Subsurface fluids interact with the rock matrix, triggering or enhancing numerous geological processes in the crust and lithosphere. For example, the presence of fluids can lead to rocks’ stress changes and reactivate pre-existing faults, therefore generating earthquakes. Fluids also play a crucial role in the development of magmatic processes and have a remarkable environmental impact. In the lithospheric mantle, fluids and melts can induce physico-chemical modifications, promote outgassing, cause a drastic reduction in rock viscosity and favor mechanisms of delamination. In addition, fluids can be a key factor in the generation of intraslab earthquakes during subduction.
To investigate the causes for fluid presence at various depths in the lithosphere, and the effects of melt/fluid-rock interactions from mantle to crust, it is necessary to adopt integrated, multi-parametric and multi-disciplinary approaches. Integrated studies, in fact, are better suited not only to image and trace melts and fluids in mantle, volcanic, tectonic and industrial exploitation environments, but also to identify specific seismicity patterns in correlation to an increase/decrease in natural and anthropogenic hazards.
The session will focus on innovative research, field studies, modeling aspects, theoretical, experimental and observational advances in detecting and tracking the migration of melts and fluids at the micro- to macro-scale.
We welcome contributions from a broad range of disciplines, including seismic monitoring, petrology, geochemistry of minerals, melt/fluid inclusions and gaseous emissions, tomography, volcanology, thermodynamic modelling. The session also encourages contributions from Early Career Scientists.
Orals: Tue, 29 Apr | Room 0.96/97
Continental mantle represents one of Earth’s most ancient and long-lived chemical reservoirs. It plays a crucial role in the global cycling of volatile elements—such as C, H, S, F and Cl —because of its unique ability to both sequester volatiles via metasomatism and release them to the atmosphere during volcanism (Gibson and McKenzie, 2023).
The widespread generation of deep-sourced, volatile-rich melts is borne out by global maps of magmas rich in CO2, H2O, S and F (e.g. kimberlites, lamproites and carbonatites). Moreover, mantle xenoliths preserve evidence of repeated episodes of pervasive, reactive percolation and stalling of these volatile-rich melts. High-precision analyses of volatile elements in the abundant nominally-volatile-free mantle minerals and accessory phases, together with analyses of volatiles of intraplate magmas, allow quantification of the storage of volatile elements in the lithospheric mantle.
Recent advances in global tomography, particularly multi-mode surface wave analysis, have significantly refined estimates of lithospheric thickness. These improvements enable more reliable calculations of lithospheric mantle volume across different geodynamic environments, including cratonic regions, continental off-craton areas and oceanic domains. The results indicate that the most significant global volatile reservoir resides within the mantle beneath ancient cratons. This is primarily due to their large volume and the elevated volatile concentrations preserved within their stable ‘roots’. Our new thermal models show that the outer ~ 50 km of craton margins is especially susceptible to devolatilisation during rifting and heating events (Gibson et al., 2024b). The thermal stability of craton interiors, however, ensures these regions have acted as long-term volatile sinks for at least the past 2.5 billion years. The volatile budget of off-craton lithospheric mantle is more dynamic. Volatiles stored in these regions may have significantly shorter residence times and can be rapidly remobilized through rifting and heating events. As a result, off-craton lithospheric mantle can transition from a volatile ‘sink’ to a ‘source’ over relatively short geological timescales, potentially within a few million years.
The ultimate source of volatiles stored in the continental mantle is challenging to decipher but 3He/4He exhibits a systematic behaviour with melt depletion in mantle peridotites and deviations from this global trend may be correlated with subduction events (Gibson et al., 2024a). The dynamic nature of volatile storage and release within Earth's lower lithospheric ‘lid’ underscores the need for continued refinement of mantle volatile estimates to improve our understanding of deep volatile cycling.
Gibson, S. A., Crosby, J. C., Day, J. A. F., Stuart, F. M., DiNicola, L. & Riley, T. R. (2024a). Systematic behaviour of 3He/4He in Earth’s continental mantle. Geochimica et Cosmochimica Acta 384, 44–64.
Gibson, S. A. & McKenzie, D. (2023). On the role of the lithospheric mantle in global volatile cycles. Earth and Planetary Science Letters 602, 117946.
Gibson, S., McKenzie, D. & Lebedev, S. (2024b). The distribution and generation of carbonatites. Geology 52, 667–671.
How to cite: Gibson, S., McKenzie, D., and Lebedev, S.: The dynamic role of Earth's continental mantle in ‘deep time’ volatile cycles , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8582, https://doi.org/10.5194/egusphere-egu25-8582, 2025.
Olivine and its polymorphs are the dominant minerals in the upper mantle and transition zone. The olivine phase transitions, determined primarily by pressure and temperature, control mantle discontinuities and influence mantle dynamics. Pressure is a first-order control on olivine phase transition and relates primarily to depth; therefore, it is commonly used to interpret the depths of mantle discontinuities. However, mantle dynamic models predicted 100-300 MPa stress levels or as high as several GPa. Such stresses would affect the positions where mineral reactions occur and, hence, large-scale mantle structure. In this work, we focus on the feedback between pressure and stress on the olivine phase transition at grain scale, and then the results can be extrapolated and upscaled to mantle scale deformation.
We use the Open Phase Studio software based on the phase field model to simulate olivine phase transitions. The phase field model uses order parameters to distinguish different phases and describe their evolution. The parameter value of 1 indicates the bulk of the phase, and a value of 0 indicates the absence of this phase and is a smooth function of position. The smooth transition of a phase parameter indicates a diffuse interface between phases. The total free energies, including temperature-related, elastic and interfacial free energies, interface properties, and initial microstructure, govern the evolution of the phase field. We applied this model to the Forsterite (Mg2SiO4)-Wadsleyite (Mg2SiO4) phase transition under different stress boundary conditions. We considered both isotropic and anisotropic boundary stress conditions. Under isotropic stress conditions, we plotted the Forsterite-Wadsleyite phase transition boundary based on our simulation results. The results indicate that local pressure variations, characterized by lower pressure within the Wadsleyite grain, hinder the occurrence of the phase transition. The depth offset would be ~30 km depressed due to this problem, which would be seismically detectable. Under anisotropic stress conditions, the Wadsleyite phase grows faster towards the maximum compression direction, leading to an elongated grain shape; however, the deviatoric stress does not shift the phase transition boundary significantly. At the same pressure, the deviatoric stress slightly slows down the Wadsleyite growth in volume.
How to cite: Lu, L. and Wheeler, J.: Grain-scale simulation of olivine phase transition under stress: implications for mantle discontinuities, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6808, https://doi.org/10.5194/egusphere-egu25-6808, 2025.
Fluid segregation in deep-seated rocks has profound implications for their physical and chemical properties. Gravity drives the segregation of fluids interconnected through grain edges and corners, along with the compaction of the rock matrix, whereas isolated fluids are retained in the rocks. For wetting fluids, the critical volume fraction (i.e., percolation threshold) separating these two cases is principally determined by the balance and anisotropy of solid-fluid interfacial tensions (i.e., dihedral angle and faceting effect); however, the processes controlling the percolation threshold for non-wetting fluids are unclear, despite their critical importance, especially in the amount of pore fluids down-dragged in subducting slabs to the Earth’s interior. Hence, we implemented a combined approach involving high-pressure rock synthesis, high-resolution synchrotron radiation X-ray computed microtomography (CT) imaging, and numerical permeability computation to better understand how the permeability decreases and fluids are retained at low fluid fractions. We chose quartzite as a well-studied natural rock analog that is simplified but does not lose its essence as a silicate polycrystalline aggregate. A mixture of finely ground quartz and amorphous silica powders was sealed in Pt-lined Ni capsules with C-O-H fluid sources at different fractions and compositions and hot-pressed using a piston-cylinder apparatus. The dihedral angles of the experimental systems were 52° and 61–71° for the wetting and non-wetting systems, respectively.
In the wetting system, fluid connectivity rapidly decreased to approximately zero when the total fluid fraction decreased to 3.0–3.7 vol. %, mainly due to the grain faceting effect, consistent with the results of the previous study. In the non-wetting systems bearing CO2-rich fluids, the cutoff of fluid tubules isolated 4.8–6.2 vol. % of the fluid. A streamline computation based on the X-ray CT images of the experimental products revealed that the fluid flow just above this threshold focused on a few channels, establishing efficient channelized fluid pathways. These retained fluid fractions are higher than those in the previous assessment based solely on the dihedral angle, that is, the pinch-off condition for ideal (isotropic and homogeneous) fluid geometry and the equilibrium fluid fraction that minimizes the total interfacial energy of the fluid-rock system. Hence, the amount of aqueous fluids dragged down to the Earth’s interior could be higher than previously estimated, although the specific volume fraction depends on the anisotropy and heterogeneity of the system of interest.
