GMPV7.2 | Volcanic and igneous plumbing systems: from magma chambers to mushy regions
Volcanic and igneous plumbing systems: from magma chambers to mushy regions
Co-sponsored by IAVCEI
Convener: Gianmarco BuonoECSECS | Co-conveners: Fabien Albino, Pavlina Hasalová, Radoslav HurtišECSECS, Juraj Kyselica, Joana MartinsECSECS, Lucia Pappalardo
| Wed, 26 Apr, 16:15–18:00 (CEST)
Room D2
Posters on site
| Attendance Wed, 26 Apr, 10:45–12:30 (CEST)
Hall X2
Posters virtual
| Attendance Wed, 26 Apr, 10:45–12:30 (CEST)
Orals |
Wed, 16:15
Wed, 10:45
Wed, 10:45
In the last few decades, the ideas on the architecture and evolution of volcanic and igneous plumbing systems (VIPS) were profoundly modified. The classical paradigm of the magma reservoir as a large and long-lived liquid-rich region slowly fractionating has been challenged by the view of liquid-poor crystal mush that is repeatedly rejuvenated over the lifespan of the magmatic system. Besides, mushy regions, multiphase regions where melt and solid coexist, appear in various other natural contexts, like sea ice, Earth's-core dynamics, icy moons or general fluid mechanics.

Recent research applying various methods to study these systems have shed light on this complexity, however many questions remain as areas of active research and debate:
• How do plumbing systems develop? How do they evolve over time and in different tectonic settings?
• What are the triggering mechanisms for volcanic eruptions in these systems (e.g., magma reservoir vs mush system)?
• How do magma ascent and dyke propagation occur? Do they occur differently in mush systems?
• What do current monitoring techniques tell us about plumbing systems and precursory phenomena of magma ascent and eruption?
• How do mushy regions evolve? How do processes like thermal and compositional convection, segregation of components, and phase changes work?

This session aims to bring together scientists working in different fields of igneous petrology and geochemistry, structural geology, geodesy, geophysics and material sciences. Studies using different methods such as field studies, compositional and textural analyses, geochronology, structural and metamorphic geology, laboratory experiments, numerical/analogue modelling, and seismic and ground deformation surveys to understand the architecture and dynamics of VIPS as well as the evolution of mushy regions are the core of this session. We, therefore, invite contributions highlighting insights from one of these fields and highly encourage contributions using multi-disciplinary approaches.

This session is sponsored by the IAVCEI Commission on Volcanic and Igneous Plumbing Systems.

Orals: Wed, 26 Apr | Room D2

Chairpersons: Gianmarco Buono, Juraj Kyselica
On-site presentation
Ludmila Maria Fonseca Teixeira, Oscar Laurent, Juliana Troch, Christine S. Siddoway, and Olivier Bachmann

Understanding magmatic activity on the Early Earth remains a challenge for geoscientists, as most of its rock record has been destroyed or altered. The oldest exposed rocks belong to the Tonalite-Trondhjemite-Granodiorite (TTG) plutonic suite, only rarely associated with volcanic units of the same age. For this reason, TTGs are often interpreted as magmas that have not erupted, and their compositions thought to represent melts. However, if TTGs are the left-overs from shallow magma reservoirs that have lost some melt to the now-eroded volcanic record, their bulk composition would be at least partly biased towards crystal cumulates. As post-emplacement metamorphism typically overprints many of the chemical characteristics of the initial magmatic minerals, the more resistant magmatic minerals (quartz and zircons) within sedimentary successions derived from these systems provide the best chance of identifying volcanic lithologies that have been completely eroded. Here we use a novel approach to show that Ti-in-quartz and Ti-in-zircon thermometers can be used to recognise different magmatic sources in sedimentary rocks. In quartz, Ti thermometry calibrated against blue cathodoluminescence obtained from scanning electron microscopy allows for fast and statistically meaningful Ti quantification in hundreds of sedimentary quartz grains. This imaging-derived Ti distribution matches well with the distribution of Ti concentrations obtained by LA-ICP-MS spot measurements of individual crystals. We compare this quartz record to Ti distributions in zircons, which have the benefit of also providing a crystallisation age. We applied these techniques to the Pikes Peak Batholith (CO, USA), a 1.1 Ga A-type granite hosting several pegmatites, and the Tava sandstone, a series of Cryogenian intra-granite sedimentary dikes that represents the oldest terrestrial sediments in the Front Ranges of Colorado. Our data successfully separates plutonic from pegmatitic crystals and shows that quartz and zircon crystals in the Tava Sandstone crystallised at statistically higher temperatures than the ones observed in the Pikes Peak Batholith, implying potential contribution from a volcanic source that is no longer available on the surface. The proposed techniques can therefore be used to identify eroded magmatic lithologies and to estimate proportions of different magmatic components (volcanic, plutonic, pegmatitic) in sediments.

How to cite: Fonseca Teixeira, L. M., Laurent, O., Troch, J., Siddoway, C. S., and Bachmann, O.: Tracking volcanic, plutonic, and pegmatitic sources in sediments: implications for the Early Earth history, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5447,, 2023.

On-site presentation
John Clemens, Scott Bryan, and Nick Petford

A crystallising magma must necessarily pass through a mushy (crystal-dominated) state before it fully solidifies. Similarly, partially melted magma source regions start out as solid-liquid mixtures, albeit with different initial conditions and physical behaviours to melt crystallisation. Thus, localised crystal mushes must be geologically commonplace. Here we examine the pervasive paradigm in which crystal mushes are thought of as the main sources of erupted silicic magmas. Combining geophysical, petrological, chemical and isotopic evidence, as well as theoretical considerations, we emphasise the following points.

  • Models of plutonic rocks as mush cumulates left in magma reservoirs after extraction of fractionated and eruptible rhyolitic magmas are untenable. Compositions of rhyolites and granitic rocks show that, in general and even in well-constrained crustal sections, these are neither compositional equivalents nor compositional complements.
  • In rhyolitic rocks, apparent resorption textures in autocrysts and antecrysts should not necessarily be ascribed to mush heating events or percolative reactive flow of melt through mushes. Embayed and partially resorbed crystals in volcanic rocks, can also reflect rapid disequilibrium crystallisation and growth, partial resorption on near-adiabatic magma ascent or pre-eruption magma mingling/mixing. Likewise, the commonly monomineralic character of glomerocrysts shows that these cannot generally represent disaggregated crystal mushes.
  • The concept of rheologically locked crystal mush is not soundly based in mechanics. Under shear stress, a magma reservoir with 20 vol.% (and less) silicic melt can undergo rapid flow and melt segregation, and potentially collapse any mush column that might exist.
  • Geological mapping demonstrates that mafic floors to silicic plutons are uncommon, calling into question the idea of mush reactivation through heating by mafic magma influx.
  • An implication of the mush model is that most magma, mush and rock that is generated cannot be erupted, and the plutonic:volcanic ratio is probably rather greater than the 10:1 that is generally supposed. Thus, very large silicic eruptions (>1000 to 10,000 km3 in erupted volume) pose problems for mush models, in terms of the complementary mush volume that would be required.

We recommend that mush-based petrogenetic models be seriously reconsidered. Crystal mushes play a role, but this model should not be invoked to explain all volcanism. We present an internally consistent vision for silicic magma systems, underpinned by fundamental geological, petrological and mechanical observations and principles. This model obviates the need for ubiquitous, expedient mush zones or columns, and allows the crust to remain mechanically stable.

How to cite: Clemens, J., Bryan, S., and Petford, N.: Silicic magmas, crystal mushes, granitic plutons and rhyolitic eruptions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3279,, 2023.

On-site presentation
Catherine Annen and Roberto Weinberg

Many conceptual models in igneous petrology and volcanology involve the protracted presence of large volumes of magmatic mushes in the crust. We used 1D numerical simulation to explore how the inflow of aqueous fluids into a section of crust facilitates melting and stabilizes columns of mush.

Inflow of H2O into a crustal section whose temperatures are above the water-saturated solidus results in the following chain of processes: it induces melting; melting consumes latent heat; latent heat consumption lowers temperatures; reduced temperatures cause an increase in heat flow into the melting region. In detail, the behaviour of the upward migration of the water-fluxed melting front depends on the relative ratios between heat and H2O diffusivities.  The upwards flow of H2O is accompanied by melting until the H2O front reaches the water-saturated solidus isotherm.  If the transfer of H2O through chemical diffusion enhanced by advection (effective diffusivity) is slower than the transfer of heat, the melting front progress smoothly upwards. If the transfer of H2O, aided by advection, is faster than the transfer of heat, then the depth of the melting front oscillates up and down, resulting in parts of the crust going through more than one episode of melting.

