Nearly 800 million people worldwide are exposed to volcanic hazards, with two-thirds of these areas located in subduction zones. Studying the movement of arc magma in subduction zones is particularly essential for volcanic hazard prevention. In particular, rapid trans-crustal movement of arc magma from the mantle can lead to volcanic eruptions with little warning, which would pose a high risk, yet research in this area is scarce. This paper reports for the first time the rapid trans-crustal movement of arc magma in the Izu-Mariana Arc. Systematic analyses on the volatile contents of melt inclusions in primitive olivine from the Pagan arc volcano yield exceptionally high CO₂ contents of up to 6000 ppm with H₂O contents of 3.7 wt%, which record magma storage at near-Moho depth of ~20 km. Diffusion chronometry of Fo, Ni and Mn in the host olivine, on the other hand, reveals that the parental magma took 15-125 days to ascend from near-Moho storage before its eruption. Such a rapid ascent of high Fo olivine from Moho to eruption is rare in arcs. That is because arc magma mostly has high water contents which would lead to viscous stalling during ascent and then delay the eruption. However, magma under Pagan volcano stored at a deeper depth than other arc volcanoes with similar water content, still ascended to eruption at a high rate. High CO₂ content and exsolution in Pagan magma, compared to other arc magmas, which could provide additional buoyancy or significant overpressure through continuous CO₂ degassing, and then result in rapid ascent.

How to cite: Huang, X., Yang, A. Y., Sun, M., Zhao, S., Tan, W., Tamura, Y., and Zhao, T.: Rapid trans-crustal movement of arc magma under Pagan volcano, Northern Mariana, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-53, https://doi.org/10.5194/egusphere-egu24-53, 2024.

Eruptions from Mauna Loa’s Southwest Rift Zone (SWRZ) pose a significant threat to nearby communities due to high eruption rates and steep slopes resulting in little time for evacuation. Despite the large body of research done on Mauna Loa, knowledge of the timing and duration of magma residence and transfer through its internal plumbing system is still poorly constrained. This study presents a first quantitative look at thermochemical conditions and timescales of potentially deep storage, and disaggregation of magmatic mush during the run-up to the voluminous 1950 AD SWRZ eruption. Details of heterogeneous compositions and textures of the macrocryst and glomerocryst cargo in 1950 AD lavas suggests magma mixing and crystal recycling along the entire plumbing system. Furthermore, the crystal cargo contains evidence for the direct interaction between primitive, deeply stored magma and pockets of more evolved magma stored at shallow to intermediate depths. An enigmatic attribute of 1950 near-vent lava is the near-ubiquitous presence of subhedral, unreacted Mg-rich orthopyroxene phenocrysts (Mg#>80). Phase-relations of Mauna Loa olivine-tholeiite indicate that orthopyroxene joins olivine as a primary phase at pressures higher than 0.6 GPa Coexisting Mg-rich olivine and orthopyroxene and the occurrence of harzburgitic (olivine-orthopyroxene) glomerocrysts provide evidence for cognate crystallization at near-Moho (~18km) depths (Thornber and Trusdell 2008).  Petrogenetically diverse populations of glomerocrysts and macrocrysts alongside evidence of multilevel magma storage indicate a network of ephemeral and possibly interconnected magma pockets from near-Moho depths to the upper/mid-crust. Fe-Mg diffusion chronometry applied to 1950 AD olivine populations implies rapid mobilization and transport of large volumes of magma (376×10⁶ m³) from near-Moho storage to the surface within less than 8 months, with little residence time (~2 weeks) in the shallow (3-5km) plumbing system.

Thornber CR, Trusdell FA (2008). Field, petrologic and experimental evidence for rapid transport of large magma volumes from great depths during the 1950 eruption of Mauna Loa, Hawai‘i. IAVCEI General Assembly, August 2008, Reykjavik, Iceland.

How to cite: Kahl, M., Morgan, D. J., Thornber, C., Walshaw, R., Lynn, K. J., and Trusdell, F. A.: Dynamics of magma mixing and magma mobilisation beneath Mauna Loa – insights from the 1950 AD Southwest Rift Zone eruption , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1683, https://doi.org/10.5194/egusphere-egu24-1683, 2024.

Mt. Etna is the most active volcano in Europe with four active vents in the summit area. The South-East Crater (SEC) is the most active crater of the last 20 years and is characterised by episodic eruptions, i.e. sequences of paroxysmal lava fountains with rather variable frequency and duration from a few weeks to months. Between December 2020 and February 2022, the SEC produced over 60 paroxysmal events divided into a first phase (December 2020 – April 2021) and a second phase (May 2021 - February 2022).

We investigated textural and chemical characteristics of the clinopyroxenes population to constrain frequency of magma recharge episodes and eruption triggering mechanisms of 6 paroxysms representative of the first phase, from February 16 to March 10 2021, including the February 28 paroxysm which erupted the most primitive magma.  Clinopyroxenes show frequent sector zoning superimposed on complex concentric zoning showing two main compositional domains: 1) augitic composition (Mg# 68-75) which mostly characterises rims and is less frequent in cores and mantles; 2) diopsidic composition (Mg# 74-80) mainly found in cores and less abundant in mantle and rims. Barometric estimates using the new GAIA deep learning-based thermobarometry (Chicchi et al., 2022 EPSL) indicate a shallow reservoir (0.4-1.0 ± 0.3 kbar) for the augitic domain and a deeper reservoir (1.7-2.7 ± 0.5 kbar) for the diopsidic domain. Fe-Mg diffusion timescales point to the occurrence of multiple episodes of mafic recharges starting in December 2020 and up to a few days prior eruption in agreement with monitoring data.

How to cite: Petrone, C. M., Corsaro, R. A., and Yannick, B.: The February-March 2021 lava fountains events of Mt. Etna South-East crater: insights from clinopyroxenes. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8840, https://doi.org/10.5194/egusphere-egu24-8840, 2024.

Investigating the dynamics and timescales of magmatic processes in active volcanoes is crucial for understanding explosive eruptions and assessing volcanic hazards. In this context, we are currently conducting a petrological survey of the Stromboli volcano (Aeolian Islands, Southern Italy), whose persistent activity is characterized by periodic and mildly explosive “Strombolian” eruptions, alternating with episodic lava effusions and more violent eruptive events, namely major explosions and paroxysms. The plumbing system is characterized by a vertically-extended mush column in which the shallow magmatic reservoir (highly porphyritic or Hp-magma) is continuously refilled with mafic recharges (low porphyritic or Lp-magma) rising from depth. During the paroxysmal events, sustained injections of Lp-magmas produce ample and continuous H₂O-rich gas phases that are released with great energy through the vent, together with ash, scoriaceous spatters, bombs and lithics traveling over long distances. With the final scope of deciphering mutual relationships between Hp- and Lp-magmas, as well as magma-mush interplay within the shallow plumbing system, we present in situ microchemical analyses of plagioclase phenocrysts from nineteen scoria clasts ejected during mild to violent explosions at Stromboli over a timespan of ~18 years, from 2003 to 2021. Major and trace element compositions, as well as Sr-isotopic data have been integrated with thermometric modeling and Mg-in-plagioclase diffusion chronometry to constrain the physicochemical changes within the plumbing system and the timescales of magmatic processes. Through this approach, a new eruptive cycle at Stromboli volcano has been identified, where more energetic open-conduit dynamics are associated with an increased intensity and frequency of eruptions due to mush disruption by sustained injections of mafic recharge magmas from depth.

