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The Vulcano-Lipari System is a volcanic complex located in the central sector of the Aeolian Archipelago in southern Italy. The edifice is affected by complex tectonics and develops upon the trans-extension of the Aeolian-Tindari-Letojanni Fault System. This fault is proposed to control magmatism and acts as a preferential pathway for upwelling of magmatic and supercritical fluids. Over the last three decades, Vulcano Island underwent several volcanic crises and since September 2021 it has been showing signs of increasing activity and volcanic unrest. Temperature, degassing, seismic activity, and deformation rapidly increased causing temporal evacuation of the inhabitants of the most affected regions. During the unrest in October 2021, we deployed 196 3C geophones all around Vulcano and south of Lipari to record the seismic signals for a full month, as part of the VulcaNODES project. The resulting seismic catalog confidently contains more than 7000 volcano-seismic and volcano-tectonic events with an average local magnitude of -0.32. This catalog is used to produce an unprecedented travel-time time-lapse tomography of the unrest. Seismic tomography is a powerful tool for observing structures at depth beneath volcanic systems, using seismic waves generated by earthquakes. Such a dense network combined with the exceptional seismic signal recorded will provide tomographic time series of the plumbing system every 1-3 days for a month. The still ongoing VulcaNODES project aims at observing fluids evolution along the volcano’s tectonic structures on a daily basis, providing new insights on processes usually difficult to record on short timeframes, and shedding light on the plumbing system on a high resolution.

The South-East Crater (SEC) at Mt. Etna started a period of lava fountaining in December 2020, producing over 60 paroxysms until February 2022. The activity had an intense sequence from February 16 to April 1, 2021, totaling 17 paroxysmal events separated by repose times varying from 1 to 7 days. The eruptive sequence was extensively monitored, providing a unique opportunity to relate the chemistry and texture of the erupted products to eruption dynamics. We investigate the temporal evolution of the magmatic system through this eruptive sequence by quantifying variations in the composition and texture of clinopyroxene. Clinopyroxene major element transects across crystals from five representative lava fountains allow us to determine the relative proportions of deep versus shallow-stored magmas that fed these events. We use hierarchical clustering (HC), an unsupervised machine learning technique, to objectively identify clinopyroxene compositional clusters and their variations during this intense eruptive phase. Our results show that variations of monitoring parameters and eruption intensity are expressed in the mineral record both as changes in cluster proportions and the chemical complexity of single crystals. We also apply random forest thermobarometry to relate each cluster to P-T conditions of formation. We suggest that the February–April 2021 eruptive sequence was sustained by the injection of a hotter and deeper magma into a storage area at 1–3 kbar, where it mixed with a slightly more evolved magma. The February 28 episode emitted the most mafic magma, in association with the highest mean lava fountain height and highest time–averaged discharge rate, which make it the peak of the analyzed eruptive interval. Our results show that after this episode, the deep magma supply decreased and the erupted magma become gradually more chemically evolved, with a lower time–average discharge rate and fountain height. We propose this approach as a means to rapidly, objectively, and effectively link petrological and geophysical/geochemical monitoring during ongoing eruptions. We anticipate that the systematic application of this approach will serve to shed light on the magmatic processes controlling the evolution of ongoing eruptions.

Open conduit volcanoes, of which Stromboli is an emblematic example, erupt with the highest frequency on Earth1. The activity at Stromboli is characterised by frequent small explosions intercalated by larger events that pose a significant risk to locals, tourists, and scientists2,3. Thus, identifying the signs of an impending larger explosion is of outmost importance for the mitigation of volcanic hazard. Here we show that the interaction between CO2-rich fluids and magma spontaneously leads to the accumulation of volatile-rich, low density and gravitationally unstable magma at depth, without the requirement of a permeability barrier4. CO2-flushing forces the exsolution of water and the increase of magma viscosity5, which proceeds from the bottom of the magma column upward. This rheological configuration unavoidably leads to the progressive thickening of a gas-rich and low density (i.e. gravitationally unstable) layer at the bottom of feeding system. Our calculations account for gas monitoring data and provide a base to trace the approach to deeply triggered large or paroxysmal eruptions and estimate their size from continuous gas monitoring data. The model we propose for Stromboli can be applied to any other open conduit volcano globally and offers a framework to anticipate the occurrence of unexpectedly large eruptions.

Evolution of volcanic plumbing systems towards eruptions of different styles and sizes largely depends on processes at crustal depths that are outside our observational capabilities. Theseprocesses can be modeled and the outputs of the simulations can be compared with the chemistry of the erupted products, geophysical and geodetic data to retrieve information on the architecture of the plumbing system and the processes leading to eruption. The interaction between magmas with different physical and chemical properties often precedes volcanic eruptions. Thus, sophisticated numerical models havebeen developed that describe in detail the dynamics of interacting magmas, specifically aimed at evaluating pre-eruptive magma mingling and mixing timescales. However, our ability to explore the parameters space in order to match petrological and geophysical observations is limited by the extremely high computational costs of these multiphase, multicomponent computational fluid dynamics simulations. To overcome these limitations, we present a statistical emulator that is able to reproduce the numerical simulations results providing the temporal evolution of the distribution of magma chemistry as a function of a set of input parameters such as magmadensities and reservoir shapes. The whole rock composition of volcanic rocks is one of the mostcommon measurable parameter collected for eruptions. The statistical emulator can be usedto invert the observed distribution of whole rock chemistry to determine the duration of interaction between magmas preceding an eruption and identify the best matching input paramaters of the numerical model. Importantly, the statistical emulator intrinsically includes error propagation, thus providing confidence intervals on predicted interaction timescales on the base of the intrinsic uncertainty of the input parameters of the numerical simulations.

