Orals: Tue, 5 May, 16:15–18:00 | Room D1
Diffusion chronometry makes use of concentration gradients to determine timescales (as examples - durations of residence in thermal reservoirs, rates of cooling or ascent) of geological and planetary processes. The governing relationship that underlies the method is that the diffusion distance (x) scales with the square root of time (t), so that shorter the length scale over which concentration gradients can be measured, the shorter the timescales of processes that may be determined. However, there are some physical effects that set natural lower and upper limits of length and time scales that are accessible using the tool – these will be discussed in this talk. At the lower end, convolution (i.e., spatial averaging) effects in the analytical instrument being used to measure concentration gradients sets a limit. However, as analytical instruments have evolved to measure concentrations on practically atomic scales, some absolute physical boundaries have become relevant. The first one is related to the statistical nature of diffusion itself – at spatial scales on the order of lattice spacings of minerals (~ 10 Å), Fick’s law of diffusion which forms the basis of most applications, ceases to be valid. Secondly, depending on the nature of concentration jumps that drive the process of diffusion (related to chemical affinity) and the nature of the surrounding medium, transient oscillatory zoning may appear instead of smooth diffusion gradients, even when the thermodynamic variables controlling element partitioning (e.g., temperature, pressure) remain constant. These set limits at the shorter end of the timescale (for a given element in a particular mineral). At the upper end, limits are set by processes of diffusive homogenization or the processes of recrystallization (dissolution of old grains to produce new ones). The latter may be caused by processes such as deformation, exposure to large chemical affinity (driving force for dissolution / growth of crystals), textural refinement related to minimization of surface free energies, or coupling between chemical diffusion and lattice strain caused by element partitioning. Specific examples of some of these instances, such as from the iconic 79 AD eruption of Mt. Vesuvius (the “Pompeii eruption”), will be shown.
How to cite: Chakraborty, S.: Upper and Lower limits of timescales accessible by Diffusion Chronometry, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6447, https://doi.org/10.5194/egusphere-egu26-6447, 2026.
Ross Hassard1, Eleanor Jennings1, Hilary Downes1 and Simon Day2
1School of Natural Sciences, Birkbeck University of London, Malet Street, London WC1E 7HX, UK
2Formerly Institute for Risk and Disaster Reduction, University College London, Gower Street, London, WC1E 7HX, UK.
Historical records of recent volcanic eruptions on the intraplate oceanic island of Fogo (Cape Verdes) reveal significant impacts on the local population, including loss of livestock, destruction of buildings and farming areas and, occasionally, death of inhabitants. The limited volcano monitoring network on the island and the lack of diffusion chronometry studies of the erupted products means there are significant gaps in our understanding of the timescales of magmatic processes at this active volcano.
This research aims to improve eruption forecasting and hazard mitigation at Fogo by using diffusion chronometry data from clinopyroxene and olivine phenocrysts in lava flows from the eruptions of 1951, 1995 and 2014-15 to obtain pre-eruption magmatic timescales.
Key research objectives are (i) to determine diffusion timescales from normally-zoned clinopyroxene and olivine crystals to understand magma and/or lava flow residence times and ascent rates; (ii) to determine whether there a link between seismicity and eruptions at Fogo through the comparison of diffusion timescales with recorded seismic activity.
Findings include an assessment of diffusion chronometry methods which shows that published Fe-Mg diffusion coefficients underestimate timescales in Al-rich clinopyroxenes in strongly alkaline magmas, such as those at Fogo. Results for the 2014-15 eruption using published Mg self-diffusion coefficients, indicate that clinopyroxene rims formed ~5-6 months prior to eruption. Diffusion chronometry from 16 olivine phenocrysts reveals timescales of hours for residence in the lava flow for proximal samples, and up to ~1 month for distal samples, comparable with recorded seismicity prior to the eruption.
How to cite: Hassard, R.: Magmatic timescales prior to the 1951, 1995 and 2014-15 eruptions at Fogo, Cape Verde: Insights from diffusion chronometry of clinopyroxenes and olivines, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13453, 2026.
The polycyclic Santorini caldera (Greece) has entered a new caldera cycle following the large-magnitude Late Bronze Age (Minoan) eruption1. In this new caldera cycle, low-magnitude effusive and mildly explosive eruptions have built up the Kameni islands inside the flooded Minoan caldera. However, an eruption deposit up to 34 m thick was recovered during the International Ocean Discovery Program (IODP) Expedition 398 to the South Aegean Volcanic Arc2 at various sites inside the Santorini caldera (U1594-U1597) and has been interpreted as produced by an explosive (VEI 5) eruption in 726 CE3. Such explosive eruptions are uncommon in the early stages of caldera cycles when the plumbing system is recharging, and the shallow magma reservoir is recovering from caldera collapse. The indication that Santorini can produce explosive eruptions early in a new caldera cycle elevates the hazard potential of future eruptions for Santorini and neighbouring islands in the eastern Mediterranean.
This study presents a petrological and geochemical investigation of juvenile material from the 726 CE eruption deposit at IODP Site U1595, encompassing the full thickness of the deposit, including light and dark grey pumice, banded pumice, scoria, mafic enclaves, dark cognate lithics and glomerocrysts. We also report the results of diffusion chronometry on the primary crystal phases, including Fe-Mg diffusion in orthopyroxene and clinopyroxene, and Mg diffusion in plagioclase. Crystal chemistry reveals the presence of mafic (Mg# 84-73 and An 86-82), intermediate (Mg# 71-69 and An 67-57), and more silicic (Mg# 67-54 and An 53-37) crystal assemblages derived from compositionally distinct magmatic sources beneath the volcano, as well as a crystal mush zone, with evidence of crystal exchange between these reservoirs. By modelling reverse-, normally- and oscillatory-zoned core-rim profiles using diffusion chronology, we constrain mafic and silicic magma recharge timescales, revealing the complex recharge dynamics of the plumbing system associated with the 726 CE eruption. Plagioclase-, clinopyroxene-, and orthopyroxene-hosted melt inclusions of dacitic composition record water concentrations between 3.1-6.1 wt% H2O (average of 4.5 wt% H2O and CO2 concentrations below detection limits (<50 ppm CO2), corresponding with shallow and upper-mid crustal storage between 2.6-7.7 km depth. The melt inclusion derived water concentrations are consistent with other explosive eruptions at Santorini4. Collectively, these results advance our understanding of post-caldera magma system evolution and the conditions under which magma reservoirs capable of large explosive eruptions can develop early in a new caldera cycle.