How to cite: Schiavon, B., Petrone, C. M., Forni, F., Pontesilli, A., Del Bello, E., Scarlato, P., Nazzari, M., Tiepolo, M., and Mollo, S.: Petrological monitoring of persistently active basaltic volcanoes: the case study of Stromboli (Aeolian Islands, Southern Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11586, https://doi.org/10.5194/egusphere-egu24-11586, 2024.

How to cite: Braschi, E., Vougioukalakis, G. E., and Francalanci, L.: Petrologic constraints on the activity of the youngest explosive events at Yali volcano (South Aegean Active Volcanic Arc, Greece): plumbing system architecture and implication for hazard assessment., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17281, https://doi.org/10.5194/egusphere-egu24-17281, 2024.

The Plio-Pleistocene volcanism of the Main Ethiopian Rift (Ethiopia) is characterized by a bimodal distribution with abundant mafic and felsic compositions and rare intermediate magmas, a feature commonly known as the Daly Gap. The Quaternary activity is characterized by large explosive eruptions associated with caldera collapses that define a regional paroxysm of silicic and basaltic volcanism. The genesis of the evolved compositions and their relationship with the basalts still represents a matter of debate, with interpretations ranging from pure fractional crystallization to more complex scenarios involving magma mixing and crustal melting. Here, we present the first volcanological, petrological and geochemical characterization of a pyroclastic sequence, located in the Central Main Ethiopian Rift, the Golja Ignimbrite (GI). GI is a crystal-poor (<10% crystals of qtz+K-feld+pl+cpx+aen), low aspect ratio ignimbrite that crops out over ~400 km² and has an estimated bulk-tephra volume of ~100 km³. The pyroclastic sequence is characterized from bottom to top by: 1) a coarsening upward basal fallout layer; 2) an obsidian vitrophyre with rare, scattered fiammae; 3) a weakly to partially welded, lithic-rich PDC deposit and 4) a thick, unwelded PDC deposit containing different types of juvenile material including white, banded pumices and fiamme, as well as dark scoria. Analyses of matrix glass and melt inclusions from all juvenile types reveal a broad compositional spectrum ranging from basalts (found only in the pl-hosted melt inclusions) to rhyolites. Remarkably, we report the occurrence of intermediate compositions (basaltic trachyandesites to trachydacites) found within the mingled pumices and dark scoria. In-situ ⁸⁷Sr/⁸⁶Sr analyses of plagioclase display homogeneous isotopic composition with mantle-like signatures akin to the Afar Plume mantle source while Sr isotopic analyses of bulk matrix glasses from the different compositions show both mantle-like and crustal isotopic signatures akin to the Pan African Upper Crust. Bulk ¹⁴³Nd/¹⁴⁴Nd isotopic compositions of matrix glasses do not show significant variations between compositions. Overall, our data indicate a complex geochemical and isotopic evolution, involving fractional crystallization, magma mixing and assimilation of old crustal material. Our data represent the first geochemical characterization of this large ignimbrite and contribute to a better understanding of silicic magmatism in the Central Main Ethiopian Rift.

How to cite: Langone, F., Franceschini, Z., Avanzinelli, R., Braschi, E., Forni, F., and Cioni, R.: Petrological and geochemical characterization of the Golja Ignimbrite (Main Ethiopian Rift), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1016, https://doi.org/10.5194/egusphere-egu24-1016, 2024.

Small-scale monogenetic volcanic systems are the most widespread type of volcanism we experience on Earth and occur in a range of different tectonic settings, including intraplate, extensional, and subduction-related plate tectonics. Formed by a single surface eruption where small batches of magma erupt effusively and explosively, these features present a range of characteristics, including eruption frequency, volume, and duration, which can be linked to local and regional tectonic regimes. This volcanism is represented by tens to hundreds of associated volcanic vents where lava can unexpectedly penetrate the crust, with a new vent forming in an unknown location. Monogenetic volcanic fields (MVFs) are incredibly important to study, as each vent represents the pathway for magma to the upper mantle. These structures however are incredibly understudied and poorly constrained in terms of volcanic eruptive histories, and questions about the origin, longevity, and spatial distribution of vents are subject to uncertainty.

A wonderful example of where this can be investigated is the Kula Volcanic Province (KVP) in Anatolia, Western Turkey, exhibiting three periods of Quaternary basaltic volcanism between 2 Ma and 10 Ka. The three periods, namely the Burgaz, Elekçitepe, and DivlitTepe have been identified as silica-undersaturated alkaline volcanism exhibited as cinder cones, parasitic cones, spatter cones, lava flows, lava tunnels and maars. Turkey is situated in one of the most seismically active regions of the world, with Western Turkey one of the most spectacular regions of widespread active continental extension. The Kula volcanics are Na-dominant in character whereas other older volcanic rocks of Western Anatolia are generally definitive K-dominant rocks, representing a unique example of volcanism, and a rationale to investigate the significant geochemical signatures.

Within this study, we present new petrological and geochemical data (XRF, XRD, SEM) between magma products from the different eruptive periods, and provide an inclusive textural, chemical, and elemental investigation evaluating magma chamber dynamics, as well as exploring the temporal and spatial variations of the 80+ volcanic cones.  In addition to this, we plan to further use core and rim analysis of the main mineral phases to identify compositional variations of major (EPMA) and trace (LA-ICP-MS) elements which will be used to develop geochemical diagrams showing the relationships between specific elements and infer any geochemical processes that may have occurred.

This work aims to contribute to understanding future volcanic scenarios for intraplate volcanism which can be applied to other comparable tectonic environments and is a fundamental rationale for understanding magma chamber processes such as magma generation, magma evolution, crystallisation pathway, and likely tectonic environment.

How to cite: Watfa, M., Anguilano, L., Collins, P., Forni, F., and Moroni, M.: Petrology and Geochemistry of the Kula Volcanic Field, Western Turkey, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6695, https://doi.org/10.5194/egusphere-egu24-6695, 2024.

The study of magma plumbing system underneath a volcano is important to understand eruption triggers, estimate the probability of another eruption, and predict future eruptive behavior. Raung Volcano, located in East Java, Indonesia, is a very active volcano with a long-established basaltic to dacitic magma system. The most recent activity in 2022 was dominated by andesitic Strombolian explosions. However, several Plinian eruptions in the VEI-4 to VEI-5 scale had been documented in both andesite and dacite composition. Despite its variety of eruptive behaviors and potential hazards, Raung magma plumbing system is poorly understood. We investigate the depth and temperature of magma storage underneath Raung volcano by applying several thermobarometer models, including clinopyroxene-melt thermobarometry, orthopyroxene-melt thermobarometry, plagioclase-melt thermobarometry, and olivine-melt thermometry. Our findings reveal that there are five levels of crystallization below Raung from the upper crust to the crust-mantle boundary, at depths of 1.5 – 11 km, 11 – 15 km, 15 – 22 km, 18 – 26 km, and 26 – 30 km. These depths correspond to the major lithological boundary of East Java's sediment thickness (10 – 15 km), crust thickness (10 – 25 km), and Moho depth (25 – 39 km). This suggests that Raung magma storage is controlled by crustal structure. Textural features such as mantled pyroxene, sieved plagioclase, and oscillatory zoned crystals indicate a significant rate of continuous hotter, mafic magma recharge, supplying heat and volatiles into shallower reservoir. These features imply that multi-level magma storage and highly dynamic magma plumbing system play major roles in triggering Raung explosive eruption. Better understanding of Raung complex magma system is important for forecasting the timing and explosivity of potential eruptions, as well as improving long-term hazard mitigation.