Since the detection of the first exoplanet orbiting a star like the Sun, the University of Geneva has been at the forefront of exoplanet research. Starting from an extensive expertise in planet detection (with radial velocity), the observatory is also now an important actor in the atmosphere characterization of exoplanets (e.g. Ehrenreich et al. 2020). Today the focus is shifting towards the atmospheric characterization of small temperate planets, such as Proxima-b and the TRAPPIST-1 planets. The university is therefore actively participating to the instruments RISTRETTO@VLT and ANDES@E-ELT which aim at characterizing the atmosphere of Proxima-b (among other goals) using a technique based on high-contrast imaging and high-resolution spectroscopy. One of the objectives of these instruments is to detect biosignatures in the atmosphere of rocky temperate planets. However, to be able to correctly identify a biosignature, one needs to be able to identify false positives. So, one needs to know how the atmosphere interacts with planetary interior, with incoming stellar radiation, and with many different other processes. A multi-disciplinary approach is therefore necessary. Recently, and following the 2019 Nobel prize in physics attributed to Michel Mayor and Didier Queloz for the discovery of 51 Peg b, the University of Geneva decided to create a faculty center: “Centre pour la Vie dans l’Univers” in French or “Center for Life in the Universe” (https://www.unige.ch/sciences/cvu/). The members of the center include experts in astrophysics, geophysics, environmental physics, chemistry, climatology and biology. The center aims at leading interdisciplinary projects on the origin of life on Earth and the search for life in our solar system and in exoplanetary systems to contribute to the world research on fundamental questions: How did life emerge and how did it diversify on Earth? Is the Universe full of life? What is the nature of life? How can we detect life elsewhere than on Earth? Several projects are starting and will start in the near future in the center on the following topics: The rise of molecular complexity on primitive Earth Multi-stability of climates and habitability Evolution under extraterrestrial conditions The atmosphere as a mirror for geological processes I will present these new interdisciplinary scientific projects, with an increased focus on the second and third ones which are already underway.

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After half a century of quiescence, activity at Cumbre Vieja volcano (La Palma, Canary Islands, Spain) restarted with a spectacular flank eruption characterized by both high fire fountaining and effusive activity. The products emitted comprise tephra fall and lava flows, ranging from tephrite to basanite. Between September 19th and December 13th 2021 the lava flows covered ~ 12,5 km2, affecting more than 3000 buildings and paralyzing the viability and the essential activity on the SW sector of the island. This scenario highlights the importance of rheological data deriving from experimental studies of such low viscosity magma to better understand lava flow emplacement dynamics, hazard and mitigate risk.We performed a detailed experimental study to characterize the rheology of the basanitic lava sampled between October 3rd and 7th in a Concentric Cylinder set-up. Starting from a superliquidus state of 1400 °C, a set of isothermal deformation experiments was carried out at different target subliquidus temperatures (from 1225 to 1175 °C) and fixed shear-rate of 10 s-1 to investigate the near equilibrium viscosity. Moreover, a series of cooling deformation experiments were performed at different cooling-rates (ranging from 0.1 to 10 °C/min) and at constant shear-rate of 10 s-1 with the aim to mimic the dynamic evolution of natural flowing lava through controlled cooling-rate conditions. In isothermal deformation experiments, the steady state conditions (i.e., stable crystal contents) were achieved faster at increasing degree of undercooling, showing a progressive increase in the final viscosity values. In cooling deformation experiments, with increasing cooling-rate applied, the onset of crystallization took place at progressively lower temperature over shorter timescales. The experiments performed at cooling-rates from 0.1 to 1 °C/min were interrupted when viscous rupture (i.e., the transition from coherent flow to shear localization and physical separation) was observed. For the experiments conducted at higher cooling-rates (i.e., from 3 to 10 °C/min), the experimental runs were stopped at viscosity values of ~104 (Pa s), when the stress limit of the device was achieved.Preliminary results show that the thermal history plays a fundamental role on the kinetics of the crystallization hence modulating the capacity of lava to flow. The different viscosity paths observed at low and high cooling-rates lead to a rheological decoupling between the slow-cooling core and the fast-cooling external part of the lava flows. This process would be key in promoting the transition from pahoehoe to ‘a‘ā emplacement regimes, ultimately controlling the runout distance of lava flows.