1Druitt et al. (1999) Geological Society of London, Memoirs, https://doi.org/10.1144/GSL.MEM.1999.019.01.1
2Druitt et al. (2024) Proceedings of the International Ocean Discovery Program,
https://doi.org/10.14379/iodp.proc.398.101.2024
3Preine et al. (2024) Nature Geoscience, https://doi.org/10.1038/s41561-024-01392-7
4Druitt et al. (2016) Journal of Petrology, https://doi.org/10.1093/petrology/egw015
How to cite: Keeley, N., Gertisser, R., Petrone, C. M., DeBari, S., Peccia, A., Druitt, T., Kutterolf, S., and Ronge, T. and the IODP Expedition 398 Scientists: Magmatic processes and timescales of the 726 CE eruption of the Kameni Volcano (Greece), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11993, 2026.
The rapid diffusivity of Li in plagioclase has been used in several studies – employing diffusion chronometry – to quantify the timescales of short-lived magmatic processes, such as degassing, or decompression-induced crystal growth [e.g. 1,2]. However, experimentally determined diffusion rates of Li in K-feldspar (K-fsp) have not been published yet, hindering its use as a diffusion chronometer. Furthermore, previous studies indicate that Li in feldspars and other silicate minerals may show a complex diffusion behavior, with diffusion along interstitial sites as well as along metal sites, producing a characteristic isotope effect [e.g. 3,4].
Here, we performed a series of diffusion couple experiments using oriented K-fsp crystal cubes (Or72, Or80, Or94) in contact with synthetic, Li-doped glass cubes of K-fsp composition (Or60), in order to quantify the (chemical) diffusion rate of Li in K-fsp (DLi) and its dependence on the feldspar composition and the crystallographic orientation. The experiments were conducted in rapid-heat / rapid-quench cold seal pressure vessels at temperatures between 540°C and 940°C and pressures between 50 MPa and 200 MPa. In the run products (crystal and glass cubes), Li concentration and Li isotopic profiles (δ7Li) were analyzed using femtosecond-laser ablation-sector field-ICP-MS and femtosecond-laser ablation-multicollector-ICP-MS, respectively.
Our results show that Li diffuses significantly faster in Or72- and Or80-crystals than in Or94-crystals: values of DLi for Or72 are almost 1.5 orders of magnitude higher than DLi for Or94 at a given temperature. Diffusion rates parallel to the crystallographic b-axis vs. perpendicular to the b- and c-axes in Or80- and Or72-crystals are very similar, suggesting that the diffusion direction relative to the crystallographic orientation has little influence on DLi. The experimentally-produced diffusion-driven δ7Li zoning in our K-fsp crystals implies that two diffusion mechanisms operate simultaneously, i.e. via interstitial sites and A sites. However, preliminary OH-concentration profiles measured by infrared microspectroscopy along the Li concentration profiles additionally indicate that Li-H inter-diffusion also influences the diffusivity of Li in K-fsp.
References:
[1] Genareau & Clarke (2010): Am. Mineral., 95, 592–601.
[2] Neukampf et al. (2021): Geology, 49, 1–6.
[3] Dohmen et al. (2010): GCA, 74, 274-292.
[4] Pohl et al. (2024): Eur. J. Mineral., 36, 985–1003.
How to cite: Oeser, M., Dohmen, R., Pohl, F., Singer, C., and Weyer, S.: Experimental determination of Li diffusion rates and mechanisms in K-feldspar, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13893, 2026.
Amphibole reaction rims are routinely treated as “thermometers and barometers” for magmas, used to back-calculate storage and ascent conditions from changes in pressure, temperature, and melt chemistry. But ascent is dynamic: crystals are transported, rotated, and strained, and those mechanical effects can modify reaction textures in ways that are easily overlooked if rims are interpreted purely in P–T–X space. We demonstrate that amphibole breakdown responds to deformation as well as to thermodynamic forcing. We integrate EBSD orientation mapping from time-resolved experiments and natural rim-bearing samples (Unzen, Soufrière Hills Volcano, Bezymianny, and El Misti) with numerical models that predict how newly formed crystals rotate during shear. The data indicate an initial topotactic relationship in which pyroxene forms in a crystallographically controlled way, replacing the parent amphibole during rim growth. Crucially, that early orientation signal can be progressively overprinted, where pyroxene grains rotate and develop systematic misorientations as strain accumulates. Two endmembers illustrate this behaviour: for amphibole reaction rims formed in petrological experiments, which are designed to be mechanically quiet, simple gravitational settling produces detectable, evolving misorientation patterns. In contrast, natural samples display stronger, more systematic orientation changes consistent with externally imposed shear during transport. Across both settings, the shape of misorientation distributions reflects not only the magnitude of strain but also the relative timing of rim crystallisation versus deformation. These results expand what amphibole reaction rims can record. Rather than archives of conditions alone, rim fabrics measured by EBSD provide a coupled record of chemical–thermal evolution and mechanical history, motivating a P–T–X–ε interpretation framework for tracking magma ascent paths and the dynamics of pre-eruptive transport.
How to cite: Wallace, P. A., Birnbaum, J., De Angelis, S. H., Mariani, E., Larsen, J., Kendrick, J. E., Christopher, T. E., Cole, P. D., Lamur, A., and Lavallée, Y.: Amphibole reaction rims as 4D petrological recorders of pre-eruptive magma transport, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18892, 2026.
Volcanic eruptions produce pyroclasts that range from microns to meters, and produce edifices and deposits that extend for kilometers. Characterization of crystal and vesicle textures on millimeter to centimeter scale samples are commonly used to interpret and quantify magmatic storage, transport conditions, and eruptive processes, despite being divorced from their initial context. Due to practical challenges, our understanding of these micro-scale textures has so far been constrained on the basis of experiments limited to millimeters to a few centimeters in total sample size, upon which numerical simulations and empirical models can be calibrated. In this work, we present results from a natural, microlite-bearing, mildly banded, rhyolitic obsidian which was heated to induce ~60 vol% vesiculation. The sample expanded primarily in one direction, along a confined cylinder to impose shear, from an initial size of 14.5 x 14.5 cm to a final experimental size of 15.0 x 36.5 cm. X-ray computed tomography at a resolution of 33 μm/pixel reveals a rich variety of textures including macro-pores up to 1.5 cm in diameter, regions of high vesicularity juxtaposed against denser regions with smaller pores, evidence of differences in vesiculation history between bands with variable initial volatiles, and densification along the sheared margins. This experiment provides new constraints on texture at the decimeter scale, and places individual sub-volumes on the centimeter scale into their broader context, allowing for analysis of shear history and connectivity on neighboring regions. On the basis of these observations, we validate multi-scale numerical simulations of coupled bubble growth, suspension-scale flow, and fluid percolation, improving our reliability in upscaling to volcanic conditions. Comparison of sample textures with the simulated bubble and fluid pressure, temperature, and strain histories results in a comprehensive picture of intra-sample gas transport and segregation, and reveals the complex vesiculation behavior of initially heterogeneous material.