How to cite: Moktikanana, M. L. A., Ohba, T., Harijoko, A., and Wibowo, H. E.: Multi-level magma storage and continuous mafic recharge controlling explosive activity in Raung volcano, Indonesia: Evidence from thermobarometric estimate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-297, https://doi.org/10.5194/egusphere-egu24-297, 2024.

The Ciomadul Volcanic Complex, Eastern Carpathians, Romania is the youngest volcano in the Carpathian-Pannonian region, eastern-central Europe, where volcanic activity occurred between 160 ka and 30 ka. It is a typical long-dormant volcano, where active stages were divided by several 10’s ka quiescence. Geophysical studies indicate that it is still underlain by a potentially active magma storage (PAMS volcano). Two main stages of volcanism are distinguished that was separated by ca. 40 ka dormancy: the first one (160–95 ka) was characterized by lava dome extrusions, whereas the second one (56–30 ka) was mostly explosive. Magma composition, however, remained homogeneous, i.e., high-K dacitic, which contains plagioclase, amphibole, biotite as well as accessory apatite, titanite and zircon. In this study, we focus on the variation of apatite composition, particularly the changes in the volatile content and its effects on the type of eruptions.

We analyzed the chemical composition of apatite microphenocrysts and inclusions enclosed by amphibole and biotite phenocrysts by microprobe, with special attention to the volatile contents (Cl, F, OH). Samples represent different eruption ages, and both effusive and explosive eruption types. In the xCl/xOH vs. xF/xOH diagram, a breakpoint in the compositional variation of apatite indicates the change of water-saturation state in the magma reservoir, due to the different behavior of Cl and F in water-saturated and unsaturated magmas. Fluorine remains in the melt during water-saturation state, and follows the same trend as in water-undersaturated conditions. In contrast Cl shows similar incompatible behavior in water-undersaurated state, but in water-(over)saturated conditions it enters to the gas phase, so its content in the melt (and in crystal lattice of apatite) is buffered or decreased. We also used MgO content of apatite to follow the behavior of the halogens during the magma differentiation, where high amount of MgO represents the less evolved magma.

We interpret our results that effusive eruptions occurred when the magma reached water-(over)saturated state (constant Cl content). In that case, the eruption triggering recharge event was not able to return the magma to water-undersaturated condition. On the other hand, the explosive events were characterized by magmas became in water-undersaturated state. In the case of the three oldest explosive eruptions the less evolved recharge material was able to return the already saturated magma to water-undersaturated state before the eruptions. The or one of the youngest explosive eruption of the Ciomadul (Bixad) was also explosive, but in this case water-saturated state was not detectable by the apatite record. Similarly to earlier studies of the Ciomadul, our results on apatite composition also indicate the role of mafic magma recharge in the petrogenesis of the rocks and shows that it could have turned the system to water-undersaturated state that eventually led to explosive eruptions.

This study belongs to the K135179 NKFIH-OTKA research project.

How to cite: Hajdu, K., Lukács, R., Popa, R.-G., Allaz, J. M., Páncél, E., Cserép, B., Bachmann, O., Pál-Molnár, E., Seghedi, I., and Harangi, S.: Control of effusive and explosive eruptions of Ciomadul volcano: constraints by apatite composition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1116, https://doi.org/10.5194/egusphere-egu24-1116, 2024.

The emplacement of magma chambers within a carbonate basement promotes a sequence of thermochemical reactions that progressively evolve from the carbonate wall-rock towards the magma, altering the chemical composition of the overall system (crystal + melt). Recent petrological and experimental studies highlight that varying degrees of limestone/dolostone assimilation controls the liquid line of descent of magmas, promoting or hindering the crystallization onset of distinct mineral phases.

In this study, we investigate how differing degrees of limestone/dolostone assimilation and deformation regimes impact the rheology of a leucite-bearing phonotephrite magma from Somma-Vesuvius (Italy). Using starting materials doped with 0, 10, or 20 wt.% of CaO and CaO+MgO, mimicking the effects of limestone/dolostone assimilation, we conducted two sets of crystallization experiments at 1180°C under static and dynamic conditions (shear strain rate of 1 and 5 s^-1).    

We observe distinct rheological behaviours among melts as a function of composition and applied shear rate, displaying significant differences in terms of crystallizing mineral phases (±clinopyroxene±melilite±leucite±nepheline in the CaO-doped samples and ±clinopyroxene±melilite±olivine±leucite±nepheline, in the CaO+MgO-doped ones) and final crystal contents. Increased alkaline earth content (both Ca and Ca+Mg) alongside higher shear rates foster crystallization, leading to heightened crystal fractions (up to 51%) and larger crystals. Consequently, in heavily doped samples and under high shear rates, viscosity increased of up to 1.5 Log Pa s due to crystallization, causing the rheological transition from coherent flow to shear localization, culminating in physical separation (i.e., viscous rupture).  

This study underscores the significant influence of deformation on magma, affecting both mineralogical assemblages and crystallization efficiency. These effects compound the pivotal role played by changing magma composition due to carbonate assimilation, governing magma’s crystallization capability, transport properties, and flow behaviour during its ascent from depth to surface.

How to cite: Giuliani, G., Di Fiore, F., Mollo, S., Romano, C., Di Genova, D., and Vona, A.: The influence of carbonate assimilation and deformation regime on the multiphase rheology of a phonotephritic melt from Vesuvius, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-459, https://doi.org/10.5194/egusphere-egu24-459, 2024.

Even small variations in minor element composition can affect the crystallization history of a magma, altering the final mineral assemblage and/or microstructural evolution during crystallization.

We discuss the results of two sets of crystallization experiments performed in a piston cylinder apparatus at 400 MPa and at fO₂ close to NNO+2, using two synthetic trachybasaltic glasses, one with no Cr2O3 added (Glass 1) and one doped with 0.4 wt.% Cr2O3 (Glass 2). Experiments were carried out under both anhydrous (0 wt.% H2O) and hydrous conditions (2 wt% H₂O).

Experiments were initially heated at 1300 °C for 30 minutes to ensure complete melting of the glass and then cooled at a rate of 80°C/min to the final resting temperature (T_rest = 1150°C, 1100°C and 1050°C). Dwell time at T_rest ranged between 5 minutes and 8 hours. The commonest crystal phases were always clinopyroxene (Cpx, up to 50 vol%) and spinel (up to 5 vol%, specifically chromite [Chr] and/or titanomagnetite [Tmt])

In all samples, some spinel grains are found isolated in the melt, while others are touching a Cpx. The ratio of isolated spinel to spinel in contact depends on the crystallization history of the sample, which varies according to the starting composition.

Experiments performed with Glass 1 consists of Tmt grains always in contact with a Cpx grain, decorating its edges and tips. More than 90% of all Tmt grains following clear crystallographic orientation relationships (CORs) with Cpx, implying heterogeneous nucleation of Tmt on Cpx.

In experiments performed with Glass 2 the amount of isolated Spinel crystals is higher. These grains are constituted by a Chr core and a Tmt rim. Even when these oxide grains are in contact with (or inside) a Cpx crystal, they rarely (<10 % of touching oxide grains) share CORs with Cpx, suggesting that the oxides were the first phases to crystallize, and were subsequently engulfed by Cpx. The rare oxide crystals sharing CORs with touching Cpx are located in the centre of the dendritic Cpx grains, suggesting that Cpx nucleated heterogeneously on the earlier-formed oxide.

We evidence that even small variations in Cr2O3 content can affect the crystallization history of a magma, thereby affecting the final mineral assemblage and the microstructural evolution during crystallization. In particular, by altering the mechanism of crystal nucleation, we speculate that the nucleation of spinel stimulated by subtle changes in the chemistry of magmas (or variations of the fO2 conditions) may result in substantial modification of magma rheology.

