This study investigates the petrological and metasomatic processes that lead to carbon enrichment in peridotites from Sal Island, Cape Verde. Geochemical and mineralogical analyses reveal a heterogeneous lithospheric mantle, consisting of harzburgites showing ultrarefractory compositions indicative of 20%- 40% melting degrees, as well as fertile spinel lherzolites. Evidence of metasomatism is demonstrated by the formation of reaction coronae around dissolving orthopyroxene, consisting of olivine, clinopyroxene, spinel, and interstitial phonolitic glass, together with trachytic/phonolitic glass + carbonate (calcite, aragonite, and dolomite) microveins associated with CO2 fluid-rich melt inclusions (Type I and II) cutting through olivine and orthopyroxene. The widely differing proportions of silicate and carbonate components in inclusions likely reflect heterogeneous trapping of melt/fluid and degassing CO2. Thermobarometric data indicate equilibration temperatures from 950 to 1060 degrees C in harzburgites and up to 1200 degrees C for reaction coronas in harzburgites and lherzolites, with pressures reaching the aragonite stability field (similar to 2.2-3.5 GPa, or 66-106 km depth). These observations indicate the infiltration at the base of the lithosphere of a silicate-carbonate melt enriched in alkalies, Al, and volatiles (Cl, S, F, N, P). In microveins, the silicate glass composition (e.g., K and Ti content) is consistent with experimental partial melts derived from carbonated sediments with a minor addition of a carbonated eclogite. Enrichments in major and trace elements in clinopyroxene in harzburgites and lherzolites suggest at least two significant metasomatic events involving alkali-rich silicate-carbonate melts at the base of the lithosphere, and CO2-rich fluid, alkali-rich silicate melts in the deep lithosphere, close to pressure conditions of the carbonate ledge. The introduction of recycled carbon into the upper mantle beneath the Cape Verde archipelago likely occurred during the multiple subduction events that affected the region in the half a billion years leading to the Pangea assembly. Major mobilisation of crustal components, generation of carbonate-rich melts, and subsequent lithospheric metasomatism were triggered by the Oligocene thermal perturbation associated with the Cape Verde mantle plume. (c) 2025 China University of Geosciences (Beijing) and Peking University. Published by Elsevier B.V. on behalf of China University of Geosciences (Beijing). This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Abstract Tectonic CO2 Earth degassing is globally relevant and has probably controlled climate on a geological scale (Brune et al., 2019, https://doi.org/10.1038/s41561‐017‐0003‐6). Endogenous CO2 outgassing from rifting areas remains poorly constrained, with most available data from the East African Rift. Here, we investigate the CO2 degassing in the European Cenozoic Rift System (ECRIS), focusing on the chemical and isotopic composition of 161 springs emerging from the Eifel‐Ardennes‐Rhenish Massif region (Eastern Belgium‐Western Germany). Theoretical water‐gas‐rock interaction models based on the chemistry of gases dissolved in East Eifel groundwaters reveal CO2 efflux takes place in a P‐T range between the aquifer depth (4 bar, 160°C) and spring emergence (1 bar, 9°C). He and C isotopes show that Ardennes, Volcanic Eifel and Rhenish Massif are all part of a unique degassing system. The average mantle CO2 flux emitted from the region is 5 ± 2 × 106 mol yr−1 km−2, corresponding to a total deeply derived CO2 emission rate of 7 ± 4 × 109 mol yr−1. These values are of the same magnitude as the global baseline defined for convective hydrothermal CO2 emitted from areas of high heat flow, demonstrating the relevance of passive rifts as CO2 emitters on a global scale.

Fluorite-rich Mississippi Valley-Type (MVT) deposits provide key constraints on the origin and evolution of fluorine-bearing hydrothermal systems in sedimentary basins. Here we present the first He-Ne-Ar elemental and isotopic data obtained from fluid inclusions hosted in fluorite from the Zaghouan Fluorite District (ZFD), northeastern Tunisia. Eighteen samples from eight fluorite-rich MVT deposits, including both stratabound and vein-type mineralization, were analyzed to investigate the sources of ore-forming fluids. Measured He-4/Ne-20 and Ar-40/Ar-36 ratios indicate a variable but generally minor contribution from atmosphere-derived fluids. Atmosphere-corrected He-3/He-4 ratios range from 0.03 to 0.08 Ra (Ra = 1.39 x 10(-6)), values that are significantly lower than those of the Sub-Continental Lithospheric Mantle (SCLM; 6.1 +/- 0.9 Ra) and are characteristic of crustal-derived fluids. Quantitative mixing calculations show that mantle-derived helium accounts for similar to 1% of the total helium budget. Overall, He-Ne-Ar systematics reveal mixing among three components-crustal, atmospheric, and a negligible mantle contribution-with crustal fluids overwhelmingly dominating the ore-forming system. These results indicate that both stratabound and vein-type fluorite deposits in the ZFD formed in a dominantly crustal environment, supporting basinal brine models for fluorite-rich MVT mineralization. The similarity in noble gas signatures across different mineralization styles further suggests a common fluid reservoir and genetic process, with structural pathways controlling fluid focusing and emplacement rather than fluid source.