How to cite: Birnbaum, J., Cordonnier, B., Kendrick, J. E., Lamur, A., Castro, J. M., Wallace, P. A., and Lavallée, Y.: Addressing the elephant in the room: combined experimental and numerical approaches for scaling to volcanic conditions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14160, 2026.
H2O and F are among the most soluble volatile species in basaltic melts, exerting strong control over volcanic eruptive style and influencing climate at regional and global scales. In this study, we aim to quantify the pre-eruptive magmatic H2O and F content of the voluminous Ambenali Formation (Wai Subgroup; ~65.9-65.8 Ma [1]) lavas in the Deccan Traps large igneous province, for which magma volatile contents have not previously been reported. Owing to the scarcity of analysable glassy melt inclusions, the pre-eruptive H₂O and F contents of Ambenali Formation are estimated using clinopyroxene-melt equilibrium calculations. The trace H2O and F contents in clinopyroxene grains were measured using Secondary Ion Mass Spectrometry (SIMS) along core-rim transects. Equilibrium melt H2O and F contents were calculated using appropriate clinopyroxene-melt partitioning (KDcpx/melt) values, which are determined based on clinopyroxene crystallisation temperature and pressure conditions, major element compositions, and degree of melt polymerisation (NBO/T). The calculated KDcpx/melt ranges from 0.012 to 0.016 for H2O, and 0.128 to 0.135 for F. Using these values, the equilibrium melt H2O and F contents are 625 ± 416 ppm and 550 ± 260 ppm, respectively. The calculated melt F contents are broadly consistent with reported melt F contents (634 ± 411 ppm) from the Poladpur and Mahabaleswar Formations of the Wai Subgroup[2]. However, the calculated melt H2O contents are substantially lower than the reported high melt inclusion H2O contents (14571 ± 2621 ppm) from the Poladpur and Mahabaleswar Formations[3]. We propose that clinopyroxene H2O contents diffusively re-equilibrated with the surrounding degassed lava during stagnation and cooling. The absence of H2O concentration variation across core-rim transects suggests ~100% re-equilibration with the degassed lava. We applied a simple one-dimensional, isothermal diffusion model to estimate the minimum timescale for the near-complete diffusive re-equilibration of H2O in our clinopyroxene crystals. Assuming an initial homogeneous clinopyroxene H2O content of 204 ppm[3] and a crystal diameter of 1.3 mm, our diffusion model indicates complete H+ re-equilibration can be achieved on timescales of ~0.01 to 1 year. Therefore, analyses of rare melt inclusions remain critical if we are to accurately estimate pre-eruptive H2O contents of Deccan magmas.
References
[1] B. Schoene, et al., U-Pb Constraints on Pulsed Eruption of the Deccan Traps across the End-Cretaceous Mass Extinction. Science (2019), 363 (6429), 862–866.
[2] S. Callegaro, et al., Recurring Volcanic Winters during the Latest Cretaceous: Sulfur and Fluorine Budgets of Deccan Traps Lavas. Sci. Adv. (2023), 9 (40), eadg8284.
[3] B. Choudhury, et al., Melt Inclusion Evidence for Mantle Heterogeneity and Magma Degassing in the Deccan Large Igneous Province, India. Lithos (2019), 346–347, 105135.
How to cite: Sen, R., Hartley, M., De Hoog, C.-J., Polacci, M., and Gupta, S.: Quantifying H2O and F Contents of Younger Deccan Traps Eruptions using Clinopyroxene-Melt Equilibrium Calculations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-606, https://doi.org/10.5194/egusphere-egu26-606, 2026.
The duration of igneous body assembly controls the thermal evolution of magmatic systems and the spatial distribution of melt during incremental construction. Thermal simulations can be used to reconstruct magma storage histories by providing strong constraints on emplacement duration, melt fraction distribution, and cooling rates. In parallel, rock microstructures (mineral morphologies, crystallisation sequences, and dihedral angles at three-grain junctions) record information on magma solidification kinetics. In particular, dihedral angles can be used to constrain magma cooling-rate variations when combined with thermal modelling.
To better understand the assembly dynamics and magma solidification kinetics in small and highly differentiated granites, we investigated the 900 m thick, incrementally emplaced Beauvoir rare-metal granite (Central Massif, France), which is composed of 18 sills identified through Li-mica (lepidolite) compositional variations. Numerical simulations of pluton construction were performed by sequentially emplacing sills once the reservoir cooled below a critical temperature. The results suggest that ~10 kyr elapsed between emplacement of the first sill and complete solidification of the system, with an averaged construction rate as low as 10-4 km3.yr-1. The solidification times of individual sills ranged from tens to thousands of years. Rapid magma solidification resulted in disequilibrium three-grain junction geometries, while localised skeletal crystal habits bear witness to an early period of high magma undercooling related to sill emplacement. Our results highlight the value of integrating thermal modelling with microstructural observations to reconstruct magma storage histories, and extend the use of dihedral angles to felsic magmas, offering a new tool for probing solidification dynamics in granitic systems.
How to cite: Esteves, N., France, L., Annen, C., Bouilhol, P., and Holness, M.: Assembly duration, cooling kinetics and associated microstructures of a small sized granite pluton, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8027, https://doi.org/10.5194/egusphere-egu26-8027, 2026.
In igneous systems, mineral compositions are controlled by the chemistry of the parental melt, thermodynamic conditions, and the kinetics of magma solidification, all of which may vary along the crystallization path and generate chemical zonation. Additional processes such as magma recharge, mixing, and reactive melt percolation in crystal-rich mushes can further induce partial dissolution and overgrowth of minerals, while diffusion-driven re-equilibration can modify initial compositions. Although point analyses provide precise compositional data, they often fail to capture the full spatial complexity of chemical variability. High-resolution chemical mapping partly overcomes this limitation and, when properly interpreted, offers powerful constraints on magma solidification histories.
The use of selected chemical elements with contrasting diffusivities and crystal–melt affinities provides key insights into successive crystallization stages, from early nucleation to the solidification of late interstitial melts. In olivine, phosphorus is a particularly robust tracer: it is preferentially incorporated during rapid growth, and diffuses extremely slowly in the crystal. It also displays slightly incompatible behaviour, leading to its enrichment in evolved melts and late-stage olivine growth. Coupling P with faster-diffusing incompatible elements such as Al allows relative differences in crystal residence histories and storage conditions to be revealed.