Funded by the Austrian Science Fund (FWF): P 33227-N

How to cite: Peres, S., Griffiths, T., Colle, F., Iannini Lelarge, S., Masotta, M., and Pontesilli, A.: On the effect of Cr2O3 addition on the crystallization of trachybasaltic melt, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17296, https://doi.org/10.5194/egusphere-egu24-17296, 2024.

Vulcano Island is characterized by transitions from phreatomagmatic to minor magmatic activity. The last eruption in 1888–90 saw powerful explosive pulses and this eruption defines what we call today ‘vulcanian’ also for other volcanoes worldwide. Since then, volcanic activity at Vulcano has been limited to the form of fumarolic emanations of variable intensity and temperature, mainly concentrated at “La Fossa” crater and on its northern slope.

In September 2021, La Fossa entered a new phase of unrest with a sudden and significant increase of degassing activity from the crater and with outstanding variations to fumarole gas composition, temperature, plume emissions, diffuse soil CO2 degassing, local seismicity and ground deformation.

We discuss a set of geophysical monitoring parameters which started evidencing changes since middle 2018, and showed an important expansion of La Fossa Cone in 2021 as the result of an increased activity inside the shallow hydrothermal system just below La Fossa.

We discuss the 2021 episode within 50 years of ground deformation and seismicity data collected by INGV, trying to define the elements of comparison, similarities and differences with the hydrothermal unrests already observed during the late 1970s to early 1990s.

How to cite: Privitera, L., Bonforte, A., Gambino, S., and Guglielmino, F.: The 2021-22 volcanic unrest at Vulcano Island (Italy) inside of 50 years of activity observed with geophysical data., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3468, https://doi.org/10.5194/egusphere-egu24-3468, 2024.

Determinations of the temperatures and pressures of volcanic products during their formation are helpful for understanding magmatic system behaviour and igneous processes. Whereas estimates of the former give insights into the thermal evolution of magmas, the latter provides estimation of the storage depth of magmatic reservoirs. Together they provide practical constraints for understanding the magma storage conditions beneath active volcanic areas and their implications in other research fields, such as geothermal exploration. The Asal-Ghoubbet rift is one of the emergent segments of the Aden Gulf oceanic ridge, which spreads westward on land into the triple junction zone of the Afar depression. The rift-in-rift area has witnessed repeated magmatic and tectonic activity over its ~1 Ma evolution. Most recently, in November 1978, a one-week-long basaltic fissure eruption led to the birth of the Ardoukôba volcano. Due to its active and unique location, the area has been subject to geothermal exploration since the 1970s. However, although intensive geological, geochemical, and geophysical studies have been conducted in the area, detailed knowledge is still lacking regarding the evolution of storage conditions in the magmatic system beneath the Asal-Ghoubbet rift. For this study, eleven samples, representing the time span from ~300 ka to today, were collected in the rift, and geochemical and geothermobarometric analyses were conducted. Two samples representing the oldest basalts in Djibouti (BD and BS) were also added for comparison. The rock samples are tholeiitic to transitional basalts with MgO contents between 3.3 and 10.2 wt%. The negative correlations of TiO₂ and FeO contents, and positive of CaO, with MgO indicate that fractional crystallization is an important process in the magmatic system. The crystal cargo of the erupted lavas consists of plagioclase, clinopyroxene and olivine, in order of decreasing amount. Anorthite contents of plagioclase vary between 45and 89, with a main population at ~An₈₅. Most crystals are in disequilibrium with their carrier melts. Clinopyroxenes have Mg# ranging from 47 to 87,with crystals of Dalha basalts (BD) being the most differentiated. Olivine cores and mantles are mostly primitive with a main composition of Fo₈₄. The majority of clinopyroxenes and olivines are in equilibrium with carrier melts, except for BD. Based on geothermobarometric calculations, we propose the existence of two magma storage depths beneath the Asal-Ghoubbet rift. A mid-deep crustal reservoir is located at ~13 km with a mean temperature of 1200°C. It represents the main magma body with higher temperatures and where most of the minerals crystallized. The second one is found at shallow crustal level (5 to 7 km) with lower temperatures (~ 1120°C). Few crystals formed at this depth, which could indicate a smaller size reservoir. Textural and chemical variations of minerals suggest a connection between the two magma bodies, forming the magma plumbing system. Magma storage conditions appear to have been maintained over time, which implies the continuous renewal of the geothermal heat source in the Asal-Ghoubbet rift.

How to cite: Ahmed Aden, A., Bali, E., Heiðar Guðfinnsson, G., Páll Hersir, G., Moussa Ahmed, K., and Monika Galeczka, I.: Characterization and evolution of the magma reservoir beneath the Asal-Ghoubbet rift, Republic of Djibouti, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19154, https://doi.org/10.5194/egusphere-egu24-19154, 2024.

The discovery of a rhyolitic magma body at a depth of 2.1 km during drilling of the first well in the Iceland Deep Drilling Project (IDDP-1) at Krafla volcano, NE Iceland, presented an unprecedented opportunity to explore shallow magma properties and the root of geothermal systems. Yet, to safely access this near-magma energy, we require an in-depth understanding of magmas’ response to drilling activity and power plant operations, which we target here using the natural samples retrieved in-situ from the magma body during IDDP-1. The glassy fragments display a spectrum of colors (light brown to black), different vesicularities and crystals of plagioclase, pyroxene, Ti-magnetite, and apatite; some crystals exhibit zonation and embayment.

In this study we experimentally explore the stability of the rhyolitic magma to different P-T-X conditions to assess magma response to perturbations prompted by drilling. We tested pressures of 16, 35, and 45 MPa (between hydrostatic pressure and the pressure as estimated by dissolved H₂O-CO₂ concentration), temperatures ranging from 880 to 920°C, and durations spanning from 6 to 48 hours. All experiments were carried out under water-saturated conditions, with oxygen fugacity fixed by Ni and Co filler-rods to NNO+1 (more oxidized) or QFM (more reducing), respectively. We used the original glass chips (without remelting them) to see how the texture would evolve when subjected to different P, T, X. The main difference observed is when comparing experimental products at NNO+1 or QFM conditions which influenced glass color: darker hues appeared under NNO+1 condition and lighter hues prevailed under QFM condition. Whilst at NNO+1 the phases present in the original mineralogical assemblage were generally relatively stable (with one exception; see below). At 45 MPa, we observe no dissolution of the original phases but overgrowth of pyroxene in all charges. By reducing temperature from 900 ºC to 880 ºC or by increasing the oxygen fugacity (to NNO+1) we observed an increase in microlite content of the same original phases (except for apatite which did not crystallize). At the lower pressure of 35 MPa, the microlite content was higher than at 45 MPa; yet, the original mineralogical assemblage remained, whereby no dissolution took place and pyroxene overgrowth occurred. Again, by decreasing temperature from 920 ºC to 880 ºC or by increasing the oxygen fugacity the microlite content increased. Importantly, quartz crystallized at 880 °C, 35 MPa and under NNO+1 conditions; indicating that these conditions were likely not met during drilling. At 16 MPA, the experiments failed as the Au capsules ruptured due to pressure from excess fluids. Our initial findings suggest that the magma may reside in the crust at a minimum temperature of 900 °C, if at 45 MPa, or 920 °C, if at 35 MPa. This work establishes a “reference frame” for understanding shifts in magmatic parameters that may be triggered by drilling into active systems.

