Orals: Wed, 30 Apr | Room 0.96/97
The ionic radii of rare-earth elements (REE: Sc, Y, and the lanthanides) are key to interpreting partitioning behavior among minerals and melts for use as petrogenetic tracers and thermometry. Here, we show that published experimental data on mineral-melt partitioning of REE imply the ionic radius of Y3+ is smaller than commonly assumed by 0.002Å for 6-fold coordination to 0.004Å for 8- and 9-fold coordination. This difference reconciles the partitioning behavior of Y3+ compared to other REE and improves reference states for interpretations of trace element systematics in rocks. Thermobarometry can be highly sensitive to assumed ionic radii, and downward correction of the radius for Y3+ improves some REE-based temperatures by hundreds of degrees. Future studies that employ the common tabulation of ionic radii from Shannon (1976; Acta Crystallographica, A32, 751-767) should use an ionic radius of Y3+ of 0.898, 1.015, and 1.071Å for 6-, 8-, and 9-fold coordination; alternatively, the ionic radius of Y can be scaled to that of Ho3+ x 0.999. More generally, trace element partitioning data coupled with theoretical models provide a novel method to critically evaluate and refine effective relative ionic radii.
How to cite: Schwartz, D. M. and Kohn, M. J.: Ionic radii of the REE, 1: A novel method to refine ionic radii shows Y3+ is smaller than assumed in common minerals, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14305, https://doi.org/10.5194/egusphere-egu25-14305, 2025.
The Beja Layered Gabbroic Sequence (LGS) is a large mafic layered intrusion, exposed across the southwestern border of the Ossa-Morena Zone (Iberian Massif), in southern Portugal. Despite its synorogenic character, this intrusion is well-preserved from post-magmatic tectono-metamorphic events. The S-SW border of LGS was intruded by an anorthosite-trondhjemite-tonalite (ATT) suite, locally injected into NW-SE shear zones, which nature and geodynamic significance are here discussed. Dykes forming the ATT suite occur mainly as coalescing, ten-meter-wide stockworks, and are essentially composed of plagioclase (often strongly zoned) and green hornblende, plus accessory quartz, zircon, ilmenite, and magnetite. Gabbroic and amphibolitic xenoliths are frequently included in these rocks presenting evidence of variable chemical digestion. Three main lithological types were recognized: anorthosites displaying mortar texture, anorthosites with hornblende megacrysts, and trondhjemites. Plagioclase cores become less calcic from the former to the latter type (median = An 48 , An 46 , An 30 , respectively), but mortar subgrains are typically more evolved (An 23-61 ). Geochemical features of ATT rocks classify them as diorites or quartzdiorites. In chondrite-normalized REE spidergrams, most samples show strong to moderate positive Eu anomalies ((Eu/Eu*) N =1.30–7.22), moderate to strong LREE fractionation ((La/Sm) N =2.34–8.34) and relatively flat to positive HREE profiles ((Gd/Yb) N =0.85–2.10), correlating with zircon accumulation (Zr<2314 ppm). More evolved facies display weak negative anomalies ((Eu/Eu*) N =0.60–0.96), plus flat to moderate LREE and HREE profiles ((La/Sm) N =0.69–3.21; (Gd/Yb) N =0.60–1.42)). CL images of zircon concentrates reveal well-defined, concentric magmatic oscillatory zoning, as well as scarce diffusive, bright domains near the crystal edges, presumably related to hydrothermal overgrowths. U-Pb SHRIMP zircon dating provided three sets of coherent weighted mean corrected ages: 330.7 ± 1.1 Ma (MSWD=0.0051), 336.5 ± 1.1 Ma (MSWD=0.092); and 348 ± 2 Ma (MSWD=0.0024). Age-corrected Sr and Nd isotopic signatures ( 87 Sr/ 86 Sr i =0.704597–0.705319; εNd i = -1.07 to +1.06) suggest the contribution of enriched mantle sources or high amounts of poorly radiogenic crustal components. Values for εHf i in zircon (-1 to +6) are homogeneous and chondritic. Lithogeochemical and isotopic data do not exclude contributions from LGS magmas (εNd 350Ma = -4.21 to +6.75; 87 Sr/ 86 Sr 350Ma =0.703001–0.707448). Nonetheless, extreme enrichments in Zr+Hf+Th+U imply important contributions from crustal components, sometimes yielding superchondritic Zr/Hf ratios (38–59). Previous studies have shown that the LGS magmas were underplated at the crust-mantle boundary, triggering the formation of a deep crustal hot zone (DCHZ). Considering the geochemical/isotopic evidence, it is suggested that the ATT suite resulted from a protracted incubation period at the transition between the highly refractory granulitic basement and overlying metasediments. ATT melt generation possibly initiated ~348Ma and proceeded until ~330Ma, implying multiple periods of basaltic melt entrainment and thermal rejuvenation into mush reservoirs at depth, subjected to multi-phased extraction periods. The wide age span of the ATT suite and resetting of LGS amphibolite country rocks (333.9 ± 1.3 Ma, MSWD=0.079; 346.1 ± 1.9 Ma, MSWD=4.7E-06) suggest that the DCHZ in Beja should have persisted for a long period of time.
Co-funded by the EU SEMACRET GA#101057741 and by FCT I.P./MCTES through national funds (PIDDAC): UID/50019/2025 and LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020).
How to cite: Oliveira, A., Jesus, A., Antunes Dias, M., Bartolomeu, B., and Mateu, A.: Anorthosite-Trondhjemite-Tonalite (ATT) dyke swarms as testimony for the longevity of the Deep Hot Crustal Zone in Beja, Southern Portugal, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21078, https://doi.org/10.5194/egusphere-egu25-21078, 2025.
Cumulates are a key concept in igneous petrology and a key component of any magmatic series. A cumulate is the result of crystal segregation from its equilibrium melt. A cumulate is therefore refractory, enriched in compatible elements (those that like minerals) and depleted in incompatible elements (those that prefer melts) relative to segregated melts. The main cumulate formation processes recognised for several decades are crystal settling and crystal-rich magma (mush) compaction. Recently, in light of the mush-dominated character of igneous reservoirs and of the importance of melt-mush reactive percolation processes, which appear to be widespread in several geodynamic contexts, an additional cumulate process has been proposed: the melt flush process (Boulanger & France, 2023). The melt flush process conceptualises a continuous reactive porous flow: in continuously (or oscillatingly) replenished mushy reservoirs, freshly recharged melt percolates through the mush, flushing out previous interstitial (and relatively more evolved) melt and reacting with the mush-forming minerals. This thermodynamically feasible process results in crystal-melt segregation as less evolved melts replace fractionated ones; the resulting assemblage is more refractory and corresponds to a cumulate.
Crystal settling, mush compaction or melt flush are three cumulate forming processes that are buoyancy assisted. Here I discuss the potential role of an alternative process, not based on melt buoyancy or the density difference between melt and crystals, in cumulate formation. I show that heterogeneous nucleation has a strong potential to locally segregate evolved melt pockets from crystal clusters when crystallization is rather static and the magma becomes a mush (>50% crystal). Crystal nucleation requires a certain nucleation energy to be overcome before crystallization can proceeds, so nucleation is often delayed during early crystallization of magmas. In heterogeneous nucleation, the presence of pre-existing nuclei or impurities can allow crystal growth without the need to overcome the nucleation energy, resulting in a heterogeneous crystal distribution within the melt that is directly related to the presence of nuclei and can ultimately form crystal clusters. The maturation of such crystal clusters can then segregate the melt from the various clusters, eventually forming evolved melt pockets, and cumulative domains. Other modes of crystal clustering (e.g. synneusis) might also be involved in the acquisition of the cumulate signature. In the natural record, such a cumulate formation process can either be locally preserved or might act as a catalyser for crystal-melt segregation by deformation or buoyancy-assisted processes. During this presentation I will show the potential chemical implications of such a process and possible natural examples.
Boulanger, M. & France, L. (2023). Cumulate formation and melt extraction from mush-dominated magma reservoirs: the Melt Flush process exemplified at Mid-Ocean ridges. Journal of Petrology 64, egad005. https://doi.org/10.1093/petrology/egad005
How to cite: France, L.: Igneous cumulate forming processes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8891, https://doi.org/10.5194/egusphere-egu25-8891, 2025.