How to cite: Nakamura, M., Fujita, W., Uesugi, K., Eichheimer, P., Thielmann, M., and Golabek, G.: Fluid segregation and retention in deep‑seated rocks near percolation thresholds, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2750, https://doi.org/10.5194/egusphere-egu25-2750, 2025.
This study investigates the potential of hydroseismograms for seismic monitoring and understanding earthquake physics, utilizing high-frequency pore pressure measurements within the Gran Sasso Aquifer (GSA) in central Italy. Hydroseismograms, obtained from a hydraulic pressure device (HPD) installed in deep, horizontal wells intersecting a major fault network within the GSA, are compared with seismic records from the nearby GIGS station to assess the HPD's earthquake detection capabilities. This unique setting, combined with the HPD's high-frequency (20 Hz) data acquisition system, offers a sensitive method for monitoring both seismic activity and pore pressure anomalies. The GSA’s fractured-karst geology and its location within a high seismic hazard zone in Italy, along with the presence of the Italian Institute of Nuclear Physics (INFN) underground laboratory (UL), create an ideal environment for studying deep, saturated aquifer-earthquake interactions, minimizing interference from shallow hydrological processes. The UL houses two horizontal boreholes, named S13 (190 m) and S14 (175 m), equipped with the HPD. Approximately 250 meters from S13, the INGV seismic station GIGS, part of the GINGER experiment, uses two broadband seismometers for continuous microseismic monitoring and global seismicity recording. The research analyzes long-term, high-frequency pore pressure data from the GSA, aiming to further understand the complex relationship between groundwater and seismic activity. The primary objective of the joint analysis of well and seismic data, spanning from May 1, 2015, to December 31, 2023 (with ongoing monitoring), is to identify and correlate earthquake occurrence with hydraulic pressure variations detected by the HPDs in S13 and S14. A statistical inferential approach was used to evaluate HPD sensitivity, comparing the number of HPD-detected events with those recorded by GIGS (1068 events) across different magnitudes and epicentral distances. Statistical analysis demonstrates the HPD’s significantly enhanced sensitivity compared to previous studies. The HPD detected 148 of the 1068 events recorded by GIGS (a 13.9% overall success rate), with this detection probability strongly influenced by earthquake magnitude and epicentral distance. Mainly for far events, the identified detection threshold significantly exceeds the “hard” detection limit for typical aquifers defined by Montgomery and Manga (2003) based on the Dobrovolski et al. (1979) criterion, a limit below which they found no detections in a large dataset.
This finding warrants further investigation into the not yet fully understood mechanisms of hydroseismic detection. This study, covering data from May 2015 to December 2023, reveals the potential of HPDs installed in carbonate rock boreholes for seismic monitoring. The GSA hydrogeological and seismotectonic conditions provide an optimal environment for HPD deployment for both medium-to-long-term and high-frequency pore pressure monitoring. The strategic borehole locations intersecting the main fault network offer a unique opportunity to study the complex interplay between hydrological processes and seismic activity. Ongoing HPD monitoring will further explore their potential as a valuable tool for future seismic studies and contribute to the advancement of earthquake science, with implications for seismic hazard assessment and early warning systems.
References
Montgomery, D. R., & Manga, M. 2003. Streamflow and water well responses to earthquakes. Science, 300(5628), 2047-2049.
How to cite: Guerriero, V., Isaya, D., De Luca, G., Di Carlo, G., Martorana, R., and Tallini, M.: Earthquake Hydrology and seismic detection capability of deep pressure devices within the Gran Sasso aquifer (central Italy), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12391, https://doi.org/10.5194/egusphere-egu25-12391, 2025.
This study investigates the mineral chemistry of olivine, orthopyroxene, clinopyroxene, and chromite phases from the Wadi Zikt high Al-chromitite within the Khor Fakkan massif of the UAE ophiolites. The ophiolites, part of the well-preserved Semail ophiolite complex, represent mantle sections formed in a supra-subduction zone (SSZ) environment. Detailed analyses reveal that the olivine exhibits high forsterite contents (Fo > 90), elevated NiO concentrations (up to 0.6 wt%), and low MnO (< 0.2 wt%), indicating significant partial melting under hydrous conditions. Orthopyroxenes display high Mg# (> 90), low Al₂O₃ (< 1.2 wt%), and elevated Cr₂O₃ (up to 0.62 wt%) contents, consistent with residues of extensive melt extraction. Clinopyroxenes are characterized by high Mg# and low TiO₂, Al₂O₃, Dy, and Yb contents suggesting a forearc setting. Chromite analyses show high Cr# (51–67), low TiO₂ (< 0.8 wt%), and low Ga/Fe3# ratio, reinforcing a fore-arc origin. The studied chromites are analogues to those of the fore-arc peridotite, indicating high degrees of partial melting (25–35%). The geochemical signatures of the studied phases, including low Ti, high Cr#, and high Mg#, suggest that the Wadi Zikt chromitite formed in a depleted mantle wedge influenced by subduction-derived fluids and boninitic melts during the early stages of subduction initiation. These findings provide critical insights into mantle wedge processes, arc magma genesis, and ophiolite formation in SSZ settings. This study underscores the significance of the Wadi Zikt chromitite as a key example of SSZ mantle dynamics and melt evolution, contributing to the broader understanding of ophiolite complexes worldwide.
How to cite: Sami, M., Mahmoud, B., Zhao, X., El-Awady, A., Ntaflos, T., Abart, R., and Fathy, D.: Petrogenetic and tectonic interpretation of Wadi Zikt Chromitite, Khor Fakkan block, United Arab Emirates: Evidence from major and trace mineral chemistry, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16196, https://doi.org/10.5194/egusphere-egu25-16196, 2025.
Metamorphic soles are key petrotectonic units that offer valuable insights into the processes governing ophiolite emplacement. Ophiolite obduction involves complex thermomechanical phenomena and is associated with limited petrological data. In this work, we have investigated the metamorphic sole of the Pindos ophiolite in northwestern Greece. In the studied locality, the sole is sandwiched between mantle peridotites and pillow lavas of N-MORB affinity. We mainly focused on two lithologies: a garnet-mica metapelite and an amphibolite. Petrographic investigation of the metapelite revealed quartz inclusions in garnet indicating syn-kinematic growth, asymmetric quartz ribbons and S-C shear bands of syn-kinematic mica, all being consistent with top-to-the-NE shearing. Petrographic and textural evidence, temperature calculations (Fe-Mg garnet-biotite exchange and paragonite-muscovite solvus thermometry), and phase-equilibria modelling using an effective bulk composition bracket metamorphism at amphibolite-facies conditions (ca. 620-640°C and 1.1-1.2 GPa). Moreover, Quartz-in-Garnet (QuiG) barometry yielded a pressure of ~1.2 GPa for 635°C demonstrating that the syn-kinematic growth of garnet took place under high-pressure conditions. New ⁴⁰Ar/³⁹Ar geochronology of syn-kinematic muscovite from the metapelite and amphibole from the amphibolite showed an apparent minimum age of 164.16 ± 0.37 Ma and a consistent age plateau at 165.5 ± 0.73 Ma respectively. Notably, the amphibole exhibited no evidence of argon loss, suggesting its apparent age closely represents the time of formation. The muscovite age, by contrast, should be considered a minimum apparent age due to the potential influence of argon diffusion. Despite this limitation, the studied metapelite represents, in all probability, metamorphosed pelagic sediments in association with oceanic crust of N-MORB affinity. A combination of heat conduction from the overlying peridotite and shear heating developed during emplacement are considered responsible for the formation of the metapelite. Our joint petrological, geochronological and structural data indicate that the Pindos metamorphic sole records evidence of rapid thrusting (<2.5Myr) of the ophiolite from a westerly oceanic tract (Pindos Ocean) onto the Pelagonian margin over to the east in Callovian times (uppermost mid-Jurassic).
How to cite: Moutzouris, D., Moulas, E., Kostopoulos, D., and Pomonis, P.: Emplacement of the Pindos ophiolite, NW Greece: P-T-t-kinematic constraints from the metamorphic sole, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4266, https://doi.org/10.5194/egusphere-egu25-4266, 2025.