Our results show that H2O-fluxed melting of an haplogranite crust produces columns of mush that are more vertically extensive and more long-lived than dehydration melting of a biotite-gneiss, with the amount of melt depending on both the quantity of H2O in the system and how fast it diffuses relative to heat. Thus, the net effect of the inflow of H2O into a hot crust is to cause cooling and lowering of the heat flow through the crust to the surface while increasing the heat content stored in the crust, in the form of a low-temperature mush column.

How to cite: Annen, C. and Weinberg, R.: H2O-fluxed melting buffers crustal temperatures and stabilizes magmatic mushes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5296,, 2023.

On-site presentation
Jennifer Castelino, Susanna Ebmeier, Samuel Pegler, and Oliver Harlen

Historically in volcanology, it was thought that a magmatic system consisted of a simple spherical liquid chamber of magma, surrounded by host rock. However, recent evidence suggests that large volumes of melt are disseminated in crystal mush regions, leading to large trans-crustal mushy-magmatic systems. The presence of a crystal mush has many implications for the characteristics of surface displacements caused by magma movements, such as during an intrusion or eruption. While many previous studies have modelled ground deformation due to magma mobilisation using a simple point source or dislocation model embedded in an elastic half space, few studies have accounted for the existence of mush as a poroelastic or viscoelastic material. 

Current studies suggest that surface deformation can be caused by both poroelastic and viscoelastic deformation of the mush. With our model we account for this behaviour on a poroviscoelastic spectrum demonstrating the significance of this rheology for observations of deformation. We expand on existing poroelastic and viscoelastic models to produce an encompassing poroviscoelastic model that can predict the characteristics of measurable deformation at the Earths surface. In order to do this, we first present a one-dimensional generalised model that describes the behaviour of a poroviscoelastic material. We then adapt this model to a relevant three-dimensional geometries to provide tools for analysing the impact of magma intrusion or eruption for a given system and to provide insight into resulting deformation signals.

How to cite: Castelino, J., Ebmeier, S., Pegler, S., and Harlen, O.: Poroviscoelastic Dynamics of Mushy Magmatic Systems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8560,, 2023.

On-site presentation
Richard F. Katz, John F. Rudge, David Kohlstedt, and Lars N. Hansen

When a confined packing of sand grains is sheared, the shear strain generates a compressive normal stress [1].  If the sand is unconfined, the shear leads to a volume expansion of the pore space between grains, low fluid pressure, and imbibition of fluid [1]. This physics is known as dilatancy [2].   We hypothesise that dilatancy occurs within a deforming, basalt-saturated aggregate of olivine grains. We extend a theory for the dynamics of partially molten rock [3,4] to describe this.  We analyse the theory in the geometry of laboratory experiments and show that the dilatancy hypothesis can explain a variety of robust, non-trivial features of experiments. These include the angle of melt bands and the inward melt segregation in torsional and Poiseuille flows [5,6].

One mechanism by which partially molten rock can deform is grain-boundary sliding with geometric incompatibility between grains accommodated by mass diffusion. Dilatancy would also accommodate granular incompatibility.  The balance of diffusive and dilatant accommodation of compatibility might depend on the ratio of shear stress to confining stress.  Rock sheared by a larger stress would strain faster and potentially undergo more dilatant accommodation.  Moreover, shear strain could be associated with an anisotropy in the generated normal stress.  At smaller melt fractions, partially molten rock might create greater dilatancy stress, but would also have a smaller resistance to (de)compaction.  Our theory addresses these issues.

A theory of anisotropic viscosity [7,8] has previously been proposed to explain the features of deformation experiments on olivine aggregates. We compare and contrast its physical basis and predictions with those of dilatancy.

[1] Guazzelli, and Pouliquen, Rheology of dense granular suspensions, J Fluid Mech, 2018.

[2] Reynolds, LVII. On the dilatancy of media composed of rigid particles in contact. With experimental illustrations. The London, Edinburgh, and Dublin Phil Mag and J Sci, 1885.

[3] McKenzie, The generation and compaction of partially molten rock, J Pet, 1984.

[4] Katz, The Dynamics of Partially Molten Rock, Princeton University Press, 2022.

[5] King, Zimmerman, & Kohlstedt. Stress-driven melt segregation in partially molten olivine-rich rocks deformed in torsion. J Petrology, 2010.

[6] Quintanilla-Terminel, Dillman, Pec, Diedrich, & Kohlstedt. Radial melt segregation during extrusion of partially molten rocks. Geochem. Geophys. Geosys., 2019.

[7] Takei & Holtzman.  Viscous constitutive relations of solid–liquid composites in terms of grain boundary contiguity: 1. Grain boundary diffusion control model. JGR: Solid Earth, 2009.

[8] Takei & Katz. Consequences of viscous anisotropy in a deforming, two-phase aggregate. Part 1. Governing equations and linearized analysis. J Fluid Mech, 2013.

How to cite: Katz, R. F., Rudge, J. F., Kohlstedt, D., and Hansen, L. N.: Granular dilatancy of deforming, partially molten rock, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3098,, 2023.

On-site presentation
Gabriel Girela Arjona, Paolo Papale, Deepak Garg, Simone Colucci, and Chiara Montagna

The Krafla caldera, located in the Northern Volcanic Zone of Iceland has become the most studied volcano in the country since its last eruption, the Krafla Fires, happened between 1975 and 1984. From that moment, an extensive monitoring system has been developed in the caldera, focused on both geothermal exploration and production, as well as scientific research. In 2009, the IDDP-1 exploratory well aiming to 4 km depth in search of supercritical hydrothermal fluids got stuck at 2.1 km, retrieving quenched glass cuttings. It was then understood that an unexpected and undetected rhyolitic magma body had been drilled. This body stood without apparent signs of crystallization at the rooftop, opposing the most common belief that magmatic bodies at shallow depths should present a mushy region adjacent to the body’s walls.

We aim to simulate the dynamics of the magma encountered in Krafla. We perform 2D numerical simulations of the magma thermo-fluid dynamics, assuming thermodynamic equilibrium in a sill-like, disk-shaped body 1200 metres wide and 260 metres deep. We include a 100 metres thick aureola with fixed boundary temperature of 350 ºC and initial linear temperature gradient up to 900 ºC in the magmatic body.

In order to simulate the magma dynamics we use the software GALES (Garg and Papale, Frontiers in Earth Sciences 2022), which solves the 4D dynamics of multi-component fluids in geometrically complex domains. Melt-solid-gas thermodynamic are computed with rhyoliteMELTS (Gualda et al., J. Petrol. 2012) using the alphaMELTS-2 front end (Smith & Asimow, GCubed 2005). The properties density, heat capacities, single-phase and multiphase non-Newtonian viscosity, thermal conductivity, and compressibility, are locally computed as a function of pressure, temperature, phase distribution, and phase composition. The results allow a first evaluation of the conditions under which a crystal mush can form and be stable close to the roof and margins of a shallow magmatic intrusion.

How to cite: Girela Arjona, G., Papale, P., Garg, D., Colucci, S., and Montagna, C.: 2D numerical simulation of the shallow magmatic body at Krafla, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2030,, 2023.

On-site presentation
Francesco Maria Lo Forte, Alessandro Aiuppa, Federica Schiavi, Estelle F. Rose-Koga, Silvio G. Rotolo, and Vittorio Zanon

Understanding the pre-eruptive volatile contents in magmas is critical to charactering the magmatic plumbying systems that feed acative volcanoes, and is key to volcano monitoring and volcanic hazard assessment. Silicate melt inclusions (MIs) hosted in primitive minerals are a powerful tool to definite parental melt volatile contents, and to track the volatile degassing path upon magma ascent and decompression.

Here, we apply different analyses (Raman Spectroscopy, Nano SIMS, Electron microprobe, Laser Ablation ICPMS) for the characterisation of major and trace elements and volatiles in silicate melt inclusions entrapped in minerals from recently erupted tephra by Fogo Volcano in Cape Verde archipelago, one of the most active intraplate volcanic systems on Earth.Our aims are to (i) characterise the pressure-dependent magma compositional changes taking place during magma storage and ascent, (ii) model magmatic degassing and (iii) constrain the magmatic source, and the rates/modes of magma ascent prior and during eruption.