How to cite: Muniz da Silva, M., Castro, J., Kendrick, J., Wallace, P., and Lavallée, Y.: Probing an active, exceedingly shallow rhyolite reservoir with experiments and petrological tools: the case of Krafla IDDP1, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16555, https://doi.org/10.5194/egusphere-egu24-16555, 2024.

Open-conduit conditions characterize several of the most hazardous and active volcanic systems of basaltic composition worldwide, persistently refilled by magmatic inputs. Eruptive products with similar bulk compositions, chemically buffered by continual mafic inputs, exhibit nevertheless heterogeneous glass compositions in response to variable magma mixing, crystallization, and differentiation processes within different parts of the plumbing system. Here we document how multivariate statistics and magma differentiation modeling based on a large data set of glass compositions can be combined to constrain magma differentiation and plumbing system dynamics. Major and trace elements of matrix glasses erupted at Stromboli volcano (Italy) over the last twenty years provide a benchmark against which to test our integrated petrological approach. Principal component analysis, K-means cluster analysis, and kernel density estimation reveal that trace elements define a multivariate space whose eigenvectors are more readily interpretable in terms of petrological processes than major elements, leading to improved clustering solutions. Comparison between open- and closed-system differentiation models outlines that steady state magma compositions at constantly replenished and erupting magmatic systems approximate simple fractional crystallization trends, due to short magma residence times. Open-system magma dynamics imply lower crystallinities pervade the magmatic storage than those associated with closed-system scenarios, allowing efficient crystal-melt separation toward the top of the reservoir, where eruptible melts continuously supply the ordinary activity at the volcano. Conversely, a mush-like environment constitutes the bottom of the reservoir, in which poorly evolved magmas result from mixing events between mush residual melts and primitive magmas injected from deeper crustal levels. 

How to cite: Pontesilli, A., Di Fiore, F., Scarlato, P., Ellis, B., Del Bello, E., Andronico, D., Taddeucci, J., Brenna, M., Nazzari, M., Bachmann, O., and Mollo, S.: Magma differentiation in dynamic mush domains from the perspective of multivariate statistics: open- vs closed-system evolution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12812, https://doi.org/10.5194/egusphere-egu24-12812, 2024.

How to cite: Geyer, A., Miranda-Muruzábal, M., Aulinas, M., Albert, H., Vilà, M., Micheo, F., Bolós, X., Pedrazzi, D., Gisbert, G., and Planagumà, L.: CatVolc: A new database of geochemical and geochronological data of volcanic-related materials from the Catalan Volcanic Zone (Spain), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12270, https://doi.org/10.5194/egusphere-egu24-12270, 2024.

Tenerife island (Canary Islands, Spain), home to nearly a million inhabitants and attracting over 5 million tourists annually, hosts one of Europe's potentially most hazardous volcanic systems. Current volcanic activity on the island is primarily located in its central region comprising the Teide-Pico Viejo volcanic complex, and extends along the Santiago del Teide and Dorsal ridges towards the NW and NE, respectively. Understanding the volcanic stratigraphy, petrology, and geochemistry of the different eruptions within the central complex and their correlation with the rift systems is crucial to comprehend how this complex volcanic system will behave in the future, thereby improving hazard assessment for the island.

In this study, we provide a comprehensive review of the geochemistry of eruptive products associated with events that occurred in the area over the last 180ka, following the El Abrigo eruption, the island's latest caldera-forming event. Special emphasis is given to Holocene eruptions sourced at the Teide-Pico Viejo volcanic complex and the two adjacent rifts. To facilitate this, we have constructed the GeoTeRi database, which includes an exhaustive compilation of whole-rock major and trace elements analyses, along with isotopic data available in the literature (over 49 consulted references). Additionally, a review of the chronostratigraphy of the eruptions included in the database was conducted, drawing on published volcanostratigraphic maps and/or existing radiometric data.

The GeoTeRi database currently includes information from 651 rock samples, comprising over 500 major and trace elements analyses, and 176 isotopic analyses. This database aims to serve as a tool for reconstructing the geochemical evolution of the active volcanic system on the island of Tenerife and it will provide a starting point for future studies. Additionally, a detailed statistical analysis of this database is planned to evaluate its robustness, the representativeness of the analysed samples, and possible knowledge gaps in the understanding of the active system.

This research was partially funded by E.G., grant EVE (DG ECHO H2020 Ref. 826292) and the Intramural CSIC grant MAPCAN (Ref. 202130E083). OD was supported by an FPU grant (FPU18/02572) and a complementary mobility grant (EST19/00297) from the Ministry of Universities of Spain.

How to cite: Dorado, O., Geyer, A., and Marti, J.: GeoTeRi: A new geochemical database of post-caldera (< 180 ka) eruptions of Teide-Pico Viejo central complex and adjacent rift systems (Tenerife, Canary Islands), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12896, https://doi.org/10.5194/egusphere-egu24-12896, 2024.

The Snake River Plain plateau and the adjacent Columbia River and Yellowstone volcanic fields form one of the world largest flood basalt provinces. Eruptive centers migrated eastward since the late Cenozoic following the Yellowstone hotspot, erupting an archetypical bimodal volcanic suite with compositions ranging from olivine-tholeiite to rhyolite. Up to 80% of the ~1600 km² eastern portion of the Snake River Plain (ESRP) is covered by mafic lava flows, from which four prominent Pleistocene rhyolite domes emerge. Closely associated with the ESPR is the Craters of the Moon (COM) volcanic field, which is considered the largest Holocene lava field in the ESRP and the United States, with more than 60 eruptions over the past ~15,000 years. Geochemically, COM lavas range from basalt and trachybasalt to trachyte.

To elucidate processes and timescales of evolved magma production, zircon from Quaternary rhyolites from the ESRP was investigated along with zircon from three of the most recent and evolved COM lava flows and those from a COM crustal xenolith. Approximately 300 individual zircon crystals were analyzed for U-Pb and U-Th geochronology, respectively, and paired with crystal-scale δ¹⁸O, ɛHf, and trace element analyses. Composite zircon separates from a COM lava flow were also analyzed by combined (U-Th)/He and U-Th dating to constrain its eruption age.

U-Pb zircon dating indicates crystallization ages between 1.54 ±0.01 Ma in the oldest and 0.335 ± 0.003 Ma in the youngest ESRP rhyolite dome, with ages increasing from west to east. For COM trachyte lavas, zircon U-Th disequilibrium corresponds to an age of  ka which along with an indistinguishable (U-Th)/He zircon age demonstrates that zircons crystallized in the evolved magma shortly before the eruption. With the exception of rare Precambrian basement-derived xenocrysts, evolved COM lavas have zircon δ¹⁸O values ranging from +5.33 to +6.02, consistent with fractionation from ESRP mantle-derived mafic magmas. On the other hand, δ¹⁸O(VSMOW) zircon composition between +1.73‰ to +4.51‰ for ESRP agree with low δ¹⁸O Yellowstone rhyolites with decreasing values from west to east. COM lavas display ɛHf zircon values between -12.0 to -8.9, whereas ESPR rhyolite ɛHf zircon ranges from -6.3 to -1.3. The crustal xenolith from COM yielded U-Pb zircon ages between 1.9 and 3.4 Ga, consistent with low ɛHf > -35. These results indicate different pathways of evolved magma production that differ between ESRP and COM.

How to cite: Angeles-De La Torre, C. A., Schmitt, A. K., McCurry, M., Danisik, M., Lovera, O. M., Hertwig, A., and Gerdes, A.: Distinct Magma Differentiation Pathways for the Eastern Snake River Plain and Craters of the Moon, Idaho, from Zircon Geochronology and Geochemistry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1798, https://doi.org/10.5194/egusphere-egu24-1798, 2024.

