Ore and rare elements were determined by the RFA method. Rare earth elements were detected using the ASP-AES method.Results. It was determined that VPF in the BON has a zonal structure. In the central parts of the BON, granite rods of the Amudzhikan-Shakhtama complex (J2-3) are located. Further, moving from the central BON parts towards its periphery, a belt of small intrusions of the Amudzhikan-Shakhtama complex (stocks of monzonite diorites, granodiorites, dikes of diorite porphyrites, lamprophyres) is located. The majority of gold deposits and ore occurrences are confined to this zone. The peripheral parts of the BON feature volcanogenic sedimentary deposits of the Shadaron series (J2-3). In composition, these deposits correspond to island-arc and post-col-lisional formations. It is shown that the intrusions of the Amudzhikan-Shakhtama complex correspond to high-potassium calc-alkaline series.Conclusions. It was found that the magmatic melts of the Mesozoic ore-bearing intrusions located in the Baleisky deposit area are more differentiated and located at lower depths compared to the rocks of similar composition in other BON parts.

Under surface structure, 3d modelling of Agung volcano in Bali had been conducted by using gravity methods. This research aims to identify the magma chamber and make a model below the surface of the Great Volcano of Bali Province by using gravity anomaly data. Data processing methods performed in this research were consists of six steps: (i) arrangement the contour map of Bouguer anomaly, (ii) spectrum analysis, (iii) anomaly regional and residual separation, (iv) Second Vertical Derivative analysis, (v) cross-section of subsurface geology construction by using 3D (inverse modelling), (vi) qualitative and quantitative interpretation. Anomaly Bougeur contour map result shows the value of Bouguer anomaly in research area around 84 mGal spreading around west-south part of research point until 279 mGal on Agung volcano body. Anomaly regional value is around 97 mGal to 253 mGal. The boundary between basement a sedimentary rock of the research area are at the depth of 0,89 km. The magma chamber of Agung volcano is in the depth of 500 to 8000 metres to a form of towing up and polluted in the middle. The density of the magma chamber is around 2,73 until 2,86 gr/cc. The magma flow in the Agung volcano of visible at the depth of 0 metres.

Abstract The Ning'er Mw 6.1 earthquake on 3 June 2007 occurred in the southwest to the Sichuan‐Yunnan rhombic block with complicated seismic structures. The focal depth determined by the U.S. Geological Survey is only 5 km, but the field investigation did not find obvious surface ruptures in the epicenter area. The magnitude obtained by inverting the broadband waveforms is Mw 6.4 that is much larger than the Mw 6.1 calculated by U.S. Geological Survey, indicating this event is complicated. The Interferometric Synthetic Aperture Radar is used to study the fault geometry, coseismic slip model, and Coulomb stress changes around the seismic region. It shows that this event is mainly dominated by a right‐lateral strike‐slip fault with a slight thrust component. The fault plane is 28‐km long along the strike and 14‐km wide along the dip. The maximum slip is up to 1.02 m at a depth of 3.6 km and the released moment is 2.57 × 1018 Nm, corresponding to a magnitude of Mw 6.25. The shallow source of this event is related to inelastic off‐fault deformations along the fault or magma chamber. The lack of obvious surface ruptures indicates the strain is not completely released. The coseismic Coulomb stress changes suggest this earthquake has enhanced the stress on the Puwen fault and Mohei fault. The future seismic risks of these two faults and its adjacent regions cannot be ignored since aftershocks are fewer and the residual strain unreleased by the Ning'er event.