The crustal structure is one of the fundamental factors that affects the type, composition, and spatial distribution of monogenetic volcanoes. The formation of maars, the second-most common type of monogenetic volcanoes, is mainly influenced by crustal lithologies, depth of explosions, and water-magma interactions together with magma rheology and tectonic structures. The Acıgöl caldera, located in the extensional setting of the central Anatolian plateau, contains both felsic and mafic maars. This rare compositional juxtaposition makes it a suitable location to better understand the relationship between magma chemistry and maar architecture. It includes closely spaced yet compositionally different monogenetic complexes (i.e., maars with either lava dome or scoria cone) and provides a fabulous opportunity to elucidate the role of crustal processes in the eruptional dynamics of maars.Here we present an integrative study with detailed morphological (drone mapping), depositional (componentry, ash morphology), and petrological (whole-rock, glass, and mineral geochemistry) characteristics of rhyolitic (whole-rock; ~76.7 wt.% SiO2, glass; ~77.2 wt.% SiO2) İnallı, Kalecitepe, Acıgöl, and Korudağ maars, and mugearitic (~52.7 wt.% SiO2) İcik maar. Our observations show a wide range of morphological features with spectacular examples of nested and compound craters. Field observations, together with the detailed stratigraphical analysis and literature-based geochronological data, reveal that the formations of maars and the subsequent lava domes or scoria cones are spatially migrating events within the same magmatic episode. We hence relate this to the rejuvenation of conduits, along with the pre-existing structures of the Acıgöl caldera that are almost perpendicular to the local extensional direction (NE-SW).Non-modal batch melting models reveal that all investigated maars have a similar parental magma source (i.e., the most primitive basalt in central Anatolia with the Mg# of 72.4). This is formed by partial melting of a metasomatized lithospheric mantle with contribution from an OIB-like asthenospheric melt. The uprising magma that also produced the entire Quaternary volcanics in central Anatolia was possibly trapped at different crustal depths beneath the Acıgöl caldera and formed the maars with various degrees of magmatic differentiation processes. We conclude that İcik maar emanated from a relatively deep (lower crustal?) mantle-derived magma source evolved by assimilation and fractional crystallization processes. In contrast, the felsic maars were presumably formed by the short-lived ponding of the same magma source at shallower depths, which was partially assimilated by the basement intrusive rocks and dominantly shaped by the feldspar-driven fractional crystallization. Finally, the well-exposed examples of felsic maars in the study area and their comparison with the mafic counterparts could be a good contribution to the ever-growing literature on maar volcanism.

Magma has a dynamic and often-complex journey from source to surface, the record of which is largely encoded in the chemistry of minerals. Its storage conditions prior to eruption and modifications during ascent can influence eruptive dynamics and eruption duration. We present quantitative 2D chemical maps of clinopyroxene crystals from the Cumbre Vieja eruption (La Palma, Canary Islands; 19th September 2021 – 13th December 2021). The histories of individual crystals are constrained using novel thermobarometric (pressure, temperature) and chemometric (equilibrium melt composition) machine learning algorithms. We identify the remobilisation of colder (~950 ˚C), deeper (2 – 3.5 kbar), and more evolved (1 – 2 wt% MgO) cores by a hotter (1050 – 1100 ˚C) and less-evolved (3.5 – 4.5 wt% MgO) carrier melt. Textural evidence shows resorption of these antecrystic cores suggesting an uninterrupted ascent through the crustal column followed by upper-crustal (~ 1kbar) crystallisation and eruption. By using both quantitative maps and reliable single-phase thermobarometric and chemometric calibrations, we overcome several issues associated with acquiring statistically representative mineral chemistry via single spot analyses. In doing so we precisely track the syn-eruptive evolution of storage pressure-temperature and magma composition. These parameters are then related to the variation of geophysical signals (seismicity, gas monitoring) recorded during the La Palma eruption.

The physical and chemical properties of magma govern the eruptive style and behaviour of volcanoes. Many of these parameters are linked to the storage pressure and temperature of the erupted magma, and melt chemistry. However, reliable single-phase thermobarometers and chemometers which can recover this information, particularly using amphibole chemistry, remain elusive. We present a suite of single-phase amphibole and clinopyroxene thermobarometers and chemometers, calibrated using machine learning. This approach allows us to intimately track the range of pre-eruptive conditions over the course of a millennial eruptive cycle on an island arc volcano (Saint Kitts, Eastern Caribbean). We unpick the story of Mount Liamuiga, a stratovolcano that pops its upper-crustal (2 kbar), dacitic cork at the beginning of the Lower Mansion Series eruptive sequence. This permits a progressive increase in the thermal maturity of the magma arriving at the surface from the middle to upper crust (2 – 5.5 kbar) through time. The temperature increase correlates well with matrix plagioclase chemistry, which itself displays a remarkable progression to less evolved (more anorthitic) composition in time. We find that amphibole is a reliable themobarometer (SEE = 1.4 kbar; 40 ˚C), at odds with previous studies. We suggest it is the regression strategy, as opposed to the abject insensitivity to pressure, that has hindered previous calibrations of amphibole only thermobarometers. By recognising this, we have constructed a high-resolution, quantitative picture of the magma plumbing system beneath an arc volcano.

Four voluminous ignimbrites (150–500 km3) erupted in rapid succession at 27 Ma in the central San Juan caldera cluster, Colorado. To reconstruct the timescales and thermal evolution of these magma reservoirs, we used zircon ID-TIMS U–Pb geochronology, zircon LA-ICP-MS geochemistry, thermal modeling, and zircon age and crystallization modeling. Zircon geochronology reveals dispersed zircon age spectra in all ignimbrites, with decreasing age dispersion through time that we term a ‘chimney sweeping’ event. Zircon whole-grain age modeling suggests that 2σ zircon age spans represent approximately one-quarter of total zircon crystallization timescales due to the averaging effect of whole-grain, individual zircon ages, resulting in zircon crystallization timescales of 0.8–2.7 m.y. Thermal and zircon crystallization modeling combined with Ti-in-zircon temperatures indicates that magma reservoirs were built over millions of years at relatively low magmatic vertical accretion rates (VARs) of 2–5 × 10–3 m y−1 (2–5 × 10–6 km3 y−1 km−2), and we suggest that such low VARs were characteristic of the assembly of the greater San Juan magmatic body. Though we cannot unequivocally discern between dispersed zircon age spectra caused by inheritance (xenocrystic or antecrystic) versus prolonged crystallization from the same magma reservoir (autocrystic), our findings suggest that long-term magma input at relatively low VARs produced thermally mature upper crustal magma reservoirs resulting in protracted zircon crystallization timescales. Compiling all U–Pb ID-TIMS zircon ages of large ignimbrites, we interpret the longer timescales of subduction-related ignimbrites as a result of longer term, lower flux magmatism, and the shorter timescales of Snake River Plain ignimbrites as a result of shorter term, higher flux magmatism.