Here we present striking examples from volcanic and plutonic settings where high-resolution P and Al maps in olivine reveal magma solidification dynamics. Chemical maps uncover hidden skeletal to dendritic growth morphologies. They record early disequilibrium crystallization followed by morphological ripening toward near-equilibrium conditions and repeated cycles of partial resorption and overgrowth. A clear dichotomy emerges between volcanic autocrysts, characterized by coupled P–Al skeletal patterns, and mush-derived crystals, in which P preserves early growth features while Al is homogenized during prolonged storage. Finally, in crystal-rich domains, the trapping of highly differentiated melt upon porosity closure is commonly quantified using chemical mass balance. Here we show for the first time that specific chemical tracers can identify olivine crystallization from such trapped, highly evolved melts. Mapping these tracers in plutonic rocks thus provides unique constraints on late-stage porosity distribution.
How to cite: France, L. and Falc'hun, C.: Chemical maps as a memory of magma solidification: from crystallization onset to trapped melt, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2830, https://doi.org/10.5194/egusphere-egu26-2830, 2026.
The 2021 Tajogaite eruption on La Palma (Canary Islands) offers an exceptional opportunity to investigate magma dynamics in an actively monitored monogenetic volcanic system. We present an interdisciplinary study integrating petrological, geochemical, and geophysical datasets to reconstruct the pre- and syn-eruptive evolution of the magmatic plumbing system and its implications for eruption forecasting. Our dataset includes whole-rock and mineral chemistry, olivine diffusion chronometry, gas geochemistry, GNSS and InSAR ground deformation measurements, seismicity, and eruptive column height monitoring.
This integrated approach allows us to constrain magma storage conditions, ascent timescales, and the temporal evolution of the magmatic plumbing system. The results reveal a multi-stage pre-eruptive history involving at least three magmatic intrusions (2017–2018, 2020, and weeks prior to the 2021 eruption) that progressively reactivated the system. Olivine diffusion modeling indicates that the eruption was triggered by a late-stage intrusion in early September 2021, with magma ascent times of approximately 10–30 days.
During the eruption, recurrent injections of deeper magma were detected through systematic changes in crystal chemistry, ground deformation, and eruptive behavior. The earliest erupted products were relatively evolved and contained olivine crystals with oscillatory zoning, reflecting rapid ascent and conduit opening. In contrast, the second half of the eruption was marked by the development of a transient crystal mush zone in the upper crust, where magma accumulated without immediate eruption. This transition is supported by longer olivine residence times and a consistent ∼5-day lag between deformation maxima and peak eruptive column heights.
These observations demonstrate the dynamic nature of magma storage in monogenetic systems and highlight the value of integrating petrological data, including timescales, with real-time geophysical and geochemical monitoring. Such multi-parameter approaches are essential for improving the interpretation of unrest signals, constraining the formation and role of transient upper-crustal magma storage zones controlling eruption dynamics, and enhancing eruption forecasting during future monogenetic eruptions.
This research was funded by the following projects: DYNAMICS (PID2023-151693NA-I00 funded by MCIN/AEI/10.13039/501100011033 and by ‘ERDF A way of making Europe’), PROMEDED (PID2019-104624RB-I00; Ministerio de Ciencia, Innovación y Universidades), and LAJIAL (PGC2018-101027-B-I00, MCIU/AEI/FEDER, EU), MESVOL (SD RD 1078/2021 LA PALMA).
How to cite: Albert, H., Torres-González, P. A., Lamolda, H., Villasante-Marcos, V., Luengo-Oroz, N., Fernández-García, A., Molina-Arias, A. J., Aulinas, M., González-Alonso, E., Prieto, F., Gisbert, G., and Troll, V. R.: Integrated petrological, geochemical, and geophysical constraints on pre- and syn-eruptive magma dynamics during the 2021 Tajogaite monogenetic eruption (La Palma, Canary Islands), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5270, https://doi.org/10.5194/egusphere-egu26-5270, 2026.
Hunga Tonga volcano, located in the Kingdom of Tonga in the southwest Pacific Ocean northeast of New Zealand, forms part of the Tonga–Kermadec subduction zone and is renowned for its VEI 6 eruption in 2022, the most explosive volcanic event of the past century. This cataclysmic eruption generated a volcanic plume rising to >58 km into the mesosphere and injected an unprecedented amount of water vapour into the upper atmosphere.
Here, we investigate the complex zoning patterns of clinopyroxene phenocrysts from tephra ejected in the 2022 eruption by integrating textural analysis, thermobarometry, and Fe–Mg diffusion chronometry. Clinopyroxene cores range from diopsidic to augitic compositions and commonly display sieved and patchy textures, indicating extensive antecryst recycling and dissolution–recrystallization processes. Multiple growth bands with diopsidic to augitic compositions record repeated magma-mixing events and variable degrees of chemical homogenization within the shallow reservoir.
Preliminary diffusion modelling indicates that the time elapsed between mafic magma injection and eruption spans from decades to a few months, with only a minor population of crystals recording timescales shorter than one month. These results suggest the absence of a direct temporal link between shallow magma mixing and the immediate trigger of the 2022 cataclysmic eruption at Hunga Tonga. We propose a decade-long pressure build-up process instead, with repeated mafic injections and magma and gas accumulation up to a few months before the eruption, in agreement with the top-down/decompression-driven trigger model of Wu et al. (in review).
How to cite: Califano, E., Petrone, C. M., Wu, J., Mollo, S., Brenna, M., Pontesilli, A., Cortes-Calderon, E. A., Buret, Y., Di Fiore, F., and Cronin, S.: Decades long priming of plumbing system preceding the 2022 eruption of Hunga Tonga Volcano, Tonga, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14893, 2026.