Seventeen MIs hosted in twelve olivine phenocrysts (Fo79-85) were examined from tephra samples of two distinct periods of the last 10 ky of activity of the volcano. In detail, we studied basanitic (SiO2 ~42 wt.%, MgO ~4.8 wt. %) and alkali-rich (Na2O + K2O = 6.9 wt.%) tephra samples of São Jorge (early Holocene activity, ~10 ka) and of the most recent eruptions (1951 and 2014/15).

Results reveal high concentrations of incompatible trace elements (e.g.,˜70 ppm Nb) and dissolved volatiles ( ˜2.1 wt.% H2O and ≥1 wt.% CO2) in the parental (un-degassed) magma. We use different H2O-CO2 solubility models to estimate MI entrapment pressures along the magma plumbing system. The deepest entrapment pressures of  ˜1000-1400 MPa (corresponding to  ˜ 30-46 km) are recorded in Holocene products, while the inclusions from the recent eruptions indicate shallower entrapment pressures of  ˜ 350-1100 MPa (˜ 11-35km). These entrapment pressure data, combined with previous independent barometric results, demonstrate a relatively deep (30-40 km) magma source for Fogo eruptions. Our results are the first to unambiguously demonstrate the CO2-rich nature of alkali-rich mafic melts feeding intraplate volcanism at Cape Verde.

How to cite: Lo Forte, F. M., Aiuppa, A., Schiavi, F., Rose-Koga, E. F., Rotolo, S. G., and Zanon, V.: A CO2-rich basanitic magma source for Fogo Volcano (Cape Verde Archipelago) inferred from volatile contents in silicate melt inclusions., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2783,, 2023.

Virtual presentation
Penny Wieser, Adam Kent, Charlotte Devitre, Esteban Gazel, Christy Till, Paul Wallace, Emily Johnson, and Geoff Abers

The Cascade Volcanic Arc consists of numerous large stratovolcanoes that stretch from Lassen Volcanic Center in northern California, through Oregon and Washington, to the Garibaldi Volcanic Belt in British Columbia, as well as ~2300 individual vents – many in distributed mafic volcanic fields. Studies in recent years have reviewed differences in the distribution and eruptive volumes of vents, geochemical compositions and heat flux along strike, including identification of a factor of two variation in the flux of mantle-derived basalt along the arc. We wish to identify whether these along-arc changes in magma flux are manifested as changes in crustal storage depth (a mantle control), or whether magma storage is controlled by crustal processes (e.g., extension state, lithological or rheological boundaries). We compile available geophysical constraints on magma storage depths (InSAR, seismics, magnetotellurics) for 13 major edifices, and compare these to pressures calculated from mineral-only barometers applied to compilations of clinopyroxene and amphibole compositions, and to melt inclusion saturation pressures. This compilation highlights the variable amount of data available for different edifices, with abundant geochemical and geophysical data available for some systems (e.g., Lassen Volcanic Center and Mount St. Helens) but very limited data available for others (e.g., Glacier Peak and the volcanoes of the Garibaldi Volcanic Belt, Mount Jefferson, Mount Rainier, The Three Sisters).

Within current uncertainties, the compiled data suggest that the storage of intermediate to felsic magma occurs at remarkably constant depths along the arc, with seismic, geodetic and petrological estimates lying within the upper 200 ± 200 MPa of the crust. These estimates are consistent with previous work suggesting widespread shallow magma storage within the upper crust in many arcs. However, the storage depths of the most mafic magmas are best constrained using melt inclusion vapour saturation pressures. While hundreds of melt inclusion analyses have been performed in the Cascades, only 7 of these melt inclusions had direct CO2 analyses performed on the glass and vapour phase (although three additional studies performed theoretical corrections as a first order estimate of bubble CO2 contents). We performed 339 Raman analyses of vapour bubbles from 9 volcanic centers, using in-situ heating methods to redissolve vapour bubble carbonate where present. Using published glass-only analyses from the same samples, we calculate that 20-95% of CO2 is held within the vapour bubble, meaning that magma storage depths have been underestimated by a factor of 2-5X in many volcanic fields. This new data supports a growing body of literature showing that the majority of CO2 in melt inclusions from all tectonic settings is held in the vapour bubble. Our results indicate that the cinder cones and mafic volcanic fields surrounding the larger Cascade edifices crystallize olivine in the middle to lower crust, deeper than has previously been inferred in most cases. We suggest that the substantial increase in storage depths revealed by analyzing melt inclusion vapor bubbles would not be isolated to the Cascades. Mafic magma storage depths in arcs worldwide likely need re-evaluating to account for vapour bubble CO2

How to cite: Wieser, P., Kent, A., Devitre, C., Gazel, E., Till, C., Wallace, P., Johnson, E., and Abers, G.: Magma Storage depths along the Cascade Arc: Knowns and Unknowns, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10236,, 2023.

On-site presentation
Carmine Magri, Elisa Trasatti, Valerio Acocella, Carlo Del Gaudio, Ciro Ricco, and Mauro Antonio Di Vito

Understanding how shallow magma transfer occurs at volcanoes is important to have a conceptual model of how a volcano works and, possibly, to forecast where and when an eruptive vent may open. However, shallow magma transfer is difficult to detect at poorly monitored volcanoes, and particularly at calderas, characterized by areal volcanism. Magma transfer before the last 1538 eruption at Campi Flegrei caldera (Italy) was previously studied using historical, archaeological, and geological data. Here, we extend that dataset to 1650, to uncover any magma transfer during overall post-eruptive phase. Results highlight two post-eruptive subsidence phases, separated by a previously undocumented uplift during 1540-1582. Uplift highlights the pressurization of the central (~3.5 km depth) and peripheral (~1 km depth) pre-eruptive sources, suggesting an aborted eruption. The subsidence events are explained by the depressurization of the central source and pressurization of a deeper magmatic layer (~8 km depth). Therefore, despite the overall post-eruptive deflation, after 1538 the deeper reservoir experienced continuous magma supply, with magma almost erupting between 1540-1582, challenging the common assumption of post-eruptive relaxation. This underlies the importance of monitoring the deeper magmatic systems, also after eruptions, to properly assess their eruptive potential.

How to cite: Magri, C., Trasatti, E., Acocella, V., Del Gaudio, C., Ricco, C., and Di Vito, M. A.: Dynamics of Campi Flegrei caldera (Italy) after the 1538 AD eruption, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3174,, 2023.

On-site presentation
Lisa Ricci, Francesco Frondini, Daniele Morgavi, Alessandra Ariano, Guillaume Boudoire, Mickael Laumonier, Stefano Caliro, Carlo Cardellini, Ulrich Kueppers, and Giovanni Chiodini

The French Massif Central (central-southern France) and the Eifel region (central-western Germany) are both young volcanic systems and considered dormant. They are part of the European Cenozoic Rift System (ECRIS) and show similar surficial manifestations of ongoing hydrothermal activity. For example, both areas exhibit numerous low flow rate CO2-rich springs, mainly occurring in concomitance of faults and fractures inherited from the Variscan orogeny.

Here, the chemical and isotopic characterization of different fresh water bodies (springs, wells, rivers and volcanic lakes) has been provided. The composition of dissolved gases and the isotopic signatures of dissolved carbon indicate that meteoric water infiltrated and then interacted with a CO2-rich, mantle-related, component. The majority of studied water samples exhibit pCO2 between 0.3 and 1 bar and the total dissolved inorganic carbon (TDIC) is of the order of 0.01 mol/kg. At surface, most spring water samples are oversaturated with calcite, dolomite, chalcedony and quartz and are in equilibrium with amorphous silica. The correlation between the TDIC and its isotopic composition (δ13CTDIC) suggests that part of the analysed water samples experienced a degassing process prior to or immediately after emergence. The computed CO2 flux transported by groundwaters is of the same order of magnitude of the global baseline theorized for geothermal areas. This indicates that passive rifts systems contribute to the atmospheric CO2 content and highlights the importance of taking into account each carbon source in the study of the global carbon cycle.

How to cite: Ricci, L., Frondini, F., Morgavi, D., Ariano, A., Boudoire, G., Laumonier, M., Caliro, S., Cardellini, C., Kueppers, U., and Chiodini, G.: Chemical and isotopic signatures of fluids circulating in the Massif Central (France) and in the Volcanic Eifel (Germany): evidences of similar features and of an ongoing degassing process., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13906,, 2023.