The Toba volcanic system in Indonesia has produced two of the largest eruptions (>2,000 km(3) dense-rock equivalent [DRE] each) on Earth since the Quaternary. U–Pb crystallization ages of zircon span a period of ∼600 ky before each eruptive event, and in the run-up to each eruption, the mean and variance of the zircons’ U content decrease. To quantify the process of accumulation of eruptible magma underneath the Toba caldera, we integrated these observations with thermal and geochemical modeling. We show that caldera-forming eruptions at Toba are the result of progressive thermal maturation of the upper crustal magma reservoir, which grows and chemically homogenizes, by sustained magma influx at average volumetric rates between 0.008 and 0.01 km(3)/y over the past 2.2 My. Protracted thermal pulses related to magma-recharge events prime the system for eruption without necessarily requiring an increased magma-recharge rate before the two supereruptions. If the rate of magma input was maintained since the last supereruption of Toba at 75 ka, eruptible magma is currently accumulating at a minimum rate of ∼4.2 km(3) per millennium, and the current estimate of the total volume of potentially eruptible magma available today is a minimum of ∼315 km(3). Our approach to evaluate magma flux and the rate of eruptible magma accumulation is applicable to other volcanic systems capable of producing supereruptions and thereby could help in assessing the potential of active volcanic systems to feed supereruptions.

Magma degassing is thought to play a major role in magma fractionation, transport, storage, and volcanic eruption dynamics. However, the conditions that determine when and how magma degassing operates prior to and during an eruption remain poorly constrained. We performed experiments to explore if the initial presence of gas bubbles in magma influences the capability of gas to escape from the magma. Vesiculation of natural H2O-poor (<, Bulletin of Volcanology, 77, ISSN:0258-8900, ISSN:1432-0819

Porphyry copper deposits, the principal natural source of Cu and Mo, form at convergent margins. Copper is precipitated from fluids associated with cooling magmas that have formed in the mantle and evolved at variably deep crustal levels, before raising close to the surface where they exsolve fluids and copper. Despite significant advances in the understanding of their formation, there are still underexplored aspects of the genesis of porphyry copper deposits. Here, we address the role played by magma injection rates into the shallow crust on the formation of porphyry copper deposits with different copper endowments. Using a mass balance approach, we show that supergiant porphyry Cu deposits (>10 Mt Cu) require magma volumes and magma injection rates typical of large volcanic eruptions. Because such volcanic events would destroy magmatic-hydrothermal systems or prevent their formation, the largest porphyry Cu deposits can be considered as failed large eruptions and this may be one of the causes of their rarity.

Thermobarometry is a fundamental tool to quantitatively interrogate magma plumbing systems and broaden our appreciation of volcanic processes. Developments in random forest-based machine learning lend themselves to a more data-driven approach to clinopyroxene thermobarometry. This can include allowing users to access and filter large experimental datasets that can be tailored to individual applications in Earth Sciences. Here we present a methodological assessment of random forest thermobarometry, using the R freeware package “extraTrees”, by investigating the model performance, tuning hyperparameters, and evaluating different methods for calculating uncertainties. We determine that deviating from the default hyperparameters used in the “extraTrees” package results in little difference in overall model performance (

The Adamello intrusive suite is a composite batholith in Northern Italy, with an estimated 2000 km3 volume, assembled incrementally over a time span of 10 to 12 million years. The history of crystallization has been studied in detail through laser ablation ICP-MS and SIMS U–Pb geochronology of zircon, which records prolonged crystallization of each of the different intrusive units at mid-crustal levels between 43·47 and 33·16 Ma. The magmas were episodically extracted from this storage area and ascended to the final intrusion level at ∼6 km paleo-depth. Each batch of melt cooled very rapidly down to the ambient temperature of 250°C, evidenced by distinct cooling paths recorded by amphibole, biotite and K-feldspar 40Ar/39Ar dates. The magma source area was moving from SW to NE with time, causing increasing thermal maturity in the mid-crustal reservoir. The resulting temporal trend of higher degrees of crustal assimiliation in the course of the evolution of the magmatic system can be traced through Hf and O isotopes in zircon. Rough estimates of magma emplacement rates (‘magma flux’) yield very low values in the range of 10-4 km3/yr, typical of mid-to-upper crustal plutons and increase with time. Although we cannot discern a decrease of magma flux from our own data, we anticipate that a dramatic decrease of magma flux between 33 and 31 Ma along the northern contact lead to cessation of magma emplacement. ISSN:0022-3530 ISSN:1460-2415