Submarine volcanoes make up ~75% of volcanism on Earth, yet they are one of the least explored volcanic features. Our understanding of these eruptions is limited due to challenges in monitoring these often remote volcanos with summits deep underwater. Nonetheless, consequences of their eruption can pose significant risks to the local economy and society (e.g. tsunamis) [1]. The recent (2018-2020), unanticipated submarine eruption of Fani Maoré ~50 km East of Mayotte island (Comoros Archipelago) [2] demonstrates this. Monitoring of the area increased only after its eruption, leading to the discovery of a submarine volcanic chain near the island of Mayotte. After the Fani Maoré eruption ended, seismicity and CO2 fluid emissions still continues below the so-called Horseshoe complex [3,4]. This complex is composed of recent phonolitic pyroclastic cones and lava flows, a number of them are of Holocene age and significant volume. Thus, it poses a critical risk to the >320000 inhabitants of Mayotte, as it is only ~10 km from the island [5]. Scenarios for future increased unrest and eruptive activity need to be considered. To contribute to this, we use diffusion chronometry in olivine to determine the maximum interaction times of Holocene magmas with peridotite and gabbro xenoliths in the Horseshoe phonolites. We find extremely short diffusion times on the order of minutes to hours (<5 ± 1 h) for pyroclastic samples, which implies rapid ascent of magma from the MOHO (~20 km). For lavas, these times are significantly longer in the range of days to months (5 ± 2 to 163 ± 17 days). While the longest times in lava flows are attributed to continued diffusion during post emplacement cooling, shorter times provide minimum ascent rates. These are 7.7 ± 4.2 m/s for explosive eruptions and 0.016 ± 0.008 m/s for effusive ones. Hence, the final warning signals of impending eruptive activity would only be detected a few hours to days before eruption. This underscores the necessity to have efficient preventive risk reducing strategies well emplaced by the time very early-warning signs of potential unrest are detected through the local Volcanological and Seismological Monitoring Network of Mayotte - REVOSIMA [6].
[1] Gusman et al. (2022) Pure Appl. Geophys., 179, 3511-3525. [2] Feuillet et al. (2021), Nat. Geosci., 14, 787-795. [3] Thivet et al. (2023) Chem. Geol.,618, 121297. [4] Lavayssière & Retailleau (2023) Volcanica, 6, 331-344. [5] Puzenat et al. (2022) C. R. Geosci., 354, 81-104. [6] REVOSIMA: https://www.ipgp.fr/en/observation/national-hosted-infrastructures/revosima/
How to cite: Brückel, K., Médard, E., Costa, F., Berthod, C., Komorowski, J.-C., Harris, A., and Gurioli, L.: Assessing the hazard of potential submarine eruptions at the Horseshoe complex through diffusion chronometry, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9437, https://doi.org/10.5194/egusphere-egu26-9437, 2026.
Recent unrest events on São Jorge Island (Azores, Portugal) may signal impending volcanic eruptions, highlighting the urgent need to better understand the island’s magma system. Some of the analyzed basaltic and hawaiitic S. Jorge lavas show evidence of magma mixing and rapid assembly of crystals shortly preceding the eruptions. A subset of the studied olivine crystals displays reverse zoning, with rimward increase of forsterite (Fo) content, while others contain distinctly different Fo values within the same rock sample. Diffusion chronometry reveal variable mixing-to-eruption timescales (years to days), but the fastest timescales occur in olivine from the two most recent eruptions on the island and possibly provide constrains for the tempo of future volcanic eruptions. Volatile analyses emphasize the role of CO2 in the magmatic system of the island. Crystallized MIs in olivine and clinopyroxene commonly contain gas bubbles, with CO2 as the sole fluid phase. Calculated CO2 concentrations in the MIs reach up to 1.5 wt%. H2O is absent in the bubbles, even if the system was probably water rich, as hydrous minerals are present in the MIs and occasionally as phenocrysts. The high CO2 and likely H2O budgets increase magma mobility and explosive potential. Findings of this study show that São Jorge mafic magmas ascend rapidly through a transcrustal system, with eruptions potentially occurring after short warning times.
How to cite: Marzoli, A., Beghini, E. L., Albert, H., Capriolo, M., Madeira, J., Mata, J., Santello, L., Meyzen, C. M., Spiess, R., Novella, D., Youbi, N., and De Min, A.: Evolution of the magma plumbing system at São Jorge Island, Azores, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9139, https://doi.org/10.5194/egusphere-egu26-9139, 2026.
The ESRF provides an exceptional experimental “fleet” to study volcanic and igneous processes directly in 3D and 4D, under realistic conditions. By combining high-flux phase-contrast tomography (XCT), high-energy imaging and diffraction (XRD), and microbeam chemical/mineral mapping (µXRF/µXANES/µXRD), we can link composition, texture, porosity and strain in a fully non-destructive workflow, from sub-micron structures to meter scales and for evolving dynamic sample.
A key asset is the ability to cover both extremes of dynamics: ultra-fast 4D imaging for transient, non-reproducible events (fragmentation, bubble/melt interactions, rapid damage or reactive infiltration), or long-duration time-lapse experiments tracking slow kinetics over days to months (crystallization, dissolution–precipitation, sealing, weakening). These studies are enabled by a broad portfolio of in situ environments at ESRF (heating, controlled atmosphere, reactive-flow, pressure/temperature and deformation rigs), coupled with robust reconstruction, quantitative segmentation, and AI-assisted analysis.
Access is supported through community frameworks and community BAG-style access, including CHRONOS for long-duration, repeatable time-lapse campaigns, and the geoscience BAG (NEXUS) to streamline proposals, beamtime coordination, and cross-beamline workflows. We welcome projects ready to exploit this “microseconds-to-months” capability and to co-build the next generation of 4D protocols for volcanic and magmatic research.
How to cite: Cordonnier, B.: Volcanoes in 4D: Imaging Magmatic Processes with the ESRF Instrument Fleet, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20895, 2026.
Periods of volcanic unrest, such as the 2021-2023 episode at La Fossa crater (Vulcano Island, Italy), present significant challenges for emergency management due to the inherent uncertainties of hydrothermal systems. This recent escalation, characterized by increased fumarole temperatures, ground uplift, and high gas fluxes highlighted the urgent need for physically based frameworks to interpret non-eruptive unrest. To address this, we present an integrated methodological workflow that bridges the gap between micro-scale rock properties and macro-scale volcanic behaviour. Our approach begins with a comprehensive stratigraphic reconstruction down to 1000 metres, achieved by correlating surface outcrop samples with deep "horizons" from historical geothermal well cores.
The core of our research leverages cutting-edge imaging technologies to quantify the reservoir-caprock system's internal architecture. We employ high-resolution X-ray microtomography (X-CT) to generate non-destructive 3D reconstructions with a 1µm voxel resolution, allowing for the precise mapping of pore-network connectivity and the distinction between effective and isolated porosity. This static characterization is further enhanced by dynamic 4D time-resolved imaging, where in-situ mechanical experiments—including uniaxial compression and tensile tests—are performed during CT scanning. This allows for the real-time visualization of fracture initiation and propagation within the volcanic matrix under simulated hydrothermal pressure.