Diffusion chronometry is used to understand various geological processes that occur in Magma reservoirs [1] and during solid state transformations. However, recrystallization restricts the timescales which can be accessed by diffusion chronometry. Recrystallization as a consequence of chemical dissolution-precipitation reactions or mechanical deformation are well known aspects of rock evolution. However, recrystallization due to a coupling of chemical and mechanical forces has not been studied yet in detail, although it is known from both natural settings [2] as well as experiments [3]. We have developed a thermodynamic multiphysics model to address this problem. We define an overall free energy function of a system that contains the standard chemical terms (enthalpy, entropy, volume) as well as the effects of mechanical stress (elastic as well as plastic). This function is minimized to study the evolution of a system, in particular with reference to evolution of the radius of a grain. It is found that the balance of chemical and mechanical forces may lead to continual growth of a mineral grain, or lead to the disappearance of a grain by shrinking (and growth of a new grain), depending on the values of different parameters. The behavior of the system is shown to be governed by four non-dimensional parameters, and the behavior of any given system may be predicted when a set of relevant material parameters are known.
In this presentation we build on the model introduced by Haddenhorst et al. [4] to describe the evolution of olivine crystals surrounded by a melt. We can use the model to calculate the lifespan of an olivine grain, the maximum size of a crystal and the time taken to reach that size as a function of pressure, temperature and a set of material parameters. Illustrative examples for magma mush zones will be shown.
References:
[1]: Chakraborty, S., & Dohmen, R. (2022). Diffusion chronometry of volcanic rocks: looking backward and forward. Bulletin of Volcanology, 84 (6), 57. Retrieved from https://doi.org/10.1007/s00445-022-01565-5
[2]: Bestmann, M., Pennacchioni, G., Grasemann, B., Huet, B., Jones, M. W. M., & Kewish, C. M. (2021). Influence of deformation and fluids on ti exchange in natural quartz. Journal of Geophysical Research: Solid Earth, 126 (12), e2021JB022548. Retrieved from https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2021JB022548
[3]: Nachlas, W., & Hirth, G. (2015). Experimental constraints on the role of dynamic recrystallization on resetting the ti-in-quartz thermobarometer. Journal of Geophysical Research: Solid Earth, 120 (12), 8120–8137.
[4]: Haddenhorst, H. H., Chakraborty, S., & Hackl, K. (2023). A model for the evolution size and composition of olivine crystals. Proceedings in Applied Mathematics and Mechanics, 00, e202300081. https://doi.org/10.1002/pamm.202300081
How to cite: Haddenhorst, H. H., Waimann, J., Chakraborty, S., and Hackl, K.: A material model for the evolution of size and composition of olivine grains in a magma mush zone as a consequence of mechano-chemical effects of diffusion, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6825, https://doi.org/10.5194/egusphere-egu25-6825, 2025.
Phosphorus and aluminum are preferentially incorporated in olivine during rapid crystal growth (skeletal morphologies). Their zonation therefore records the early growth event, while the morphological evidence gets erased during subsequent crystal maturation. Here we focus on plutonic and volcanic olivine grains from slow-spreading ocean ridges, using P & Al chemical maps obtained via EPMA. Our study reveals the existence of a plutonic signal based on the decoupling of these elements due to their difference in diffusion rates (DP < DAl) within the olivine crystal. As the zonation in aluminum fades over time, the zonation in phosphorus persists. The coexistence, or lack thereof, of the skeletal enrichments of aluminum and phosphorus in olivine serves as an indicator of the environment in which the crystal resided. Using this criterion, we show that most of the olivine grains from the lavas studied here are inherited from the disruption of a long-lasting mushy domain as they record a chemical zonation that is similar to that of plutonic crystals. Lava thus represents a minestrone-like igneous assemblage of various melts and crystals inherited from several molten domains within the crustal plumbing system. The use of bulk-rock compositions to discuss mantle processes thus appears delusional. The crystal cargo derived from the disaggregation of mush zones provides a unique access to processes occurring in the deep active mushy reservoirs, which can usually only be reached by studying plutonic rocks (gabbros) after mush solidification.
How to cite: Falc'hun, C., France, L., Laubier, M., Pereira, T., Bouilhol, P., and Tissandier, L.: Phosphorus zonation in olivine reveals the long-lasting history of basalt crystal cargo, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11528, https://doi.org/10.5194/egusphere-egu25-11528, 2025.
Constraining the temperature evolution of magma reservoirs constitutes an important scientific and societal challenge in order to mitigate future volcanic hazards. In the last decades, diffusion chronometry emerged as a valuable tool to track the timescales of magmatic processes and is now routinely applied on erupted volcanic products to infer crystal residence times and mixing-to-eruption timescales. As such, calibrating the diffusion rates of Sr and Ba in plagioclase, the most abundant mineral in the Earth’s crust, is critical to place timing constraints on different magmatic systems. However, discrepancies between previous studies investigating the diffusion rates of divalent cations in plagioclase persist (1–6). Here we report diffusion experiments that aim to constrain the diffusivities of Sr and Ba in oligoclase and labradorite at 1 atm pressure, between 900 and 1200 °C, and as a function of the crystallographic orientation and aSiO2. The experimental products were analysed by SIMS depth profiling and LA-ICP-MS line scanning. The analysed annealed crystals reveal no resolvable dependence of Sr and Ba diffusion in plagioclase upon aSiO2 or crystal orientation. However, Sr and Ba diffusivities are found to vary with plagioclase anorthite content. The diffusion rate of Sr in plagioclase determined in this study is ~1.5–2 orders of magnitude slower than previously determined, whereas Ba diffusion is similar to previous studies. This is likely due to Ba-feldspar stability at the experimental conditions employed by previous studies, whereas Sr-feldspar was absent from their source powder assemblage. By applying the Sr and Ba diffusivities determined in this study to plagioclase crystals from the Cerro Galán ignimbrite (Argentina) and Santorini caldera (Greece), we find timescales of ~105 years, with a good agreement between results from Sr and Ba diffusion modelling. Therefore, our data reconcile experimental diffusion data with measured Sr and Ba profiles in plagioclase and suggest that, at least regarding the Cerro Galán ignimbrite and Santorini caldera, plagioclase records the time needed to differentiate magma reservoirs and assemble large volumes of eruptible magma.
1. Cherniak, D. J., Watson, E. B. (1992). Earth Planet. Sci. Lett. 113, 411–415.
2. Cherniak, D. J., Watson, E. B. (1994). Geochim. Cosmochim. Acta 58, 5179–5190.
3. Cherniak, D. J. (2002). Geochim. Cosmochim. Acta 66, 1641–1650.
4. Faak, K., Chakraborty, S., Coogan, L. A. (2013). Geochim. Cosmochim. Acta 123, 195–217.
5. Gilleti, B. J., Casserly, J. E. D. (1994). Geochim. Cosmochim. Acta 58, 3785–3793.
6. Van Orman, J. A., Cherniak, D. J., Kita, N. T. (2014). Earth Planet. Sci. Lett. 385, 79–88.
How to cite: Grocolas, T., Bloch, E., Bouvier, A.-S., and Müntener, O.: Diffusion of Sr and Ba in plagioclase: New experimental data and application to ignimbrites and calderas, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8398, https://doi.org/10.5194/egusphere-egu25-8398, 2025.
Magmas on Earth are more or less crystallized and they may display a wide range of crystal type, sometimes referred as the crystal cargo. First, crystals may entrap silicate melt from magma reservoirs as melt inclusions, acting as witness of magma storage conditions at the time of their entrapment. By analyzing them carefully we can retrieve information on magma pounding zones and thus about the architecture of magma plumbing system through time as well as magma ascent path and degassing. Crystals act also as key archives of magmatic processes, enabling a deeper understanding of the physico-chemical conditions during magma evolution and its pathways through Earth's crust. In particular, crystals in disequilibrium emphasized have a relevant role as a witness to trace crystallization conditions and magmatic dynamics. As this session aims to explore the reconstruction of magmatic history through crystal studies, I will present recent results on crystal analyses, particularly linking melt inclusion composition, and crystal textures and compositions to specific processes such as fractionation, recharge, mixing, assimilation, and degassing. In addition, the use of crystals as chronometers, particularly through diffusion chronometry, provides valuable insights into the timescales of different magmatic processes, contributing to volcanic monitoring and eruption forecasting. The rise of diffusive chronometry has thus made it possible to better constrain the dynamics of magmatic systems, with its advantages and limitations. Given this approach, we can now move to interdisciplinary approaches integrating petrological and volcanological investigations and human and social science researches.
