GMPV7.4 | Understanding magmatic processes: from magma storage to eruptive behaviour, and implications for volcanic hazard
EDI
Understanding magmatic processes: from magma storage to eruptive behaviour, and implications for volcanic hazard
Convener: Eleonora Braschi | Co-conveners: Maren Kahl, Fabrizio Di FioreECSECS, Alessio PontesilliECSECS, Fabio Arzilli, Giuseppe La Spina, Chiara Maria Petrone
Orals
| Tue, 16 Apr, 08:30–12:25 (CEST)
 
Room D2
Posters on site
| Attendance Tue, 16 Apr, 16:15–18:00 (CEST) | Display Tue, 16 Apr, 14:00–18:00
 
Hall X2
Orals |
Tue, 08:30
Tue, 16:15
Processes occurring in magma storage regions control magma compositions and properties, which in turn affect ascent dynamics, eruptive behaviour, and emplacement mechanisms of volcanic products thus representing a paramount factor for the environmental and societal impact of volcanic eruptions.
Magma fractionation, degassing, mixing, and country-rock assimilation occur on a wide range of timescales and depths. Decompression and cooling driven by the ascent of magmas in volcanic conduits also impart their signature on eruptive products, complicating the interpretation of physico-chemical changes of the system. Indeed, during magma ascent, several physical and chemical processes are taking place, which can affect eruptive behavior and the style of activity.
Textural, chemical, and isotopic characteristics of eruptive products can be used as forensic tools to elucidate the inner workings of magmatic plumbing systems as well as pre- and syn-eruptive processes. Similarly, analytical/field observations, laboratory experiment and numerical modelling can also provide a useful tool to investigate pre- and syn-eruptive processes. Together, these information are of paramount importance for policymakers in charge of mitigating the risks associated with volcanic eruptions.
In this session we welcome a wide range of petrological, geochemical, geophysical and volcanological studies, based on natural, experimental, theoretical, or numerical-based approaches, with the scope of shedding light on magmatic processes occurring at depth and during ascent towards the surface. We also encourage submissions of contributions that deal with the mitigation of the hazards associated with volcanic activity. Interdisciplinary work considering the close and complex interplay between magmatic processes, conduit dynamics, eruptive behaviour, and emplacement mechanisms are of particular interest.

Orals: Tue, 16 Apr | Room D2

Chairpersons: Eleonora Braschi, Maren Kahl, Alessio Pontesilli
08:30–08:40
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EGU24-1847
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ECS
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On-site presentation
Anna Theurel, Marielle Collombet, Alain Burgisser, Caroline Martel, Laurent Arbaret, and Rémi Champallier

Magmatic outgassing plays a crucial role in the eruptive dynamics of silicic volcanoes. Gas escape from the volcanic conduit is facilitated by the coalescence of gas bubbles, leading to permeable bubble chains that are usually constrained by a crystalline framework within the magma. Our research provides experimental evidence of decompression-induced permeability in gas-poor crystal-rich silicic magmas that are not subjected to external strains. Synthetic samples were produced in Internally Heated Pressure Vessels (IHPV) to constrain and compare gas behavior with varying crystal content and size, and dwelling time. The permeable samples have a mean gas permeability of 10-14 m² for bulk porosity lower than 10% and bulk crystal contents of up to 75 vol%. Our results show that outgassing is possible in stagnant conduit at greater depths than initially assumed. This outgassing occurs even at low gas content, provided that the high crystallinity contains at least a microlite population with possible phenocrysts. Results also reveal a strong time dependence of the permeable bubble-chain lifetime in a closed magmatic system. If the dwelling time is too short, the coalescence process is incomplete, whereas if it is too long, the bubble chains resorb and become impermeable. Even with no magma deformation, the phenomenon of coalescence and percolation, therefore, remains dynamic. Our findings imply a new mechanism of deep outgassing for immobile magmas dominated by capillary forces, which has key implications on the explosive–effusive transition.

How to cite: Theurel, A., Collombet, M., Burgisser, A., Martel, C., Arbaret, L., and Champallier, R.: What happens before eruption? Effect of strong crystal content and time dependence of permeability at very low gas content in immobile silicic magmas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1847, https://doi.org/10.5194/egusphere-egu24-1847, 2024.

08:40–08:50
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EGU24-1079
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ECS
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On-site presentation
Garance Hervé, Olgeir Sigmarsson, and Guðrún Larsen

The last five eruptions at Mt Hekla, Iceland (1947, 1970, 1980, 1991 and, 2000) occurred at a frequency ranging from several decades to every ten years since 1970. The eruptions start with an explosive sub-Plinian phase during which most tephra is emitted. A decrease in eruptive intensity cause basalt-andesite lava emission (SiO2~54 wt%). Hautemann et al. (2017) linked the regular dynamic of Hekla to the accumulation of gas in a deep plumbing system (< 10 km) during periods of quiescence between eruptions. In this study we determine whether the proposed gas accumulation affected 210Pb-226Ra radioactive disequilibrium.

Radon being a noble gas has great affinity for the gas phase, but due to its low concentrations in magma is not able to form a mobile bubble. However, if a major gas phase such as CO2 is released, Radon can diffuse rapidly into the gas-bubble and therefore appears to be a good tracer for tracking a potential gas accumulation. One of its radioactive isotopes present in the 238U series is 222Rn (half-live 3.82 days). It is produced by the decay of 226Ra (half-live 1600 yrs) and quickly decays to form 210Pb. Because 210Pb has a half-life of 22.3 years and higher affinity for the melt phase than Rn, it can be measured in the erupted products. If gas accumulates at the top of the basalt andesite magma chamber, 222Rn carried by the major gas phase should accumulate in the upper part of the reservoir and disintegrate rapidly to 210Pb The first erupted products could thus register an excess of 210Pb over its parent isotopes, 226Ra.

The alpha and gamma spectrometry analysis of the initial tephra from the five most recent eruptions at Hekla volcano reveals a (210Pb/226Ra) of 1.057±0.014 (2σ), (210Pb/226Ra)=1.093±0.020 (2σ) for the 1947 and 1970 eruptions, respectively, while a radioactive equilibrium is observed for the 1980, 1991 and 2000 eruptions. Recalculated to the time of eruption, the ratios amount to (210Pb/226Ra)0=1.58±0.14 (2σ), (210Pb/226Ra)0=1.47±0.09 (2σ) and equilibrium, respectively. These results are consistent with an accumulation of Radon at the top of the magma chamber reflecting CO2 accumulation. At first glance, the rate of gas accumulation seems to be linked to the quiescent time between eruptions. However, other factors, including decrease of the mass of the degassing deep magma may affect this accumulation phenomenon. Evidence of gas accumulation is restricted to the tephra whereas (210Pb/226Ra)0 is equal to unity in the lava, which magma neither accumulated nor degassed Radon. Therefore, a deeper magma (basalt) contributed the CO2 and Radon to the Hekla plumbing system. The decrease in the (210Pb/226Ra)0 in the tephra over the past 70 years coincides with the decline in tephra volume, strongly suggest diminishing mass of deep degassing basalt. The decrease in gas supply and accumulation may explain the current dormancy of Hekla volcano.

References:

Hautmann, Stefanie, I. Selwyn Sacks, Alan T. Linde, and Matthew J. Roberts. 2017. « Magma Buoyancy and Volatile Ascent Driving Autocyclic Eruptivity at Hekla Volcano (Iceland) ». Geochemistry, Geophysics, Geosystems 18 (9): 3517‑29. https://doi.org/10.1002/2017GC007061.

How to cite: Hervé, G., Sigmarsson, O., and Larsen, G.: Discussing the timescales of pre-eruptive gas accumulation beneath Hekla volcano, Iceland, from 210Pb-226Ra systematics., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1079, https://doi.org/10.5194/egusphere-egu24-1079, 2024.