By integrating these advanced imaging data with laboratory measurements of hydraulic and elastic properties, we define the geomechanical thresholds that govern fluid-driven failures. This multi-analytical methodology not only provides new insights into the tectonic and stratigraphic controls of Vulcano’s hydrothermal system but also establishes a robust, technology-driven protocol for assessing volcanic hazards in complex systems where subsurface data are sparse.
How to cite: Falasconi, A., Buono, G., Pappalardo, L., and De Astis, G.: From micro-scale pore networks to macro-scale volcanic hazard: characterizing the hydrothermal reservoir system via non-destructive 3D imaging, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4976, https://doi.org/10.5194/egusphere-egu26-4976, 2026.
The Campi Flegrei caldera is an outstanding example of large silicic calderas, offering critical insights into magma storage, transfer dynamics, and eruptive precursors in such systems. Since the last eruption in 1538 CE, the caldera experienced subsidence, interrupted by unrest episodes in 1950–52, 1970–72, 1982–84, and ongoing unrest since 2005. Here we integrated the results from recent 2D/3D microstructural and chemical characterizations of representative natural eruptive products with advanced high-temperature, high-pressure experiments conducted under controlled conditions to comprehensively investigate the magma storage and ascent conditions of this volcanic system. Petrological evidence reveals a long-lived, multi-level magmatic system, with a deep mafic reservoir (~300–400 MPa, 12–16 km depth) and a shallower, zoned, sill-shaped chamber (~150-200 MPa, 6–8 km depth), still detected today by recent geophysical surveys in this area. Small-volume intrusions occasionally reach upper crustal levels, near lithological discontinuities, to rapidly cool or erupt. These shallower intrusions are typically linked to small-scale eruptions, marked by slow magma ascent, open-system degassing and potential stasis at shallower depths, leading to prolonged unrests or failed eruptions. In contrast, large explosive eruptions involve rapid, sustained magma ascent and closed-system degassing, likely associated with fast conduit propagation and brief, deeper precursory signals. In this context, the combination of these petrological results with geochemical data highlights that the recent dynamics started during the 1982–84 unrest, reflects significant magma transfer (~1-3 km³) in the deeper part of the system (≥200 MPa), which released hot gases into the overlying hydrothermal system, deforming and fracturing the upper crust.
How to cite: Buono, G., Pappalardo, L., and Fanara, S.: Insights into the processes and timescales of magma storage and ascent at Campi Flegrei caldera: From natural samples to experiments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16884, 2026.
The Campi Flegrei caldera represents an ideal natural laboratory for investigating volcanic carbon dynamics, offering a unique opportunity to explore the interplay between magmatic and hydrothermal processes. This work synthesizes recent studies to provide a comprehensive overview of key processes such as magmatic degassing, hydrothermal decarbonation, and carbon sequestration via calcite precipitation. These phenomena not only shape the geochemical signals crucial for volcanic risk assessment but also drive significant chemical and physical transformations within the caldera fill deposits. Specifically, the precipitation of hydrothermal calcite occurs at the expense of the alteration of caldera-filling tuffs, leading to changes in their porosity and permeability. This, in turn, modifies the mechanical properties of these rocks, with critical implications for their deformation and fracturing behaviour under stress. Such changes play a fundamental role in influencing the mechanical stability of the caldera system and the evolution of hydrothermal reservoirs, with direct consequences for volcanic hazard scenarios. Moreover, the findings underscore the complex interplay between magmatic and non-magmatic contributions to CO2 emissions. Hydrothermal calcite emerges as a dual agent in this context: functioning as a carbon sink during quiescent phases and as a potential source during periods of hydrothermal perturbation or reactivation. These dual roles highlight the dynamic nature of carbon cycling within the caldera and the need for integrative approaches to monitor and model these processes. By advancing the understanding of volcanic carbon cycling, this work provides a framework for investigating similar systems worldwide. Methodologies and conceptual models developed here could serve as benchmarks for studying other calderas, enhancing global capabilities in volcanic monitoring and risk mitigation.
How to cite: Pappalardo, L., Aiuppa, A., Buono, G., Caliro, S., Paonita, A., and Chiodini, G.: Magma Degassing Models and Decarbonation Processes Affecting Hydrothermal Calcite , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18285, 2026.
Chlorites are rock-forming layered silicates with a predominantly trioctahedral cation arrangement. The clinochlore (nominally Mg5Al(Si3Al)O10(OH)8) – chamosite (nominally Fe2+5Al(Si3Al)O10(OH)8) series are the most widespread chlorite solid solution, which occurs in diverse geological settings. These can range from sedimentary rocks and low- to medium-grade metapelites and metagreywackes in oceanic crust, to hydrothermal settings as the typical alteration products of ferromagnesian magmatic minerals and deep-seated ultramafic hydrated peridotite mantle wedge reaching depths of 120 km [1-3]. Chlorite commonly contains up to 13 weight percent H2O, contributing therefore in the volatile cycling and mass transport in subducting lithosphere. Thus, the accurate crystallochemical characterization of chlorites while they are still intact in the original mineral assemblages, like in thin sections prepared for polarization microscopy, will provide a better insight into how these layered silicates formed and changed over time. Furthermore, the determination of the crystallochemical composition of chlorites can broaden the knowledge in fields where sampling is either too complicated, e.g. extraterrestrial missions on Mars, or entirely prohibitive, for instance in cultural heritage [4]. For the latter, a non-destructive, non-invasive (i.e. preparation-free) and non-destructive (object remains intact during the measurement) analytical approach is needed, to establish quantitative relationships between the crystallochemical composition and the Raman signals of chlorite, similar to the strategies developed for other complex hydrous silicates [5-6]
This study focuses on a series of 11 chlorite-group minerals from the collection of the Mineralogical Museum, Hamburg, covering the whole clinochlore – chamosite solid-solution series, which were analyzed by Raman spectroscopy, wavelength-dispersive electron microprobe analysis (WD-EMPA), and Mössbauer spectroscopy. The goals were (i) to build up quantitative correlations between the Raman scattering of both framework (15-1215 cm-1) and OH-bond stretching (3200-3800 cm-1) vibrations with the chemical composition of chlorites, particularly when partitioning of Fe2+ and Fe3+ over the tetrahedral and octahedral sites is known., and (ii) to understand how the Raman spectral pattern depends on chlorite orientation. We demonstrate that tetrahedrally coordinated Si and Al can be quantified from the position of the strongest Raman peak at ~ 675 cm-1 , arising from the TO4-ring mode, whereas the amounts of octahedrally coordinated Mg, Fe2+ and Fe3+ can be quantitatively estimated through the fractional intensities of the the multi-component Raman scattering generated by the OH stretching, with typical peaks at ~ 3678, 3655, 3625, 3587, and 3570 cm-1 assigned to specific local chemical configurations.