Posters on site: Wed, 26 Apr, 10:45–12:30 | Hall X2

Chairpersons: Gianmarco Buono, Juraj Kyselica
Juraj Kyselica and Peter Guba

Aqueous salt solutions are the simplest systems in which to study multicomponent solidification with the mushy-layer growth [1]. The reactive melting/dissolution often leads to the formation of so-called chimneys, narrow channels devoid of solid through which the buoyant fluid escapes the mush. In sea ice, the channels provide the flux of saltier water into the ocean [2]. Tabular dunite bodies are believed to provide the evidence for channel formation due to the reactive dissolution of the partially molten mantle [3]. The channelized transport of volatiles is relevant for magma chamber evolution [4].

Modelling coupled with experiments play a crucial role in the investigation of mushy layers. Of importance is the relationship between the initial conditions, the cooling history and the evolution of the mush. The full model of transient evolution of a mushy layer with chimneys is too complicated even for numerical treatment ([5], [6]). To date, most of the theoretical studies focused on the steady-state mushy layers with constant growth rate. We aim at understanding some aspects of the evolution of the channelized mushy-layer convection related to the more realistic situations, namely finite extent of the domain and time-dependent cooling.

We report on a combined experimental and theoretical study directed to investigate the interaction of chimney convection and solidification in a binary fluid cooled from below. The experiments with aqueous ammonium chloride are conducted in a tank where temperature, concentration, and mush thickness have been monitored.  We quantify a solute flux between the mush and the liquid, and determine a relationship between the time-dependent cooling rate, the released potential energy, the porosity and the mush height, describing the temporal evolution of the system towards a steady state. To understand the behavior of the system, we develop a model of the evolution of the gross characteristics of the mush/liquid system, where the velocity of the fluid leaving the chimney is a function of the difference between the concentration in the liquid and the vertically averaged  concentration in the mush.

This research was funded by the Mobility Plus Project supported by the Czech Academy of Sciences (SAV-23-06) and the Slovak Academy of Sciences (CAS-SAS-2022-01). We thank J. Šimkanin for technical assistance with the experiments.


[1] Kumar, V., Sakalkale, K., Karagadde, S., Convection-induced bridging during alloy solidification. Phys. Fluids 34, 053605, 2022

[2] Anderson, D. M. and Guba P., Convective phenomena in mushy layers. Annu. Rev. Fluid Mech. 52, 93-119, 2020

[3] Rees Jones, D. W. and Katz, R. F., Reaction-infiltration instability in a compacting porous medium. J. Fluid Mech. 852, 5-36, 2018

[4] Annen, C. and Burgisser, A., Modeling water exsolution from a growing and solidifying felsic magma body. Lithos 402-403, 105799, 2021

[5] Wells, A. J., Hitchen, J. R. and Parkinson, J. R. G., Mushy-layer growth and convection, with application to sea ice. Phil. Trans. R. Soc. A 377, 20180165, 2019

[6] Katz, R. F. and Worster, M. G., Simulation of directional solidification, thermochemical convection, and chimney formation in a Hele-Shaw cell. J. Comput. Phys. 227, 9823-9840, 2008

How to cite: Kyselica, J. and Guba, P.: Channelized convection and solidification of a binary melt cooled from below: an experimental and theoretical study, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1928,, 2023.

Francesca Silverii, Lorenzo Mantiloni, Eleonora Rivalta, and Torsten Dahm

The Rhenish Massif in Central Europe, which includes the Eifel Volcanic Fields, has shown ongoing ground deformation and signs of possible magmatic activity. A buoyant plume with distributed partial melts exerting uplift forces at the bottom of the lithosphere has been proposed to explain the current deformation; the hypothesis that melt is accumulating in the crust or lithospheric mantle has not been explored yet. Here, we test deformation models in an elastic half space considering sources of varying aspect ratio, size and depth. We explore the effects of data coverage, noise and uncertainty on the inferred source parameters. We find that melt accumulation within the lithosphere cannot be ruled out if this emplacement occurs in sub-horizontal structures expanding at the rate of 0.045 km^3/yr. We discuss our results in the context of plume and underplating models worldwide and elaborate on what further observations may be needed to better constrain the structure of the Eifel magmatic system.

How to cite: Silverii, F., Mantiloni, L., Rivalta, E., and Dahm, T.: Lithospheric sill intrusions and present-day ground deformation at Rhenish Massif, Central Europe, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6119,, 2023.

Gianmarco Buono, Stefano Caliro, Giovanni Chiodini, Flora Giudicepietro, Francesco Maccaferri, Giovanni Macedonio, Lucia Pappalardo, Giacomo Pozzi, Elena Spagnuolo, and Anna Tramelli

The Campi Flegrei caldera is in an unrest phase, manifested by increasing ground uplift, seismicity and hydrothermal activity since 2005. The seismicity mainly involves the first 3 km below the main hydrothermal site of Solfatara-Pisciarelli, where an intensifying heating and pressurization phase is inferred by gas geothermobarometers. Geodetic data inversions generally localize the deformation source around this depth in the central sector of the caldera. Two driving mechanisms of magmatic and non-magmatic unrest have been proposed. Recent studies have demonstrated that the main magma storage area is localized at a depth of ~8 km and is periodically recharged by a mafic deeper source. Magmatic fluid transfer from these reservoirs toward the surface can occur through small-volume shallow intrusions, and can occasionally culminate in an eruption. In this frame, investigating the physical properties of subsurface rocks can be valuable to define the source of the current and past unrest. In fact, they can largely affect local stress and strength, controlling volcano dynamics. We explored subsurface rocks of the Campi Flegrei caldera, extracted from 3-km-deep exploratory geothermal wells. X-ray microtomography investigations were combined with in-situ mechanical experiments (4D imaging at room temperature and dry conditions) to characterize rock properties and link them with 3D microstructural changes. The cores were collected according to the most representative stratigraphic levels and are dominated by tuffs alternating with minor lavas. The mineralogical assemblage reflects different depth-dependent T-P conditions ranging from argillic alteration (150 °C) to thermometamorphism (350 °C). Their tensile strength varies between 2 and 15 MPa and shows a general increase with depth, suggesting that a similar excess pressure is required within a potential shallow chamber to drive magma transfer. Combining this preliminary data with correspondent elastic properties, it can be inferred that a volume change between 0.001 and 1 km3 is sufficient to cause rupture conditions in a sill with radius between 0.5 and 5 km, respectively. These results are in agreement with magma volumes erupted during past eruptions at Campi Flegrei caldera, and particularly consistent with volcanological and petrological data of products from small-scale events.

How to cite: Buono, G., Caliro, S., Chiodini, G., Giudicepietro, F., Maccaferri, F., Macedonio, G., Pappalardo, L., Pozzi, G., Spagnuolo, E., and Tramelli, A.: The influence of physical properties of crustal rocks on volcanic unrest at Campi Flegrei caldera, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11866,, 2023.

Anna Tramelli, Flora Giudicepietro, Cataldo Godano, Patrizia Ricciolino, Massimo Orazi, Stefano Caliro, Prospero De Martino, and Giovanni Chiodini

The knowledge of the dynamic of the Campi Flegrei calderic system is a primary goal to mitigate the volcanic risk in one of the most densely populated volcanic areas in the world. From 1950 to 1990 Campi Flegrei suffered three bradyseismic crises with a total uplift of 4.3 m. After 20 years of subsidence, the uplift started again in 2005 accompanied by a low increment of the seismicity rate. In 2012 an increment in the seismic energy release and a variation in the gas composition of the fumaroles of Solfatara/Pisciarelli (in the central area of the caldera) were recorded. Since then, a slow and progressive increase in phenomena continued until today. We analyzed the Campi Flegrei seismic catalogue from 2000 and the main seismic swarms in order to look for any variation in the seismic parameters and compare them with other geophysical information. A remarkable correlation between earthquake cumulative number, CO/CO2 values and vertical ground deformation is evidenced. Moreover, the focal mechanisms show an agreement with the tensional stress induced by the caldera uplift. Most of the swarms and remaining seismicity delineate a highly fractured volume extending vertically below the Solfatara/Pisciarelli vents, where gases find preferential paths to the surface triggering earthquakes. The main swarms are located below this volume where the presence of a rigid caprock is still debated.

The correlation between the seismological, geochemical and geodetic observables can be interpreted in terms of injection of magmatic fluids into the hydrothermal system or its pressurization. The comparison between the geophysical information and the seismicity leads us to interpreted the current unrest in term of a gradual increment in the activity of the wide hydrothermal system whose most evident manifestation is the enlargement of the fumarolic field of Pisciarelli.