Carbonatites are spatially and temporally associated with Large Igneous Provinces (LIPs) such as the Siberian traps, the Paraná-Etendeka and the Deccan traps. Carbonatites, and the associated alkaline rocks, can both predate and postdate the main tholeiitic volcanism. For example, the Sarnu Dandali complex (68.57±0.08 Ma) and the Mundwara complex (68.53±0.16 Ma), both characterized by high 3He/4He, predate the Deccan traps, whereas the 65±0.3 Ma carbonatites in the Narmada Rift postdate it. Similarly, carbonatites from the Amambay alkaline province (Eastern Paraguay) predate the Paraná-Etendeka LIP by several million of years, whereas the Jacupiranga carbonatites (130 Ma) in South America and the Damaraland carbonatites (129-123 Ma) in Namibia postdate the main tholeiitic pulse (134-132 Ma).
The origin of carbonatites remains a matter of debate, albeit radiogenic isotope ratios, trace element variations and primordial noble gases from most carbonatites support a plume origin. For carbonatites predating LIPs, a generally accepted model invokes partial melting of carbonate-metasomatized lithospheric mantle, heated by the plume. The implicit assumption is that heat, slowly diffused from the plume, can reach the lithosphere before buoyant melts from the plume itself, which is not obviously plausible.
Our 3D-numerical simulations of a mantle plume with millions of carbon- carrying tracers enable us to calculate the depth at which carbon-rich fluids form. These fluids, because of their physical properties, are highly mobile and separate from the solid matrix even at low melt fractions. At each time-step we calculate their ascent velocity (i.e., a linear combination of the solid matrix velocity and of the separation velocity) and their 3D-trajectories. We span a range of carbon concentrations in the plume source (196 ≤ C ≤ 440 ppm), and we explore different depths of redox melting and P-T conditions for the solidus of carbonated peridotite.
We find that, if mantle redox conditions allow for deep (>200 km) carbon-rich melting, then the fast rising carbonatitic fluids can reach the lithosphere 2-3 Myr before the onset of anhydrous peridotite melting. This key result reveals the existence of a precursory carbon flux (of order 10e+12 - 10e+13 mol/yr) across the base of the lithosphere (i.e., 140 km depth). When melting of anhydrous peridotite starts in the plume head, a total mass of 10e+16 kg C has already reached the lithosphere. This precursory carbon flux provides a new framework to interpret carbonatite complexes predating the earliest LIP's volcanism.
We also find that the radial extent of the zone permeated by carbon-rich fluids is much broader than the zone undergoing anhydrous peridotite melting. These vast lithospheric domains, fertilized during several millions of years by plume-derived carbon-rich fluids might be mobilized by peripheral tholeiitic magmas. Possibly, this scenario could explain the occurrence of carbonatites that postdate LIP's emplacement, but which carry a distinctive plume-like geochemical fingerprint (e.g., the high 129Xe/130Xe of the Jacupiranga carbonatites).
How to cite: Farnetani, C. G. and Richards, M. A.: The origin of carbonatite magmas predating main-phase LIPs eruptions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16266, https://doi.org/10.5194/egusphere-egu25-16266, 2025.
The European Variscan orogen (EVO) originated through tectonic accretion of few continental ribbons followed by collision of Gondwana and Laurussia, including docking of mantle parts of incoming terrains to the mantle wedge. At the late- and post-orogenic stage, the thickened orogenic root (Moho depth ca 55-60 km) flattened by lateral crustal flow and gravitational collapse [1], although this was not uniform across the EVO. In the Bohemian Massif, the crust is still fairly thick (ca. 35 km) and the impact of gravity-driven lateral flow of partially molten orogenic root was rather limited [2]. In contrast, the geology of French Massif Central (FMC) reflects the importance of lateral flow of the partially molten crustal orogenic root and its exhumation in crustal-scale domes beneath low-angle detachments. Where flattening occurred, it produced a relatively flat Moho at ca 30-32 km depth [3]. Thus, the lithospheric and asthenospheric mantle underlying the orogen must have been exhumed by 20-30 km.
The mantle parts of the EVO are sampled – as peridotite xenoliths – by numerous Cenozoic alkaline lavas of the Central European Volcanic Province. Despite locally strong Cenozoic metasomatic overprint, these xenoliths offer the opportunity to decipher the evolution of lithospheric mantle from which they come [4] including whether the xenoliths can constrain which parts of the Variscan orogen escaped delamination.
Slices of Variscan “orogenic peridotites”, attached to the growing orogen, now occur in the exposed basement “massifs”. They usually belong to the peridotite garnet facies (e. g. [5]), whereas the peridotite xenoliths occurring in Cenozoic lavas are exclusively spinel peridotites [6], confirming that large part of lithospheric mantle underlying EVO was exhumed from garnet- to spinel-facies P-T conditions. This decompression is recorded by spinel-pyroxene symplectites after garnet in some xenoliths, such as at Montboissier in the northern FMC domain.
Indeed, the xenoliths sampling large parts of the EVO lithospheric mantle are clinopyroxene-poor and depleted in major melt-mobile elements, suggesting that they represent lithospheric mantle fragments tectonically attached to the orogen root during orogenesis (“Variscan orogenic mantle” of [5]) which escaped subsequent delamination.
Our analysis suggests that lithospheric mantle evolution deciphered from xenoliths, if combined with geological data on crust evolution, allow to elaborate more pertinent tectonic-geodynamic models of EVO.
Funding. This study originated thanks to the project of Polish National Centre of Research 2021/41/B/ST10/00900 to JP.
[1] Vanderhaeghe, O., Laurent, O., Gardien, V.Moyen, J.-F., Gébelin, A., Chelle-Michou, C., Couzinie, S., Villaros, A., Bellanger, M., 2020. BSGF-Earth Sciences Bulletin 191, 25.
[2] Schulmann, K., Lexa, O., Janoušek, V., Lardeaux, J.M. and Edel, J.B. 2014. Geology, 42, 275–278
[3] Artemieva, I., Meissner, R., 2012. Tectonophysics 530-531, 18-49.
[4] Puziewicz, J., Aulbach, S., Kaczmarek, M.-A., Ntaflos, T., Matusiak-Małek, M., Ziobro-Mikrut, M., Gerdes, A., 2025. Lithos 494-495, 107908.
[5] Kubeš, M., Čopjaková, R., Kotková, J., Ackerman, L., Haifler, J., Výravský, J., Holá, Škoda, R., Leichmann, J., 2024. Journal of Petrology 65, egae108.
[6] Puziewicz, J., Matusiak-Małek, M., Ntaflos, T., Grégoire, M., Kaczmarek, M.-A., Aulbach, S., Ziobro, M., Kukuła, A., 2020. Lithos 362-363, 105467.
How to cite: Puziewicz, J., Aulbach, S., Vanderhaeghe, O., Grégoire, M., and Ziobro-Mikrut, M.: Evolution of the of Variscan orogenic mantle root in Europe viewed through combined analysis of tectonic models and mantle xenoliths, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2372, https://doi.org/10.5194/egusphere-egu25-2372, 2025.
Knowledge of plumbing systems architecture and dynamics has increased in recent years. However, while the mid- to shallow-crustal regions are well-explored, the deepest parts of plumbing systems remain poorly understood. The Middle Triassic magmatic event in the Dolomites (Southern Alps; Italy) provides an exceptional opportunity to study all sections of ancient plumbing systems, owing to the excellent exposure and preservation of different magmatic lithologies representing various magma storage levels. Here, we present detailed textural and compositional analyses of ultramafic xenoliths embedded in mafic volcanic breccia from a diatreme outcropping in the Triassic Latemar carbonate platform (Zan de Montagna locality; 2576 m.a.s.l.). Ultramafic nodules have cumulate equigranular to inequigranular texture and are mainly clinopyroxenites, with subordinated wehrlites and websterites. Clinopyroxene goes up to 3 mm in size in all samples, while olivine in the wehrlite samples attains sizes of up to 1.5 mm. Clinopyroxene is diopsidic in composition (Wo45-49 En42-48 Fs4-10) with Mg# [MgO/(MgO+FeOtot) mol%] of 82-93 and CaO, TiO2, Cr2O3 and Al2O3 contents in the range of 22-24 wt%, 0.1-1.2 wt%, 0-0.7 wt% and 0.9-5.5 wt% respectively. Olivine has Fo contents between 84 and 89 and NiO concentration from 0.10 to 0.15 wt%. Notably, more primitive olivine can be found in the host lava, where crystals reach Fo92 and NiO content of 0.4 wt%. Orthopyroxene in the websterite is <1 mm in size and has enstatite (Wo1-4 En76-79 Fs17-23) composition, with Mg# values ranging from 77 to 82 and Al2O3 contents between 1.1 wt% and 1.8 wt%. Spinel is ubiquitous, occurring as chromite, magnetite and Ti-magnetite (Cr2O3=0.1-45.5 wt%; TiO2=0.8-16.7 wt%; FeOtot=29.0-81.0 wt%).