Abstract Although it is widely accepted that shallow silicic magma reservoirs exist, and can feed eruptions, their dynamics and longevity are a topic of debate. Here, we use field mapping, geochemistry, 3D pluton reconstruction and a thermal model to investigate the assembly and eruptive history of the shallow Reyðarártindur Pluton, southeast Iceland. Primarily, the exposed pluton is constructed of a single rock unit, the Main Granite (69.9–77.7 wt.% SiO2). Two further units are locally exposed as enclaves at the base of the exposure, the Granite Enclaves (67.4–70.2 wt.% SiO2), and the Quartz Monzonite Enclaves (61.8–67.3 wt.% SiO2). Geochemically, the units are related and were likely derived from the same source reservoir. In 3D, the pluton has a shape characterized by flat roof segments that are vertically offset and a volume of >2.5 km3. The pluton roof is intruded by dikes from the pluton, and in two locations displays depressions associated with large dikes. Within these particular dikes the rock is partially to wholly tuffisitic, and rock compositions range from quartz monzonite to granite. We interpret these zones as eruption‐feeding conduits from the pluton. A lack of cooling contacts throughout the pluton indicates rapid magma emplacement and a thermal model calculates the top 75 m would have rheologically locked up within 1,000 years. Hence, we argue that the Reyðarártindur Pluton was an ephemeral part of the wider plumbing system that feeds a volcano, and that timeframes from emplacement to eruption were rapid.

The numerical simulation framework for modeling porphyry magma cooling and crystallization. [Display omitted] • A hybrid numerical approach has been proposed for modeling magma dynamics. • This hybrid method combines numerical modeling and thermodynamics calculation. • Moderate initial magma temperature is favorable for porphyry mineralization. • Slow boundary heat transfer is beneficial for metal enrichment in porphyry magma. The ore-forming metals (such as Cu, Mo, and Au) and hydrothermal fluids necessary for the formation of porphyry copper deposits (PCDs) are separated and precipitated from the felsic magma during its cooling and crystallization process, due to changes in physical and chemical conditions triggered by magma ascending and emplacement. Magma cooling and crystallization process is influenced by various factors, mainly including the initial cooling temperature of magma, the startup speed of magma chamber circulation inherited from the pulsations of deep-seated magma, and the cooling rate caused by the contact between magma chamber and surrounding rocks. However, the precise mechanisms of these factors triggering the evolution of porphyry magma in the shallow crust and their role in controlling ore-forming during this process are still not clearly understood. Therefore, this study proposes to use multiphysics numerical modeling in conjunction with thermodynamic calculations to investigate porphyry magma cooling and crystallization control of mineralization. Firstly, based on the whole-rock geochemical data of porphyry intrusions in the world's famous Bingham Canyon cooper deposit, we utilized MELTS to calculate the thermodynamic properties including density, melt fraction, thermal conductivity and heat capacity of porphyry magma. Then, we established the finite element numerical model coupled heat transfer and fluid flow that employed these four thermodynamic properties to simulate the dynamic processes of porphyry magma cooling and crystallization. Finally, we conducted numerical modeling experiments by varying the three parameters, including the initial temperature and startup cycling speed of magma, as well as heat transfer coefficient at the up boundary of magma chamber, to investigate their controls on magma evolution and mineralization of PCDs via calculating and analyzing temporal and spatial variations of the magma temperature, crystallinity, velocity, and metal (i.e. copper) concentration. The results show that the evolution of a porphyry magma chamber is primarily controlled by its initial temperature and the heat transfer coefficient of its upper boundary. 900 °C is the most favorable initial cooling temperature for forming both porphyry magma plumes with high metal endowment, and connected tunnels for volatile to rapidly migrate upward and concentrate to apical parts of the magma chamber. A lower heat transfer coefficient, indicating a magma chamber in a relatively closed tectonic environment, is more beneficial for forming metal migration tunnels within the magma chamber. The startup cycling speed significantly influences the early circulation and convective patterns within the magma chamber, may leading to heterogeneous mixing of magmas with different properties inside the chamber. [ABSTRACT FROM AUTHOR]

Explosive eruptions are the surface manifestation of dynamics that involve transfer of magma from the underground regions of magma accumulation. Evidence of the involvement of compositionally different magmas from different reservoirs is continuously increasing to countless cases. Yet, models of eruption dynamics consider only the uppermost portion of the plumbing system, neglecting connections to deeper regions of magma storage. Here we show that the extent and efficiency of the interconnections between different magma storage regions largely control the size of the eruptions, their evolution, the causes of their termination, and ultimately their impact on the surrounding environment. Our numerical simulations first reproduce the magnitude-intensity relationship observed for explosive eruptions on Earth and explain the observed variable evolutions of eruption mass flow rates. Because deep magmatic interconnections are largely inaccessible to present-day imaging capabilities, our results motivate the need to better image and characterize extant magma bodies.