How to cite: Balcone-Boissard, H.: Magma plumbing system architecture and dynamics, a crystal perspective, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20350, https://doi.org/10.5194/egusphere-egu25-20350, 2025.
Following periods of unrest in 2020 and late 2023, a sequence of eruptions started in December 2023 in the Svartsengi system, on Iceland’s Reykjanes peninsula. By the end of 2024, seven eruptions had occurred along the Sundhnúksgígar crater row. We undertook extensive sampling campaigns throughout and following each eruption in order to identify and characterise the properties of the pre-eruptive magma accumulation region and the chemical variability it hosts [1]. While the 2021 eruption in the neighbouring Fagradalsfjall complex provided a near real-time view of magmatic processes occurring near the Moho [2,3]; the eruptions in Svartsengi provide us with a view into the workings of mid-crustal magma domains.
Eruptions in Iceland fed from magma reservoirs in the mid-crust generally erupt lavas with next to zero mantle-derived geochemical variability (e.g., in radiogenic isotopes or incompatible trace element ratios) [4,5]. Extraordinarily, within the first hours of the eruptions at Svartsengi, high amplitude mantle-derived variability was erupted from the same fissure, indicating the involvement of multiple magma reservoirs. The amplitude and mean composition characterising the variability have changed from eruption to eruption, showing that the magma domain feeding these eruptions is dynamic. Magma storage and mobilisation in the mid-crust may be more complex than geochemical and petrological observations often suggest, which must be considered when interpreting real-time monitoring data.
[1] Matthews et al., Science (2024); [2] Halldórsson et al., Nature (2022); [3] Marshall et al. AGU Advances (2024); [4] Halldórsson et al., CMP (2018); [5] Caracciolo et al., EPSL (2023)
How to cite: Matthews, S., Bali, E., Halldórsson, S. A., Sigmarsson, O., Guðfinnsson, G. H., and Pedersen, G. B. M.: A dynamic mid-crustal magma domain revealed by the 2023-24 Sundhnúksgígar eruptions, Iceland, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13554, https://doi.org/10.5194/egusphere-egu25-13554, 2025.
Near real-time petrological monitoring represents a major advancement for volcanology, offering potential insights into magmatic plumbing systems, unravelling mechanisms driving volcanic eruptions, with strong implications for eruption forecasting and volcanic hazard assessment, aiding decision-making during volcanic crises.
Thanks to recent technological and procedural advances, petrological monitoring using trace elements geochemistry of groundmass glasses by LA-ICP-MS is highly promising, as it can be completed in a relatively short time without requiring additional sample preparation compared to SEM analysis. Here we present LA-ICP-MS trace elements analyses of groundmass glasses of lapilli samples from the 2020–2022 paroxysmal sequence produced by the South-East Crater (SEC) at Mt. Etna volcano (Sicily). Mt. Etna is an open-vent basaltic volcano characterized by periods of explosive activity of variable intensity, which, in some cases, lasts months. Between December 2020 and February 2022, about sixty paroxysms (lava fountains) occurred at SEC, with frequency varying throughout the period. Paroxysms were divided into two eruptive sequences1,2: 13 December 2020 to 1 April 2021 (SEQ1) and 19 May to 23 October 2021 (SEQ2), separated by 48 days of stasis; two paroxysms also occurred on 10 and 21 February 2022. The strong impact of erupted pyroclastic material on aviation, traffic, agriculture, and human life led us to investigate whether it is possible to quickly identify waxing and waning phases of activity.
Previous studies based on major elements, mineral compositions, and diffusion timescales have linked magma dynamics and eruptive activity, and, thanks to sampling of most lava fountains, a near real-time petrological monitoring was addressed mainly through major elements analyses of groundmass glasses and bulk-rock1,2. Trace elements analyses of groundmass glass are more sensitive than major elements to small and subtle changes in melt composition due to processes such as recharge, mixing, and crystal fractionation, changes that may be partly hidden in major oxides data of high-porphyritic bulk-rock. Thus, trace elements analyses of groundmass glasses can potentially fasten and improve petrological insights detecting magma evolution trends during eruptions.
We analyzed changes in the chemical composition of erupted magma throughout the entire sequence using a data-driven approach on glass analyses, employing hierarchical clustering (HC) to identify compositional groups based on trace element chemistry. This method allowed the fast and accurate recognition of different types of magmas involved in each examined lava fountain, the detection of mafic recharges, as well as the involvement of magma stored in different portions of the plumbing system, as stated in previous works1,2.
This information is also post-validated combining HC with textural analysis of investigated samples, providing a more complete knowledge of eruptive dynamics. From a petrological monitoring perspective, the acquisition of a large dataset on volcanic glass, combined with unsupervised learning, allows tracking eruptive episodes by recognizing different magmas using objective compositional criteria. At well-monitored volcanoes, this approach can aid in tracking the progression of eruptive activity, its climax, and/or its decline, offering valuable insights to complement data and results from geophysical and geochemical monitoring networks.
1 Corsaro, R.A., Miraglia, L. (2022); https://doi.org/10.3389/feart.2022.828026;
2 Corsaro R.A., Miraglia L., Arienzo I., Di Renzo V. (2024); https://doi.org/10.1007/s00445-024-01770-4;
How to cite: Costa, S., D'Oriano, C., Petrelli, M., and Corsaro, R. A.: LA-ICP-MS trace elements analyses of groundmass glasses for petrological monitoring: a data-driven study of magmatic processes in the Dec 2020–Feb 2022 lava fountains series at Mt. Etna, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19688, https://doi.org/10.5194/egusphere-egu25-19688, 2025.
Sill emplacement is fundamental to the development of volcanic plumbing systems and their impact on volcanic hazard assessments, geothermal heat potential estimates and critical hydrothermal ore deposit models. Accurate interpretations of geological, magnetic, and petrographic evidence of magma flow provides essential and independent insights into the physics of sill emplacement but are rarely considered in combination with one-another. We integrate multiscale observations of the Whin Sill, located in the north of England, to discern between syn- and post-emplacement processes. The Whin Sill is a mafic sill that intruded into Carboniferous-aged sediment 295 ± 6 Ma, which is outcrops across northern England with coastal exposures and ridges, such as below Hadrian’s Wall.
Field observations of sill finger orientation and ropy structures provide the best indication of primary magma flow directions, whereas plagioclase feldspar crystals do not as they show weak shape and crystallographic preferred alignments (SPO and CPO). Early Ti-poor titanomagnetite with a low-inclination Kmax anisotropy of magnetic susceptibility (AMS) tensor records magma finger inflation and variable flow during sill growth. A second Ti-poor titanomagnetite population records the migration of melt upwards and the post-solidification influx of hydrothermal fluids via cooling joints. This is captured through a steep Kmax anhysteretic anisotropy of remanent magnetisation (AARM) and inverse AMS fabrics. By integrating our results from multiple techniques, we have proposed a multi-stage emplacement mechanism for the Whin Sill in this area: 1) initial propagation as magma fingers based on field observations, 2) magma finger inflation and variations in magma flow direction, based on weak CPO and low-inclination AMS Kmax tensors, and 3) influx of fluids and upward melt migration syn-emplacement, based on high-inclination AARM and inverse AMS fabrics. These novel results highlight the complex dynamics of sill emplacement that can be reconstructed only through multiscale and multimethod analysis. Conducting similar analysis on samples taken from multiple locations across an intrusion would allow for further detail to be obtained, and for a greater understanding of the complex processes occurring. Not using an integrated approach risks over simplistic models with incorrect magma flow trajectories and inaccurate source locations.