Overall, these xenoliths show compositional similarities with clinopyroxenitic nodules already reported in other localities of the Latemar platform (Nardini et al., 2024) and differ only for the wehrlite presence.
These new data represent an advancement in tracking back to the early stages of the liquid line of descent of the Middle Triassic magmas and help to reconstruct the deepest portion of the plumbing system of these ancient volcanoes. Moreover, the composition of clinopyroxene hosted by these nodules brings another piece of evidence about the source of the high-Mg# and high-Cr diopsidic antecrystic cores in the trachy-basaltic effusive rocks associated with this magmatism (Nardini et al., 2024).
Reference
Nardini, N., Casetta, F., Petrone, C.M., Buret, Y., Ntaflos, T., Coltorti, M., 2024. Modelling ancient magma plumbing systems through clinopyroxene populations: a case study from Middle Triassic volcanics (Dolomites, Italy). Contrib. Mineral. Petrol. 179, 22.
How to cite: Nardini, N., Casetta, F., Ntaflos, T., and Coltorti, M.: Exploring the roots of a plumbing system: insights from ultramafic xenoliths ejected during the Middle Triassic magmatic event in the Dolomites (Southern Alps; Italy)., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17535, https://doi.org/10.5194/egusphere-egu25-17535, 2025.
Posters on site: Wed, 30 Apr, 14:00–15:45 | Hall X2
Fluid injection activities cause pore pressure perturbations within the reservoir's rocks, which can potentially trigger fractures, faults failures, and alter the elastic properties of the surrounding rocks. Thus, monitoring stress conditions of the reservoir medium and the evolution of pore pressure around wells, is crucial for hazard assessment in injection areas.
We present a rock physics-based approach using induced micro-seismicity to track pore pressure temporal evolution from Vp/Vs ratio variations. Additionally, focal mechanisms analysis (BISTROP, De Matteis et al., 2016; TESLA, Adinolfi et al. 2023) of microearthquakes revealed insights into local stress patterns within the host rocks, in relation to induced seismicity.
The method was applied to wastewater disposal-induced micro-seismicity detected near of the Costa Molina 2 injection well (High Agri Valley, Southern Italy) in the Val d’Agri oilfield, the largest onshore oil and gas field in Western Europe. We used as dataset the enhanced seismic catalogue obtained in the Costa Molina area by Stabile et al. 2021. It comprises 196 induced micro-earthquakes, occurred between 2016 and 2018 around the injection well. The catalogue has events magnitudes ranging between − 1.2 ≤ Ml ≤ 1.2.
Accurate arrival time measurements are essential for calculating the Vp/Vs ratio using the Wadati method. Therefore, we first refined the first P- and S-wave arrival times using waveform cross-correlation and hierarchical clustering method. Then, the Vp/Vs ratio was estimated for each source-station pair and averaged across events at the four nearest stations to the well. This allowed us to track the temporal evolution of elastic properties in the well’s surrounding region and compare it with injection parameters (i.e., injection volume and pressure). Our findings show that variations in the Vp/Vs ratio, especially for the station closest to the reservoir, closely correlate with injection parameters.
Additionally, the obtained focal mechanisms reveal strongly contrasting behaviors, ranging from strike-slip to reverse faulting. For the latter events, we identified highly anti-correlated seismic waveforms. The presence of anti-repeaters, as described by Cesca et al., 2024, has been observed in various settings and is often associated with transient stress perturbations. Since many of these phenomena have been attributed to fluid migration processes, they could provide valuable insights into subsurface fluid movements and help track their dynamics over time.
These findings demonstrate the potential of integrating accurate locations, seismic velocity monitoring and focal mechanism analysis to enhance reservoir monitoring systems. This method improves understanding of induced seismicity and offers a valuable tool for risk assessment and fluid injection management, applicable to various reservoir contexts.
References:
De Matteis R, Convertito V, Zollo A. 2016. Bayesian inversion of spectral-level ratios and P-wave polarities for focal mechanism determination. Seismol Res Lett. 87:944–954. https://doi.org/10.1785/0220150259.
Adinolfi G.M., Convertito V, De Matteis R. 2023. TESLA, A Tool for Automatic Earthquake Low‐Frequency Spectral Level Estimation: The Study of 2013 St. Gallen Earthquake Fault‐Plane Solutions. Seism ReS Lett. 94 (5): 2441–2455. https://doi.org/10.1785/0220230033
Stabile, T.A., Vlček, J., Wcisło, M. et al. Analysis of the 2016–2018 fluid-injection induced seismicity in the High Agri Valley (Southern Italy) from improved detections using template matching. Sci Rep 11, 20630 (2021). https://doi.org/10.1038/s41598-021-00047-6
Cesca, S., Niemz, P., Dahm, T. et al. Anti-repeating earthquakes and how to explain them. Commun Earth Environ 5, 158 (2024). https://doi.org/10.1038/s43247-024-01290-1
How to cite: Panebianco, S., De Landro, G., Muzellec, T., Adinolfi, G. M., Serlenga, V., and Stabile, T. A.: Tracking fluid-induced seismicity: integrating Vp/Vs ratio variations and focal mechanism analysis for reservoir monitoring, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20133, https://doi.org/10.5194/egusphere-egu25-20133, 2025.
On June 10, 2021, a M 5.1 earthquake occurred in the region between two large parallel strike-slip faults in Shuangbai County, Yunnan Province. To investigate the earthquake's mechanism, the spatial and temporal distribution characteristics of the mainshock and its aftershock sequence were analyzed using template matching detection and relocation methods. Additionally, the regional stress field and fault slip tendency were examined. Other factors, such as tidal stress and the triggering effects of previous seismic events, were also considered. The results reveal that the 2021 M 5.1 Shuangbai earthquake sequence exhibited fluid-driven outward migration from the initial hypocenters. The study area is characterized by a strike-slip stress regime, with a nearly horizontal σ1 oriented in the NNW-SSE direction and a horizontal σ3. It was found that the seismogenic fault of the Shuangbai earthquake sequence was not optimally aligned with the regional stress conditions. The findings suggest that fluid overpressure played a primary role, while tidal stress had a secondary influence, in the occurrence of the mainshock and its aftershocks.
How to cite: Xie, C., Huang, M., and xu, Y.: Physical mechanism of the 2021 M 5.1 Shuangbai earthquake and its aftershock sequence in Yunnan Province, China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1917, https://doi.org/10.5194/egusphere-egu25-1917, 2025.
Geochemical anomalies are widely recognized as potential precursors to earthquakes. Recent studies on precursor signals and phenomena of the seismic process have demonstrated that significant transients in geochemical parameters may occur prior to moderate-to-high magnitude earthquakes (Magnitude > 4). Among the geochemical processes investigated, notable variations have been observed in the ion concentrations and dissolved gases in groundwater, as well as in the composition of crustal and mantle-derived gases emanating from soils.
Soil gas anomalies, particularly diffuse degassing of CO2, serve as critical indicators for identifying fault zones due to their strong correlation with increased crustal permeability in the fault zones. Temporal variations in the degassing rate are modulated by changes in crustal stress preceding or accompanying seismic events. Hydrogen, in particular, has emerged as a promising indicator of seismic activity. Observations have revealed that hydrogen anomalies in soil gas decrease with increasing distance from the seismic source and occur both prior to and during earthquakes. The existing literature suggests that hydrogen is produced in the crust through water-rock interactions, generating concentration anomalies that can exceed four orders of magnitude relative to atmospheric hydrogen.
This study outlines the implementation of a monitoring network designed to measure soil CO₂ flux, hydrogen concentrations in soil gas, and selected atmospheric variables (e.g., temperature, pressure, rainfall, wind speed, and wind direction) that may influence the emissions of soil gases. The network consists of four stations strategically deployed near the Matese-Irpinia region, an active seismic zone in the southern Apennine chain, Italy. This area hosts several active fault systems where earthquakes with magnitudes > 3.0 have been recorded over the past two decades. The region is characterized by normal faulting and shallow hypocentral depths (less than 15 km). Notably, the Monti del Matese area has experienced several prolonged seismic swarms, including more than 250 earthquakes within a month during 2013, culminating in a moderate-magnitude event (ML 4.9) on December 29, 2013.