The segregation and accumulation of felsic melts, from crystallising crustal magma reservoirs, is essential for the chemical evolution of the crust and is a phenomenon preceding some of the largest eruptions on Earth. The physical properties of residual melt and magma and the time over which the conditions remain appropriate for melt extraction are important factors controlling the efficiency of melt extraction and the distribution of melt in magma reservoirs. Here we focus on the initial water content (H2Oi) of magma as it affects both the physical properties of the residual melt and the timescales at which conditions remain appropriate for melt extraction during progressive magma crystallisation. We use rhyolite-MELTS simulations to evaluate the physical evolution of crystallising granodioritic (or dacitic) hydrous magma (i.e. ≥1 wt.% H 2 O i ) at shallow depth at 200 MPa. To constrain the solidification timescales of reservoirs containing magmas with initially different water content, we perform 2.5D thermal modelling. We combine these results with calculations of melt extraction velocity by compaction and hindered settling to identify the optimal conditions at which melt segregation occurs. These calculations suggest that hydrous felsic magmas that attain water saturation after 40 wt.% crystallisation (rheological locking point) are best suited for melt extraction. Once water-saturation is achieved, the rate of release of latent heat of crystallisation and with it the time magma spends within a given temperature interval increases while the viscosity of the residual liquid and crystal–liquid density contrast remain favourable for melt segregation. We first test our findings on the Takidani pluton (Japan) because it shows evidence of residual melt segregation from crystallising magma, and is associated with caldera-forming eruptions. We finally generalise our results to crustal magma reservoirs containing hydrous felsic magmas. Our results suggest that if segregation starts at rheological locking (i.e. crystallinity of 40–50 wt.%) upper crustal reservoirs of ≥100 km3 granodioritic (i.e. dacitic) magma with >2 wt.% H 2 O i can produce large melt-rich caps at the top of partially crystallised magma reservoirs in few hundreds to few thousands of years. The formation of separate melt lenses becomes more likely when segregation of melt starts at crystallinities >0.6. Our results suggest that H 2 O i plays an important role in modulating the distribution of eruptible melt in upper crustal reservoirs. Reservoirs of felsic and water-poor magma ( H 2 O i ) tend to be associated with the formation of isolated pockets of crystal-poor and eruptible magma, which could account for the often-observed geochemical heterogeneity of the products of large caldera-forming eruptions in the Snake River Plane. The limited dimensions of these eruptible magma pockets make their detection by geophysical methods challenging.

Magma reservoirs represent areas of large variation in the physico-chemical properties of magmas and are directly associated with volcanic activity. Understanding the processes acting at inaccessible depths is of crucial importance to interpret monitoring signals and to develop quantitative models to forecast volcanic activity. Minerals are witnesses of the temporal evolution of the physico-chemical conditions within magma reservoirs recording variations of intensive parameters as chemical signals. However, the competition between crystal growth and elements diffusion in the melt phase can also modulate the chemical zoning of minerals, therefore complicating the interpretation of chemical zoning patterns. To disentangle this complexity, chemically zoned minerals are synthetically grown at the Petro-Volcanology Research Group of the University of Perugia, under controlled conditions. For these experiments tephra from 2002-03 Mt. Etna eruption is used as starting material. The zonation in minerals is been forced inside a high-temperature furnace by oscillating the temperature with three different setups: static conditions, using a controlled deformation gradient (Concentric Cylinder Apparatus) and using a chaotic mixing regime (Chaotic Magma Mixing Device). The zoned crystals are analysed for major and trace elements by Electron Probe Micro Analyzer (EPMA) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS), respectively. High spatial resolution elemental maps (0.5 micrometres) are also collected to characterise the zoning of selected crystals. The data are analysed using a series of custom-built machine learning algorithms to disentangle zoning related to variations of the thermodynamic conditions of crystal growth from the effects of the competition between diffusion and growth. The main target of this project is to provide quantitative tools to distinguish between chemical zoning forced by thermodynamic conditions of growth and chemical zoning produced by competition between crystal growth and element diffusion.

Melt inclusions provide a window into the inner workings of magmatic systems. Both mineral chemistry and volatile distributions within melt inclusions can provide valuable information about the processes modulating magma ascent and preceding volcanic eruptions. Many melt inclusions host vapour bubbles which can be rich in CO2 and H2O and must be taken into consideration when assessing the volatile budget of magmatic reservoirs. These vapour bubbles can be the product of differential volumetric contraction between the melt inclusion and host phase during an eruption or indicate an excess fluid phase in the magma reservoir. Thus, determining the distribution of volatiles between melt and vapour bubbles is integral to our fundamental understanding of melt inclusions, and by extension the evolution of volatiles within magmatic systems.A large dataset of 79 high-resolution tomographic scans of clinopyroxene and leucite phenocrysts from the Colli Albani Caldera Complex (Italy) was recently acquired at the German Electron Synchrotron (DESY). These tomograms allow us to quantify the volume of melt inclusions and associated vapour bubble both glassy and microcrystalline melt inclusions. Notably, in the glassy melt inclusions the vapour bubbles exist either as a single large vapour bubble in the middle of the melt inclusion or as several smaller vapour bubbles distributed around the edge of the melt inclusion. These two types of melt inclusions can coexist within a single crystal. We suggest that the occurrence of these rim- bubbles is caused by one of two exsolution pathways, either pre-entrapment and bubble migration or post entrapment with preferential exsolution at the rims. By combining the analysis of hundreds of melt inclusions with the chemistry of the host phase we aim to unveil magma ascent rates and distribution of excess fluids within the magmatic system of Colli Albani, which produced several mafic-alkaline large volume ignimbrites.

The Colli Albani volcano is an ultrapotassic caldera complex located 30 km to the SE of Rome and has displayed a wide range of eruptive behaviors, ranging from effusive activity to highly explosive and large volume eruptions (up to 63 km3 dense rock equivalent per eruption) despite its mafic nature.We combine physical volcanology, petrology, and geochemistry to focus on the mildly explosive to effusive products of two sections (Tuscolo and Artemisio) which are located on opposite sides of the main caldera and stratigraphically between the last large ignimbrite, Villa Senni. The target of this study is to identify the processes responsible for the transition from the smaller explosions to the larger caldera-forming ignimbrite eruptions, and eventually trace how the magmatic system rebuilds in the interim.Whole rock analyses, mineral chemistry, and petrography of fall deposits from both field localities are compared with an existing dataset for the Villa Senni ignimbrites. We will use unsupervised and supervised machine learning approaches to identify similarities and differences between large caldera-forming eruptions and mild-explosive to effusive activity and identify the processes modulating the transition between these two behaviours.