How to cite: Williams, K., Urbani, S., Mariani, E., Biggin, A., Wheeler, J., and Kavanagh, J.: Unravelling the complex record of magma flow and solidification in sills, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-348, https://doi.org/10.5194/egusphere-egu25-348, 2025.
Nearly all geochemical applications of ionic radii appeal to the classic tabulation of Shannon (1976; Acta Crystallographica, A32, 751-767). In that work, smoothing was applied to the crystallographic systematics of lanthanides to ensure consistent decreases in cationic radii with increasing atomic number – the lanthanide contraction. Recent work of Hawthorne and Gagné (2024; Acta Crystallographica, B80, 326-339) has now updated preferred radii, based on a vastly larger database of crystal structures. However, values have not been smoothed, and several average radii violate the lanthanide contraction principle. Here, we propose a set of effective ionic radii for trivalent lanthanides using simple regressions, based in part on atomic theory, and verify that these radii satisfy theoretical principles of lattice strain:
r = 1/(0.0235·ne - 0.035·CN – 0.0015·ne·CN + 1.150)
where ne is electron number (0 to 14 for La to Lu) and CN is coordination number (6 to 12). Expressions for ionic radii of lanthanides in xenotime, zircon, monazite, and apatite are:
r = 1/(0.01593·ne + 0.8773) [xenotime and zircon
r = 1/(0.01148·ne + 0.8270) [monazite]
r = 1/(0.01143·ne + 0.8344) [apatite]
The ionic radius of Y3+ can be refined to high precision using partitioning data (= 0.999·rHo; see Schwartz and Kohn, this session), but the ionic radius of Sc3+ cannot because its ionic radius is so different from lanthanides, and because it does not necessarily substitute equivalently into mineral structures.
How to cite: Kohn, M. J. and Schwartz, D. M.: Ionic radii of the REE, 2: A practical revision to REE3+ radii in common minerals, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14341, https://doi.org/10.5194/egusphere-egu25-14341, 2025.
Lamprophyres are a group of igneous rock that are volumetrically minor and inherently restricted to continental setting. These volatile- rich, mantle derived alkaline rock, carry hydrous mineral such as amphibole and biotite within feldspathic groundmass and sometimes xenolith and xenocrysts, provide direct sample of the sub-continental lithospheric mantle. As such the porphyritic nature of the lamprophyres are known to preserve evolutionary processes of magma through open and closed system magma chamber processes (i.e., magma mixing, mingling, recharge, remobilization, assimilation and crystallization) reflecting cognate (phenocryst) as well as disequilibrium (antecryst) relationship in a complex magmatic plumbing systems whereas the latter are interpreted as xenocrystic fragments from amphibole-rich metasomatic veins in the upper mantle. Major and trace element mineral chemistry data are presented for amphibole phenocrysts from lamprophyric calc-alkaline magmatism from Jonnagiri schist belt, Eastern Dharwar Craton, southern India. Variability in major oxide geochemical signatures (e.g., Mg#, temperature, pressure, fO2) of amphibole phenocrysts indicate phenocrysts cores to be representative of early-crystallised phenocrysts, whereas rims crystallised in equilibrium with amphibole microphenocrysts during final emplacement of host melts. Amphibole trace element concentrations offset together with trace element modelling signatures in host rock – amphibole phenocryst pairs suggest a non-cognate relationship that likely represent the amphibole phenocryst cores as remnants of fractionated phase belonging to evolved lamprophyric melts. Our study reflect interaction between heterogeneous lamprophyric melt and/or cumulate amphiboles in the crustral levels that experienced localised varying degree of mantle melting in a moderately heterogeneous SCLM source.
How to cite: Naskar, S., Rao, N. V. C., and Pandey, R.: Petrogenesis of calc-alkaline lamprophyre from Jonnagiri green schist belt, Dharwar craton, southern India: Insights from major and trace element chemistry of amphiboles. , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-645, https://doi.org/10.5194/egusphere-egu25-645, 2025.
Several important processes in the petrogenesis of granite are still debated due to poor understanding of complex interactions between minerals during the melting and melt segregation processes. To promote improved understanding of the mineral-melt relationships, we present a systematic petrographic and geochemical analysis for melanosome and leucosome samples from the Triassic Jindong migmatite, South China. Petrographic observations and zircon U-Pb geochronology indicate that the Jindong migmatite was formed through water-fluxed melting of the Early Paleozoic gneissic granite (437±2 Ma) during the Triassic (238±1 Ma), with the production of melt dominated by the breakdown of K-feldspar, plagioclase and quartz. The Jindong leucosomes may be divided into lenticular and net-structured types. Muscovite, plagioclase and K-feldspar in the net-structured leucosome show higher Rb and much lower Ba and Sr contents than those in the lenticular leucosome. This may be attributed to elevation of Rb and decreasing Ba and Sr abundances in melts during the segregation process, due to early fractional crystallization of K-feldspar and plagioclase. These leucosomes show negative correlation between εNd(t) and P2O5, reflecting increasing dissolution of low εNd(t) apatite during melting process. The continuous dissolution of apatite caused saturation of monazite and xenotime in melt, resulting in the growth of monazite and xenotime around apatite in the melanosome. This process resulted in a sharp decrease of Th, Y and REE with increasing P2O5 in the leucosome samples. This complex interplay of accessory mineral reactions in the source impact REE geochemistry and Nd isotope ratios of granites. As the granites worldwide exhibit similar compositional and isotopic patterns with the Jindong leucosomes, we suggest that both the melting and melt segregation processes strongly control the granitic melt compositions.
How to cite: Yu, Y., Huang, X.-L., Weinberg, R., Sun, M., He, P.-L., and Zhang, L.: Melting and melt segregation processes controlling granitic melt composition, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7637, https://doi.org/10.5194/egusphere-egu25-7637, 2025.
The complex mineral assemblages and zonal texture in granites might be the outcome of multiple batches of magma convergence and mixing. Here, we delineate the genesis of the adakitic granite porphyry in the Gangdese belt, southern Tibet and analyze the chamber dynamic process of rapakivi feldspars based on the mineral assemblage and mineral compositions. The influences of magma mixing and post-magma alteration on the composition of granite porphyry and its metallogenic potential were examined by in-situ geochemical data of minerals and whole-rock geochemical data. The Quxu granite porphyry has high contents of SiO2 (68.14–69.36 wt%) and K2O (3.08–3.42 wt%), high ratios of Sr/Y (180.04–202.15) and (La/Yb)N (33.89–43.66) and low contents of Y (4.21–4.68 ppm) and YbN (1.97–2.29), characterized by of high-K adatikic granite. The granite porphyry has positive zircon εHf(t) values ranging from 6.27 to 11.55 and apatite εNd(t) values ranging from -0.65 to 1.06, and low plagioclase (87Sr/86Sr)i ratios from 0.704037 to 0.705084, as it originated from a juvenile crust source. Mafic microgranular enclaves (MMEs) in the granite porphyry are regarded as wall rock fragments due to their angular shape and relative older crystallization age of 48.6 Ma, while felsic microgranular enclaves (FMEs) are defined as the magma schlieren because its crystallization age and major- and trace-element contents are consistent with the host granite porphyry. The granite porphyry undergoes magma mixing with more mafic magma in the magma chamber, resulting in the magma being slightly enriched in TiO2, MnO, MgO, and P2O5 and depleted in CaO content and Sr-Nd isotopes. The magma mixing also supplies heat for the formation of the rapakivi texture of K-feldspar megacrysts in the magma chamber. Additionally, the high oxygen fugacity (ΔFMQ = 1.46) and water content of granite porphyry and its adakitic characteristics indicate its favorable metallogenic potential. This study provides new insights into the petrogenesis and metallogenic potentials of adakitic rapakivi granites in the Gangdese belt.
How to cite: Meng, Y. and Yuan, H.: Petrogenesis and metallogenic implications of the rapakivi granites: evidence from in-situ geochemical data of minerals, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1634, https://doi.org/10.5194/egusphere-egu25-1634, 2025.