08:50–09:00
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EGU24-551
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ECS
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Highlight
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On-site presentation
Alberto Caracciolo, Enikö Bali, Eemu Ranta, Saemundur A. Halldórsson, and Guðmundur H. Guðfinnsson

The Reykjanes Peninsula, in southwest Iceland, has recently undergone magmatic reactivation with the 2021, 2022 and 2023 AD Fagradalsfjall eruptions. Considering the eruptive history of the peninsula in the past 4000 years, characterized by ~400-year-long rifting episodes at time intervals of 800-1000 years, the current magmatic reactivation could mark the onset of a new rifting episode in the most populated area of Iceland. In this contribution, we present results about magma plumbing configurations1 and SO2 emission potentials2 during past eruptions across the peninsula, which are vital aspects for interpreting pre-eruptive signals and assessing the impact of sulfur release on human health, respectively. We target 16 basaltic lava units erupted in the volcanic systems of Reykjanes, Svartsengi, Krýsuvík and Brennisteinsfjöll during the last medieval rifting episode: the 800-1240 AD Fires. We analysed major and minor element contents of glasses, mineral phases and melt inclusions, and we reconstructed magma storage depths and SO2 emission potentials across Reykjanes Peninsula. Independent clinopyroxene-melt and melt-based barometry show consistent results and suggest that magmas from the western part of the peninsula were extracted from magma reservoirs located at about 5-10 km depth. In contrast, and similar to observations from recent eruptions at Fagradalsfjall, the easternmost system, Brennisteinsfjöll, was fed from deep crustal reservoirs, at about 14-21 km depth. Starting from published lava volumes, we calculate SO2 emission potential across the peninsula to be in the range 0.004-7.4 Mt. These estimates correspond to daily SO2 emissions in the range 600-53000 tons, higher than the mean SO2 field measurements of 5240 ± 2700 tons/day during the 2021 AD Fagradalsfjall eruption. Also, we develop an empirical approach to calculate end-member SO2 emission potentials of any past or ongoing RP eruption of known volume or effusion rate. We conclude that the potential sulfur emissions across the RP can be significantly higher than observed during the 2021 AD Fagradalsfjall eruption, mainly because of the more evolved nature and higher sulfur contents of magmas erupted during the 800-1240 AD Fires. In the light of the ongoing magmatic unrest at Svartsengi, our work emphasizes the significance of petrological and geochemical studies of past eruptions for interpreting future pre-eruptive signals and developing future eruption mitigation strategies.

1 Caracciolo, A. et al. Magma plumbing systems and timescale of magmatic processes during historical magmatism on Reykjanes Peninsula. Earth and Planetary Science Letters  621, 118378 (2023). https://doi.org/10.1016/j.epsl.2023.118378

2 Caracciolo, A. et al. Reykjanes Peninsula's historical eruptions: SO2 emissions and future hazard implications (GPL, under review). Preprint https://doi.org/10.31223/X5TX05

How to cite: Caracciolo, A., Bali, E., Ranta, E., Halldórsson, S. A., and Guðfinnsson, G. H.: Medieval eruptions in the Reykjanes Peninsula, Iceland: magma storage depths and SO2 emission potentials for future eruption hazard assessment , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-551, https://doi.org/10.5194/egusphere-egu24-551, 2024.

09:00–09:10
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EGU24-10731
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ECS
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On-site presentation
Melina Hoehn, Brendan McCormick Kilbride, and Margaret Hartley

Rabaul is a large caldera system located at the northeastern tip of the island of New Britain, Papua New Guinea. Historically, it has been the most active volcano in Papua New Guinea. Rabaul is capable of large volume, high intensity caldera-forming eruptions (high-risk, low-probability events occurring every ca. 2 ka, most recently the Rabaul Pyroclastics event ca. 1400 years ago) and lower intensity but more frequent intra caldera eruptions. All eruptions at Rabaul pose a significant risk to nearby populations and settlements [1,2].

Rabaul’s volcanic rocks vary in composition from basaltic andesite to rhyolite and mostly lie on a common liquid line of descent, controlled by fractional crystallization under reducing conditions [1,2,3,4]. Magma mixing and mingling are common, evidenced by basaltic enclaves and mafic minerals in andesitic and dacitic eruption products [1,2,4]. These enclaves signify regular mafic recharge of the main dacitic reservoir, which primes the system for eruptions [4]. Seismic tomography imaging suggests the presence of an extensive, tabular magma body at a depth of 3-6 km with a volume of about 15-150 km3 [5,6].

The main goal of this study is to determine how the petrology and geochemistry vary between magmatic products erupted from different intervals in the caldera cycle of Rabaul volcano. In addition, we aim to get a better understanding of the primitive magmas that feed and sustain volcanism at the Rabaul Caldera Complex. Furthermore, we identify the key magma chamber processes influencing mineral chemistry and texture.

Here, we present EPMA mineral analysis and thermobarometry model outputs for products of the 1937, 1994 and 2014 eruptions as well as for the most mafic eruption products known, the Kombiu basalts. Our thermobarometry data complement existing geophysical observations of the structure of Rabaul’s magma plumbing system. Furthermore, we present SEM imagery to reveal how mineral textures (zoning, resorption, grain size, grain boundaries) in samples from different eruptions at Rabaul reflect magma chamber processes such as mafic recharge, magma mixing and crystallisation.

 

References: [1] Patia H et al. (2017) J Volcanol Geotherm Res 345:200-217; [2] Fabbro G et al. (2020) J Volcanol Geotherm Res 393:106810; [3] Wood CP et al. (1995) J Volcanol Geotherm Res 69:285-302; [4] Bouvet de Maisonneuve C et al. (2016) GSL; [5] Finlayson et al. (2003) J Volcanol Geotherm Res 124: 153-171; [6] Bai and Greenhalgh (2005) Phys. Earth Planet. Inter. 151: 259-275

How to cite: Hoehn, M., McCormick Kilbride, B., and Hartley, M.: Petrographic and geochemical investigation of magma reservoir processes at Rabaul Caldera, Papua New Guinea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10731, https://doi.org/10.5194/egusphere-egu24-10731, 2024.

09:10–09:20
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EGU24-2154
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ECS
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On-site presentation
Mónica Ágreda López, Corin Jorgenson, Luca Caricchi, Guido Giordano, and Maurizio Petrelli

The effusive-explosive transition in mafic systems is a complex and still largely debated phenomenon in volcanology. Understanding this transition is crucial for hazard assessment and risk mitigation since explosive eruptions can pose significant dangers to nearby populations and infrastructure. In this study, we investigate this transition focusing on a natural study case: the Colli Albani volcano. The Colli Albani is an ultrapotassic caldera complex located 30 km SE of Rome. This volcano has exhibited a wide range of eruptive behaviours throughout its history, ranging from effusive activity to highly explosive eruptions (Giordano & CARG Team, 2010). Here, two main eruptive sequences were selected: The Fontana Centogocce formation (SLV) and the Villa Senni ignimbrites (VSN). SLV represents a period of effusive to mild-explosive eruptions and preceded the emplacement of the 50 km3 Villa Senni ignimbrites (VSN), which represent the last caldera-forming event of the volcano.

This study integrates field and petrographic observations, clinopyroxene textural and chemistry analyses and machine learning thermobarometry to understand and constrain the variables influencing the shift from mildly-explosive to caldera-forming eruptions. We present a reconstruction of the volcanic plumbing system's architecture and offer insights into how the system rebuilds in its interim after one of these large events.

 

Giordano, G., & CARG Team. (2010). Stratigraphy, volcano tectonics and evolution of the Colli Albani volcanic field. In: Funiciello, R., Giordano. G. (eds). The Colli Albani volcano. Special Publications of IAVCEI, vol 3, Geological Society, London, 43-98.

How to cite: Ágreda López, M., Jorgenson, C., Caricchi, L., Giordano, G., and Petrelli, M.: The mildly explosive to caldera-forming transition at Colli Albani volcano , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2154, https://doi.org/10.5194/egusphere-egu24-2154, 2024.