References
[1] M.W. Schmidt and S. Poli, Earth Planet. Sci. Lett. 1998, 163, 361.
[2] G. Manthilake, N. Bolfan-Casanova, D. Novella, M. Mookherjee, D. Andrault, Sci. Adv. 2016, 2, e1501631
[3] A. Steudel, R. Kleeberg, C. Bender Koch, F. Friedrich, K. Emmerich, Appl. Clay Sci. 2016, 132-133, 626.
[4] S. Aspiotis, A. Dietz, Z. Földi, F. Hildebrandt, J. Schlüter, B. Mihailova, J. Raman Spectrosc. 2025, 56, 228.
[5] S. Aspiotis, J. Schlüter, G.J. Redhammer, B. Mihailova, Eur. J. Mineral. 2022, 34, 573.
[6] N. Waeselmann, J. Schlüter, T. Malcherek, G. Della Ventura, R. Oberti, B. Mihailova, J. Raman Spectrosc. 2020, 51, 1530.
How to cite: Aspiotis, S., Redhammer, G. J., Peters, S., and Mihailova, B.: Crystal chemistry of the clinochlore – chamosite solid-solution series quantified by Raman spectroscopy, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16594, 2026.
Nanoscale crystals, or ‘nanolites’, are becoming increasingly recognised in both experimental products and natural samples of volcanic eruptions, across a range of magma compositions and explosivity. Nanolites can increase magma viscosity and influence eruptive style, due to the rheological impact of the nanoparticle suspension, by inducing chemical and structural changes in the residual melt and by facilitating heterogeneous bubble nucleation. Due to their large surface area, nanolites are also prone to aggregation. However, their morphology, spatial distribution and interaction in 3D has not yet been investigated.
Here we present a 3D, nanometre-scale visualisation and quantification of nanolites within scoriae of highly explosive basaltic volcanic eruptions, obtained using X-ray ptychography, a nanoscale microscopy technique. We find that titanomagnetite nanolites aggregate, forming elongate, irregular structures in 3D. Compositional heterogeneities are also observed within the matrix glass, as extraction of Fe and Ti from the melt during nanolite crystallisation forms differentiated, Si-rich boundary layers surrounding nanolites with higher viscosity. We support our 3D nanoscale observations with images acquired using SEM and STEM, utilising multi-scale imaging methods to visualise nanolite crystallisation in basaltic magmas. We find that syn-eruptive nanolite crystallisation can increase magma viscosity through their aggregation and impact on the composition of the residual melt, increasing the potential of magma fragmentation during ascent. Our results provide insight into the nanoscale structure of volcanic products and also the driving mechanisms of highly explosive basaltic volcanic eruptions.
How to cite: Bamber, E. C., Arzilli, F., Cipiccia, S., Batey, D. J., La Spina, G., Polacci, M., Gholinia, A., Bagshaw, H., Di Genova, D., Brooker, R., Giordano, D., Valdivia, P., and Burton, M.: 3D visualisation of nanolite aggregation in basaltic magmas using X-ray ptychography: Implications for magma rheology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14577, 2026.
Understanding the chemical and physical behaviour of silicate melts requires direct constraints on melt structure at the nanoscale. Recent studies suggest that variations in melt nanostructure exert a primary control on magmatic properties (e.g., melt viscosity), yet their evolution at deep undercooling remains poorly constrained. Here, we investigate nanoscale melt structure dynamics in alkaline and alkaline-earth–rich volcanic melts using a combination of synchrotron-based small- and wide-angle X-ray scattering (SAXS–WAXS) and Raman spectroscopy. All investigated compositions are X-ray amorphous at room temperature. However, upon heating above the glass transition temperature (Tg), SAXS–WAXS data reveal the rapid development of nanoscale heterogeneities rich in Fe and Ti. The onset and evolution of this nanostructuration are strongly dependent on the initial redox conditions and melt composition. Mössbauer spectroscopy indicates that rapid nanostructuration correlates with higher proportions of tetrahedrally coordinated Fe3+, which is in turn interpretable as originating from differences in the network modifiers content of the melts. Our findings have important implications for the interpretation of viscosity measurements and for the understanding of the non-equilibrium evolution of magmatic liquids.
How to cite: Calabrò, L., Zandonà, A., Dominijanni, S., Stopponi, V., Abeykoon, S., Bondar, D., Valdivia, P., Bamber, E. C., Arzilli, F., Longo, A., Romano, C., and Di Genova, D.: Chemically controlled nanostructuration in alkaline silicate melts, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20012, 2026.
Understanding the architecture and temporal evolution of magmatic plumbing systems remains a central challenge in volcanology, particularly for remote and limited-access volcanic systems such as those found in Antarctica. Due to their remoteness and limited monitoring, the eruptive behaviour and hazard potential of Antarctic volcanoes remain poorly constrained. This underscores the urgent need to better characterise the magmatic systems of Antarctic volcanoes and assess their potential for hazardous, large-scale explosive eruptions.
In this contribution, we present an integrated framework combining major and trace element geochemistry, crystal-scale chemical mapping, thermobarometry, and machine-learning tools to investigate the structure and evolution of magmatic plumbing systems beneath the Mount Melbourne Volcanic Field (northern Victoria Land, Antarctica). In particular, we focus on using the crystal cargo (clinopyroxene, plagioclase, and olivine) to reconstruct crystallisation conditions and reservoir dynamics through time, providing new constraints on magma storage depths and plumbing system evolution, and improving our understanding of subglacial volcanic hazards in glacial environments. Results indicate a complex magmatic history, as recorded by distinct mineral populations and chemical zoning patterns, reflecting evolving magma storage conditions and dynamic processes of magma recharge and differentiation. More broadly, this work demonstrates the potential of integrating advanced petrological observations with machine-learning approaches to decipher deep-to-surface magmatic processes in remote volcanic systems.
How to cite: Ágreda López, M., Rocchi, I., Giacomoni, P. P., Petrelli, M., Masotta, M., and Rocchi, S.: Plumbing system evolution beneath the Mount Melbourne Volcanic Field (northern Victoria Land, Antarctica): insights from the crystal cargo, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16496, 2026.