Constraining the assembly and evolution of granitic intrusions and the kinematics associated with their magmatic differentiation remain a major objective in igneous petrology. To progress on those issues, we took advantage of a 900m long drilled core of the Beauvoir granite, a rare metal granite intrusion from the French Massif Central, allowing a high-resolution sampling of a fully recovered plutonic body. Based on structural data, and high-resolution major and trace element composition of the mineral phases (in-situ measurements and chemical map) associated with cathodoluminescence imaging, we provide constraints on the differentiation processes and its dynamics during the construction of the intrusion. Mostly based on mineral composition and morphologies, we show that the granite formed via the stacking of deca- to hectometric crystal-poor sills, corresponding to the different sub-units of the Beauvoir granite. Furthermore, the detailed study of sill boundaries provides a dynamic record of the pluton assembly: although globally constructed from bottom to top, sill emplacement can also occur through off-sequence intrusion within partly crystallized sub-units.
Once intruded, early crystallised quartz and topaz will be accumulated at the base of their sills while residual melts progressively differentiate, that is recorded by the progressive metal (e.g., Li, Be) and fluxes (e.g., F and P) enrichment from bottom to the top of each sub-units. Textural and mineralogical evidences suggest an efficient extraction of these residual melts from the quartz-rich mush as these residual liquids are under the form of segregates dominated by albite, lepidolite (Li-mica) and amblygonite (Li-phosphate). These segregates can accumulate below an overlying sill or percolate through the upper solidification front of their sill, developing typical dendritic morphologies. In addition, these residual melts have also been observed as fragmented and dismembered mm to cm albite-rich ovoids, representing mixing features between two magmas. Such processes of residual melts collection and segregation contributed to the global enrichment in rare metals observed towards the top of the granite. This study eventually provides fundamental constraints on the processes leading to the construction and subsequent magma differentiation and melt extraction in rare metal granite bodies.
How to cite: Bouilhol, P., Esteves, N., France, L., and Cuney, M.: Plutonic construction and residual liquid segregation: Insights from the Beauvoir granite mineral record, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18708, https://doi.org/10.5194/egusphere-egu25-18708, 2025.
The UG2 Chromitite of the ~2 Ga Bushveld Complex (South Africa) is one of the largest platinum-group element (PGE) deposits on Earth. It is ~1 m thick and can be traced for virtually the entire circumference of the eastern and western lobes of the Bushveld. Despite its economic importance and a plethora of studies devoted to understanding its petrogenesis, there is no consensus on how the UG2 body formed (see recent studies by Robb & Mungall, 2020; Latypov et al. 2023; Maier & Barnes, 2024). Models invoking fractional crystallization, in situ crystallization, gravity settling within crystal-rich slurries and crustal contamination have all been proposed. Recent studies on chromitite formation in other layered intrusions have demonstrated significant mineral chemical and textural disequilibrium features associated with chromitite layers, attributed to a reactive origin for these bodies (Hepworth et al. 2020). This study aims to test the hypothesis that reaction between incoming magma and anorthositic footwall triggered crystallization of some or all of the massive UG2 Chromitite. Specifically, we focus on microtextural variations at the mm-to-cm-scale across silicate to massive chromitite contacts in the UG2 and associated leader seam from a drill core sampled on the Magazynskraal farm in the western lobe of the Bushveld intrusion. We have carried out petrographic analysis and quantitative textural approaches including crystal size distribution (CSD), dihedral angle measurements, as well as mineral chemical and in-situ 87Sr/86Sr laser ablation inductively coupled-plasma mass spectrometry (LA-ICPMS) in plagioclase samples leading up and into the base of the UG2 Chromitite. We also studied materials at the contacts of the overlying leader seam. Petrographic observations reveal disequilibrium textural relationships in the footwall pyroxenite; e.g., chromite is typically separated from orthopyroxene by thin (µm-scale) rims of plagioclase. Interstitial plagioclase is chemically zoned and the anorthite content of the plagioclase shows a distinct increase (An58 to An92) near chromite. CSD analysis yields mainly log-linear plots suggesting in-situ crystallization with some evidence for postcumulus textural modification. Apparent chromite-chromite-plagioclase dihedral angle measurements reveal median values (for a given ~1 cm thick interval) of 65-75° and suggest that textural equilibrium has not been achieved. The 87Sr/86Sr variability points to the interaction between isotopically distinct signatures at the postcumulus stage. Our combined observations suggest disequilibrium between mineral phases and hint at reactive (dissolution-reprecipitation) crystallization in the UG2 Chromitite.
- Robb & J. Mungall (2020). Earth and Planetary Science Letters 534, 116084.
- Latypov et al. (2023). Lithos 460–461, 107374.
- D. Maier & S.-J. Barnes (2024). The Canadian Journal of Mineralogy and Petrology 62(5), 731-745.
- Hepworth et al. (2020). Nature Geoscience, 13(5), 375–381.
How to cite: Scoging, V. and O'Driscoll, B.: A reactive in-situ crystallization origin for the UG2 Chromitite of the Bushveld Complex, South Africa?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-696, https://doi.org/10.5194/egusphere-egu25-696, 2025.
This study presents first report on composition of olivines and associated minerals in eleven distinct olivine-bearing mafic dykes of the Dharwar Craton, representing the 2.37 Ga and 2.21 Ga large igneous provinces (LIPs). These dykes comprise of olivine, clinopyroxene (augite and pigeonite), plagioclase (labradorite to bytownite) and minor orthopyroxene (enstatite) in association with oxides (titano-magnetite, ilmenite, spinel) and sulphide (chalcopyrite). The olivine grains vary from being unzoned (Ol-I, Mg# 84–63) to zoned (Ol-II, Mg# 78–38), and represent primary and secondary growth during magmatic crystallization. Continuously zoned grains show decrease in Ni, Cr, Al, Ca contents and an increase in Mn, Co and Ti concentrations, from core to rim. Increase in the Ni/(Mg/Fe)/1000 ratios (0.7 to 3.0) and a decrease in 100Mn/Fe ratios (1.5 to 1.0) in olivines from the 2.37 Ga dykes to the 2.21 Ga dykes may be interpreted as a transition of the subcontinental lithospheric mantle (SCLM) from a peridotite-dominated composition with lower proportions of recycled oceanic crust (XROC=0.2–0.3) at 2.37 Ga, to pyroxenite composition having higher proportions of recycled oceanic crust (XROC>0.3), at 2.21 Ga. Fractional crystallization modelling suggests that the olivines crystallized first, followed by clinopyroxenes and later by plagioclases within both the dyke swarms however, the two swarms exhibits diverse magmatic processes: 2.37 Ga dykes essentially reflect fractional crystallization and magma mixing processes while, the 2.21 Ga dykes, reflect multiple episodes of magma fractionation and recharge. Calculated NiO/MnO ratios in Fo89 olivines of the dykes show gradual increase from the eastern (1.16–1.36) through central (1.69–1.81), to the western parts (1.88–2.92) of the craton irrespective of their ages, indicating a thicker lithosphere for the Western Dharwar Craton. Al-in-olivine geothermometer registers high olivine crystallization temperatures of 1294–1466°C (±25°), compatible with the olivine crystallization temperatures of several worldwide LIPs (NAIP, Emeishan, Karoo) and suggests involvement of mantle plume. However, olivine compositions along with negative Nb-Ta anomalies, fractionated LREE with flat HREE patterns, variable (Dy/Yb)N values (0.94–1.69), and largely negative ԐNd(t) values independent of SiO2, indicate essential role of SCLM in the genesis and suggests generation of the 2.37 Ga and 2.21 Ga mafic dyke swarms through plume-lithosphere interaction.
How to cite: Yadav, P.: Early crystallizing magmatic olivines as probes into mantle sources, magma crystallization and lithospheric thickness: Insights from the 2.37 Ga and 2.21 Ga mafic dyke swarms of the Dharwar Craton, India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1318, https://doi.org/10.5194/egusphere-egu25-1318, 2025.