09:20–09:30
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EGU24-5141
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On-site presentation
Heather Handley, Ray Cas, Thomas England, and Eric Hellebrand

Australia hosts at least two active continental basaltic volcanic fields with Holocene eruption ages yet very little is understood about magma ascent and mantle to surface ascent pathways and timescales. In this study we use textural and chemical information stored within minerals from two of the youngest volcanic eruptions in northeast and southeast Australia to investigate magmatic plumbing systems and magma ascent in Australia’s intra-plate volcanic fields. Volcanic rock samples from the three main eruptive phases at Mt Schank volcano in the Newer Volcanics Province, South Australia, reveal textural and mineralogical differences throughout the evolution of the eruption that correspond to variations in eruption style and the availability of external water. Crustal xenoliths (e.g., quartz and limestone) are abundant in the middle, maar-forming phase of the eruption. The lack of mantle-derived xenoliths and xenocrysts throughout the eruption, olivine compositions and sector and oscillatory zoned, euhedral clinopyroxene suggest a more stalled ascent pathway of magma compared to the mantle xenolith-bearing volcanoes in parts of the Victorian sector of the province. Skeletal olivine crystals and dendritic clinopyroxene microlites indicate moderate degrees of undercooling at Mt Schank during magma ascent. In northeast Queensland, interaction of magma with mantle xenolith’s are used to determine magma ascent dynamics. Disequilibrium and quench textures and chemical zoning patterns in olivine, clinopyroxene, orthopyroxene and spinel on xenolith margins and within host glass reveal a detailed and complex history of magma ascent.

How to cite: Handley, H., Cas, R., England, T., and Hellebrand, E.: Magma ascent in active Australian intraplate basaltic volcanic provinces, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5141, https://doi.org/10.5194/egusphere-egu24-5141, 2024.

09:30–09:40
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EGU24-11135
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On-site presentation
Lorenzo Cappelli, Paul A Wallace, Evelyne Mbede, Shimba Kwelwa, Edista Abdallah, and Karen Fontijn

The eruptive style and explosivity of volcanic eruptions primarily depend on conduit dynamics (e.g., ascent rate and degassing efficiency) and the rheological behaviour of the pre-eruptive magma, which is controlled by its composition and conditions within the reservoir. In the case of highly alkaline magmas (i.e., agpaitic index > 1), the depolymerisation of silica bonds exerted by alkaline elements promotes a relatively low-viscosity rheological response and therefore theoretically less explosive eruptive behaviour, even for silica-rich magmas. However, several well-studied eruptions show that peralkaline magmas, like trachyte and phonolite, can also experience highly explosive Plinian events, suggesting other parameters might influence the eruption style. In the East African Rift, several such volcanoes with peralkaline magma compositions have erupted both explosively and effusively in the past. We investigated the pre-eruptive magmatic system of the Plinian eruption that produced the Rungwe Pumice (RP) deposit in southern Tanzania. The type section of the RP consists of a ~2.5 m thick fall deposit of peralkaline trachytic/phonolitic pumices. Syn-eruptive volatile exsolution is a crucial parameter controlling the eruptive style and is related to the volatile budget within the reservoir. Therefore, water concentrations in haüyne-hosted melt inclusions (MIs) were characterised using transmitted Fourier-transformed infrared spectroscopy. Preliminary results indicate substantial water concentrations within the reservoir (i.e., 2.60-5.59 wt.%) while the water retained by the glassy matrix of pumices reveals that the magma was almost entirely degassed during ascent. The modelled evolution of magmatic composition within the reservoir suggests closed conduit fractional crystallisation (~80% fractionation) of a parental mafic magma to generate the RP trachyte/phonolite within a compositionally homogeneous magmatic reservoir. Finally, by applying petrological models, we estimated a MI entrapping temperature of ~1147 ± 92 K and a minimum lithostatic pressure ranging from ~28 to 184 MPa (~1-7 km depth).

How to cite: Cappelli, L., Wallace, P. A., Mbede, E., Kwelwa, S., Abdallah, E., and Fontijn, K.: Pre-eruptive magmatic reservoir conditions controlling explosivity of a trachytic Plinian eruption: case for the Rungwe Pumice (Tanzania), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11135, https://doi.org/10.5194/egusphere-egu24-11135, 2024.

09:40–09:50
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EGU24-11281
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ECS
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On-site presentation
Beitris Morrison-Evans, Elena Melekhova, and Jonathan Blundy

Many volcanoes erupt a limited compositional range of magmas over their lifetime. The composition of these erupted magmas is thought to be buffered by the crystal-rich mush from which melts are sourced (Blundy, 2022). Identifying the origin of erupted magmas helps us to constrain possible locations of melt accumulation in the mush and improve our interpretation of geophysical signals at restless volcanoes.

La Soufrière volcano, St Vincent (Eastern Caribbean), has throughout its lifetime produced predominantly basaltic andesite magmas, including most recently in 2020-21. We explore the origin and phase relations of these erupted magmas by performing a series of high-pressure, high-temperature experiments. Melt extracted from a mush will be multiply-saturated on its liquidus with the mush mineral assemblage at the P-T-fO2-XH2O conditions at the time of segregation. In a system with relatively low thermodynamic variance, for example, five or six independent chemical components (as determined by principal component analysis), a large number of coexisting mineral phases (e.g. plag+cpx+amph+oxides) and a well-constrained fO2, multiple saturation can be reduced to an invariant point on the liquidus of the melt in P-T-H2O space. The approach of finding liquidus multiple saturation for igneous rocks offers a novel magma source thermobarometer and hygrometer.

Equilibrium high-pressure, high-temperature experiments were performed at 3-8 kbar and 980-1200ºC, fO2 ≈ Ni-NiO buffer, with initial H2O contents of 2-10 wt%. Plagioclase, clinopyroxene and magnetite are found to be ubiquitous in the melt source region. Amphibole is a peritectic phase and forms on the rim of clinopyroxene, with decreasing temperature, in experiments with high water contents. The peritectic reaction involving amphibole is also observed in St Vincent xenoliths (Brown, 2023). Orthopyroxene is stable at high pressures (8 kbar) and low water contents (≤ 6wt% H2O), with its stability field decreasing with pressure. Five-phase multiple saturation at the liquidus (melt fraction ≥85%) is found for initial H2O contents of 7-8 wt%, at 6 kbar pressure (~22 km depth) and temperatures of 1030-1050ºC. The saturating assemblage is a hornblende-gabbro (cpx+plag+amph+Fe-Ti oxides), consistent with the mineralogy of plutonic xenoliths from historic eruptions of St Vincent (Tollan et al., 2012; Fedele et al., 2021). Mineral compositions in these multiply-saturated runs (e.g. very calcic plagioclase An75-85) are similar to those in the xenoliths. Temperatures agree with mineral geothermometry estimates of the 2020-21 eruption (Weber et al., 2023), suggesting little cooling of the magma during ascent from its source region. Seismicity prior to the 2020-21 eruption is also consistent with mid-crustal source depths (Joseph et al., 2022). Magmas sourced from similar depths can account for the limited compositional diversity of La Soufrière over its volcanic history (Fedele et al., 2021).

 

References

Brown, JR. (2023) Doctoral dissertation, Durham University. 

Blundy, J. (2022) Journal of Petrology63(7), egac054.

Fedele et al. (2021) Lithos, 392, p.106150

Joseph et al. (2022) Nature Communications13(1), p.4129.

Tollan et al. (2012) Contributions to Mineralogy and Petrology163, pp.189-208.

Weber et al. (2023) Geological Society, London, Special Publications, 539(1), pp.SP539-2022.

How to cite: Morrison-Evans, B., Melekhova, E., and Blundy, J.: Source depth of basaltic andesite magma beneath La Soufrière, St Vincent., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11281, https://doi.org/10.5194/egusphere-egu24-11281, 2024.

09:50–10:00
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EGU24-19483
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ECS
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On-site presentation
Ariane Loisel, Edward Llewellin, Richard Brown, Antonio Capponi, Tim Orr, and Matthew Patrick

Basaltic eruptions produce lava flows that have the potential to destroy local infrastructure and emit toxic gas and particles that may adversely impact public health. Predicting their style and evolution is therefore a key goal in volcanology. This requires an understanding of the multiphase flow processes that operate within the sub-volcanic system.