Inherited/xenocrystic zircons entrained in magmas offer a unique opportunity to identify cryptic magmatic episodes in the deep crust and thus to image lithospheric thickening and crustal evolution. We investigated zircon xenocrysts within igneous rocks (mostly granitoids) from the Northern Xinjiang region in the southwestern part of the Central Asian Orogenic Belt (CAOB) to evaluate their potential as a probe of crust evolution, by using the previously ignored information of our newly obtained and compiled dataset of xenocrystic/inherited zircons (e.g., U-Pb age and Hf-O isotopic data). Different ancient age distributions of these zircons and the varying U-Pb ages and heterogeneous Hf isotopes demonstrate the ancient magmatic pulses in the crust of NW CAOB. Combined with the information from detrital zircons, and through the published plate motion models, we further compare these ancient age peaks in variable time-slices, e.g., from Proterozoic to Paleozoic, to interpret the recycling and transport of continental material. This innovative approach enhances our understanding of orogenic processes, shedding light on imaging the recycling and transport of deep continental materials.

How to cite: Zhang, J., Wang, T., Tong, Y., Huang, H., and Song, P.: Combined analysis on information of xenocrystic/inherited zircons within igneous rocks of Northern Xinjiang in northwestern China: imaging the deep crustal components through time, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14289, https://doi.org/10.5194/egusphere-egu24-14289, 2024.

Amphibole is a common mineral in arc magmas, occurring in a wide temperature and pressure range. Its composition is sensitive to the crystallization condition that helps to quantify the magma storage depth, temperature, and redox conditions as well as to characterize the equilibrium melt composition including the water content. It can also be used to reveal the magma evolution pathways and processes occurring in the magmatic reservoir system. We provide here a comprehensive characterization of amphibole formed at different stages of magma evolution in the complex magmatic plumbing system of Ciomadul volcano, the youngest one in eastern-central Europe. A central dacitic lava dome complex built-up 160–96 ka ago, and it was partly destructed by explosive eruptions in the youngest volcanic stage (56–30 ka). We have characterized amphibole compositions both for major and trace elements in the dacitic lava dome and pumice samples.

Amphibole populations can be well discriminated by major and trace element compositions. Amphibole compositions of the 160–90 ka dacites suggest two distinct magmatic environments. (1) A cold (670–750 C°), silicic (70–77 wt% melt_SiO2) crystal mush with high crystallinity emplaced in the shallow crust at 8–15 km depths. These low-Al-Mg amphiboles show low Zr, Hf, Ti, Sr, Ba, Cr, and Ni concentrations, a negative Eu anomaly, moderate La/Sm ratio and high Nb, and Dy concentrations reflecting the evolved nature of the host melt. (2) A relatively mafic (52–60 wt% melt_SiO2), hotter (940–980 Cº) magma, accumulated presumably in the lower crust. Amphibole crystallizing within this environment has high Al-Mg content and low Ni and Cr, moderate La/Sm ratio, lack of negative Eu-anomaly, and high Nb, Ta, Dy, Zr, Hf, Ti, Sr and Ba concentrations.

During the explosive eruption-dominated period (56–30 ka), the cold crystal mush environment remained, but amphibole records the presence of two additional, more primitive, hydrous and oxidized recharge magmas: (3) A magma with 56–69 wt% melt_SiO2, 880–980 °C, with high Al-Mg amphibole having moderate Zr, Hf, Ti, Sr, Ba, Nb, Ta, Dy, Cr, Ni and without negative Eu-anomaly. (4) A mafic magma containing unique low-Al, high-Mg amphibole with high Cr–Ni concentrations. It crystallized at >800 °C temperature and has low Zr, Hf, Ti, Ba, Nb, Ta, Dy, and La/Sm ratio. Recharge of these mafic magmas into the felsic crystal mush initiated rapid remobilization, hybridization and thin amphibole overgrowth with transitional compositions during magma ascent. We demonstrate how amphibole compositions can be used to track deep to shallow fractionation within the magma plumbing system at various conditions. Notably, a compositional shift can be observed in the recharge magma amphibole compositions from the extrusive to the younger explosive eruption stage. The mafic magmas became more hydrous and oxidized with time that could contribute to the change in eruption style.

This study is supported by the ÚNKP-23-3 New National Excellence Program of the Ministry for Culture and Innovation and by the Hungarian National Research Fund project (K 135179).

How to cite: Cserép, B., Erdmann, S., Lukács, R., Bachmann, O., Seghedi, I., Szemerédi, M., and Harangi, S.: Amphibole trace element signatures of magmatic environments  within the magmatic plumbing system of the 160–30 ka Ciomadul volcanic complex, Eastern Carpathians, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19374, https://doi.org/10.5194/egusphere-egu24-19374, 2024.

Vesteris Seamount is a solitary, alkaline intraplate volcano of non-plume and non-rifting origin located in the Norwegian-Greenland Basin. During RV Maria S. Merian Cruise MSM86 highly detailed sampling of the Seamount recovered over 70 rock samples from the whole volcanic edifice during TV-Grab and ROV Marum SQUID operations. Major- and trace element geochemical analyses of matrix compositions and phenocrysts were conducted by electron microprobe and laser ablation ICP-MS. To investigate the petrogenesis of the Vesteris rock suite and the magma plumbing dynamics the analytical results were applied to least-squares mass balance and clinopyroxene-liquid thermobarometry models.

Primitive basanites and alkali-basalts reflect individual melt batches from a deep mantle source. A tight liquid line of descent can be observed from basanitic to trachytic compositions. The main control on the magmatic evolution is exerted by fractional crystallization. Textural and chemical evidence indicate a more pronounced influence of magma mixing during the genesis of the evolved tephriphonolitic and trachytic compositions.

Results from our clinopyroxene-melt thermobarometry calculations show a bimodal pressure distribution that indicates upper mantle storage between 500 and 850 MPa (15-27 km depth) and shallower crustal storage between 250 and 460 MPa (7-14 km). The magmatic evolution of basanites and alkali-basalts by crystal fractionation began in the upper mantle and subsequently migrated into crustal levels where phonotephritic to trachytic magma compositions developed. A multi-stage model for the evolution of the magma plumbing system below Vesteris Seamount is proposed based on the geochemical and thermobarometric data.

Initially, dykes transported deep mantle melts to the surface. Subsequent dyke and sill emplacement and high magma fluxes led to the formation of a reservoir in the upper mantle and magma accumulation zone at the uppermost mantle to Moho levels. Progressive weakening of the crust and continuing high magma fluxes led to and development of a crustal storage zone. At a later stage volcanic activity became more episodic and magmatic evolution was controlled mainly by fractional crystallization. The basanites and phonotephrites were stored at upper mantle levels, evolved tephriphonolitic and trachytic magmas were stored at crustal levels prior to eruption. During episodes of increased volcanic activity, the crustal reservoir was recharged by batches of poorly differentiated melts and initiated magma mixing.

How to cite: Röhler, A., Beier, C., Klügel, A., Bach, W., and Haase, K.: Vesteris Seamount - Magma plumbing dynamics and petrological evolution of an alkaline intra-plate volcano of non-plume and non-rifting origin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19962, https://doi.org/10.5194/egusphere-egu24-19962, 2024.