Measurements are collected hourly and telemetered to the INGV in Palermo. An automated software platform, adapted from a pre-existing gas hazard monitoring system, has been optimized for the specific objectives of this study. This platform (Gas Net Analytics), which has several tools for the automated analysis of the geochemical data, adopts high standard for data management, including security. It facilitates automatic statistical analysis and visualization of the data, ensuring low latency in delivering the geochemical information.
The implementation of the monitoring network aims to characterize hydrogen concentrations and CO₂ flux as potential tracers of the local response to regional variations in crustal stress field which is associated with the seismic processes. The data collected on H2 and CO2 are further utilized to refine physical-mathematical models of gas transfer through crustal rocks. These models incorporate mechanisms of advective and diffusive gas transport through porous media, enabling the interpretation of diffuse degassing variations in the context of crustal stress dynamics. The integration of geochemical monitoring and modelling offers a robust framework for elucidating the relationship between soil gas anomalies and seismic activity, thereby advancing our understanding of earthquake precursors.
How to cite: Francofonte, V., Di Martino, R. M. R., Gurrieri, S., Mastrolia, A., and Altavilla, F.: Geochemical anomalies in the soil gases as potential precursors to seismic events: a case study in the Appennines, souther Italy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16410, https://doi.org/10.5194/egusphere-egu25-16410, 2025.
The Mefite d’Ansanto is the largest non-volcanic low temperature CO2 natural emission on the Earth (Di Luccio et al., 2023). It is located in the Southern Apennines, about 25 km away from the northern tip of the seismogenic structures of the November 23, 1980 MS = 6.9 earthquake. The main gas emissions manifest in a roughly circular depression with about 100 m of diameter, whose centre is characterized by bubbling mud. The emissions of CO2, likely of mantle origin, are probably fed by the reservoir found at Mt. Forcuso 1 well (Chiodini et al., 2010), located approximately 2 km east of Mefite area. In the framework of the Strategic INGV FURTHER Project, on 29 September 2020 a local seismic network was installed to investigate on the possible links between the fluid movements at depth and the seismicity of the area surrounding the CO2 emission site (Cusano et al., 2021; Morabito et al., 2023). With the aim of obtaining information on how large the emission area is and on its sub-surficial structure, we investigated the crustal structure beneath Mefite d’Ansanto and the surrounding area analysing the waveforms of teleseismic events. We selected deep and intermediate earthquakes that have impulsive onset, epicentral distance ∆ ≤ 90° and magnitude M ≥ 6.0. The seismic traces are those recorded by MEFA, a temporary seismic station installed at Mefite d’Ansanto, and by CAFE, SNAL and RFS3, permanent seismic stations belonging to the INGV National Seismic Networks. We, first, utilized cross-correlation technique to check the similarities among the waveforms (Milano et al., 2023). Successively, we computed synthetic seismograms to obtain the best fit with the recorded seismograms. The synthetic seismograms were computed by means of QSEIS6 software (Wang, 1999), fixing a starting velocity model extracted from that IASPEI91 (www.iris.edu). Successively, we perturbed it beneath the study area taking also into account the upper crustal structure recently retrieved for the Irpinia region (e.g., Feriozzi et al., 2024). The cross-correlation analysis had already revealed some particularities in the waveforms suggesting similarities in the uppermost crust beneath MEFA and RSF3 stations, approximatively 2.5 Km apart. The first results from the synthetic seismograms evidence that the phase with the on-set in the range 4.5-5 s from the first arrival at each stations, is compatible with the P-to-S converted phase at Moho discontinuity.
Chiodini et al., 2010, Geophys. Res. Lett., 37, L11303.
Cusano et al., 2021, https://doi.org/10.5194/egusphere-egu21-10625.
Di Luccio et al., 2022, https://doi.org/10.1016/j.earscirev.2022.104236.
Feriozzi et al., 2024, https://doi.org/10.1029/2023TC008056.
Milano et al., 2023, https://doi.org/10.4430/bgo00416.
Morabito et al., 2023, https://doi.org/10.3390/s23031630.
Wang, 1999, Bulletin of the Seismological Society of America, 89(3), 733-741.
How to cite: Milano, G., Morabito, S., Cusano, P., and Gervasi, A.: Mefite d’Ansanto CO2 emission area (Southern Apennines, Italy): first results on the uppermost crustal structure from teleseismic data., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19823, https://doi.org/10.5194/egusphere-egu25-19823, 2025.
Central Italy is affected by a significant migration of deep CO2 through the crust. CO2 upraise gives rise to numerous gas emissions in the western Tyrrhenian domain where extensional deformation has dismantled the compressional structures, enabling fluid emissions through a mature set of normal faults. Conversely, the thickened crust and the abundant groundwater circulation in carbonate aquifers of the Apennine “trap” migrating deep fluids. Here, in the eastern Apennine sector, deep CO2 dissolves in the large carbonate aquifers, while the CO2 anomalies disappear in the easternmost Adriatic domain. This divide is reflected in seismicity patterns, with Apennine earthquakes clustering close to the degassing anomaly boundary. Significant variations in dissolved deep CO2 were observed in some springs from large Apennine aquifers during the seismic crises of L’Aquila 2009 and Central Italy 2016-17, suggesting feedback mechanisms between CO2 degassing and seismicity. The region is also characterised by a dense hydrological network (i.e., the Tiber River Basin, TRB) running in the different tectonic settings, with some major rivers collecting water from areas where CO2-rich springs, sensitive to the seismic activity, are present. In this framework, a two-year geochemical survey of the major rivers of TRB was conducted aimed to explore the reliability of investigating the regional CO2 degassing process and its relations with the seismicity by studying the river’s waters. In addition to the geological peculiarities, this area is suitable for this objective, due to the well-developed hydrometric network managed by local authorities, allowing to couple geochemical and hydrological data. More than 350 river water samples were collected from the Tiber river and its 12 main tributaries. A large geochemical dataset including major ions and dissolved inorganic carbon isotopic compositions was produced covering different hydrological periods. Results show that river waters exhibit compositions and variability resembling those of the Apennine groundwaters, allowing to identify different fluids circulating in the crust. Compositional variation remains appreciable for long distances downstream of mixing between shallow and groundwaters and between rivers with different compositions, highlighting the preservation of the geochemical information over large areas. In particular, the content of dissolved carbon in river waters and its isotopic composition shows and preserves for long distances the signature of the input of deep CO2-rich waters. Coupling river’s geochemical and flow rate data, fluxes of dissolved deep CO2 were computed, providing results that closely match previous estimates based on spring data, indicating minor carbon loss along rivers. These findings highlight rivers as valuable indicators of deep CO2 flux across large areas and potentially to investigate temporal variation of the flux. This study has been also focused on the definition of ‘easily detectable parameters’ (EDP) which correlate to dissolved deep CO2. Measuring EDP at high frequency, together with the water flow rate, could provide a tool for monitoring variations of the deep CO2 flux to enhance a possible geochemical monitoring of the seismic activity.
How to cite: Tieri, M., Cardellini, C., Chiodini, G., Caliro, S., Frondini, F., Cinti, D., Barberio, D., Di Renzo, D., Santi, A., Cuoco, E., Rufino, F., and Caracausi, A.: Deep fluids transported by Apennine rivers: quantification of deep CO2 emission and implications for geochemical monitoring of the seismic activity., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6264, https://doi.org/10.5194/egusphere-egu25-6264, 2025.
Combining the geochemistry of gas emissions in active volcanic regions with the signature of mineral-hosted fluid inclusions in mantle-derived xenoliths is the next frontier in geodynamics and volcano monitoring and can provide important clues on: i) the nature and evolution of the lithospheric mantle; ii) the storage and mobility of fluids through the lithosphere; and iii) the origin of fluids migrating within the mantle and in the plumbing system underneath active volcanoes.
In this study, we present new mineral and fluid inclusion chemistry (noble gases and CO2) data on a unique suite of mantle-derived xenoliths hosted in phonolite pyroclastic deposits in Mayotte island (Comoros archipelago, Indian Ocean), which was the scene of one of the largest submarine eruptions ever documented from 2018 to 2021 (Jacques et al. 2024).