Field observations of both solidified and erupting basaltic fissures at Kīlauea volcano (Hawai‘i, USA) are synthesised with laboratory analogue experiments to determine the evolving organisation of gas-driven flow patterns within basaltic feeder dyke systems, and their effects on eruptions. Our laboratory kit was designed to perform scaled analogue experiments of bubbly flows in a 3.0 x 2.0 x 0.03 m glass-walled slot. This geometry mimics the geometry of dykes that feed most basaltic eruptions, whereas previous experimental studies have usually assumed a cylindrical conduit. The role that localization of fissure segments plays in shaping eruption behaviour is explored by occluding parts of the top of the slot. We also consider the role played by flooding of the vent with lava, focussing on long-lived systems that are reproduced by a conical vent geometry.  We collate the imagery acquired during our analogue experiments with recent monitoring datasets and a detailed field investigation of the spatial organization of vents and drain-back structures on solidified fissures at Kīlauea to improve our understanding of the controls on the eruptive behaviour of basaltic systems. This study will help interpret the underlying flow patterns within feeder dykes from real-time gas and erupted lava flux measurements.

How to cite: Loisel, A., Llewellin, E., Brown, R., Capponi, A., Orr, T., and Patrick, M.: The evolution of a basaltic fissure eruption, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19483, https://doi.org/10.5194/egusphere-egu24-19483, 2024.

10:00–10:10
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EGU24-6405
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solicited
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On-site presentation
Catherine Annen, Roberto Weinberg, Virginie Pinel, and Alain Burgisser

H2O and other volatiles play a major role in the dynamics of magmatic systems from magma source to volcanic eruption. At the source, H2O facilitates melting and within the crust, H2O fluxing of hot rocks favours the formation and stabilisation of magma mush. H2O dissolved in melt lowers its viscosity and density and thus helps melt extraction and transport. H2O exsolution during magma transport causes crystallisation and stalling of the magma, while further exsolution in a crystallizing magma chamber increases pressure on the chamber walls and facilitates chamber failure and eruption. During the magma final journey towards the surface, formation and expansion of bubbles fragment the magma, increasing the explosivity of the volcanic eruption.

We have developed numerical simulations that model flux melting in the deep crust, and other simulations that model H2O exsolution in a growing and crystallising magma chamber in the upper crust. A parameter that is crucial in both processes is the permeability of the magma, mush, and solid rocks through which H2O is moving.

Our flux melting models show that due to complex interactions between the effect of H2O and heat, the amount of melt produced by flux melting depends on how fast H2O is transferred relative to heat. By absorbing latent heat, H2O flux melting decreases temperatures and promotes heat transfer in the melting areas. The extent of the melting region depends on the competition between the transfer of H2O, which induces melting and cooling, and the transfer of heat that smooths temperature anomalies. The amount of crustal melting also depends on permeabilities contrast. The presence of an impermeable layer above a more permeable layer increases the production of melt by trapping H2O in the permeable layer.

The ease of transfer of exsolved H2O within a crystallising magma body depends on crystal fractions. Our models of magma chambers growth and solidification show that preferential transfer of H2O through the mush that surrounds a magma chamber results in the formation of H2O layers at the top the mush and in the chamber’s roof. If the permeability of the country rocks is low, the H2O layers grow, their buoyancy increases, and the pressure eventually exceeds the yield strength of the country rock and causes fracturing. Depending on how well the H2O layers connect to the liquid magma in the chamber below, fracturing of the country rock can result either in the release of H2O only and possibly causes a bradyseismic crisis, or in the release of H2O, mush, and magma, and triggers a crystal-rich eruption.

We know from volcano degassing and from petrological data that magmas are rich in H2O. However, our knowledge of how this H2O is transferred from magmas and through the crust is limited. This knowledge is important though as our simple numerical models indicate that the modalities of H2O transport and accumulation strongly affect the dynamics of a magmatic system.

How to cite: Annen, C., Weinberg, R., Pinel, V., and Burgisser, A.: How H2O transport and trapping affect the dynamics of magmatic systems from melt generation to eruption triggering, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6405, https://doi.org/10.5194/egusphere-egu24-6405, 2024.

Coffee break
Chairpersons: Chiara Maria Petrone, Fabio Arzilli, Giuseppe La Spina
10:45–10:55
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EGU24-11166
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ECS
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On-site presentation
Nicolò Nardini, Federico Casetta, Massimo Coltorti, and Theodoros Ntaflos

The preservation of volcanic and plutonic records holds the potential to improve our comprehension of plumbing systems. It is widely accepted that numerous magmatic complexes are fed by crystal-rich magma ponding at mid to shallow crustal depth, which is periodically remobilized by the intrusion of hotter melts over extended periods. However, these mechanisms are rarely recorded in plutons. The Dolomites (Southern Alps; Italy) host large volumes of Middle Triassic volcanic and plutonic outcrops, characterized by an excellent state of preservation. This condition enables us to deeply investigate the plumbing system dynamics and connect the effusive and intrusive components of the Middle-Triassic magmatism in the Southalpine domain. In this study, a detailed textural and compositional investigation of clinopyroxene crystals in shallow crustal pyroxenites and gabbros has been done to link plutonic features to the already investigated volcanic counterparts (Nardini et al. 2022). Augitic clinopyroxene is the dominant mineral phase, with euhedral to subhedral crystals up to cm-sized dimensions. Its compositions show Mg# [MgO/(MgO+FeOtot) mol%] from 62 to 75 coupled with low Cr2O3 concentration (< 0.1 wt.%) and 0.5-1 wt.% of TiO2. The crystals occasionally show step zoning patterns towards diopsidic domains having high-Mg# (80-90), higher Cr2O3 and lower TiO2 (both from 0.1 to 0.5 wt.%) organised as outer rims, intermediate bands or as resorbed cores. These preliminary data confirm what recorded by the volcanic counterparts, suggesting a periodical mixing between trachyandesitic and trachybasaltic melts (see Nardini et al. 2022). The remarkable preservation of zoning patterns in the plutonic rocks, coupled with the consistency of clinopyroxene composition and zoning in alignment with the lavas and dykes, provides a powerful volcano-plutonic link. The analyses of exposed plutonic rocks, chemically associated with the erupted materials, provide concrete evidence of the magmatic processes that are inferred through petrogenetic modelling in volcanic rocks, with the potential to deepen our understanding of the plumbing system dynamics.


References
Nardini, N., Casetta, F., Ickert, R. B., Mark, D. F., Ntaflos, T., Zanetti, A., & Coltorti, M. (2022). From the Middle Triassic Cima Pape complex (Dolomites; Southern Alps) to the feeding systems beneath active volcanoes: Clues from clinopyroxene textural and compositional zoning. Journal of Volcanology and Geothermal Research, 422, 107459.

How to cite: Nardini, N., Casetta, F., Coltorti, M., and Ntaflos, T.: Shedding light on the volcano-plutonic link: evidence of magma mixing dynamics in the shallow crustal plutonic rocks from the Dolomites (Southern Alps; Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11166, https://doi.org/10.5194/egusphere-egu24-11166, 2024.

10:55–11:05
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EGU24-13229
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ECS
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On-site presentation
Caroline Tisdale and Bruce Houghton

Eruptions labeled "Strombolian" – characterized by spaced discrete explosions that occur when gas pockets burst at the magma free-surface  – represent an endmember of basaltic volcanism, yet the term's applicability outside Stromboli volcano (Italy) itself remains controversial. The occurrence of Strombolian-like activity in diverse settings necessitates a more nuanced approach to classification and characterization. This study presents a quantitative analysis of transient short-lived (seconds to tens of seconds) mafic explosions from two eruptions: the 2011 Kamoamoa eruption of Kīlauea and the 2018 Lower East Rift Zone eruption of Kīlauea (USA, Hawai'i). Ground-based video recordings are the primary data source. Advancements in image processing allow for the efficient analysis of key eruption parameters including explosion frequencies, durations, and repose intervals, as well as 2D particle exit velocities, size distributions, and mass eruption rates and total mass per explosion. Preliminary results revealed that compared to “normal” Strombolian activity at Stromboli, discrete explosions at Kīlauea in 2011 and 2018 were often shorter lived, more closely spaced, and less intense. These findings suggest a spectrum of Strombolian-like behavior, influenced by factors such as magma composition, shallow conduit geometry, and most importantly gas behavior and flux. This diversity of activity challenges the application of the "Strombolian" label and emphasizes the need for quantitative characterization of discrete basaltic explosions outside of Stromboli.