Crystal size distributions (CSDs) preserved in volcanic rocks elucidate important pre and syn-eruptive parameters including magma residence time, viscosity (and thus eruptibility), and ascent rate. Despite their importance, quantifying 3D CSDs using X-Ray Tomography remains limited by resolution trade-offs, small N, and time intensive crystal classification following image acquisition. To address these limitations, we take ~30 sub-samples of one Bishop Tuff pumice clast and image ~10 sub-samples per resolution (1.24, 3.18, 5.72 µm/voxel) building on Pamukçu & Gualda (2010). Images were acquired at Argonne National Lab’s Advanced Photon Source (GSECARS), which is a synchrotron CT facility. This method captures ~ 10,000 crystals per resolution for a wide range of crystal sizes (Spherical Equivalent Diameter ~ 0.001-1 µm). Following image acquisition, we train a single 2D U-Net model per resolution using Dragonfly 2025.1 segmentation software. Our models successfully identify 6 phase groups: pore space, finely vesiculated glass, quartz/feldspar, pyroxene/biotite, and accessory minerals. From these classified image stacks, we extract ~90 crystal size distributions (1 per sub-sample). We find that distributions vary by sub-sample within a given resolution and phase group. This is most obvious for the feldspar/quartz group, wherein CSDs for some sub-samples fit a power law distribution, indicating fragmentation, and others fit multiple exponential distributions, indicating several episodes of continuous nucleation and growth. Fragmentation seems to be at least partly associated with melt inclusion decrepitation. These results indicate that intra-sample textural variability can be significant. As such, future work should utilize multiple sub-samples in tandem with machine learning for image segmentation, which can speed up lengthy post-processing from weeks to days.
How to cite: Ward, S., Gibson, B., and Gualda, G.: 3D Crystal Size Distribution Analysis using Machine Learning for Image Segmentation: Application to the Bishop Tuff, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13098, 2026.
The Reykjanes Ridge (RER) is a 1000 km-long slow-spreading segment of the Mid-Atlantic Ridge that extends southwest from the Reykjanes Peninsula, Iceland. The Icelandic mantle plume exerts a chemical and thermal influence on the ridge that varies spatially, expressed in systematic changes in glass geochemistry, magma flux, crustal thickness and magma storage depths along the ridge [1, 2]. The RER is arguably one of the best-studied segments of mid-ocean ridge globally. However, very little is known about the nature of magmatic processes along the RER. Specifically, we do not know whether there are systematic changes in the assembly, storage and transport of magmas along the ridge with varying proximity to the mantle plume.
We present the first systematic investigation of magmatic processes along the RER with a geochemical and petrological study of mid-ocean ridge basalts (MORB) dredged from a ~900 km transect along the ridge. The crystal cargoes of these samples preserve records of recharge, mixing and ascent, as well as the pressure-temperature conditions of magma storage. We combine EPMA analyses with textural observations from BSE and EDS mapping to reconstruct the complex magmatic histories of individual crystals and of crystal populations. Zoning and resorption textures in individual crystals reveal how magmatic conditions changed during crystal storage and growth. We observe different types of crystal textures and different crystal populations that recur along the ridge, and we determine the spatial distribution of these variations.
Our goal is to identify signatures of mush disaggregation and mixing between magma and crystal populations, and to assess whether the relative importance of these processes changes along the RER with proximity to the Iceland mantle plume. This work represents a new contribution to the relatively limited data on crystal cargoes in global MORBs, and will allow us to place constraints on how crystallisation and magma storage at mid-ocean ridges may vary according to magma flux, crustal thickness and mantle chemistry on a global scale.
References
[1] Murton, B. J., Taylor, R. & Thirlwall, M., 2002. Plume-Ridge Interaction: A Geochemical Perspective from the Reykjanes Ridge. Journal of Petrology, 43.
[2] Baxter, R.J.M. & Maclennan, J., 2024. Influence of magma flux on magma storage depths along the Reykjanes Ridge. Earth and Planetary Science Letters, 631.
How to cite: Hughes, R., Hartley, M., Murton, B., and Neave, D.: Crystal cargoes along the Reykjanes Ridge: insights into magmatic processes at a slow-spreading, plume-influenced mid-ocean ridge, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3088, https://doi.org/10.5194/egusphere-egu26-3088, 2026.
Türkiye hosts a wide variety of natural landscapes and geological features and is therefore a region worthy of investigation. Owing especially to its active volcanic areas, it has been the subject of numerous scientific studies. Within the scope of this study, a zone in the Malatya–Pütürge–Kayadere area was investigated. The region is widely characterized by ophiolitic stratigraphic units and alteration zones, representing remnants of the Neo-Tethys Ocean formed between the African–Arabian and Eurasian plates during the Mesozoic tectonic evolution of the region.
An unusual internal structure exhibiting distinctive formation characteristics was identified during microscopic examination of a drill core sample from the Malatya–Pütürge–Kayadere area. Since no surface occurrence of this unit has been documented to date, the material was accessed at undersurface levels through drilling and investigated using optical microscopy, whole-rock geochemical analyses (XRF, XRD), and electron microscopy.
The rock is characterized by dendritic, platy, and radial micro-textures composed of pyroxene frameworks. Although these microstructures were initially thought to be conodont- or graptolite-like fossils, their occurrence within a matrix composed of amorphous volcanic glass indicates that they represent mineral forms crystallized in this distinctive manner. The aphanitic textured rock locally contains gas cavities infilled with zeolites and carbonates. Minor amounts of olivine grains are also present. Based on its mineralogical and textural characteristics, the rock is classified as a pyroxenite dike. Such examples are scarce globally, and no comparable study has been documented from Türkiye to date.
SEM analyses have confirmed that the crystalline phases are pyroxenes, displaying weak compositional zoning with Mg-rich cores and Fe-rich rims. Major oxide chemical analyses, normalized to 100 wt.%, indicate values of SiO₂ 42.5 wt.%, Fe₂O₃ 13.1 wt.%, MgO 13.2 wt.%, Al₂O₃ 14.9 wt.%, CaO 9.2 wt.%, K₂O 1.4 wt.%, TiO₂ 0.8 wt.%, and Na₂O 0.7 wt.%. This study presents the preliminary results of investigations on an interpreted ultramafic dike, while future studies aim to constrain its formation conditions, stratigraphic affiliation, and genetic interpretation.
How to cite: Kaya, S., Türeli, T. K., Çubukçu, H. E., Kurt, H., Yurtyeri, E., and Köse, B.: A Pyroxenite Dike? of Stunning Textural Beauty: An Unexpected Geological Occurrence from Türkiye, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2581, https://doi.org/10.5194/egusphere-egu26-2581, 2026.