Australia hosts at least two continental basaltic volcanic provinces with Holocene eruption ages, yet little is understood about magma ascent and mantle to surface magmatic pathways and timescales in these regions. Such information advances our understanding of potential eruption warning timeframes of future volcanic activity. In this study we conducted mineral-scale textural and chemical investigation of a suite of stratigraphically constrained volcanic rocks from the Mount Gambier (Berrin) volcano. The ~5 ka maar-cone complex is the youngest volcano within the Newer Volcanics Province and mainland Australia and produced effusive magmatic to explosive (VEI 4) phreatomagmatic eruptions. The textural diversity and chemical zoning patterns in olivine and clinopyroxene in the volcanic rocks reveal a complex history of magma ascent. Olivine is classified into several types based on texture and composition: Normally zoned olivine at the margins of mantle xenoliths and rims of mantle-derived xenocrysts; skeletal, euhedral and polyhedral diffuse normally zoned (dominant type); reversely zoned olivine; and as reaction rims on xenocrystic orthopyroxene. Olivine compositions and zoning (diffusion) profiles are used to map out the magmatic plumbing system and determine the timescales of magma ascent to the surface. The information gained from this work provides new insight into pre-eruptive magmatic history and magma ascent at Australian volcanoes. These results yield important implications for better preparedness to future volcanic hazards in Australia.
How to cite: Handley, H., Cas, R., and Hellebrand, E.: Magma ascent dynamics at Mount Gambier (Berrin) Volcano, Newer Volcanics Province, Australia: Insights from olivine textures and compositions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5750, https://doi.org/10.5194/egusphere-egu25-5750, 2025.
Diffusion is a key to understand the timescales of magma dynamics, and thus the evolution of igneous systems. As K-feldspar is a major mineral in felsic plutonic rocks, investigating the diffusion behaviour of trace elements in K-feldspar provides valuable information on magma dynamics. K-feldspar has been used to determine timescales of crystal growth or residence times for volcanic and plutonic systems (e.g., [1], [2]).
To provide better constraints on the duration of magmatic processes (e.g., magma replenishment, magma mixing, etc.), there is a need for accurate diffusion coefficients. Therefore, our study focuses on the results of experiments that aim to constrain diffusivities of Sr, Ba, Ti and P in sanidine (Or98). We performed experiments at 1 atm pressure, between 825 and 1050 °C, for diffusion normal to (010) at controlled aSiO2. The polished sections of sanidine were surrounded by source powders in Pt capsules and annealed in air, from times ranging from 1 month to 6 months. Sources of diffusant were SrO-, BaO-, TiO2- and P2O5-doped cristobalite or SrO- and BaO-doped cristobalite (made using the sol-gel method) mixed with finely ground sanidine (1:1), or with finely ground sanidine and apatite (1:1:1). The experimental products were then analysed by secondary ion mass spectrometry (SIMS) depth profiling. The absolute depth of the profiles was determined with white light interferometry. Diffusion rates in sanidine determined in this study are different from earlier studies ([3], [4], [5]). Sr diffusion rate is ~1.5–2 orders of magnitude slower than previously determined, while Ba, Ti and P did not show any measurable diffusion profiles, indicating that Ba and Ti likely diffuse more slowly than previously determined. Zoning in Ba in natural K-feldspar megacrysts thus predominantly records crystal growth processes that are weakly affected by diffusion.
[1] Chamberlain, Morgan, Wilson (2014) Contrib Mineral Petrol; [2] Rout, Blum-Oeste & Wörner (2021) Journal of Petrology; [3] Cherniak (1996) Geochimica et Cosmochimica Acta; [4] Cherniak (2002) Geochimica et Cosmochimica Acta; [5] Cherniak & Watson (2020) American Mineralogist.
How to cite: Toussaint, A., Bouvier, A.-S., Plane, F., and Müntener, O.: Multicomponent diffusion in K-feldspar: Sr, Ba, Ti and P diffusion experiments in sanidine, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4157, https://doi.org/10.5194/egusphere-egu25-4157, 2025.
The eruption of Somma-Vesuvius in 79 CE is considered one of the most iconic eruptions of the last two millennia. It was the first documented Plinian eruption and caused the destruction of the Roman cities of Pompeii and Herculaneum. Previous petrological studies provided useful insights into the dynamics of the magma reservoir and pre-eruptive processes, such as the episodic mafic recharge, that is considered the growing mechanism of the 79 CE reservoir. Scattered knowledge exists about reservoir properties and the magmatic processes leading to this Plinian event.
In this study, we performed high-spatial resolution analyses of zoned clinopyroxene crystals from selected eruptive units representing the phonolitic (white pumice) and tephri-phonolitic (grey pumice) magmas of the 79 CE eruption. The Mg# [molar MgO/(MgO+Fetot)*100] of clinopyroxene ranges between 91 and 39, with a notable compositional variation ascribable to five distinct compositional populations. The relationship among the compositional populations tracks the sequential growth of crystals in different magmatic environments, reflecting crystallization at different conditions.
The combined use of chemical data on zoned clinopyroxene and whole rocks, of isotopic data and numerical models allowed us to simulate the evolution of a primitive Vesuvius magma and constrain the physico-chemical conditions of the magmas feeding the 79 CE eruption. Magma temperatures, calculated with different thermometric and MELTS models, vary in the range 870–1120°C across the identified populations. Moreover, this approach allows identifying a vertically extended magmatic system beneath Somma-Vesuvius prior to the eruption, with various melt reservoirs at pressures of 2–4.5 kbar. These reservoirs were interconnected, facilitating prolonged crystal transfer. A phono-tephritic reservoir (at ~1010°C and >7.5 km depth) possibly constituted the lower part of the reservoir that fed the Pompeii eruption, where most of the magmatic interaction(s) took place. Diffusion modelling applied to the clinopyroxene zoning pattern allowed us to infer crystals residence times, mostly in this part of the magmatic system. The clinopyroxene crystals resided in the phono-tephritic and phonolitic magma reservoirs for 30–20 years, and most of them for less than 10 years (mostly less than 5 years) before the eruption. This time is related to the last episodes of magma recharge and crystal transfer before the eruption, and aligns with historically verified and archeologically inferred seismic precursors.
How to cite: Romano, P., Pelullo, C., Chakraborty, S., Rizzo, A. L., Balcone Boissard, H., Sparice, D., Doronzo, D., Di Vito, M. A., and Arienzo, I.: Timescales and dynamics of magmatic processes in a Plinian eruption's feeding system: The 79 CE eruption of Somma-Vesuvius, Italy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13369, https://doi.org/10.5194/egusphere-egu25-13369, 2025.
We introduce Orange-Volcanoes, an add-on for the open-source Orange Data Mining platform, designed to enhance data-driven workflows in petrology, geochemistry, and volcanology. Orange-Volcanoes extends the core features of Orange by incorporating tools for Compositional Data Analysis (CoDA), geochemical data preprocessing, and thermobarometric estimations.
These integrated tools enable users to perform machine learning, statistical evaluations, and predictive modeling on large petro-volcanological datasets while providing intuitive, interactive visualizations. The visual programming framework of the platform fosters collaborative research and ensures accessibility for a wide audience (e.g., scientists, educators, and students) without requiring programming expertise.
The combination of advanced machine learning and explainable artificial intelligence techniques, such as feature importance and Shapley additive explanations, supports deeper insights into geochemical variability and improves the interpretation of magmatic processes.
We explore the potential of Orange-Volcanoes through various case studies, showcasing applications such as clustering geochemical data and conducting petrological analyses. As the volume of volcanological and geochemical data continues to grow, this tool facilitates the integration of machine learning and data mining into standard scientific practices. The ability to apply diverse statistical and machine learning tools to geochemical data, while interactively visualizing step-by-step results, makes Orange and Orange-Volcanoes valuable assets for managing large multivariate datasets and supporting petrological volcano monitoring. Orange-Volcanoes represents a significant step forward in promoting reproducible, transparent, and collaborative research methodologies.
How to cite: Musu, A., Parodi, V., Toplak, M., Carfì, A., Ágreda López, M., Mastrogiovanni, F., Perugini, D., Blaž, Z., and Petrelli, M.: Orange-Volcanoes: Enhancing Data-Driven Petro-Volcanological Analysis with Applications in Petrological Volcano Monitoring, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18450, https://doi.org/10.5194/egusphere-egu25-18450, 2025.