How to cite: Tisdale, C. and Houghton, B.: "Strombolian" explosions in Hawai'i, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13229, https://doi.org/10.5194/egusphere-egu24-13229, 2024.

11:05–11:15
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EGU24-20705
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ECS
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Highlight
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On-site presentation
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Charline Lormand, Luca Caricchi, Guido Giordano, and Roberto Isaia

The largest deformation since the start of the ongoing unrest at Campi Flegrei caldera, Italy, was recorded in 2023 with an average uplift rate of 17 cm/year [1]. This coincides with the exponential increase of seismic events since 2017 by a factor of 32 (i.e., 6065 events in 2023 versus 3181 in 2022, 2232 in 2021, 1520 in 2020, 799 in 2019, etc.). Such observations raise questions regarding the origin and the future of the ongoing unrest especially in determining if the underlying cause involves ascent of magmatic fluids only or if magma is also involved. To this end, a forensic approach focusing on the characterisation of crystal cargoes from past eruptions help understanding of the conditions and pre-eruptive processes that occur within magmatic plumbing system prior to eruptions of different styles and comparing these possible scenarios with the current unrest.

Juvenile clasts found in the base layer from deposits of past eruptions (e.g., Agnano-Monte Spina, Solfatara, Averno, Astroni, Monte Nuovo) of different eruption styles and size were collected. The 1538 eruption of Monte Nuovo is the ideal benchmark to link the petrological evidence to the precursory deformation documented, whereas the historical eruptions selected allow for consideration of a wider range of eruption scenarios. We will present machine learning thermobarometric data and chemical patterns inferred by clustering techniques used to constrain the temperature-pressure paths of the magma and to identify possible systematics during the period of magma migration to the surface preceding the eruption. Ultimately, we aim to link the petrological signatures conveyed by antecrysts with the deformation triggered during magma intrusion and expansion of volatiles upon ascent.

Reference: [1] INGV. Bollettini di sorveglianza dei vulcani campani. http://www.ov.ingv.it/ov/bollettini-campi-flegrei/ (2016-2023).

How to cite: Lormand, C., Caricchi, L., Giordano, G., and Isaia, R.: Ongoing unrest at Campi Flegrei, Italy: clues from the antecrystic records, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20705, https://doi.org/10.5194/egusphere-egu24-20705, 2024.

11:15–11:25
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EGU24-6455
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ECS
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On-site presentation
Haiyang Hu, Matthew Jackson, and Catherine Booth

We use a one-dimensional numerical model to investigate how the presence of a volatile phase such as water impacts the creation and dynamics of a magma reservoir in the mid- to lower crust. We assume that the reservoir is created and sustained by the repeated intrusion of mantle-derived basalt sills containing a few wt% volatiles. Our numerical model solves the equations governing heat transfer by conduction and advection; two- and three-phase flow of the solid, melt and volatile phases assuming porous flow and compaction at low melt fraction and hindered settling at high melt fraction; and handles phase exchange using a two-component (SiO2 and volatile) chemical model fitted to experimental melting data.  The solidus and liquidus temperatures are functions of bulk SiO2 content and melt volatile content. The volatile exchange between solid and melt phases is modelled using a partition coefficient and the maximum volatile content of the solid phase is capped based on mineralogical data. The melt phase has a maximum volatile saturation above which a free volatile phase is formed. There is no direct transfer of volatiles from the solid to the volatile phase.

We find that the highly non-linear coupling between melt volatile content and the solidus and liquidus temperatures, flow of melt and (when present) volatile phases, and the exchange of latent heat, gives rise to complex emergent behaviour.  We do not observe a simple, upwards propagating volatile front below which melt is always present in a stable mush column as has been proposed in some previous studies.  Rather, we observe the formation of transient, high melt fraction, evolved and volatile-rich layers interspersed with refractory and volatile-poor mush.  The high melt fraction layers can propagate upwards, merge and split.  The layers are typically thin and likely below geophysical resolution.  The dynamics of mush reservoir growth are strongly influenced by the fertility of the overlying crust: if the crust can melt in response to the addition of heat and volatiles, then the top of the reservoir migrates upwards until it reaches mid-crust depth, creating a reservoir that spans the lower- to mid-crust and hosts numerous melt-rich layers.  Our results so far suggest a highly dynamic magmatic system characterized by significant melt fraction variations in time and space.  Much of this dynamic complexity is lost in geophysical images that are interpreted to suggest reservoirs have low and uniform melt fraction.

How to cite: Hu, H., Jackson, M., and Booth, C.: Effects of a volatile phase on the Creation and Dynamics of Lower Crustal Magma Reservoirs: A Three-Phase Numerical Model Study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6455, https://doi.org/10.5194/egusphere-egu24-6455, 2024.

11:25–11:35
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EGU24-16330
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ECS
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On-site presentation
Daniel Weller, Cristian Montanaro, Donald Dingwell, Shane Cronin, and Bettina Scheu

Various processes involving nucleation, growth, and interaction of bubbles occur as water-rich magma —e.g., of andesitic composition— ascends through a volcanic conduit towards shallower depths. These mechanisms significantly affect the properties of the magma upon fragmentation, including porosity, permeability, and magma strength. Such properties, in turn, can influence the dynamics of fragmentation —such as its speed and efficiency— thus impacting eruptive behaviour. Precisely measuring and understanding how the pre-eruptive bubble size distribution and texture affect fragmentation dynamics poses a scientific challenge that lacks comprehensive quantification methods to date.

In this study, we employed a combination of analytical and experimental methods to explore the processes governing bubble formation and to quantify the impact of their size, distribution, and texture on andesitic magma fragmentation. Our investigation utilised a series of andesitic products originating from the AD 1655 Burrell eruption of Mt. Taranaki, New Zealand. The pyroclasts from this eruption exhibited varying porosity (10 – 80 %) and permeability (10-16 - 10-11 m²). Using scanning electron microscope imagery, we employed FOAMS, an image analysis software, to compute bubble size distributions. Subsequently, we performed rapid decompression experiments on selected samples, capturing the process of fragmentation and clast ejection using two synchronized high-speed cameras. This approach allowed us to track fracture location and evolution over time, enabling the assessment of fragmentation speed and fracture density. Further analyses involved examining the grain size distribution of generated clasts to evaluate the efficiency of fragmentation.

Our texture analysis unveiled that bubble nucleation and growth occurred concurrently during various eruption stages, as evidenced by changes in bubble number density, porosity, and polydispersivity. Correlating these results with the high-speed camera analysis, we observed a significant influence of bubble number density and average diameter on fragmentation speed. Moreover, large bubble clusters appeared to intensify fragmentation speed by weakening local rock strength. Both the number and diameter of bubbles exhibited additional relationships with particle size, efficiency of fragmentation, and fracture density in our samples.

Drawing from the correlation between bubble texture and petrophysical properties, we proposed a conceptual model elucidating the impact of bubble textures on fragmentation dynamics. Furthermore, we evaluated and discussed our findings in the context of previously developed eruptive models of Mt. Taranaki. Our findings, together with variation in the density of the expelled particle-gas mixture, align well with the model depicting a transition in eruptive behaviour and plume stability of Mt. Taranaki during the deposition of the Burrell formation.

 

How to cite: Weller, D., Montanaro, C., Dingwell, D., Cronin, S., and Scheu, B.: The role of pre-eruptive bubble characteristics in modulating andesitic magma fragmentation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16330, https://doi.org/10.5194/egusphere-egu24-16330, 2024.