The studied samples are spinel-bearing harzburgites and lherzolites, and are composed of Cr-spinel (Cr# = 0.4-0.55), Mg-rich olivine (Fo90-92, NiO = 0.3-0.5 wt%), orthopyroxene (Mg# = 91-92; Al2O3 = 1.5-3.0 wt%), and clinopyroxene (Mg# = 91-94; Al2O3 = 2.0-3.5 wt%). The mineral major and trace element distribution indicates that the xenoliths represent fragments of a residual lithospheric mantle which experienced 20 to 25% partial melting.
Olivine-, orthopyroxene-, and clinopyroxene-hosted fluid inclusions are CO2-dominated and have air-corrected 3He/4He isotopic ratios of 5.6-6.8 Ra that are intermediate between the typical signature of Mid-Ocean Ridge Basalt (MORB = 8±1 Ra) and Sub-Continental Lithospheric Mantle (SCLM = 6±2 Ra). Such He isotopic signature is similar to that of subaerial and submarine gaseous emissions in the Mayotte area (Liuzzo et al. 2021; Mastin et al. 2023).
With respect to the mantle xenoliths from the neighbouring Grande Comore Island (Coltorti et al. 1999; Bordenca et al. 2023), the peridotites from Mayotte lie within a narrower compositional range, being moderately depleted and not showing significant metasomatic enrichment. Despite comparable 3He/4He ratios, fluid inclusions in the Mayotte samples have higher 4He/40Ar* values than those of the refractory mantle (Rizzo et al. 2021), likely indicating a shallow overprint by magmatic fluids.
Mantle xenoliths and hosted fluid inclusion data are used here to model the melt-fluid/rock reactions in the lithospheric mantle, the genesis and ponding of magmas linked to the recent volcanic activity at Mayotte and the geodynamic setting of the Comores archipelago.
References
Coltorti, M., Bonadiman, C., Hinton, R. W., Siena, F., & Upton, B. G. J. (1999). Journal of Petrology, 40(1), 133-165.
Jacques, E., Hoste-Colomer, R., Feuillet, N., Lemoine, A., van der Woerd, J., Crawford, W. C., ... & Bachèlery, P. (2024). Earth and Planetary Science Letters, 647, 119026.
Liuzzo, M., Di Muro, A., Rizzo, A. L., Caracausi, A., Grassa, F., Fournier, N., ... & Italiano, F. (2021). Geochemistry, Geophysics, Geosystems, 22(8), e2021GC009870.
Mastin, M., Cathalot, C., Fandino, O., Giunta, T., Donval, J. P., Guyader, V., ... & Rinnert, E. (2023). Chemical Geology, 640, 121739.
Rizzo, A. L., Faccini, B., Casetta, F., Faccincani, L., Ntaflos, T., Italiano, F., & Coltorti, M. (2021). Chemical Geology, 581, 120400.
How to cite: Casetta, F., Faccincani, L., Rizzo, A. L., Faccini, B., Liuzzo, M., Nardini, N., Di Muro, A., and Coltorti, M.: Volcanic gases vs. mantle fluids: clues from mineral-hosted fluid inclusions in ultramafic xenoliths from Mayotte island (Comoros archipelago, Indian Ocean), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8395, https://doi.org/10.5194/egusphere-egu25-8395, 2025.
The eruption risk of a volcano depends on how much melt and gas have built up in its magmatic hydrothermal system in the upper crust. However, it is still challenging to characterize their spatial distributions and quantitatively estimate their concentrations. By integrating geophysical imaging results, petrological analysis and rock physics models, we mapped the migration pathways of fluids and gases and estimated their concentrations beneath Uturuncu volcano in Bolivia. This volcano last erupted 250,000 years ago, and our results explain why it still shows activity and are helpful for assessing its future eruption risks. This study shows how combining seismology, petrology and rock physics can help resolve the internal structure and composition of hydrothermal system beneath a volcano.
How to cite: Liu, Y., Kendall, M., Zhang, H., Blundy, J., Pritchard, M., Hudson, T., and MacQueen, P.: Unraveling the structure of the magmatic hydrothermal system beneath Uturuncu Volcano by joint seismological and petrophysical analysis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4668, https://doi.org/10.5194/egusphere-egu25-4668, 2025.
Hydrothermal alteration and geofluid transport in magmatic systems plays a crucial role in the development of ore deposits, the systematics of geothermal resources and the structural stability of volcanic edifices. Characterising the type, intensity and distribution of alteration associated with geofluid pathways is therefore critical to understanding how essential resources form. However, alteration is routinely classified on the basis of highly subjective evaluations made by individual geologists or on single semi-quantitative datasets such as hyperspectral core analysis. Similarly, the role of alteration in controlling the distribution of strain is poorly constrained within magmatic systems. This study adopts a semi-quantitative approach to characterising hydrothermal fluid alteration using a novel combination of hyperspectral and magnetic analysis to efficiently characterise the silicate, oxide and sulphide mineralogy of a hydrothermally altered granitoid shear zone and its impact on strain development.
The monzodioritic Fand Pluton, NW Ireland, is a late Caledonian intrusion crosscut by a NE-SW shear zone in its eastern periphery. Field observations across the ≈10m wide shear zone show partitioned strain development, with ≈0.5m wide bands of heavily sheared and foliated granite interspersed between regions of strongly altered yet relatively undeformed granite. Alteration systematically intensifies toward the core of the shear zone, from a partial alteration of the host intrusion to a complete destruction of original rock texture.
Lab analysis aims to quantitatively evaluate the type and intensity of alteration across the shear zone and evaluate if zones of high strain systematically map to zones of high or low alteration. Hyperspectral reflectance data were collected using airborne multispectral and handheld hyperspectral instruments to characterise hydrous mineral phase assemblages within each alteration type. Magnetic characterisation experiments including hysteresis, first order reversal curves and temperature dependent susceptibility were combined to characterise the ferromagnetic mineral assemblage. Anisotropy of magnetic susceptibility and anhysteretic remanent magnetisation were measured to determine the distribution of strain across the shear zone, evaluating the role of alteration intensity in the observed partitioning of strain.
Our results outline a multi-disciplinary method of mapping late-stage fluid transport within igneous intrusions, identifying pathfinder signatures and fabric parameters, linking them to alteration intensity from distance from fluid pathways.
How to cite: Latimer, B., McCarthy, W., Mattsson, T., and Reavy, J.: Tracing Late-Stage Fluid Migration within Intrusions via Magnetic and Spectral Characterisation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13892, https://doi.org/10.5194/egusphere-egu25-13892, 2025.
The Jurassic western-type ophiolites of the Tethyan Pindos oceanic basin are part of an ophiolite belt that extends within the Apulian and Pelagonian subcontinents in the Balkan Peninsula. These ophiolites tend to display MORB geochemical affinities, in contrast to the adjacent eastern-type ophiolites with SSZ affinities. The Orliakas locality in Pindos (Greece) and Krrabi in the Mirdita ophiolite (Albania) are two characteristic localities, representative of the south and north branches respectively of the Pindos western-type ophiolitic belt. Both localities include rodingitized gabbroic dykes hosted in highly serpentinized peridotites.
We report the occurrence of gabbronorite and olivine gabbro dykes of comparable thickness (0.5- 1.0 m) that were partly affected by rodingitization processes. In some cases, the gabbroic protoliths were found almost intact at the central parts of the dykes. Protoliths from the two localities exhibit highly comparable whole-rock geochemical properties: SiO2: 48.1-49.3 wt.%, TiO2: 0.08-0.11 wt.%, Al2O3: 16.7-18.0 wt.%, MgO: 12.2-13.5 wt.%; analogous REE patterns [(La/Yb)CN=0.2-0.4; EuCN/Eu*= 1.65-1.82]. PM-normalized multi-element patterns are also evidently comparable: noticeable LILE enrichments (e.g. Cs, Ba), higher ThPM-N and UPM-N compared to NbPM-N and TaPM-N, striking positive Pb and Sr anomalies, negative Zr and Ti anomalies.
Within the same dykes from the two localities, rodingites are also highly comparable in terms of: i) participating minerals and modal composition; ii) presence of hydrogarnets of similar composition (Avg. Adr4.0Grs94.3Prp1.6Sps0.1Uv0.1); iii) subparallel whole-rock PM-normalized multi-element patterns. In addition, the REE patterns obtained from LA-ICP-MS of the garnets, vesuvianites and clinopyroxenes display similar profiles. These features signify that similarities between the south and north branches of the Pindos ophiolitic belt are likely not limited to their magmatic lithotypes but may have also experienced comparable post-magmatic rodingitization processes, assigned to extensive infiltration of alkaline, Ca-rich, and Si-poor fluids.