This contribution was funded by the MIUR project PRIN-2017 WZFT2p “Stochastic forecasting in complex systems” and by the INGV Project LOVE-CF.

How to cite: Tramelli, A., Giudicepietro, F., Godano, C., Ricciolino, P., Orazi, M., Caliro, S., De Martino, P., and Chiodini, G.: The seismicity of Campi Flegrei in the contest of the current unrest, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12800,, 2023.

Lucia Pappalardo, Stefano Caliro, Anna Tramelli, and Elisa Trasatti

The Campi Flegrei caldera (Italy) is one of the most dangerous volcanoes in Europe and is in a new phase of an unrest that has persisted intermittently for several decades. The geophysical and geochemical changes accompanying the unrest stimulated a number of scientific investigations that resulted in a remarkable production of articles over the last decade. However, large uncertainties still persist on the architecture of the caldera plumbing system and on the nature of the subsurface processes driving the current (and previous) unrest. LOVE-CF is a 4-years project started in October 2020 and funded by INGV, with the aim of improving our ability to forecast the behaviour of the restless Campi Flegrei caldera, through a multi-disciplinary approach based on a combination of volcanological, petrological, geochemical, seismological and geodetic observations, as well as experiments and numerical models. We aim at reconstructing a comprehensive view of the architecture and the dynamics of the plumbing system, through the investigation of representative past events, as a framework to interpret geochemical and geophysical changes observed during past and current unrests. This will allow us to better evaluate the source of the current volcanic unrest (magmatic or not magmatic) and to forecast its possible evolution towards an eruption. Merged petrological and geochemical results show the existence of a multi-depth magmatic system constituted by a shallow (150–200 MPa, corresponding to 6–8 km) felsic (trachyte-phonolite) storage area, recharged by a mafic (trachybasalt-shoshonite) deeper (>200 MPa, > 8 km) source. Model simulations of magma degassing show that the measured (N2-He-CO2) geochemical changes at the fumaroles of Solfatara hydrothermal site in the last decades are the result of massive (about 3 km3) magma degassing in the deep portion (≥200 MPa, >8 km of depth) of the plumbing system. This degassing mechanism would be able to flood the overlying hydrothermal system with hot magmatic fluids, thus heating and fracturing the upper crust inducing the shallow seismicity and deformation measured at the caldera.  Moreover, numerical simulations have been applied to model the actual deformation time series as well as those obtained by archeological data regarding quote variation since 35 BC until the last 1538 AD Monte Nuovo eruption. Results show that the combined activity of the magmatic fluids sources recognized at different depths can justify the ground deformation observed during the whole caldera history. 

How to cite: Pappalardo, L., Caliro, S., Tramelli, A., and Trasatti, E.: Linking surface Observables to sub-Volcanic plumbing-system:a multidisciplinary approach for Eruption forecasting at Campi Flegrei caldera (Italy)., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13708,, 2023.

Craig Magee, Christopher Jackson, and Jonas Kopping

The structure of magma plumbing systems controls the distribution of volcanism and influences tectonic processes. Yet determining the structure of such plumbing systems is difficult because: (1) active intrusion networks cannot be directly accessed; (2) field outcrops are commonly limited; and (3) geophysical data imaging the subsurface are restricted in areal extent and resolution. Our current view is thus that plumbing systems are dominated by the vertical transfer of magma via dykes and/or some form transcrustal networks of conduits and reservoirs, extending from a melt source to overlying reservoirs and eruption sites. Whilst there is a wealth of evidence to support the occurrence of vertically dominated systems, field- and seismic reflection–based observations highlight that extensive lateral magma transport (over 10’s to 1000’s kilometres) may occur within mafic sill-complexes. Most mafic sill-complexes occur within sedimentary basins, but some intrude crystalline continental crust and volcanoes, and consist of interconnected sills and inclined sheets. Yet the extent to which active volcanic systems and rifted margins are underlain by sill-complexes remains poorly constrained, despite important implications to elucidating magmatic processes, melt volumes, and melt sources. Furthermore, questions remain as to how magma can travel through sill-complexes, across vast areas, without erupting or freezing. Here, we demonstrate how we can use geophysical data (particularly seismic reflection), tempered with geological structural, petrological, and chemical data, to map sill-complexes and understand their construction.

How to cite: Magee, C., Jackson, C., and Kopping, J.: Lateral magma flow in sill-complexes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13263,, 2023.

Andreas Möri, Dmitry Garagash, and Brice Lecampion

Buoyant hydraulic fractures (HF) are a viable approach to model propagating magmatic intrusions in the lithosphere. Solutions for fully planar three-dimensional (3D) HF suggest the existence of a family of solutions as a function of fluid and solid properties [1]. Theoretically, such buoyant fractures ascent in a self-sustained manner if no heterogeneities exist.

We investigate the presence of a neutral buoyancy line (NBL) as a possible arrest mechanism of such buoyant self-sustained fractures. The NBL stems from a change in solid density and leads to a reversed buoyancy. In other words, the rock density in the upper layer is smaller than the density of the fluid, whereas the inverse is true in the lower layer (see figure 1). When a vertically propagating dike encounters this kind of heterogeneity, three outcomes are possible: The fracture can laterally spread along the NBL, arrest without lateral propagation and possibly initiate an intermediate magma chamber, or “burst” through the upper layer and become a feeder dike.

We focus on the first two possible outcomes and exclude the emergence of feeder dikes. Using numerical simulations, we delimit the conditions distinguishing the arrest from lateral spreading and characterize the transition from vertical to lateral dike propagation under various conditions.

Our simulations emphasize the dependence of lateral diking on the ratio between the total volume release and a limiting, minimal volume required for the emergence of self-sustained vertical dikes [2, 3, 4]. If the release volume is sufficient, the dike spreads laterally along the NBL. In the resulting horizontal intrusion, two-dimensional (2D) solutions of horizontal cross-sections in the viscosity- [5] and the toughness-dominated regime emerge. The emergence of the respective limits strongly correlates with the depth of the source magma chamber, a problem parameter we vary to compare simulation results with observations from lateral dike rifting intrusions. In particular, we discuss if these rifting sequences require a shallow, proximal to the NBL magma chamber or can originate from a deeper source as vertical dikes and then transition to lateral propagation.

Figure 1: Buoyant hydraulic fracture encountering a neutral buoyancy line.


[1] A. Möri and B. Lecampion. Three-dimensional buoyant hydraulic fractures: constant release from a point source. J. Fluid Mech., 950, A12, 2022.

[2] D. I. Garagash and L. N. Germanovich. Gravity driven hydraulic fracture with finite breadth. In Proceedings of the Society of Engineering Science 51st Annual Technical Meeting, 2014.

[3] D. I. Garagash and L. N. Germanovich. Notes on propagation of 3D buoyant fluid-driven cracks. arXiv:2208.14629, 2022.

[4] T. Davis, E. Rivalta, and T. Dahm. Critical fluid injection volumes for uncontrolled fracture ascent. Geophys. Res. Lett., 47, 14, 2020.

[5] J. R. Lister. Buoyancy-driven fluid fracture: similarity solutions for the horizontal and vertical propagation of fluid-filled cracks. J. Fluid Mech., 217:213–239, 1990.

How to cite: Möri, A., Garagash, D., and Lecampion, B.: Transition from Vertical to Lateral Diking at the Neutral Buoyancy Line, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15623,, 2023.

Luca Kiri, Máté Szemerédi, and Elemér Pál-Molnár

The Ditrău Alkaline Massif (DAM; Eastern Carpathians, Romania) is a unique pluton with a presently tilted vertical cross-section of a pre-existing alkaline magma storage system, which consists of various rock types from ultramafic cumulates to granitoid rocks, crosscut by lamprophyre, syenite, ijolite and tinguaite dykes. The igneous event took place in an intra-plate, rift-related tectonic environment during the Middle–Late-Triassic.

During the roughly 190 years of scientific exploration of the DAM, felsic rocks were considered as homogeneous, uniform units of the massif. However, recently identified structural, textural and geochemical features revealed open-system magmatic processes that operated during the crystallization of the DAM (e.g., Batki et al., 2018). The heterogeneity of the felsic rocks can only be revealed on micro-scale and is mostly determined by the presence of mafic mineral aggregates. However, felsic minerals are also characterised by disparate microtextural traits. The felsic rocks in the northern part of the DAM were classified into two groups based on their field occurrence and microtextural features: (1) felsic rocks (lacking or containing scant mafic phases) spatially related to mafic rocks and (2) felsic rocks (with mafic minerals and clusters) spatially unrelated to mafic rocks (Kiri et al., 2022).