11:35–11:45
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EGU24-4346
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On-site presentation
Philipp Ruprecht

Most eruptions tap magmas from a range of pressures and storage environments within the crust and potentially even in the mantle. In this context, early crystallizing phases, such as olivine, provide a unique perspective into the deeper parts of many eruptions. When considering large olivine populations, compositional spectra of those populations serve as proxies for the different batches of magma that constitute the sometimes complex assembly of an eruption. While major element compositions in olivine provide links to melt compositions, minor and trace elements fingerprint deviations from simple liquid lines of descent. Moreover, Fe-Mg isotope signatures demonstrate whether magmas equilibrated diffusively or whether some mineral zoning retains growth histories prior and during assembly.

To reveal the full picture of the assembly of an eruption and potentially changes during the eruption it is essential to collect olivine “interviews” from a large population as they exit the volcano. Here I show that such magma assembly prior to eruption varies greatly from one eruption to the next and that simple monogenetic cones may contain much more complex histories as they quickly pass the crust and may extract crystal cargo from a variety of locations and conditions, while many volumetrically larger more long-lived systems retain a simpler story despite their polybaric magma storage.

How to cite: Ruprecht, P.: Olivine exit interviews – gaining insights into magma assembly from olivine populations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4346, https://doi.org/10.5194/egusphere-egu24-4346, 2024.

11:45–11:55
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EGU24-16546
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On-site presentation
Paul Wallace, Sarah H. De Angelis, Jessica Larsen, Luca Caricchi, and Yan Lavallée

Amphibole phenocrysts are common in intermediate to felsic magmas where they record information on magma evolution through breakdown rim textures marking shifts in pressure, temperature, volatile concentrations, oxygen fugacity and melt chemistry during ascent. Our ability to track these variables throughout the volcanic plumbing system (e.g., via phase equilibria experiments, geothermobarometry, disequilibrium textures, melt inclusions) has provided the means for interpretating eruption trigger mechanisms, yet a lack of calibrated data on their influence on amphibole stability (and thus reaction rim formation) makes unambiguously distinguishing the mechanism problematic. One such elusive example is the role of CO2 flushing, deemed a likely phenomenon in magmatic systems, precluding an accurate interpretation of natural rim formation, previously assigned to decompression or heating. We performed high-temperature (830–880ºC), high-pressure (120 MPa) experiments to investigate the effects of XCO2 (0.3–0.7) on amphibole reaction rim development in H2O-saturated silicic magmas in shallow volcanic systems, providing new insights for interpreting amphibole rim textures. Our experiments quantify the significant impacts of CO2 on rapidly triggering amphibole breakdown over shorter timescales compared to heating or decompression. 2D textural analysis of the breakdown rim microlites reveal that crystal size, aspect ratio, number density and preferential alignment, together with mineralogy, can be related to a distinct breakdown mechanism. Furthermore, we apply high-resolution electron backscatter diffraction (EBSD) analysis to >100 experimental and natural amphibole reaction rims (Soufrière Hills Volcano, Unzen Volcano, Bezymianny and El Misti). Quantitative mapping reveals systematic variations in crystallographic orientations of the rim microlites relative to the host amphibole, enabling the development of an EBSD criteria that differentiates decompression-, heating-, and CO2-induced amphibole breakdown. The distinct textures produced provides new markers and a new framework for the interpretation of natural rim formation processes. Application of this new quantitative approach over a range of magmatic systems worldwide will improve interpretations of intensive parameters, ascent paths, eruption triggers, and amphibole stability from crystal record archives.

How to cite: Wallace, P., H. De Angelis, S., Larsen, J., Caricchi, L., and Lavallée, Y.: Amphibole breakdown rim textures as archivists of pre-eruptive magmatic processes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16546, https://doi.org/10.5194/egusphere-egu24-16546, 2024.

11:55–12:05
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EGU24-6291
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On-site presentation
Jacopo Taddeucci, Corrado Cimarelli, Giacomo Pozzi, Jackie E. Kendrick, and Piergiorgio Scarlato

Electron BackScatter Diffraction can be used to measure misalignment in the lattice of crystals. Non-reversible crystal lattice deformation by migration of dislocations, i.e., crystal plasticity, has been observed and recreated under controlled experimental conditions in effusive volcanic rocks. There, crystal plasticity increases with increasing stressing of the magma, and precedes crystal failure. Here, we present the first observation of crystal plasticity in pyroclasts. We found lattice misalignment mainly in plagioclase microlites within ash- and lapilli-sized pyroclasts of mafic composition from explosive eruptions of Etna (Italy), Paricutin (Mexico), and Cumbre Vieja (Spain) volcanoes. Misalignment is found both in visibly curved and apparently undeformed crystals, its magnitude increasing with increasing aspect ratio of the crystals. Plastically deformed crystals are unevenly distributed within the pyroclasts, and often clustered. Similar to observations made in effusive rocks, crystal plasticity in pyroclasts is marked by the presence of broken crystals. But unlike the effusive case, fragments of broken crystals in pyroclasts show little or no plastic deformation, while more deformed crystals are found around zones with broken crystals. Textural evidence from natural and experimental samples show that these zones underwent localized damage by brittle fracturing. Coexisting broken and plastically deformed crystal reveal millimetre-scale patterns of stress localisation in magma during fragmentation

How to cite: Taddeucci, J., Cimarelli, C., Pozzi, G., Kendrick, J. E., and Scarlato, P.: SEM-EBSD reveals crystal plasticity in pyroclasts, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6291, https://doi.org/10.5194/egusphere-egu24-6291, 2024.

12:05–12:15
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EGU24-16972
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On-site presentation
Jackie E. Kendrick, Paul Wallace, Takahiro Miwa, and Yan Lavallée

The physical evolution of multiphase magmas during shear remains a critical question in volcanology. The presence of solid, liquid, and gaseous phases (with contrasting strength and rheology) serves to partition strain and concentrate stress on each phase when the system is subjected to deformation. For example, gas bubbles generally deform relatively easily, whilst melt can stress and relax repeatedly, erasing its deformation history, and crystals can accumulate stress and suffer permanent damage. In suspensions with high interstitial melt viscosity, high crystal content, or low vesicularity, large stresses may accumulate in the crystalline phase, which may result in crystal plasticity and rupture. All minerals may be subject to crystal plasticity if the conditions are suitable: Whereas diffusion creep may be common in deep magmas deforming slowly over long timescales; dislocation creep is likely more common in shallow magma mushes and erupting lavas.

Recent evidence from natural samples and controlled laboratory experiments suggests that even under very low confinement, the crystals present in lavas may deform by dislocation creep prior to failure. EBSD mapping of experimentally deformed, porous, crystal-rich dome lavas (at magmatic temperature) revealed that crystals underwent dislocation creep. For further analysis we focussed on plagioclase (which dominates the crystal assemblage), and found the misorientation of the crystal lattices within the microlites increased as a function of stress and strain, until rupture. Grain size reduction was seen synchronous to deformation, and fragments of broken microlites recorded the highest distortions; thus, crystals exhibit a plastic limit during dislocation creep. The systematic variation in plasticity with applied conditions demonstrates the key role of crystal plasticity in the deformation of crystal-rich lavas, and the possibility to interpret deformation from the imparted dislocations. To test this, we mapped crystal-plasticity across the shear zone at the margin of the lava spine erupted at Mount Unzen (Japan) in 1994−1995. We found that the degree of crystal lattice misorientation in plagioclase microlites increased systematically across the shear zone towards the marginal shear plane, and also that weak phenocrysts such as mica suffered substantial crystal plasticity.

Whilst the ostensible absence of crystal plasticity in deformed igneous bodies has previously been argued to indicate that melt accumulates all the strain during deformation (particularly if melt viscosity is very low), the lack of deformed crystals may also indicate post-deformation crystallisation or longer deformation timescales (i.e., slower strain rates) which would limit stress accumulation in the crystalline phase (due to both efficient rearrangement during flow and the inability for the melt phase to build stress at slow strain rates). Our work demonstrates how crystal plasticity can be utilised to detail strain localisation textures formed during magma deformation, and although, to date, insufficient data exists to define the stress–strain history of magmas and lavas from the vestiges of crystal-plasticity, there remains hope for its use as a strain marker in the future, with further systematic quantification. Our work further demonstrates that rheological models for multiphase suspensions require consideration of crystal-plastic deformation, which may contribute towards the apparent non-Newtonian behaviour of magmatic suspensions.