Zoned minerals preserve information about their growth conditions, by changing their composition as function of temperature, pressure and melt composition. By carefully looking at a zoned minerals we can determine characteristics of the main stages of the evolution of magmatic systems.We study alkali feldspar megacrysts from the Tuolumne Intrusive Complex in California, with the aim of deciphering chemical signatures of rejuvenation events. We characterize the chemical zoning of alkali feldspar using X-ray tomography, BSE imaging, EDS-SEM analysis and LA-ICPMS analysis along profiles. We use hierarchical clustering based on major and trace elements to objectively identify compositional groups for each chemical profile. By reducing the complexity of chemical zoning to one dimension (i.e. cluster number) we can trace the evolution of the conditions of growth and identify rejuvenation events.Alkali feldspar megacrysts (up to 20 cm in size) from the Cathedral Peak unit of the Tuolumne Intrusive Complex occur predominantly disperse and only make between 8 - 12 % of the total crystal population. They are mostly homogeneous in major element, and markedly oscillatory zoned in trace elements such as Ba, Sr, and Rb. Using hierarchical clustering we identify four different chemical groups within the alkali feldspar crystals. Each chemical group is repeated multiple times in a single crystal. Overall the crystals show a decreasing trend of Ba towards the rim. Extended alkali feldspar crystallization would lead to a depletion of Ba in the melt and consequently to the growth of low Ba-zones of alkali feldspar. In some crystals the sequence of decreasing Ba is repeated twice. We propose that this reflects melt recharge in a melt-rich magmatic system.

Establishing a quantitative link between magmatic processes occurring at depth and volcanic eruption dynamics is essential to forecast the future behaviour of volcanoes, and to correctly interpret monitoring signals at active centres. Chemical zoning in minerals, which captures successive events or states within a magmatic system, can be exploited for such a purpose. However, to develop a quantitative understanding of magmatic systems requires an unbiased, reproducible method for characterising zoned crystals. We use image segmentation on thin section scale chemical maps to segment textural zones in plagioclase phenocrysts. These zones are then correlated throughout a stratigraphic sequence from Saint Kitts (Lesser Antilles), composed of a basal pyroclastic flow deposit and a series of fall deposits. Both segmented phenocrysts and unsegmented matrix plagioclase are chemically decoupled from whole rock geochemical trends, with the latter showing a systematic temporal progression towards less chemically evolved magma (more anorthitic plagioclase). By working on a stratigraphic sequence, it is possible to track the chemical and textural complexity of segmented plagioclase in time, in this case on the order of millennia. In doing so, we find a relationship between the number of crystal populations, deposit thickness and time. Thicker deposits contain a larger number of crystal populations, alongside an overall reduction in this number towards the top of the deposit. Our approach provides quantitative textural parameters for volcanic and plutonic rocks, including the ability to measure the amount of crystal fracturing. In combination with mineral chemistry, these parameters can strengthen the link between petrology and volcanology, paving the way towards a deeper understanding of the magmatic processes controlling eruptive dynamics. Supplementary Information The online version contains supplementary material available at 10.1007/s00445-021-01476-x.

Assessing the potential and likelihood of explosive eruptions is vital for almost 800 million people living near active volcanoes. Magma reservoirs are not directly accessible, limiting our capability to understand the prerequisites for an explosive eruption and our ability to perform experiments that simulate magmatic processes at depth. Therefore, deciphering volcanic precursors is key to forecasting volcanic eruptions. In this study, we used synchrotron-based X-ray tomographic microscopy to observe felsic magma vesiculation at high temperature (1,100°C) to establish the pre-eruptive conditions that favor explosive activity. Specifically, we studied the increase of seismic attenuation with increasing gas content during magma vesiculation. These results are applied to the natural range of volcanic tremors (0.2–5 Hz) to detect the proximity of gas-charged magma to the surface prior to volcanic eruption: gas-rich, crystal- free felsic magmas are detected at larger depth (40 MPa) than gas-rich, crystal-bearing systems (10 MPa).