Distinct attributes (e.g., idiomorphic–hypidiomorphic feldspars aligned parallel to their crystal faces, contact melting and embayment, feldspar aggregates) of Group 1 suggest the settling and accumulation of the rock-forming minerals. Such textural features can also be observed in Group 2. Isolated mafic phases are scant in rocks of the latter group; however, different variants of clusters containing identical or different mafic minerals are prevalent. There are other particular textural properties: feldspar megacrysts, adjacent feldspars with contrasting zoning sequences and biotite clusters in the metamorphic country rock and xenoliths.

The formation of mafic clusters could be associated with: (1) mineral accumulation, (2) magma mixing–mingling and (3) entrainment of exotic (crustal or restitic) materials. Petrologic and geochemical evidences of such processes have already been reported from the DAM (e.g., Batki et al., 2018). Some of the clots are polycrystalline pseudomorphs after antecrysts and/or xenocrysts (e.g., clinopyroxene, green amphibole, garnet) that were entrained by the interplay between different magma batches or by country rock contamination. All cluster varieties revealed a transition from fresh aggregated crystals through imperfect to complete replacement. Hence, disparate clots could imply different phases of hybridisation of the incorporated materials.

Micro-scale characteristics of felsic crystal accumulation, mafic clusters and flow fabrics as well as metamorphic wall rock xenoliths indicate that the studied rocks were formed under dynamic magmatic circumstances. Crystal settling, shear flow, convection, along with numerous open-system igneous processes (e.g., magma mixing and mingling, magma recharge, crystal/mush transfer and recycling, wall rock assimilation) played an important role in the petrogenesis of the felsic suite of the DAM.



Batki, A., Pál-Molnár, E., Jankovics, M.É., Kerr, A.C., Kiss, B., Markl, G., Heincz, A., Harangi, Sz. (2018). Lithos, 300–301, 51–71.

Kiri, L., Szemerédi, M., Pál-Molnár, E. (2022). Central European Geology, 65, 1, 49–76.

How to cite: Kiri, L., Szemerédi, M., and Pál-Molnár, E.: Petrographic traces of open-system magmatic processes in the felsic suite of the Ditrău Alkaline Massif (Eastern Carpathians, Romania), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1158,, 2023.

Anna Fehleisen, Christoph Anton Hauzenberger, Etienne Skrzypek, and Daniela Gallhofer

Two volcanic phases took place within the Styrian basin: an older one during the Miocene and a younger one during the Pliocene. While the alkaline basalts of the Pliocene phase have been studied in detail in the recent years (e.g. Ali et al. 2013), the Miocene volcanism around Bad Gleichenberg has not received much attention. The hills of Gleichenberg and Bschaidkogel are composed of trachyandesites and rhyolites with a calc-alkaline to shoshonitic affinity. A crystallization age of 13 ± 1 Ma was determined by K/Ar dating (Balogh et al., 1990), which clearly differentiates the Gleichenberg formation from the younger Pliocene alkaline basaltic magmatic formations that characterize the Styrian Basin. To further characterize and determine the age of the Gleichenberg volcanic formation, samples from different locations around Bad Gleichenberg were analyzed by petrological and geochemical methods. The majority of the samples are trachyandesites that follow typical calc-alkaline differentiation trends with SiO2 varying from 57 to 62 wt%; CaO, FeO and MgO decrease with increasing SiO2, while Al2O3, K2O, Na2O and P2O5 increase with increasing SiO2. The second main lithology – although much less voluminous - are rhyolites with SiO2 contents >71 wt%. Biotite and apatite are commonly found in both rock types. The fluorine content is high in both biotite and apatite with values up to 2 and 3 wt%, respectively. TiO2 contents in biotite can be as high as 8 wt%. U-Pb zircon dating by LA-MC-ICP-MS was carried out on zircons from two samples. Idiomorphic zircons, partly with abundant apatite inclusions or visible zircon cores and zonation, could be found in almost all samples. No age difference between zircon cores and rims or between zoned and homogeneous grains was observed. The analyzed samples yielded homogeneous crystallization ages of ~14 Ma for both volcanic rock types. Therefore, the Gleichenberg formation is likely related to the Balatonmária and Bükkalja volcanic fields in the Western Pannonian Basin System (Harangi et al. 1995). Based on similar geochemical characteristics, both occurrences can be related to the opening of the Styrian/Pannonian Basin, which resulted from slab retreat after collision between the Adriatic plate and Europe.


ALI, S., NTAFLOS, T., UPTON, B. (2013). Petrogenesis and mantle source characteristics of Quaternary alkaline mafic lavas in the western Carpathian–Pannonian Region, Styria, Austria. Chemical Geology. 337. 10.1016/j.chemgeo.2012.12.001.


BALOGH, K., HARALD, L., PÉCSKAY, Z., RAVASZ, CS., SOLTI, G. (1990). K/Ar radiometric dating of the Tertiary volcanic rocks of East-Styria and Burgenland. MÁFÍ Évi Jel. 1988-ról, 451-468. 


HARANGI, S., VASELLI, O., TONARINI, S., SZABÓ, C., HARANGI, R., CORADOSSI, N. (1995). Petrogenesis of Neogene extension-related alkaline volcanic rocks of the Little Hungarian Plain volcanic field (Western Hungary). Acta Vulcanologica, 7, 173-188.

How to cite: Fehleisen, A., Hauzenberger, C. A., Skrzypek, E., and Gallhofer, D.: New petrological, geochemical and geochronological data on Miocene volcanism in the Styrian Basin, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7829,, 2023.

Olgeir Sigmarsson

Rate of magma transfer and differentiation processes can be estimated from radioactive disequilibria between radionuclides in the 238U-chain if the mechanism that fractionate the nuclides can be constrained. Once constrained, the variable half-lives of the radionuclides allow to restrict the time elapsed from the fractionation. Over the last centuries, eruptions from Mt. Hekla have terminated with emission of phenocryst-poor Fe-rich basaltic andesite (or icelandite) of uniform composition, produced by approximately 50% fractional crystallisation from basalt. The crystallising mineral assemblage is composed of 8-13% olivine, 34-40% clinopyroxene, 32-41% plagioclase (An50-65) og 15-17% Fe-Ti oxides (Sigmarsson et al., 1992; Chekol et al., 2011).

Both 238U-230Th disequilibria and Th isotope ratios are identical in the basaltic andesite and basalt erupted around the volcano consistent with magma differentiation by fractional crystallisation. Modest radioactive disequilibrium is observed between thorium and radium that decreases from the basalt to the basaltic andesite with (226Ra/230Th) from 1.16 to 1.01. Such a decrease may represent decay of 226Ra (T1/2: 1600 yrs) if the fractional crystallisation took longer than 200 years, which is the minimum time for measurable effect of 226Ra disintegration. On the other hand, if Ra enters the extracted mineral phases, the time of fractionation would be much shorter.

Radium is an incompatible element which concentration increases with magma differentiation. Its bulk partition coefficient (DRa; min-melt)) between the minerals fractionating and the derived melt can be estimated from the variations of Ra and Th concentrations as 0.12 ± 0.03. Since Ra only enters plagioclase of the fractionating mineral assemblage, the plagioclase DRa (plag-melt) is 0.12/0.4 = 0.3. Melting experiments result in partiioning of Ra between plagioclase and melt close to 0.3 for An50 plagioclase (Fabbrizio et al., 2009), consistent with measured Ra and Th variations in Hekla lavas. Consequently, the lower (226Ra/230Th) in the basaltic andesite is fully explained by plagioclase fractionations on a timescale significantly shorter than 200 years.

Radium disintegrates to 222Rn, which in turn decays with a half-life of only 3.8 days to 210Pb. The volatile behaviour of the inert gas Radon is thus the main fractionation process generating 226Ra-210Pb disequlibrium, whereas the D (min-melt) for Pb and Ra is comparable. Hence, outgassing or accumulation of gas containing Radon is an effective fractionation mechanism on a short timescale causing Ra-Pb disequilibria that can be studied for approximately a century. Indeed, the first emitted tephra of the last Hekla eruptions display excess 210Pb over 226Ra suggesting volatile accumulation in a hermetic magma chamber explaining the initial explosive character of Hekla eruptions (Garance and Sigmarsson, 2023). Taken together, U-series disequilibria suggests that magma residence and transfer to surface occurs on a decadal timescale beneath Hekla volcano with important role for gas accumulation in the basaltic andesite affecting the repose time between eruptions.