Intraplate volcanism occurs within tectonic plates and is associated either with hotspots or with the development and propagation of fractures induced by intraplate stresses, and thinning of the crust. In northeastern Mexico, specifically in San Luis Potosí (SLP), Plio-Quaternary intraplate volcanic activity has been documented, linked to normal faulting. Notable examples include the Los Encinos and Santo Domingo volcanic fields, which host intraplate lava cones of trachybasaltic and basanitic composition, dated at 10.6–13.6 Ma and ~0.35 Ma, respectively. This activity, occurring along the boundaries of geotectonic provinces, forms the primary focus of this study.
Monogenetic volcanic complexes are aligned in a NW-SE direction across SLP, together with regional fault systems associated with the western margin of the Sierra Madre Oriental fold and thrust province. The peculiar occurrence of this volcanism motivated this research, with the aim to determine the geometry and extent of volcanic conduits through potential field methods, morpho-structural analysis and geochemistry.
For this study, a regional geophysical analysis was conducted using magnetometry and gravimetry. Eleven volcanic structures located along the NW-SE alignment were sampled. Petrographic analyses revealed that nine cones exhibit trachybasaltic compositions, characterized by high concentrations of olivine, clinopyroxene, alkali feldspar, and calcic plagioclase phenocrysts. One cone displays a trachyandesitic composition with amphibole, pyroxene, and sodic plagioclase crystals, while another is dacitic, containing pyroxene, amphibole, and biotite crystals. Gravimetric data indicate high anomalies over the trachybasaltic monogenetic complexes, underscoring density contrasts with the dacitic cone and emphasizing structural alignments of N–S faults in the NW region of the studied area and NW–SE faults in the SE region. Additionally, magnetometric data further revealed three primary anomalies, potentially corresponding to remnants of conduits that facilitated magma ascent, with the central region displaying the highest structural complexity.
How to cite: Marcial, V., Yutsis, V., Guevara-Betancourt, R., and Davila, P.: Delimitation of volcanic conduits in intraplate settings in Northeastern Mexico: coupling geophysics, structural geology and geochemistry, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12374, https://doi.org/10.5194/egusphere-egu25-12374, 2025.
Surface deformation at active volcanoes is often a direct consequence of magma movements at depth. These dynamics create pressure changes within magmatic systems, altering the stress state of the surrounding rocks. The resulting deformation signals propagate to the surface, where they are captured by monitoring networks, offering a potential for valuable insights into the magmatic activity.
To improve near-real-time detection and response during volcanic unrest, we are developing a digital twin for volcanic unrest induced by dike intrusions at Mount Etna. This innovative framework integrates 3D numerical simulations with artificial intelligence (AI) to enhance early warning capabilities and crisis management.
The project involves two interconnected AI modules: the first (AI1) scans multi-parametric monitoring data to identify signs of unrest, while the second (AI2) analyzes surface deformation patterns to infer the distribution of probability for the underlying pressure forces. The AI2 model is trained on a dataset derived from an order of 10 million numerical simulations of dyke intrusions beneath Mount Etna, performed using the open-source, multi-physics finite element software GALES on the HPC Leonardo pre-exascale machine at CINECA. These simulations account for a distribution of dyke characteristics - size, location, orientation, and dip - replicating the variability observed at Mount Etna. The 3D computational framework incorporates the latest DEM topography and heterogeneous rock properties from recent seismic tomography surveys. By solving elastostatic equations, the simulations establish input-output relationships between source parameters and deformation patterns. The trained AI2 is designed to reconstruct the probability distribution of source parameters from deformation datasets as recorded by the real GNSS stations on the volcano. The whole workflow, triggered by AI1, instructed by GALES, analysed by AI2, and automatically fed by real data every 30 – 60 minutes, provides a near-real-time picture of dyke propagation allowing a quick and robust interpretation of ground deformation data and assisting in early warning and volcanic crisis management.
All of the software and procedures will be available open source for direct use as well as for replicating the approach at other volcanoes.
How to cite: Bruni, R., De Paolo, E., Garg, D., Allegra, M., Cannavò, F., Montagna, C. P., Papale, P., and Carpenè, M.: A digital twin for volcanic unrest at Mount Etna, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16108, https://doi.org/10.5194/egusphere-egu25-16108, 2025.
Numerical simulations of magma dynamics have revealed that Ultra-Long Period (ULP) ground displacements can be attributed to deep magma convection. This research produces a series of one-way coupled, time-dependent models of magma and rock dynamics during multicomponent magma convection and mixing are simulated in different chamber-dyke systems using a multiphysics finite element software, GALES (Garg et al., Comp. Math. Appl., 2021).
Modelled firstly by simulating 2D magma mixing during a replenishment scenario whereby magmas of variable compositions and temperatures are free to interact at an interface, the properties of which were constrained using the estimated saturation conditions of melt inclusions. The overpressures at the fluid-solid interface are then imposed as a boundary condition to simulate the elastostatic response of the surrounding medium. These 2D models were then extended and embedded into a 3D domain (Longo), with dimensions of 100 x 100 km and a depth of 50 km, that accounts for topography, the heterogeneous rock property profile (seismic tomography data) and incorporates the INGV’s multiparametic stations on the surface.
This setup not only aided in constraining the characteristics of the Mount Etna volcanic system but also enabled the derivation of detailed synthetic space-time series of ground deformation at each of the stations for each of the pre-defined chamber geometries. Analysis of these respective synthetic signals reveal oscillations in a period range of approximately 150-300 seconds and changes in tilt in the order of milliradiants.
Direct comparisons with recorded tilt measurements, obtained on Mount Etna as part of IMPROVE’s multiparametric experiment in July 2023, can potentially identify sets of geophysical signals that are diagnostic of magma movements at depth and help develop our interpretation of the dynamics between storage regions throughout the volcanic system and their overall contributions to the resultant deformation patterns.
How to cite: McCluskey, O., Papale, P., Montagna, C., Longo, A., Garg, D., Carthy, J., Benitez, C., and Pagli, C.: Implementing GALES, a multiphysics Finite Element software, to model magma replenishment dynamics and associated Ultra-Long Period deformation patterns and tilt at Mount Etna, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3618, https://doi.org/10.5194/egusphere-egu25-3618, 2025.
Volcanic plumbing systems comprise a complex series of interconnected intrusions (sills and dykes), which store and transport magma laterally and vertically. The movement of magma within these systems can be inferred using geophysical and geodetic techniques. Surface displacement measurements are one of the most common tools used to monitor the state of volcanoes, where ground motion can be related to inflation and deflation of magma reservoirs at depth and therefore record potential precursors that help forecast an eruptive event. Satellite-based interferometric synthetic aperture radar (InSAR) and global navigation satellite system (GNSS) provide data for surface changes on a near-daily basis; however, interpretation of deformation sources and mechanisms is limited by modelling approaches. Inversion models (such as the Mogi model) are often used to interpret surface displacements in terms of the underlying structures, but these rely on assumptions and simplifications that may result in inaccurate estimations of intrusion sizes and volumes of eruptible magma.
To address this gap in understanding, we have developed a new synthetic volcano observatory to monitor scaled analogue volcanic plumbing system experiments. The first experiments we have tested include the simplest scenario for volcanic plumbing: a transparent gelatine solid (homogeneous or layered elastic crust analogue) injected by water (a Newtonian fluid magma analogue) to form an intrusion (a dyke or a dyke-fed sill). Over the course of the experiment, surface deformation is monitored using two CCD (charge-coupled device) cameras positioned above the tank, which track the vertical and lateral displacements of passive-tracer particles placed on the surface of the gelatine. Deformation of the surface above the dyke comprises an elongated central depression directly above the propagating tip of the dyke and parallel to its strike, and two inflated domes on either side of the elongated depression. In contrast, deformation of the surface above the sill forms a single inflated dome, with the area of greatest deformation centred above the connection between the sill and its feeder dyke. By analysing the experimental data with the same inversion approach used on natural magma intrusion events, we can explore how well factors such as intrusion geometry, depth, and volume are resolved, and how modelling algorithms can be improved to enhance volcanic eruption forecasting.