How to cite: Koutsovitis, P., Tsiarsioti, L., Tsikos, H., Mason, P., Ntaflos, T., Pomonis, P., Karkalis, C., Rogkala, A., Petrounias, P., and Onuzi, K.: Comparable rodingitization processes identified in ophiolites from Pindos (Greece) and Krrabi (Albania) , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7412, https://doi.org/10.5194/egusphere-egu25-7412, 2025.
Cenozoic volcanic rocks occurring in Devès volcanic field (3.5 – 0.5 Ma) in the southern mantle domain of the French Massif Central (FMC) carry abundant peridotite xenoliths sampling Continental Lithospheric Mantle (CLM) [1, 2]. CLM in this area is fertile and might have formed due to 1) extraction of small amounts of partial melt(s) from mantle, and/or 2) refertilization of depleted mantle by asthenosphere-derived melts [1, 2]. We present mineral data for peridotites from several xenolith localities at Devès, in order to shed new light on the problem and document regional-scale CLM variability. Here, we complement the existing set of mineral chemical data from Allègre [2], Mt. Coupet [3] and Mt. Briançon [4] with a new data set on peridotitic xenoliths from Allègre volcano.
Peridotite xenoliths from Allègre (n = 16) are represented mostly by fine- to medium-granular lherzolites. Forsterite in olivine varies from 89.34 to 91.42%. The Mg# and Al content in orthopyroxene are: 0.89 – 0.92 and 0.06 – 0.22 apfu, respectively. In clinopyroxene, Mg# is 0.88 – 0.93 and Al content is 0.03 – 0.32 apfu. In spinel, Cr# and Mg# are: 0.09 – 0.50 and 0.63 – 0.76, respectively. Three major groups are recognized based on clinopyroxene REE patterns: (A) LREE-depleted, (B) LREE-enriched and (C) moderately LREE-enriched (spoon-shaped). However, two samples are characterized by significantly higher Cr# (0.38 – 0.50), lower Mg# (0.63 – 0.68) in spinel and lower Al in Opx and Cpx (0.06 – 0.13 and 0.03 – 0.20 apfu, respectively), along with strong LREE-enrichment and were classified as group D.
The mineral major element compositions for peridotite xenoliths from Allègre resemble those from other xenolith suites at Devès [2, 3, 4]. The only difference is recognized in the composition of spinel, which in peridotites from Allègre has higher Cr# (higher by up to ~0.20) and lower Mg# (~0.05) than that from other Devès localities (including previous data from Allègre [2]). Moreover, the trace element composition of pyroxenes is very similar in all three localities. Therefore, we assume that Allègre peridotites share an evolution with peridotites from other Devès localities. They record multi-stage metasomatism, including reaction with MORB-like melt (group A) and overprint by percolating alkaline melts (group B), additionally documented by transitional lithologies (group C). On the other hand, the chemical composition of group D peridotites, which are more refractory but more strongly incompatible element-enriched, suggests the existence of mantle domains, which were not affected by MORB-like metasomatism observed in group A. Thus, despite the generally fertile composition of peridotites typical for the southern FMC mantle domain [1, 2], isolated relic pockets of more refractory material persist in the CLM, offering the rare opportunity to unravel regional CLM evolution prior to pervasive refertilization.
Funding. We gratefully acknowledge funding by the project of Polish National Centre of Research 2021/41/B/ST10/00900 to JP.
[1] Lenoir et al. (2000). EPSL 181, 359-375.
[2] Puziewicz et al. (2020). Lithos 362–363, 105467.
[3] Mazurek et al. (2024). Abstract EGU24-8658
[4] Ziobro-Mikrut et al. (2024). Lithos 482-483, 107670.
How to cite: Matusiak-Małek, M., Mazurek, H., Puziewicz, J., Aulbach, S., and Ntaflos, T.: Multi-stage evolution of Continental Lithospheric Mantle beneath Devès volcanic field (Massif Central, France): an example from Allègre xenolith suite, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20279, https://doi.org/10.5194/egusphere-egu25-20279, 2025.
The evidences of deep melting processes in xenolith bearing mafic rocks in Southern Thrace region: The new insights for peridotite and the pyroxenite source melting
Xenolith bearing mafic rocks with late Miocene age are widely distributed in southern Thrace region. Primitive mantle - normalised multi-element diagrams of these mafic rocks display OIB signature and specific incompatible element ratios such as Nb/La (1.65-2.05) Nb/U (37.81 -48.74), Zr/Ba (0.45-0.72) further indicate that mafic rocks were originated from the OIB-like component. Re content of xenoliths range between 0.09 – 0.44 and similar with fertile mantle values (0.26 ppb) suggested by Morgan (1986), besides, xenoliths (0.1191-.0.1379) and the host rocks (0.1279-0.1439) have the similar 187Os/188Os isotopic compositions.
Geothermobarometric analyses of clinopyroxene (Putirka, 2008) from host basalts express that the melting source resides at an estimated depth of around 85 km. In addition, Gd/Yb ratios span between 0.97-3.3 in xenoliths and also span between 3.92-5.24 in basaltic rocks, suggest melting from a deep source.The mafic lavas of Thrace region with high Tb/Yb(N) values (2.33 – 3.16) seem to be derived from garnet bearing peridotite (Tb/Yb(N) >1.8 Wang et al., 2002) and these ratios also gain significant support from Dy/Yb values that range between 2-2.43 for xenoliths and 1.98-3.27 for host rocks. High Nb/U, Gd/Yb ratios, Re-Os isotopic compositions, and the REE-based melting model starting from the primitive xenoliths (from study region) and pyroxenite source (Van Nostrand, 2015) reveal that single source melting is not capable of producing the mafic lavas, instead, these rocks appear to originate from the melting of the deeper part of the mantle rather than shallow asthenosphere.
How to cite: Kurkcuoglu, B., Yürür, M. T., Günes, B., Furman, T., and Hanan, B.: The evidences of deep melting processes in xenolith bearing mafic rocks in Southern Thrace region: The new insights for peridotite and the pyroxenite source melting, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-840, https://doi.org/10.5194/egusphere-egu25-840, 2025.
Collision of the Indian and Asian continental plates and subsequent northwards subduction of the Indian plate beneath the active Andean-type southern margin resulted in the intrusion of a 2500km long Trans-Himalayan calc-alkaline batholith known as the Ladakh Plutonic Complex, or Ladakh Batholith. The Ladakh batholiths lies sandwiched between the Indus Suture Zone in the south and is unconformably overlain by the post-collisional Indus Molasse Group. In the Chumathang area, SE of Leh, the batholith (⁓ 400 mts high) is represented by two major granitoid phases exposed on the eastern side of Indus river. The granodiorite (57.7 ± 0.2 Ma) is dark-colored, massive, medium to coarse grained composed of plagioclase, quartz, hornblende, biotite with minor titanite, apatite, zircon, epidote, magnetite, ilmenite. The younger leucogranite (47.1 ± 0.1 Ma) is a relatively fine-grained rock containing quartz, plagioclase, and biotite with minor muscovite, zircon, tourmaline, and allanite. Several pegmatite veins of variable thickness are seen cross-cutting both phases of granite and at times intrude into the older metasediments.
Compositionally, these veins are dominated by quartz, plagioclase, orthoclase, microcline and minor biotite, muscovite, and zircon. Minerals like tourmaline, chlorite, fluorite, aquamarine, baryte etc. are commonly observed along vein margins. The Chumathang granitoids exhibit pervasive hydrothermal alteration, with pronounced chloritization observed in proximity to fluorite mineralization zones. Chlorite is seen closely associated with biotite (K = > 1wt.%) with enriched Fe, Mn and Mg concentrations indicating elevated oxygen fugacity conditions. Flourite typically occurs in variable colors like green, purple, white and brown indicating different stages of fluid evolution. Ca contents vary between 55.27 wt.% to 60.85 wt. % with F varying between 41.33 to 46.39 wt.% higher than previous reports. Allanite, a REE-rich mineral belonging to the epidote group, has been identified in the present study. Allanites exhibit compositional zoning with rims enriched in Ca, Mg and Al as compared to core. Aquamarine, the blue to greenish-blue gem variety of beryl has also been identified in the pegmatites from the study area. Presence of predominant minerals like biotite, amphibole and epidote clearly suggest that both phases of granites and pegmatites were formed from a high temperature magma source. Secondary minerals like chlorite, fluorite, allanite and aquamarine found associated with the host rocks indicate derivation from a complex interplay of both late stage pegmatitic as well as hydrothermal melts. The observed accessory and secondary minerals from the study area provide key insights into magmatic differentiation, post-magmatic fluid activity, thermal history, and mineralization potential and economic potential of such plutonic complexes.