The last four caldera-forming ignimbrites in the central San Juan caldera cluster, Colorado, erupted 1400 km3 in ≤80 kyr and alternated between zoned crystal-poor rhyolite to crystal-rich dacite and unzoned, crystal-rich dacite. The zoned 150 km3 Rat Creek Tuff (26·91 Ma), unzoned 250 km3 Cebolla Creek Tuff, and zoned 500 km3 Nelson Mountain Tuff (26·90 Ma) formed the nested San Luis caldera complex with slightly offset calderas, and the unzoned 500 km3 Snowshoe Mountain Tuff (26·87 Ma) formed the Creede caldera to the south. The Rat Creek Tuff, Nelson Mountain Tuff, and Snowshoe Mountain Tuff have similar mineral assemblages of plagioclase, sanidine, quartz, biotite, hornblende, clinopyroxene, Fe–Ti oxides, and accessory zircon, titanite, and apatite. The Cebolla Creek Tuff differs from the other three ignimbrites with more abundant hornblende and a lack of quartz and sanidine. Trace element compositions of interstitial glass are unique to each ignimbrite, correlating with mineral assemblages and inferred crystallization depths. Glass, feldspar, hornblende, and clinopyroxene thermobarometry calculations provide evidence for vertically extensive crustal magma reservoirs with a common magmatic zone at ∼435–470 MPa (∼16–17 km) showing a transition into shallow pre-eruptive reservoirs between ∼110 and 340 MPa (∼4–13 km), similar to the estimated magma reservoir architecture of the Altiplano Puna Volcanic Complex. The upper portions of the eruptible parts of the magma reservoirs of the Rat Creek Tuff (215 ± 50 MPa, ∼810–820 °C), Cebolla Creek Tuff (340 ± 20 MPa, ∼860–880 °C), Nelson Mountain Tuff (215 ± 20 MPa, ∼745–800 °C), and Snowshoe Mountain Tuff (110 ± 40 MPa, 825 ± 10 °C) occupied shallow levels in the crust similar to other magma reservoirs of the central San Juan caldera cluster. Trace element modelling correlates with a deep crystallization signature in the unzoned Cebolla Creek Tuff and Snowshoe Mountain Tuff, typified by a flat trend in Ba versus Sr whole-rock and glass chemistry. The zoned Rat Creek Tuff and Nelson Mountain Tuff are typified by a steep trend in Ba versus Sr chemistry interpreted as a shallower crystallization signature. Similarly, the unzoned Cebolla Creek Tuff and Snowshoe Mountain Tuff have flatter slopes in FeO versus An space of plagioclase chemistry interpreted as more abundant deep plagioclase crystallization and a difficulty in physically mixing with Fe-rich mafic recharge magma owing to higher viscosity. The zoned Rat Creek Tuff and Nelson Mountain Tuff have higher slopes in FeO versus An space of plagioclase chemistry interpreted as more abundant shallow plagioclase crystallization and more feasible mixing with Fe-rich mafic recharge magma owing to lower viscosity. The eruption of the Rat Creek Tuff was probably triggered by mafic injection, but the other three ignimbrites lack mingling textures in pumice, suggesting that other mechanisms were important in causing such large eruptions. After a prolonged period of mantle-derived magma injection and crustal heating (∼25 000 km3 Conejos Formation erupted during ∼35–29 Ma), the San Juan magmatic body became a robust and versatile producer of diverse eruptible magmas in short time periods during its Oligocene ignimbrite flare-up.

The Takidani pluton (1·1–1·6 Ma) represents a shallow magmatic reservoir at the base of an exhumed caldera floor. The deposits of two large caldera-forming eruptions, the Nyukawa Pyroclastic Flow Deposit (1·76 Ma; crystal-rich dacite) and the Chayano Tuff and Ebisutoge Pyroclastic Deposits (1·75 Ma; a sequence of crystal-poor rhyolite), are distributed concentrically around the pluton. We use major and trace element chemistry of whole-rock, glass and minerals to show that (1) the crystal-rich dacite (>400 km3 DRE; dense rock equivalent) is the erupted portion of a shallow mush zone constituting the Takidani pluton and (2) the crystal-poor rhyolite (>100 km3 DRE) was extracted from a deeper part of this vertically extended magmatic plumbing system. Whole-rock geochemistry indicates that the Nyukawa and Takidani compositions were produced dominantly through crystal fractionation of amphibole, pyroxene and plagioclase in the mid to lower crust and subsequently emplaced in the upper crust prior to eruption and solidification, respectively. The crystal-poor Chayano–Ebisutoge rhyolite (>100 km3 DRE) is compositionally distinct from the Nyukawa and Takidani magmas and its generation is associated with a substantial contribution of crustal melts. However, plagioclase and orthopyroxene textures and chemistry provide strong evidence that the ascending rhyolite percolated through the upper Takidani–Nyukawa mush zone prior to eruption. Overgrowth of ‘rhyolitic plagioclase’ on ‘xenocrystic dacitic plagioclase’ typical of the Takidani–Nyukawa magmas indicates that the extraction and accumulation of the rhyolitic melts could have occurred in less than 10 kyr (i.e. the time between eruptions) prior to eruption, providing maximum timescales for pre-eruption storage. Overall, our findings show a progressive growth and thermal maturation of a vertically extended magmatic plumbing system over hundreds of thousands of years and imply that large volcanic eruptions can occur in relatively short succession without dramatic changes in the plumbing system, thus complicating the identification of signs of an impending large eruption.

Ciomadul is the youngest volcano in eastern-central Europe. Although its last eruption occurred at ca. 30 ka, there are independent indications for a high-crystallinity magma reservoir persisting beneath the volcano until present. In order to further test the hypothesis of long-lived melt presence and to better constrain the nature and timescales associated with the subvolcanic magma storage system, over 500 zircon U-Th and U-Pb spot ages (crystal interiors and outer surfaces) were interpreted from dacitic rocks of the most productive eruptive period (the Young Ciomadul Eruptive Period; YCEP, 160-30 ka). Zircon surface ages from lava dome and pumice samples range from ca. 600 ka up to the youngest eruption event at 30 ka. They form a continuous age distribution and some single crystals reveal significant age zonation (>150 kyr difference from core to rim). The oldest zircon ages of YCEP overlap with the last eruption events of the Old Ciomadul Eruptive Period (1000–330 ka). The zircon age spectra, combined with textural data, point to a prolonged (several 100's kyr) residence in a highly crystalline mush state. The range in zircon crystallization temperature (from ∼750 °C to the solidus at ∼680 °C) is consistent with the results of thermometry on amphibole and plagioclase from felsic crystal clots, which represent crystal mush fragments. To maintain magma reservoir for such a long time above solidus, continuous magma input by deeper recharge is required. Zircon crystallization model calculations constrained by thermal modelling imply an average rate of magma input of about 1.3 × 10−4 km3/yr over 2 Myr. Such estimate allows us to calculate an extrusive/intrusive ratio of 1:25–1:30. The model calculations suggest that a crystal mush zone of about 35 km3 is still present within the subvolcanic magma reservoir. Importantly, the Ciomadul plumbing system thus remains thermally primed and renewed magma injection could lead to rapid reawakening and eruption of the apparently inactive volcano.