How to cite: Kavanagh, J., Williams, K., Bagnardi, M., Chalk, C., and Poland, M.: How do surface displacements reflect the structure of volcanic plumbing systems below?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8206, https://doi.org/10.5194/egusphere-egu25-8206, 2025.
Tenerife, the largest and most populous island of the Canary Archipelago (Spain), is characterized by a prominent central volcanic complex (Teide-Pico Viejo) and two highly active rift zones (the Santiago and La Dorsal rift zones). The interaction between the rift systems, dominated by mafic monogenetic volcanism, and the central complex, which exhibits compositions ranging from basanites to phonolites, results in multifaceted volcanic activity that poses significant risks not only to the population of Tenerife but also to the broader Canary Archipelago and regions affected by potential ash dispersion. Both systems, particularly the central complex, have been the focus of numerous field-based, petrological, geochemical and geophysical studies, providing valuable insights into the island's interior and its magmatic plumbing system.
Despite the extensive geophysical research conducted on Tenerife in recent past decades, a comprehensive integration of these datasets has yet to be undertaken to provide a unified interpretation. Such an integrated approach is crucial, as individual geophysical techniques often have limitations that prevent a full characterization of the subsurface structures. However, by combining multiple techniques, these limitations can be addressed, offering a more comprehensive and holistic understanding.
In this study, we review and integrate available geophysical data to develop a new conceptual model of Tenerife’s interior. We analyzed 52 references encompassing seismic, gravimetric, magnetic, electrical, InSAR, GPS, and numerical modelling studies. Relevant observations (e.g., anomalies, measurements, discontinuities) and their interpretations were compiled into a visual database. This database facilitates a detailed and comparative analysis of existing geophysical findings, allows synthesizing the geological structures identified through one or more techniques, and highlights discrepancies between different methods.
The results were used to construct a series of interpretative cross-sections of Tenerife's interior, including its magmatic plumbing system. This new model serves as a foundation for multidisciplinary interpretations, such as integrating petrological data from recent studies on Tenerife’s magmatic plumbing system. By combining geophysical and petrological perspectives, our work offers a more comprehensive understanding of the island’s subsurface, contributing to improve the volcanic hazard assessment.
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).
How to cite: Dorado, O., Geyer, A., Barde-Cabusson, S., de Bolós, X., and Martí, J.: Towards a comprehensive understanding of Tenerife’s subsurface: review and integration of geophysical studies., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11890, https://doi.org/10.5194/egusphere-egu25-11890, 2025.
Posters virtual: Tue, 29 Apr, 14:00–15:45 | vPoster spot 1
EGU25-20055 | Posters virtual | VPS22
Magmatic processes driving the 1970 eruption on Deception Island, (Antarctica)Tue, 29 Apr, 14:00–15:45 (CEST) | vP1.2
Deception Island, the most active volcanic system in the South Shetland Islands (Antarctica), has recorded over 20 explosive monogenetic eruptions in the past two centuries. The island’s most recent eruption in 1970 was one of its most violent, with a Volcanic Explosivity Index (VEI) of 3. This event generated a column height of up to 10 km and produced an estimated bulk eruptive volume exceeding 0.1 km³, with tephra fallout recorded over 150 km away on King George Island. To investigate the magmatic processes leading up to this significant eruption, we conducted detailed geochemical and textural analyses of near-vent pyroclastic deposits and distal tephra fall-out layers preserved in Livingston Island’s glaciers. Near-vent deposits include dilute pyroclastic density currents (PDCs) and lithic-rich breccias. Olivine crystals in these deposits exhibit two distinct populations: low-forsterite (Fo65–70 mol.%) and high-forsterite (Fo80–85 mol.%), with similar CaO contents (0.1–0.5 wt.%) but varying NiO concentrations (0–0.4 wt.% in low Fo; 0.02–0.10 wt.% in high Fo). Pyroxene microanalyses also reveal two distinct populations: i) augite-diopside (En45–50, Fs5–25, Wo38–50) and ii) enstatite (En90, Fs10, Wo0). Augite-diopside crystals can be further subdivided based on their Mg# (Mg# = Mg/(Mg+Fe) x 100) and TiO2 contents. The first group shows Mg# values between 80–85 mol.% and TiO2 ranging from 0.5 to 3.0 wt.%, while the second group displays Mg# values of 55–70 mol.% and narrower TiO2 concentrations (0.5–1.25 wt.%). Notably, the enstatite population was not found in distal tephra layers. Plagioclase crystals range in composition from Bytownite to Andesine (An85–40 mol.%). Comparative analyses with distal tephra layers confirm the presence of both olivine populations and overlapping augite-diopside compositions but lack enstatite. Plagioclase compositions show consistency between near-vent and distal deposits. These findings align the 1970 eruption deposits with compositional trends observed in other post-caldera collapse eruptions, shedding light on the island's eruptive history and magmatic evolution.
This work has been partially financed by the grant PID2023-151693NA-I00 funded by MCIN/AEI/10.13039/501100011033.This work is part of the CSIC Interdisciplinary Thematic Platform (PTI) Polar zone Observatory (PTIPOLARCSIC) activities. This research was partially funded by the MINECO VOLCLIMA (CGL2015-72629-EXP) and HYDROCAL (PID2020-114876GB-I00) MICIU/AEI/10.13039/501100011033 research project. Sampling was founded by CICYT (ANT91-1270, ANT93-0852 and ANT96-0734) and MICINN grant CTM2011-13578-E.
How to cite: Albert, H., Ruiz, J. L., Hopfenblatt, J., Pedrazzi, D., Geyer, A., Aulinas, M., Polo-Sánchez, A., Álvarez-Valero, A. M., and Vilanova, O.: Magmatic processes driving the 1970 eruption on Deception Island, (Antarctica), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20055, https://doi.org/10.5194/egusphere-egu25-20055, 2025.
EGU25-1988 | ECS | Posters virtual | VPS22
Apatite compositional constraints on the magmatic to hydrothermal evolution of lamproites from Raniganj Basin, eastern IndiaTue, 29 Apr, 14:00–15:45 (CEST) | vP1.3
A mineralogical study of early Cretaceous lamproite sill intrusions from the Raniganj Gondwana sedimentary basin in eastern India shows that apatite occurs as both phenocrystic and groundmass phase. Based on texture and compositional zoning patterns of apatite in lamproites from the Rajpura and Ramnagore collieries, three paragenetic stages of apatite are identified. Early-magmatic apatite (Ap-I), which forms the core of zoned grains, is Sr-rich–LREE-poor fluorapatite. This apatite underwent resorption prior to the growth of a second generation of magmatic fluorapatite (Ap-II). In Rajpura, Ap-II overgrowth rim is richer in Sr and LREE compared to Ap-I core. The increase in LREE is explained by the substitutions: (Na,K)+ + ∑LREE3+ = 2Ca2+, and [2∑LREE3+ + ₶ = 3Ca2+]. Ramnagore Ap-II overgrowth rim is oscillatory-zoned with fluctuations in Sr and LREE, which likely resulted from slow rate of diffusion of these elements relative to fast growth of crystals. Apatite of the third generation (Ap-III) forms the outermost rim of zoned grains and is marked by enrichment in Na, K and Ba. The substitutional schemes which explain the increase in Na and K from Ap-II to Ap-III are: (Na,K)+ + CO32– = Sr2+ + PO43– and [(Na,K)+ + (F,OH)– = ₶ + ₶]. The role of carbonate in the former substitution is supported by high content of stoichiometrically calculated carbon (0.21–0.30 apfu) in Ap-III. The formation of Ap-III is attributed to metasomatic alteration of Ap-II by CO2-bearing hydrothermal fluid and is associated with sodic metasomatism. Microporous texture has developed in Rajpura Ap-III which suggests a dissolution–reprecipitation mechanism for its development. This study demonstrates that compositional variations among different generations of apatite provide a meaningful record of melt evolution from early magmatic to magmatic-hydrothermal stages.
How to cite: Saini, J., Patel, S. C., and Kaur, G.: Apatite compositional constraints on the magmatic to hydrothermal evolution of lamproites from Raniganj Basin, eastern India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1988, https://doi.org/10.5194/egusphere-egu25-1988, 2025.