Chekol et al. 2011

Fabbrizio et al. 2009

Hervé and Sigmarsson 2023

Sigmarsson et al. 1992

How to cite: Sigmarsson, O.: Magma residence and transfer rate from U-series disequilibria: the case of Hekla volcano, Iceland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9046,, 2023.

Anne Sturm, Axel K Schmitt, Katharina Cionoiu, and Martin Danišík

The Quaternary East Eifel volcanic field (EEVF) comprises three major evolved, phonolitic to trachytic centers (from old to young: Rieden, Wehr, and Laacher See) in addition to ~80 scoria cones. The prominent Laacher See eruption ca.13.000 years ago ranks among the largest Quaternary volcanic events in Europe, with the phonolitic Laacher See tephra (LST) being widely dispersed and of great relevance as a tephrochronological marker horizon1. Magmatic activity as recorded by zircon indicates that evolved magma was present underneath Laacher See at least 50 ka prior to its eruption. Continuous degassing and deep low-frequency earthquakes presumably related to fluid migration in the crust hint at ongoing magmatic activity.

Multiple eruptive phases characterize the older volcanic complexes of Rieden and Wehr, and it is therefore relevant to compare them to Laacher See center with presently only one eruption. Here, we focus on three eruptions that are associated with the Wehr depression or nearby centers, and where existing eruptive geochronology based on 40Ar/39Ar suggest eruptions <116 ka, bridging the transition of activity from Wehr to Laacher See. Three composite pumice samples were collected from previously established type localities (Dachsbusch, Herchenberg) comprising the Hüttenberg Tephra (HT), Glees Tephra (GT), and Dümpelmaar Tephra (DT). Whereas HT and GT are generally attributed to the Wehr depression, DT is presumably sourced from a small vent west of the Herchenberg scoria cone2.These trachytic-phonolitic magmas evolved from parental basanite, similar to LST, although there are major and trace element as well as isotopic differences3.

SIMS U-Th zircon crystallization ages for HT ( ka; MSWD= 0.83; n=27, uncertainties 1σ) and GT ( ka, MSWD= 1.71; n=32) are nominally older than published 40Ar/39Ar eruption ages2 by at most 15 ka, but zircon crystallization and eruption ages overlap within uncertainty. The U-Th zircon age for DT of  ka (MSWD= 1.02; n=33) also overlaps with the published 40Ar/39Ar age (116 ±16 ka), but this is only based on two sanidine analyses with the lowest ages that were interpreted as maximum eruption age2. Crustal zircon xenocrysts are common in all pumices, but morphologically distinguishable from the juvenile zircon population dominated by dipyramidal morphology. Glass geochemistry indicates high abundances of Zr, which is a pre-requisite for zircon saturation in highly alkaline melts.

In contrast to 40Ar/39Ar ages for individual K-feldspar crystals that display significant age heterogeneity2, in part exceeding the onset of volcanism in the EEVF, juvenile zircon crystals from HT, GT, and DT define a single population based on their individual isochrons. No carry-over of older zircon crystals into younger eruptions was detected, suggesting either eruption from distinct magma reservoirs, or complete resorption of pre-existing crystals between eruptive pulses. Future (U-Th)/He zircon geochronology will further constrain the temporal evolution of the evolved EEVF complexes.

1Bogaard, v. d. P., Schmincke, H.-U., 1985. Geol. Soc. Am. Bull. 96, 1554–1571.
2Bogaard, v.d. P., Hall, C.M., Schmincke, H.-U., York, D., 1989. Nature 342, 523–525.
3Wörner, G. et al., 1988. N Jb Miner Abh, 159, 73–99.

How to cite: Sturm, A., Schmitt, A. K., Cionoiu, K., and Danišík, M.: Crystallization timescales for the Wehr complex (East Eifel Volcanic Field): Insights from zircon geochronology and glass geochemistry, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6534,, 2023.

Francisco Cáceres, Jacopo Taddeucci, Mathieu Colombier, Javiera Terán, Joaquin Flores, Kai-Uwe Hess, Caron E.J. Vossen, and Donald B. Dingwell

All magmas form crystals upon cooling and volatile loss, following shifts in the melt liquidus during both decompressive ascent and eruption. Crystallisation modifies the melt chemistry and adds solid particles (crystals) in suspension in a magma. Both changes increase the bulk viscosity of the magma, potentially affecting the final eruptive style. Hence, it is crucial to understand the complete evolution of viscosity in a magmatic system in order to properly constrain its role in the evolution of a magma from depth to surface.

Here we measured the viscosity of magma feeding five events of lava fountaining at Etna volcano, Italy, during a period of seven months in 2021. All measurements were performed using remelted lapilli samples of trachybasalt composition (47-48 wt.% SiO2, 5.37-5.78 wt.% Na2O+K2O), originally collected during or immediately after each explosive event. Rheology analyses were performed at superliquidus conditions between 1198-1490°C in a concentric cylinder rheometer. The results show low viscosity variations - up to 0.14 log units at 1198°C - in time among the explosive events. These results are consistent with calorimetric analyses performed in both the remelted and natural samples. Additionally, pre-eruptive crystal contents vary between 21-53% of mainly clinopyroxene, plagioclase, olivine and orthopyroxene, as well as some oxide minerals, while interstitial melt compositions show an enrichment of up to 7 wt.% in SiO2 and more than 2 wt.% in Na2O+K2O after microlite crystallisation, which affects the magma bulk viscosity. Further analyses will help constrain such evolution of magma bulk viscosity. These results help to better constrain the minimum viscosity for the pre-eruptive magmas, as well as the shifts in bulk viscosity that the magmas experienced during ascent and eruption before quenching in air, potentially affecting the eruptive behaviour.

How to cite: Cáceres, F., Taddeucci, J., Colombier, M., Terán, J., Flores, J., Hess, K.-U., Vossen, C. E. J., and Dingwell, D. B.: The rheology of magma feeding the February-September 2021 lava fountains at Etna volcano (Italy), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17320,, 2023.

Dario Pedrazzi, Daniela Cerda, Jordi Granell, Gabor Kerestzuri, Adelina Geyer, Llorenç Planagumà, Joan Martí, and Xavier Bolós

The Garrotxa Volcanic Field (GVF) is one of the monogenetic Quaternary volcanic fields associated with the intraplate European Cenozoic Rift System. The GVF is located between the cities of Olot and Girona, NE Spain, and it covers an area of about 600 km2. This volcanic field ranges in age from 0.7 Ma to early Holocene and is considered active since the last eruption dated 11,000-13,000 years ago.

The volcanic activity, mainly controlled by regional normal faults generated during the Neogene extension, was highly variable with over 50 scattered eruptive vents that were produced during short-lived monogenetic eruptions. Scoria cones represent the most common landforms of the GVF with subordinate maars and tuff rings/cones. Most of the volcanoes are located in the northern sector between the towns of Olot and Santa Pau and they stand on a folded Eocene basement. Volcanoes located in southern area of the field, close to the city of Girona, stand mainly on a fractured Paleozoic basement.

The objective of this work is to identify eruptive processes and the geomorphic evolution of volcanic edifices and related them to environmental influencing factors. The best volcanic structures in the GVF have been selected due to their well-preserved morphologies. Cones (Wco) and craters (Wcr) mean diameters, as well as cones maximum height (Hmax), maximum crater depth (Dcrmax) and external slope of the cones (Smedian) have been measured.

This study shows that it is possible to create a catalogue of likely eruption sequences based on field evidences and morphological/morphometric data. In this way, a more realistic eruption scenarios can be developed for different parts of the volcanic field. Morphometry can also provide rough relative age constraints on edifices. These methodologies can improve our understanding for a better evaluation of volcanic hazards in urbanized volcanic fields as the GVF.

How to cite: Pedrazzi, D., Cerda, D., Granell, J., Kerestzuri, G., Geyer, A., Planagumà, L., Martí, J., and Bolós, X.: Eruptive processes and landforms recognition in the Garrotxa Volcanic Field, Iberian Peninsula, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8444,, 2023.