How to cite: Kendrick, J. E., Wallace, P., Miwa, T., and Lavallée, Y.: Interpreting deformation conditions from crystal-plasticity in extrusive lavas , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16972, https://doi.org/10.5194/egusphere-egu24-16972, 2024.

12:15–12:25
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EGU24-6616
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On-site presentation
John Eichelberger, Amel Barich, Bjorn Gudmundsson, Yan Lavallee, John Ludden, Bjarni Palsson, Paolo Papale, and Freysteinn Sigmundsson

How can we not afford to scientifically probe magma? Fifteen years of accidental drilling encounters with magma have shown that it can be done safely with recovery of magmatic and partial melt samples quenched in situ. More could be gained if preceded by thorough scientific preparation and followed by long-term monitoring. Through the panoply of instruments now available, we can measure temperature, pressure, strain, heat and mass transport and changes over time. In 2009, the Iceland Deep Drilling Program well #1 reached rhyolitic magma at 2100 m depth under Krafla Caldera. The project was exemplary in sharing provocative results, but only hints at what is possible. Equilibrium temperatures were estimated by traditional petrologic techniques to be 850 – 1100 C. Pressure estimates range from 40 – 90 MPa with both extremes seemingly problematic, because for the first time we know the depth of a magma body to 4 significant figures. The lowest value is below lithostatic and the highest could be inherited from deeper levels. Now it appears that the lower pressure is what magma “feels”. But without drilling, would traditional estimates be good enough? Magma is somewhere between 1500 – 4000 m depth and with temperature corresponding to some type of magma? Actually, we would not even know that shallow magma is there but now in hindsight we see it geophysically. Ground-truth testing is how methodologies are improved. Our situation is like speculating about the nature of the Moon without sampling it. The cost of probing Earth’s magma is high and the probability of success uncertain, but far less so on either count than for extraterrestrial exploration. On Earth we are more restrained by self-imposed limits than by our technical capabilities. Besides understanding the differentiation of our planet, we have two compelling reasons for bold exploration: 1) We need the baseload, magma resource with its far higher temperature, energy density, and more extensive thermal fracturing than conventional geothermal; 2) We need to raise the level of reliability of eruption forecasts by testing our magma-dynamic models directly, thereby saving countless lives. As with other endeavors that are expensive for a single country to undertake but that benefit all humankind, a way forward is through an international infrastructure, where teams of scientists can conduct experiments with magma and superhot fluids. This is analogous to particle accelerators and the complement to outer space travel: inner space.  The Krafla Magma Testbed is a much-needed step and an opportunity for all planetary, magma, volcano, and hydrothermal scientists to test their methods and ideas. KMT will drill a doublet of wells to magma for long-term monitoring and experimentation, respectively. The project, now organized as a legal entity within the Iceland Geothermal Research Cluster (GEORG), in partnership with the National Power Company of Iceland (Landsvirkjun), Iceland Energy GeoSurvey (ISOR), and a multinational team of scientists and engineers, under the aegis of the International Continental Scientific Drilling Program (ICDP), is ready. Magma could have been intentionally explored before. It is time to ask, “Why not now?”

How to cite: Eichelberger, J., Barich, A., Gudmundsson, B., Lavallee, Y., Ludden, J., Palsson, B., Papale, P., and Sigmundsson, F.: Why not drill into magma to understand the “dynamics and timescales in magmatic reservoirs”?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6616, https://doi.org/10.5194/egusphere-egu24-6616, 2024.

Posters on site: Tue, 16 Apr, 16:15–18:00 | Hall X2

Display time: Tue, 16 Apr 14:00–Tue, 16 Apr 18:00
Chairpersons: Fabrizio Di Fiore, Alessio Pontesilli, Eleonora Braschi
X2.55
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EGU24-53
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ECS
Xiaohan Huang, Alexandra Yang Yang, Mingdao Sun, Siyu Zhao, Wei Tan, Yoshihiko Tamura, and Taiping Zhao

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.

X2.56
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EGU24-1683
Maren Kahl, Daniel J. Morgan, Carl Thornber, Richard Walshaw, Kendra J. Lynn, and Frank A. Trusdell

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.

X2.57
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EGU24-8840
Chiara Maria Petrone, Rosa Anna Corsaro, and Buret Yannick

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.

X2.58
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EGU24-11586
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ECS
Beatrice Schiavon, Chiara Maria Petrone, Francesca Forni, Alessio Pontesilli, Elisabetta Del Bello, Piergiorgio Scarlato, Manuela Nazzari, Massimo Tiepolo, and Silvio Mollo

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.

X2.59
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EGU24-17281
Eleonora Braschi, George E. Vougioukalakis, and Lorella Francalanci

The Yali volcanic centre is a relatively young volcano that was active within the last 40,000 year and is part of the Nisyros-Kos volcanic field, representing the most recent evidence of magmatic activity in the western part of the South Aegean Active Volcanic Arc, together with the post-caldera lava dome activity occurred at the nearby Nisyros volcano.  

The Yali volcanic activity (bot explosive and effusive) is still poorly studied, and the plumbing system architecture and magma ascent pathways are barely defined, although it represents an important element to be considered for the evaluation of the volcanic hazard and the potential risk in the area, associated to the accumulation of evolving magma body in the crust.  

The aim of our study is thus to detail the nature of juvenile materials and the evaluation of the magmatic processes occurring in the plumbing system. This would provide important information to define the relationships between the different eruptive events that occurred during the Yali volcano evolution.  

The present-day edifice is constituted by the remnant of the original volcano after intense tectonic and erosion processes. It is composed by two distinct parts with difficult stratigraphic correlation due to the limited exposure and continuity of the deposits. The SW part is built up by a thick succession of pyroclastic materials, generated by the eruption of a submarine pyroclastic deposit (Lower Pumice -YLP) followed by a subaerial activity leading to the emplacement of a pumice-rich pyroclastic fallout (Upper Pumice-YUP) that is topped by two layers of reworked pumice-rich deposits (YRL), separated by a thin paleosoil. The NE part is formed by the eruption of large perlitic lava flows and obsidian lava domes associated to an explosive episode generating the Kamara tuff cone.   

The main volume of the erupted products (pumices and lavas) is composed by evolved juveniles of rhyolitic composition. All the pyroclastic deposits, including the Kamara tuff cone host a variable amount of mafic, crystal-rich clasts (SiO2 from 52.5 to 67.5 wt.%) suggesting the occurrence of mingling processes between different evolved magmas in the feeding reservoir/s, thus implying a mafic, deep, refill of the plumbing system. Our data show that the YLP and YUP pumice have similar homogeneous composition, with the latter having a slightly less evolved character. They also display a quite distinct major, trace elements and Sr-Nd isotopes behavior compared to pumices of the YRL. The lavas are even more evolved than pumices. Moreover, the mafic components reveal a heterogeneous composition and isotopic signatures, suggesting the presence of a complex plumbing system feeding the different explosive and effusive eruptions. 

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.

X2.60
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EGU24-1016
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ECS
Federica Langone, Zara Franceschini, Riccardo Avanzinelli, Eleonora Braschi, Francesca Forni, and Raffaello Cioni

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.

X2.61
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EGU24-10917
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ECS
A journey into the Monte Amiata mafic magmatic enclaves world: from fieldwork observations to chemistry
(withdrawn)
Lucrezia Valeriani, Simone Paternostro, José Pablo Sepulveda Birke, Martina Casalini, Eleonora Braschi, Andrea Orlando, Raffaello Cioni, Lorella Francalanci, Simone Tommasini, and Sandro Conticelli
X2.62
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EGU24-6695
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ECS
Megan Watfa, Lorna Anguilano, Philip Collins, Francesca Forni, and Marilena Moroni

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.