The 1631 CE eruption is the most violent and destructive event of the last millennium at Mt. Vesuvius, followed by a persistent small magnitude activity that has lasted until the 1944 CE. Selected units of the proximal stratigraphic section cropping out at Cognoli di Ottaviano (Monte Somma), <2 km from the current Vesuvius crater, have been sampled. To retrieve information on types and timescales of magmatic processes and to possibly link them to precursory phenomena, the chemical composition of clinopyroxene crystals has been acquired. Mineral chemistry (Si, Ti, Al, Fe, Mg, Mn, Ca, Na and Cr) has been obtained on the core and the rim of 50 unzoned crystals well-characterized in terms of texture. Mineral microanlaysis were realized along core-to-rim transects, varying from 40 μm to 500 μm in length, in 59 zoned crystals using a beam diameter of 2 μm and 1 μm spacing between individual points.

The mineral composition allows to characterize the zoning patterns and provides information on the environments in which crystals grew. About 70% of the zoned crystals show patchy zoned cores with-or-without- complex zoning in the outer bands. The other crystals show normal zoning, normal-to-reverse zoning, reverse zoning and complex zoning (e.g., oscillatory zoning). Zoned clinopyroxenes have a diopsidic/Fe-diopsidic composition (Wo_52-48-En_47-30-Fs_17-5). Mg# [molar Mg²⁺/ (Mg²⁺ +Fe_tot) *100] of the zoned clinopyroxene ranges between 90 and 62, with some differences observed in the different bands of the crystals.

The zoning pattern shows two or more bands with constant Fe-Mg and/or Al and/or Ti composition separated by both either sharp or diffuse boundaries. The occurrence of bands of constant composition in the zoning patterns of minerals suggests that crystal growth occurred for certain several periods of time under stable conditions, separated by events involving fast changes of thermodynamic variables (pressure, temperature, oxygen or water fugacity). Different compositional populations have been distinguished in the clinopyroxene zoning pattern, e.g., through the Mg# parameter, but also other elements concentrations such as Al₂O₃. Each population results from growth under a Magmatic Environment (ME), namely specific thermodynamic conditions. The connections between MEs recorded by clinopyroxene zoning pattern allow to accurately reconstruct the history of the magmatic processes across the clinopyroxene growth. As a whole, the zoned clinopyroxenes from the 1631 CE eruption record a huge variety of MEs, testifying to a complex history of crystallization under different conditions, reflecting long-lasting magmatic processes from mantle depth to shallow reservoir(s).

How to cite: Pelullo, C., Balcone-Boissard, H., Cariddi, B., Chakraborty, S., D'Antonio, M., De Lucia, M., de Vita, S., Di Vito, M. A., Petrosino, P., Piochi, M., Rividi, N., Solomita, G., Sparice, D., Zanon, V., and Arienzo, I.: The ultimate 1631 CE sub-plinian eruption of Mt. Vesuvius: hints on pre-eruptive magmatic processes from zoned clinopyroxenes                               , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19813, https://doi.org/10.5194/egusphere-egu24-19813, 2024.

Active magma degassing is the release of slightly over-pressurized gas pockets from volcanic vents. This activity can shed light on the geometry of the shallow plumbing system of volcanoes and its internal dynamics. During a summer 2023 field campaign, we conducted comprehensive recordings, including thermal infrared, high-speed, and high-resolution video, as well as broadband microphone signals, capturing ten consecutive days of active degassing events at the Bocca Nuova crater of Mt. Etna. Two distinct vents exhibited notable degassing activity. The first, henceforth referred to as 'Sboffer,' was a crater characterized by the emission of loud, low-frequency sounds accompanying each degassing event (hence the name). The second vent, smaller than the first one and designated as 'Ringer,' took the form of a circular pit on the Bocca Nuova crater floor, emitting volcanic vortex rings—reminiscent of smoke rings (hence the name)—during events. We focused our analysis on the thermal data, characterizing emissions from both vents by examining brightness temperature anomalies along horizontal measurement lines in the thermal video recordings. Both vents exhibited a bimodal distribution in the intensity and duration of events. Specifically, Sboffer produced larger events with a mean amplitude of 100-160°C and a recurrence time of approximately 500 seconds, along with smaller events with amplitudes of 20-24°C occurring every 200-400 seconds. Ringer, on the other hand, featured larger events with amplitudes of 70-100°C and smaller events with amplitudes of 20-23°C, occurring at much higher frequencies of every 4 and 1.5 seconds, respectively. The maximum temperature recorded during the larger events reached nearly 600°C for Ringer and 500°C for Sboffer. The exit velocities for large events were measured at 15 m/s for Sboffer and 10 m/s for Ringer. Remarkably, all parameters at both vents remained consistently stable throughout the ten-day observation period. Preliminary investigations were conducted to explore potential correlations between the acoustic signal and thermal data. The aim was to ascertain the depth of the explosive events and examine potential correlations with temperature variations and the intensity of the explosions.

How to cite: Biensan, C., Taddeucci, J., Ricci, T., Del Bello, E., Scarlato, P., and Palladino, D.: Multiparametric exploration of active magma degassing at Mt. Etna in 2023, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10251, https://doi.org/10.5194/egusphere-egu24-10251, 2024.

During magma ascent, the growth, ascent, and bursting of bubbles play a pivotal role, intricately linked with the rheological properties of magma. In the realm of this complexity, viscoelasticity stands out as a crucial factor influencing infrasound generation resulting from bubble bursting in volcanic systems. The linear Maxwell model, a fundamental representation of magma viscoelasticity, serves as a starting point for our investigation.

In this study, we explore acoustic wave generation induced by bubble bursting in two distinct fluids: a Maxwell-type viscoelastic fluid (CTAB) and a Bingham-type yield-strength fluid (GEL). Despite both fluids exhibiting similar rigidity in the linear elastic regime, their fracture and flow behaviors diverge significantly. The acoustic signals generated by these fluids display pronounced variations, contingent upon factors such as flux (Q) and the depth of air injection (h).

In the case of CTAB, bursting sounds are observed exclusively in the brittle regime at elevated Q, characterized by successive fractures within the fluid. At shallow injection depths, these fractures extend from the nozzle to the fluid surface, creating distinct acoustic waves. Deeper air injection results in crack growth, detachment from the nozzle, ascent to the surface, and subsequent acoustic wave generation. Interestingly, a round cavity, exclusive to small Q, does not produce acoustic waves.

In contrast, GEL consistently forms a round air cavity, with the initial bursting being silent within the same range of Q and h as observed in CTAB. Brittle fractures are notably absent, and acoustic wave generation occurs only with continued air injection, indicating that rigidity alone does not dictate bursting sound; rather, it hinges on fluid brittleness and gas-flow conditions, including rate, depth, and injection history. This experimental exploration sheds light on the nuanced interplay between fluid properties and gas-flow dynamics in the context of acoustic wave generation during bubble bursting.

How to cite: Sánchez, C., Ichihara, M., and Muramatsu, D.: Viscous-Flow-to-Fracture Transition in Linear Maxwell Fluids vs. Yield-Strength Materials: Implications for Magma Fracturing and Acoustic Emission, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5456, https://doi.org/10.5194/egusphere-egu24-5456, 2024.

The mobility and the rheological behaviour of magma within the Earth’s crust is controlled by magma viscosity. Crystallization and crystal morphology strongly affect viscosity, and thus mobility and eruptibility of magma, by locking it at depth or enabling its ascent towards the surface. However, the relationships between crystallinity, rheology and eruptibility remain uncertain because it is difficult to observe dynamic magma crystallization in real time.

Here we show the results of in situ 3D time-dependent, high temperature, moderate pressure experiments performed under water-saturated conditions to investigate crystallization kinetics in a basaltic magma. 4D crystallization experiments with in situ view were performed using synchrotron X-ray microtomography, which provides unique quantitative information on the growth kinetics and textural evolution of pyroxene crystallization in basaltic magmas.  Crystallization kinetics obtained with 4D experiments were combined with a numerical model to investigate the impact of rapid dendritic crystallization on basaltic dike propagation, and demonstrate its dramatic effect on magma mobility and eruptibility.