Posters virtual: Wed, 26 Apr, 10:45–12:30 | vHall GMPV/G/GD/SM

Chairpersons: Gianmarco Buono, Juraj Kyselica
Garima Shukla, Jyotirmoy Mallik, and Pratichee Mondal

The Deccan Continental flood basalts are associated with three major dyke swarms, namely the Narmada-Satpura-Tapi (N-S-T), the Western Coastal and the Nasik-Pune dyke swarm. The Pachmarhi dykes are located in the eastern part of the Narmada-Satpura-Tapi (N-S-T) dyke swarm in Madhya Pradesh, India. Here, we used the structural attributes of Pachmarhi dykes to quantify the magmatic overpressure and the source depth of the magma chamber and further compared the results with the Newer dolerite dykes (NDDs) of Singhbhum. There are ~244 mappable doleritic and basaltic dykes around Pachmarhi with the shortest and longest dykes of 140 m and 22 km, respectively (Shukla et al., 2022). The mean dyke length is ~5.15 km. The Pachmarhi dykes are in general shorter than those exposed in the Western end of the N-S-T swarm in the Dhule-Nandurbar area in Maharashtra (Das et al., 2021; Ray et al., 2007). The thickness of the Pachmarhi dykes varies between 3.5 m and 35 m. The Pachmarhi dykes exhibit a preferred orientation of N82°E that is parallel to the general trend of the Narmada-Son Lineament (NSL). The calculated magmatic overpressure for Pachmarhi dykes varies between 3.71 MPa to 52.22 MPa, with an average of 23.08 MPa, whereas the source depth of the magma chamber varies between 1.81 km to 25.38 km with an average of 11.21 km; considering average Young’s modulus of 11 GPa (Shukla et al., 2022). We compared the inferred magma source depths of the Pachmarhi and Dhule - Nandurbar dykes of Deccan (Ray et al., 2007); confirming the presence of numerous shallow magma chambers in the upper crustal levels for both cases (Shukla et al., 2022). The Singhbhum NDDs have fewer shallow crustal magma chambers compared to the Pachmarhi and Nandurbar-Dhule dykes. The emplacement of NDDs could be directly from the plume-induced Sub-Continental Lithospheric Mantle (SCLM; Pandey et al., 2021) and/or from the shallow crustal magma chambers, which can serve as a trap or barrier to store the magma from deeper magma sources (Shukla et al., 2022).


  • Das, A., Mallik, J., Banerjee, S., 2021. Characterization of the magma flow direction in the Nandurbar-Dhule Deccan dyke swarm inferred from magnetic fabric analysis. Phys. Earth Planet. Inter. 319, 106782.
  • Pandey, O.P., Mezger, K., Upadhyay, D., Paul, D., Singh, A.K., Söderlund, U., Gumsley, A., 2021. Major-trace element and Sr-Nd isotope compositions of mafic dykes of the Singhbhum Craton: Insights into evolution of the lithospheric mantle. Lithos 382–383, 105959.
  • Ray, R., Sheth, H.C., Mallik, J., 2007. Structure and emplacement of the Nandurbar-Dhule mafic dyke swarm, Deccan Traps, and the tectonomagmatic evolution of flood basalts. Bull. Volcanol. 69, 537–551.
  • Shukla, G., Mallik, J., Mondal, P., 2022. Dimension-scaling relationships of Pachmarhi dyke swarm and their implications on Deccan magma emplacement. Tectonophysics 843.


How to cite: Shukla, G., Mallik, J., and Mondal, P.: Structural attributes of Pachmarhi Deccan dykes and Newer Dolerite dykes of Singhbhum Craton: implications in magma emplacement mechanism, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1324,, 2023.

Patrizia Fiannacca, Damiano Russo, Eugenio Fazio, Davide Fiducia, Rossana Merlo, and Rosolino Cirrincione

Except in migmatite complexes, well-displayed field evidence of the possible physical behaviour of magma-crystal mush-solid rock systems is quite uncommon. Tonalites from Capo Vaticano Promontory, making up the oldest and deepest granitoid unit of the c. 13 km-thick late Variscan Serre Batholith, show outstanding examples of magma-mush interaction, at the transition with both underlying migmatite host rocks and overlying porphyritic granodiorites. Basal tonalites exhibit varying stages of interaction with garnet-bearing or garnet-free granitic magma produced by melting of the metapelitic migmatites after tonalite intrusion. Initial stages are characterized by infiltration of the granitic magma through the mushy tonalite along irregular channels, then forming an interconnected network of cm- to dm-wide channels. In some outcrops with high volumetric proportions of granitic magmas, peculiar hybrid rocks, characterized by pervasive intermingling of granite and tonalite, occur as the result of cm-scale disaggregation of the mushy tonalites.  In other outcrops, evidence of interaction between a crystal-poor tonalitic mush and the granitic magma is only provided by the occurrence of large peritectic garnet in apparently homogeneous tonalite. At the roof of the tonalitic unit, emplacement of the overlying porphyritic granodioritic magma involved displacement of the mushy tonalite, with local disaggregation in rounded blocks up to 1.5 meter in size. Compared to the basal tonalites, such evidence indicates a more rigid state of the roof tonalites at the time of granodiorite emplacement, even though rare occurrence of hybrid rocks testifies for possible mixing processes also between the granodioritic magma and mushy tonalite. Finally, an outstanding field evidence of the physical behaviour of mush systems, with significant implications for the mechanisms of magma differentiation, is given by mechanical accumulation of K-feldspar megacrysts at a place where the granodioritic magma was intruding the mushy tonalite, but only the liquid part of the magma was able to pass through, depicting a clear filter-press mechanism. This preliminary work aims to contribute to the general understanding of the evolution of mushy regions by presenting some outstanding examples of magma-mush interactions taking place during the construction of the deep-intermediate levels of the Serre Batholith (depth of c. 20-17 km depth), as a base for further in-depth multidisciplinary investigations.

How to cite: Fiannacca, P., Russo, D., Fazio, E., Fiducia, D., Merlo, R., and Cirrincione, R.: Magma-mush interaction at the base of a post-collisional batholith: field evidence from Capo Vaticano Promontory granitoids (Calabria, southern Italy), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9102,, 2023.

Cristina de Ignacio, Elena Real, Tomás Martín-Crespo, David Gómez-Ortiz, Silvia Martín-Velázquez, José Arnoso, and Fuensanta Montesinos

La Palma is one of the youngest and the most active island of all the Canary archipelago, with a total of seven subaerial eruptions over the last 500 years. This magmatic activity is linked to the undergoing growth and development of the youngest volcanic complex in the island: the Cumbre Vieja edifice, a 20 km long and 1950 m high, north-south trending ridge with aligned volcanic cones and fissures forming its summit and flanks. The youngest of them is the Tajogaite volcanic vent, which is located in the western flank of the Cumbre Vieja ridge, and was built up by a mainly strombolian eruption from 19th September to 13th December 2021. The first erupted, clinopyroxene-amphibole-phyric tephrite lavas, are more evolved in composition than the subsequent clinopyroxene-olivine-phyric basanite flows, in a pattern resembling those described from the two former eruptions in Cumbre Vieja: Teneguía (1971) and San Juan (1949). Furthermore, the detailed study of lava samples from the Tajogaite volcano reveals not only a drastic change in mineralogy, from amphibole-rich to olivine-rich lavas, but also the existence of complex textures and chemical zoning patterns including: 1) different olivine crystal populations, with and without disequilibrium textures (reverse zoning trends; reaction rims or coronae); 2) sodium-rich corroded clinopyroxene cores -with occasional titanite inclusions- overgrown by oscillatory zoned euhedral rims in equilibrium with groundmass; 3) a range of oxide mineral compositions from magnetite to chromite and spinel and, 4) the occurrence of early, nickel-bearing sulphides as inclusions in clinopyroxene. All these features record the interaction between ascending primitive mantle magmas and, at least, one shallow reservoir where differentiation had already taken place leading to iron, alkalis and water enrichment. This kind of interaction probably triggered the onset of the eruption, and could also be responsible for episodic phreatomagmatic activity pulses during the whole length of the volcanic process.   

How to cite: de Ignacio, C., Real, E., Martín-Crespo, T., Gómez-Ortiz, D., Martín-Velázquez, S., Arnoso, J., and Montesinos, F.: Equilibrium-disequilibrium textures and mineral chemistry of lavas from the Cumbre Vieja 2021 eruption, La Palma, Canary Islands, Spain: insights into magma plumbing systems under intraplate ocean islands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16267,, 2023.