X2.63
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EGU24-297
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ECS
Mradipta Lintang Alifcanta Moktikanana, Tsukasa Ohba, Agung Harijoko, and Haryo Edi Wibowo

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.

X2.64
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EGU24-1116
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ECS
Krisztina Hajdu, Réka Lukács, Razvan-Gabriel Popa, Julien Marius Allaz, Emese Páncél, Barbara Cserép, Olivier Bachmann, Elemér Pál-Molnár, Ioan Seghedi, and Szabolcs Harangi

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.

X2.65
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EGU24-459
Gabriele Giuliani, Fabrizio Di Fiore, Silvio Mollo, Claudia Romano, Danilo Di Genova, and Alessandro Vona

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.

X2.66
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EGU24-17296
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ECS
Stefano Peres, Thomas Griffiths, Fabio Colle, Stefano Iannini Lelarge, Matteo Masotta, and Alessio Pontesilli

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 (Trest = 1150°C, 1100°C and 1050°C). Dwell time at Trest 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.

X2.67
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EGU24-3468
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Highlight
Laura Privitera, Alessandro Bonforte, Salvatore Gambino, and Francesco Guglielmino

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.

X2.68
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EGU24-19154
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ECS
Araksan Ahmed Aden, Enikő Bali, Guðmundur Heiðar Guðfinnsson, Gylfi Páll Hersir, Kayad Moussa Ahmed, and Iwona Monika Galeczka

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.

X2.69
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EGU24-16555
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ECS
Marize Muniz da Silva, Jonathan Castro, Jackie Kendrick, Paul Wallace, and Yan Lavallée

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.

X2.70
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EGU24-12812
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ECS
Alessio Pontesilli, Fabrizio Di Fiore, Piergiorgio Scarlato, Ben Ellis, Elisabetta Del Bello, Daniele Andronico, Jacopo Taddeucci, Marco Brenna, Manuela Nazzari, Olivier Bachmann, and Silvio Mollo

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.

X2.71
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EGU24-12270
Adelina Geyer, Martín Miranda-Muruzábal, Meritxell Aulinas, Helena Albert, Miquel Vilà, Fus Micheo, Xavier Bolós, Dario Pedrazzi, Guillem Gisbert, and Llorenç Planagumà

The Catalan Volcanic Zone (CVZ) in northeastern Spain constitutes an intraplate alkaline volcanic region linked to the opening of the Western Mediterranean and the development of the European Rift System. Volcanic activity in the CVZ started in the L’Empordà area (ca. > 12 - 8 Ma), extended to La Selva (7.9 - 1.7 Ma), and finally migrated to the Garrotxa Volcanic Field (< 0.7 - 0.01Ma). Despite ongoing scientific interest in the CVZ dating back to the early 19th century, certain aspects remain insufficiently defined. These include a comprehensive understanding of the spatial and temporal evolution of the magma plumbing system(s) and ascent mechanisms, as well as the chronology of volcanism across the CVZ. Unraveling these unresolved questions requires geochemical, petrological, and geochronological data, which, in the case of the CVZ, are scattered and have never been integrated or analysed within a unified framework. This study introduces the CatVolc (Catalan Volcanism) database, consolidating existing geochemical and geochronological data of volcanic-related materials within the CVZ. The current version of the database incorporates geochemical analyses from 405 rock samples (296 juvenile magmatic rocks -including lavas and pyroclasts- and 109 xenoliths), and radiometric/thermoluminescence dating data from 57 rocks (55 volcanogenic and two dykes), 4 paleosols samples developed between volcanic deposits and 1 sample from sediments. Each entry in the CatVolc database provides general information about the sampling site, sample lithology, whole-rock analyses (including major and trace elements), isotopic ratios, mineral chemistry, and radiometric/thermoluminescence dating details, if available. An initial analysis of the information contained in the CatVolc database highlights the critical limitations of the current state of knowledge and allows suggesting potential future directions for volcanic-driven investigations in the CVZ. Furthermore, the outcomes affirm the CatVolc database as an essential tool for understanding the spatial and temporal evolution of magmatic systems and volcanic activity in the CVZ, particularly within the Garrotxa Volcanic Field. This validation is crucial for advancing the assessment of volcanic hazards in the region and gaining a comprehensive understanding of future volcanic activity.

This work has been developed under the financial support of the Institut Cartogràfic i Geològic de Catalunya (ICGC), the Parc Natural de la Zona Volcànica de La Garrotxa (PNZVG), the Fundación General CSIC's ComFuturo programme and the Marie Skłodowska-Curie grant agreement No. 101034263, the collaboration grant 2021 COLAB 00367 funded by the MEFP,  and the grant PID2022-139047NA-I00 funded by MCIN/AEI/ 10.13039/501100011033 and by “ERDF A way of making Europe”.

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.

X2.72
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EGU24-12896
Olaya Dorado, Adelina Geyer, and Joan Marti

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.

X2.73
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EGU24-1798
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ECS
Carlos A. Angeles-De La Torre, Axel K. Schmitt, Michael McCurry, Martin Danisik, Oscar M. Lovera, Andreas Hertwig, and Axel Gerdes

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.

X2.74
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EGU24-14289
Jianjun Zhang, Tao Wang, Ying Tong, He Huang, and Peng Song

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.

X2.75
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EGU24-19374
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ECS
Barbara Cserép, Saskia Erdmann, Réka Lukács, Olivier Bachmann, Ioan Seghedi, Máté Szemerédi, and Szabolcs Harangi

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% meltSiO2) 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% meltSiO2), 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% meltSiO2, 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.

X2.76
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EGU24-19962
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ECS
Aaron Röhler, Christoph Beier, Andreas Klügel, Wolfgang Bach, and Karsten Haase

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.

X2.77
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EGU24-19813
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ECS
Carlo Pelullo, Hélène Balcone-Boissard, Bruna Cariddi, Sumit Chakraborty, Massimo D'Antonio, Maddalena De Lucia, Sandro de Vita, Mauro Antonio Di Vito, Paola Petrosino, Monica Piochi, Nicolas Rividi, Germano Solomita, Domenico Sparice, Vittorio Zanon, and Ilenia Arienzo

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 (Wo52-48-En47-30-Fs17-5). Mg# [molar Mg2+/ (Mg2+ +Fetot) *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.

X2.78
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EGU24-10251
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ECS
Clothilde Biensan, Jacopo Taddeucci, Tullio Ricci, Elisabetta Del Bello, Piergiorgio Scarlato, and Danilo Palladino

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.

X2.79
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EGU24-5456
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ECS
Claudia Sánchez, Mie Ichihara, and Dan Muramatsu

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.

X2.80
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EGU24-2569
Fabio Arzilli, Margherita Polacci, Giuseppe La Spina, Nolwenn Le Gall, Edward W. Llewellin, Richard A. Brooker, Rafael Torres-Orozco, Danilo Di Genova, David A. Neave, Margaret E. Hartley, Heidy M. Mader, Daniele Giordano, Robert Atwood, Peter D. Lee, and Mike R. Burton

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.

X2.81
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EGU24-15563
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ECS
Fabrizio Di Fiore, Alessandro Vona, Danilo Di Genova, Alessio Pontesilli, Laura Calabrò, Silvio Mollo, Jacopo Taddeucci, Claudia Romano, and Piergiorgio Scarlato

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.

X2.82
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EGU24-7627
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ECS
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Pedro Valdivia, Alessio Zandonà, Jessica Löschmann, Dmitry Bondar, Cécile Genevois, Aurélien Canizarès, Nobuyoshi Miyajima, Alexander Kurnosov, Tiziana Boffa Ballaran, Fabrizio Di Fiore, Alessandro Vona, Claudia Romano, Mathieu Allix, Joachim Deubener, and Danilo Di Genova

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.

X2.83
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EGU24-5289
Giuseppe La Spina, Jacopo Taddeucci, Laura Spina, Francesco Pennacchia, and Piergiorgio Scarlato

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.

X2.84
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EGU24-13126
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ECS
Jing Chen, Shuang-shuang Chen, and Qiu-ming Cheng

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.