We observe dendritic growth of pyroxene on initially euhedral cores, and a sur- prisingly rapid increase in crystal fraction and aspect ratio at undercooling ≥30 °C. Rapid dendritic crystallization favours a rheological transition from Newtonian to non-Newtonian behaviour within minutes. Modelling results show that dendritic crystallization at moderate undercooling (30-50 °C) can strongly affect magma rheology during magma ascent within a dike with important implications for the mobility of basaltic magmas within the crust. Our results provide insights into the processes that control whether magma ascent within the crust leads to eruption or not.

How to cite: Arzilli, F., Polacci, M., La Spina, G., Le Gall, N., Llewellin, E. W., Brooker, R. A., Torres-Orozco, R., Di Genova, D., Neave, D. A., Hartley, M. E., Mader, H. M., Giordano, D., Atwood, R., Lee, P. D., and Burton, M. R.: Quantifying dendritic crystallization in hydrous basaltic magmas through 4D experiments with in situ view: implications for magma mobility within the Earth’s crust, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2569, https://doi.org/10.5194/egusphere-egu24-2569, 2024.

Magma ascending through Earth's crust undergoes complex chemical and physical changes that may induce crystallization, a solidification process that deviates from the thermodynamic state of equilibrium. The diverse cooling and deformative regimes suffered by magmas heavily influence crystallization rates, solidification timescales, and consequently, the rheological evolution of magma. This, in turn, significantly impacts the dynamics of volcanic plumbing systems and the associated eruptive styles.

We investigate the rheological changes in Stromboli magma (Italy) during disequilibrium crystallization under non-isothermal sub-liquidus conditions. By systematically varying the cooling rate (1-10 °C/min) and the shear rate (1-10 s^-1), we found that cooling rates significantly influence the solidification path of the basalt, while shear rates have a subordinate effect. By comparing our results with literature data on basalts from Mt. Etna (Italy), we observed distinct timescales and rates of solidification, contributing to unique eruptive dynamics in these volcanic plumbing systems.

How to cite: Di Fiore, F., Vona, A., Di Genova, D., Pontesilli, A., Calabrò, L., Mollo, S., Taddeucci, J., Romano, C., and Scarlato, P.: Disequilibrium viscosity of Stromboli basalt: Implications for magma dynamics in active basaltic systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15563, https://doi.org/10.5194/egusphere-egu24-15563, 2024.

Explosive volcanic eruptions pose significant threats to populated areas by injecting substantial amounts of gas and ash into the atmosphere. These events, resulting from magma fragmentation, are triggered by factors such as limited bubble expansion and relatively high strain rates during ascent, predominantly controlled by chemical composition. Less evolved melts, like andesites and basalts, present challenges in achieving fragmentation conditions due to their inherently low viscosities. Despite this, explosive activity of these magmas occurs. Recent studies highlight the role of Fe-Ti-oxide nanocrystals (nanolites) in increasing viscosity during laboratory measurements. Interestingly, nanolites have been found in natural volcanic products erupted during explosive events. However, the mechanisms and the extent to which nanolite formation affects magma viscosity remain a subject of ongoing debate. Here, we present the first in situ imaging observation of nanolite formation in andesitic melt and thoroughly quantify the impact on melt viscosity. To establish a robust point of comparison, we develop multiple novel viscosity models exclusively using viscosity data from nanolite-free samples. Our findings reveal that above the glass transition temperature, iron oxidation and nanocrystallization readily occur, inducing structural heterogeneities in the nanoscale. The precipitation of magnetite nanocrystals induces a heterogeneous distribution of elements in the residual melt, generating a relatively SiO₂-enriched matrix and Al-enriched shells around the nanolites. This phenomenon results in a substantial, up to 30-fold, surge in magma viscosity at eruptive temperatures. This noteworthy increase in magma viscosity has profound implications for the physical properties of andesitic plugs and domes and could play a critical role in driving the magma towards fragmentation during eruption.

How to cite: Valdivia, P., Zandonà, A., Löschmann, J., Bondar, D., Genevois, C., Canizarès, A., Miyajima, N., Kurnosov, A., Boffa Ballaran, T., Di Fiore, F., Vona, A., Romano, C., Allix, M., Deubener, J., and Di Genova, D.: In situ nanoscale insights on magma viscosity and explosive eruptions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7627, https://doi.org/10.5194/egusphere-egu24-7627, 2024.

Volcanic eruptions show a wide range of eruptive stiles, from low intensity effusive eruption to energetic and powerful explosive eruptions. Different styles of activity can be also seen during the same volcanic eruption, particularly when low viscosity magmas, such as basalts, are involved. Yet, the conditions by which fragmentation of basaltic magmas is achieved (and thus the generation of explosive eruption) are not fully understood. This poses a real challenge to policymakers tasked with mitigating the risks associated with eruptions of basaltic volcanoes.

In order to better understand the fragmentation of low viscosity magma, we employed a brand new apparatus combining a shock-tube apparatus together with a high-speed Schlieren shadow photography and acoustic sensors.

We present preliminary results obtained with this new apparatus performing experiments either with water or different analogue materials. We performed experiments varying also parameters, such as the length and the diameter of the conduit, the fractal dimension of the tube and the pressure gradient.

How to cite: La Spina, G., Taddeucci, J., Spina, L., Pennacchia, F., and Scarlato, P.: Shock-tube experiments and high-speed Schlieren shadow photography for low viscosity analogue materials, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5289, https://doi.org/10.5194/egusphere-egu24-5289, 2024.

To address the nature of mantle-derived melts and submarine geohazards of the Japan Sea, we present new in-situ compositions for clinopyroxene (trace elements) and plagioclase (trace elements and Sr isotopes) from Sites 794 and 797 tholeiitic basalts. Plagioclase and clinopyroxene from Upper Site 797 and Lower Site 794 are characterized by relatively lower incompatible elements relative to those of Lower Site 797 and Upper Site 794. Lower Site 794 bulk-rocks and minerals have slight enrichment in Sr isotope compositions but depletion in trace element ratios. The observed zoning textures together with in-situ geochemical and isotopic diversity within individual plagioclase indicate fractional crystallization and the contribution of heterogeneous melt. In-situ Sr isotopic disequilibria between plagioclase phenocrysts and groundmass likely have important ramifications for the enriched compositional heterogeneity with the significant influence of recycled subduction-related oceanic fluid/sediment beneath the Japan Sea. The initial extension of the Japan Sea was relatively slow, resulting in the slow replenishment of depleted MORB-type melts derived from the upper mantle, and the extensive mixing of the migrating depleted melt with the preformed surrounding enriched melts. It thus forms the slight depletion of the highly incompatible elements but the enriched invariability of the isotopic compositions of Lower Site 794 bulk- rocks and minerals due to the relatively long half-life of the radiogenic elements. In summary, the expansion velocity of the Japan Sea varies from slow to rapid, which leads to time-progressive variations in the mineral and bulk-rock compositions beneath the Japan Sea. The maximum seismic depth of the earthquake decreases with the increase of the expansion velocity of the Japan Sea.

How to cite: Chen, J., Chen, S., and Cheng, Q.: The tectono-magmatic formation and submarine geohazards of the Japan Sea: Constraints from in-situ trace elements and Sr isotopes of plagioclase and clinopyroxene, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13126, https://doi.org/10.5194/egusphere-egu24-13126, 2024.