Volcano deformation and gas emissions provide insights into subsurface magmatic systems. Large discrepancies are observed between the volumes calculated from deformation data, mass of emitted gases, and volumes of erupted magmas. Such discrepancies hinder our capacity to predict the magnitude and intensity of imminent eruptions and are ascribed to the amount of excess fluids stored in magma reservoirs. High-pressure (1240 bar) and high-temperature (1200 °C) hot isostatic press experiments show that the amount of trapped excess fluids in haplogranitic magmas with variable crystal contents (30, 50, 60, and 70 vol.%) depends strongly on fluid composition. Magmas with CO2 excess fluids become permeable at much larger porosities (44% higher) with respect to the H2O-rich counterparts at equivalent crystallinity. Available excess gas geochemistry data calculated from volatile-saturated melt inclusion record, syn-eruptive SO2 emission, and erupted juvenile porosity data collected for crystal-rich andesite and crystal-poor dacite/rhyolite volcanoes with known eruption magnitude and intensity (Mt St Helens 1980, Pinatubo 1991, Soufrière Hills 1996, and Merapi 2010) reveal that the discrepancy between erupted magma volume and SO2 released during the eruption increases with CO2 excess in magmas. In agreement with our experiments, these data highlight that CO2-rich fluids enhance magma’s capacity to store excess volatiles and shed light on the largest discrepancies between pre-eruptive deformation, gas emissions, and eruption intensity and magnitude.

The petrologic diversity of volcanic rocks reflects the dynamics of magma reservoirs and the temporal evolution of magma chemistry can provide valuable information for hazard assessment. While some stratovolcanoes monotonously produce intermediate magmas (55–68 wt% SiO2), dominantly erupted magma types (e.g., basaltic andesite, andesite or dacite) frequently differ even between neighboring volcanoes. If such differences arise due to thermal maturation processes over time or are predetermined by other properties of magmatic systems remains poorly understood. This study helps to elucidate the underlying factors modulating the chemistry of the magma preferentially erupted by Nevado de Toluca volcano in Central Mexico. We present a new dataset of bulk-rock and mineral chemistry spanning the entire 1.5 Million years of the volcanos’ eruptive history. The results reveal that Nevado de Toluca dacites and minor andesite originate in a stable configuration of pre-eruptive processes and plumbing system architecture by hybridization between an upper crustal silicic mush and deeper sourced basaltic andesite magmas. Yet, a subtle trend toward increasing silica content with time (2 wt% in 1.5 Ma) and episodicity in magma hybridization conditions are observed. We use thermal simulations of pulsed magma injection to probe the controlling variables on the temporal variation and compositional mode of magma geochemistry. The results show that the subtle temporal trend toward increasing bulk-rock SiO2 content is plausibly explained by slightly dropping recharge rates and continued upper crustal reservoir growth. Our modeling also shows that the dominant composition of eruptible magmas (“petrologic mode”) can shift as a function of magma flux, extrusive:intrusive ratio and temperature of the recharge magma. A comparison of SiO2 whole rock distributions for monotonous Mexican stratovolcanoes and their peripheral cones shows that their petrologic modes vary in concert, indicating that the recharge magma chemistry or temperature is a major control on the preferentially erupted magma composition for these volcanoes.

Linking tectonic setting to eruptive activity in volcanic arcs provides a framework to understand processes that control the production, accumulation and eruption of magma on Earth. We use the Holocene eruptive records of 162 volcanoes, which are selected based on an assessment of recording biases, to calculate the probability of recording large eruptions (between Magnitudes 4 and 7). We quantify regional variability in the sizes of volcanic eruptions and compare it with subduction parameters influencing the generation, transport and storage of magma. Given the tectonic setting of a subduction zone is multidimensional (e.g., age, speed, obliquity of the subducting plate) we use a graphical model to explore the strength of probabilistic relationships between tectonic and volcanic variables. The variable that exhibits the strongest probabilistic relationship with eruption size is convergence obliquity, with larger eruptions favored in settings where convergence is normal. Normal convergence favors the storage and accumulation of larger volumes of magma, whereas oblique convergence favors the transport and eruption of smaller volumes of magma. In low-obliquity arcs where magma storage is promoted, the subduction of older slabs results in higher mantle productivity, which thermally favors the accumulation of eruptible magma and larger eruptions on average. However, the highest mantle productivity also results in more frequent magma injection and pressurization of crustal reservoirs. Consequently, arcs with moderate slab ages and low obliquity produce the highest proportion of larger eruptions. In high-obliquity arcs mantle productivity does not dominantly control eruption sizes. Instead, thinner crust facilitates frequent transport of magma to the surface, resulting in smaller eruptions. For the largest eruptions on Earth (e.g., Magnitude 8), however, accumulation of eruptible magma will be dominantly controlled by thermomechanical modification of the crust and not the frequency of magma intrusion. Despite the importance of convergence obliquity, our results show that variability in the sizes of volcanic eruptions is controlled by complex relationships with other parameters including slab age and crustal thickness. By using a graphical model, we have been able to explore complex volcano-tectonic relationships. We suggest a similar approach could be extremely valuable for exploring other complex multidimensional datasets within the Earth Sciences.