Keywords: Ladakh Batholith, Chumathang granitoids, pegmatites, magma crystallization, hydrothermal alteration
How to cite: Bhoir, D., Jonnalagadda, M., Walunj, G., Sanklecha, H., Bose, R., Kulkarni, B., Duraiswami, R., and Karmalkar, N.: Petrogenesis of magmatic and hydrothermally derived late stage minerals associated with granitic plutonic complexes: A case study from the Ladakh Batholith, NW Himalayas, India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-331, https://doi.org/10.5194/egusphere-egu25-331, 2025.
Posters virtual: Tue, 29 Apr, 14:00–15:45 | vPoster spot 1
EGU25-8654 | Posters virtual | VPS22
Two different mantle types as evidenced from a geochemical and petrological study of peridotites from the Ivrea-Verbano ZoneTue, 29 Apr, 14:00–15:45 (CEST) | vP1.13
A petrological and geochemical study was performed on 5 selected samples of peridotites from two different sites (Finero and Balmuccia) outcropping in the Ivrea Verbano Zone, with the aim to investigate the processes occurring in the deep lithosphere and the possible interaction with the lower crust.
The peridotites from Finero area fall in the harzuburgite (FIN1, FIN3, FIN4) field whereas those from Balmuccia are lherzolithes (BALM1) and werlhites (BALM4), highlighting respectively the presence of a more fertile and primordial mantle for two sites.
The rocks from Finero are featured by higher MgO (42-45.7 wt%) and lower Al2O3 (0.6-2.4 wt%), CaO (0.42-2.09 wt%) content with respect to Balmuccia (MgO: 39.6 wt%, Al2O3: 2.9 wt%; CaO: 2.8 wt%) as a consequence of their harzburgitic nature. They display an enrichment in large-ion lithophile elements (LILE), light rare earth elements (LREE, LaN/YbN:13.6) and depletion in high field strength elements (HFSE) differently from the Balmuccia peridotites, which are featured by a light depletion in LREE (LaN/YbN:0.4-0.8) and nearly flat HREE pattern. The LILE and LREE enrichment measured in the Finero peridotites could suggest that a portion of the mantle below Ivrea Verbano area was influenced by metasomatic fluids/melts. The BALM4 sample is characterized by anomalously low values of MgO (16.05 wt%) and high values of Al2O3 (16.3 wt%) and CaO (14.5 wt%), reflecting the high modal proportion of spinel.
Even the higher Sr (86Sr/87Sr= 0.70736-0.72571) and lower Nd (143Nd/144Nd=0.51236) isotopic values measured in selected mineral phases from Finero with respect to Balmuccia (86Sr/87Sr= 0.70268-0.70644; 143Nd/144Nd=0.51334) allow to speculate a relation with crustal fluids in the Finero mantle.
The composition of fluid inclusions entrapped in olivine and pyroxene crystals from Finero peridotites evidenced CH4 and CH4-N2 associated with antigorite and magnesite whereas prevalent CH4 associated with antigorite, magnesite and graphite was measured in the rocks from Balmuccia area. The origin of CH4 could be related to synthesis via reduction of CO2 by H2 from internal/external serpentine to minerals or re-speciation of initial CO2-H2O fluids associated to graphite precipitation during cooling by obduction after orogeny; differently, the CH4-N2 fluids could be introduced by past subduction-related processes.
The isotopic helium (3He/4He ratio) varies between 0.08 and 0.17 Ra in the Finero peridotites and among 0.18 and 0.48 Ra in the Balmuccia ones, evidencing an isotopic difference between the two sites that cannot be explained by 4He radiogenic production. Differently, the Finero-Balmuccia variability could reflect the helium signature recorded in deep by subduction events and confirm the previous petrologic and geochemical evidences in favour of a metasomatised mantle by crustal fluids in the Finero area with respect to a more primordial in the Balmuccia one.
How to cite: Correale, A., Romano, P., Arienzo, I., Caracausi, A., Carnevale, G., Fazio, E., Mormone, A., Paonita, A., Piochi, M., Rotolo, S. G., and Zucali, M.: Two different mantle types as evidenced from a geochemical and petrological study of peridotites from the Ivrea-Verbano Zone , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8654, https://doi.org/10.5194/egusphere-egu25-8654, 2025.
EGU25-17921 | ECS | Posters virtual | VPS22
Interrelationship between the electrical and elastic properties using effective medium theoriesTue, 29 Apr, 14:00–15:45 (CEST) | vP1.14
This study focuses on characterizing seismogenic zones by establishing a interrelationship between electrical and elastic properties using Effective Medium Theories (EMTs). The seismogenic zones exhibit complex geological and geophysical signatures that can be explored through joint analysis of electrical resistivity and elastic moduli. The research applies EMTs such as Self-Consistent Approximation (SCA), Generalized Effective Medium (GEM), and Differential Effective Medium (DEM) to model the physical properties of rocks under varying conditions of pressure, porosity, and fluid saturation.
The study compares theoretical predictions with observed data to understand how resistivity, influenced by fluid connectivity and composition, correlates with elastic properties, which are sensitive to stress and fracture networks. The study can reveal critical insights into the mechanical and fluid characteristics of seismogenic zones. By integrating theoretical models with available geophysical data, this work provides a framework for analyzing the interdependence of electrical and elastic properties in seismogenic regions. The findings contribute to advancing the understanding of fluid dynamics, and rock deformation in seismogenic zones, offering a valuable tool for seismic hazard assessment and monitoring.
How to cite: Raju, K. and Siniscalchi, A.: Interrelationship between the electrical and elastic properties using effective medium theories, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17921, https://doi.org/10.5194/egusphere-egu25-17921, 2025.
EGU25-20441 | ECS | Posters virtual | VPS22
Spatial distribution of b-values for microseismicity in the SWIR Longqi hydrothermal field and magmatic-tectonic interpretationTue, 29 Apr, 14:00–15:45 (CEST) | vP1.15
Natural microseismicity serves as a potent tool for exploring smaller-scale hydrothermal and tectonic phenomena. Investigating seismic activities within the hydrothermal fields of mid-ocean ridges(MORs) offers profound insights into earth's internal dynamics. However, studies on natural earthquakes at ultra-slow spreading ridges, especially the Southwest Indian Ridge (SWIR), remain relatively scarce. To investigate the microseismic distribution, heat flow pathways, and tectonic characteristics of the Longqi hydrothermal field, a typical representative of SWIR, this paper processed one month of passive source OBS data from the DY43 cruise through microearthquake detection and relocation, obtaining a catalog of over 3000 earthquakes, significantly expanding the earthquake database for the Longqi field and improving the magnitude completeness. And the b-value calculation and imaging of the earthquake catalog were carried out using the maximum likelihood method and grid search method, respectively. The research results indicate that: ① The overall b-value of the SWIR Longqi field is 0.989; ② The b-value at the center of the Longqi hydrothermal vent is approximately 0.8, while the b-value around the vent is around 1.2; ③ High and low b-value areas alternate at a depth of 10km along the ridge axis; ④ There is an anomalously low b-value area of around 0.5 at depths of 12-16 km to the north across the ridge axis. Combining previous research results on b-values at MORs, this paper suggests that the background b-value of less than 1 in the Longqi field is consistent with its tectonic-type hydrothermal origin. The detachment fault beneath the Longqi hydrothermal vent leads to high stress and a low b-value, while the microseismic activity around the vent originates from rock fracturing caused by the combined effects of cold seawater and hydrothermal fluids. The uneven distribution of high and low b-values in the deep part of the hydrothermal field may reflect the uneven distribution of subsurface magma. The low b-value area in the north is speculated to be due to high stress resulting from torsional compression at the bottom of the detachment fault. In summary, it can be anticipated that the spatial distribution of b-values will serve as an indicator and reference factor for stress, fault structure, and magmatic-hydrothermal activity in MOR hydrothermal field in the future.
How to cite: wang, K.: Spatial distribution of b-values for microseismicity in the SWIR Longqi hydrothermal field and magmatic-tectonic interpretation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20441, https://doi.org/10.5194/egusphere-egu25-20441, 2025.