Plinian eruptions are the most common high impact explosive events, causing severe local impacts and influencing human settlement or migration and global climate. Understanding their pre-eruptive processes and timescales is crucial for forecasting eruptions and mitigating hazards. The iconic 79 CE Somma-Vesuvius eruption (Italy) is considered the archetype of Plinian eruptions. However, knowledge of its plumbing system architecture and pre-eruptive magmatic processes remains incomplete. Chemical and isotopic data, clinopyroxene zoning analysis, and numerical modelling reveal a vertically extended plumbing system with deep mafic magma batches refilling a tephri-phonolitic reservoir multiple times before the eruption. Diffusion modelling constrains recharge events in timescales from decades to less than a year, which align with historically well-documented seismicity ("non desiit enim assidue tremere Campania", Seneca; "Praecesserat per multos dies tremor terrae", Pliny the Younger) preceding the eruption. These findings enhance our understanding of volcanic behaviour, aiding in hazard assessment and risk mitigation for future similar eruptions. (c) 2026 China University of Geosciences (Beijing) and Peking University. Published by Elsevier B.V. on behalf of China University of Geosciences (Beijing). This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

This work presents the chemical and isotopic (delta O-18-H2O and delta D-H2O) composition of five thermal areas from the Atacama region (northern Chile), namely Laguna Verde, Juncalito, Termas de Rio Negro, Pante & oacute;n de Aliste, and Salar de Piedra Parada. The chemical and isotopic (He-3, He-4, delta C-13-CO2, and delta C-13-CH4) composition of gases bubbling from Juncalito is also reported. This work aims to (i) constrain the origin and physicochemical processes controlling the chemical and isotopic composition of bubbling gases and (ii) estimate the equilibrium temperatures of hydrothermal reservoirs. The thermal springs are fed by meteoric waters whose chemistry, during the underground circulation, is mainly controlled by water-rock interaction involving volcanic rocks and volcano-sedimentary sequences. Notable Li, B, and As enrichments are recognized, likely related to the leaching of hydrothermally altered andesitic to rhyolitic rocks and the presence of sedimentary sequences, distinctly below the Claudio Gay Cordillera. The He-3/He-4 ratios (similar to 1.4-1.5 Ra), within the range of the typical values for low-temperature hydrothermal gases from the Central Volcanic Zone, likely represent a mixture of an atmospheric endmember mixed with a differentiated cooling magma residing within the crust for a long time. The delta C-13-CO2 values suggest a dominant crustal CO2 source with a minor (1 %) mantle contribution. Chalcedony geothermometer provides reservoir temperatures up to 91 and 88 degrees C in Termas de Rio Negro and Laguna Verde, respectively. Further geophysical and geostructural investigations are recommended to constrain the source of heat in the Laguna Verde area, especially considering the presence of the quiescently degassing Ojos del Salado volcano.

The Earth's mantle is considered to be geochemically heterogeneous, which is reflected by the diverse compositions of oceanic island basalts (OIB). The mantle enrichment resulting in this is primarily attributed to the influx of recycled crustal materials into the mantle through subduction. Additionally, the subcontinental lithospheric mantle (SCLM) complicates the elucidation of mantle heterogeneity. From this perspective, Northeast Asia, where the Pacific stagnant slab in the mantle transition zone and the SCLM distribution are presented, is the suitable site for examining the upper mantle scale enrichment. Here we report He-Sr-Nd-Pb-O isotope compositions of Cenozoic basalts found around the Korean Peninsula to illustrate the source lithology and components that caused mantle heterogeneity. Our measured helium isotope ratios ranging from 5.7 to 7.3 Ra (3He/4He ratio of air, Ra = 1.39 x 10-6) are mostly within the SCLM range (6.1 +/- 0.9 Ra) but lower than the mid-ocean ridge basalt range (MORB; 8 +/- 1 Ra). The Sr-Nd-Pb isotope compositions of the basalts generally display a mixture of depleted MORB mantle (DMM), enriched mantle 1 (EM1), and enriched mantle 2 (EM2) components. In addition, the basalts have d 18 O olivine (vs. V-SMOW) values ranging from 4.7 to 5.7 %o that deviate from the DMM range (d 18 O olivine = 5.1 +/- 0.2 %o). Our isotopic analysis results highlight the role of a pyroxenite source in the metasomatized SCLM in the genesis of basalts, and the low 3 He/ 4 He ratios of the basalts indicates a significant contribution of SCLM. Moreover, the delaminated cratonic SCLM and asthenosphere-lithosphere interaction are scenarios for the low 3 He/ 4 He ratios. Therefore, we propose that mixing of DMM (high 3 He/ 4 He ratio; 7 to 9 Ra) and the metasomatized SCLM (low 3 He/ 4 He ratio; 5 to 7 Ra) allowed enrichment within the upper mantle scale for the Cenozoic intraplate magmatism in Northeast Asia. (c) 2024 International Association for Gondwana Research. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

Within the framework of SANTORY (SANTORini’s seafloor volcanic observatorY) project, funded by the Hellenic Foundation for Research and Innovation and with the financial support of the Municipality of Thira, three oceanographic cruises were performed in December 2022 and June and October 2023, with the research vessels PHILIA and AEGAEO of the HCMR at the submarine volcano Kolumbo, 7 km NE of Santorini. Kolumbo is considered to be one of the most active submarine volcanic complexes in the Eastern Mediterranean Sea, while being easily accessible from land.. The oceanographic surveys were mainly aimed at the deployment of a new generation observatory along with several multiple innovative sensors such as temperature sensors, inclinometers, pressure gauges, optical cameras, multispectral and stereo camera, radioactivity sensor gSniffer and the γ-radiation imager. During the surveys, several water column profiles were also performed in order to collect seawater samples for chemical analysis. At the bottom of the Kolumbo crater (500m depth), acidic and slightly reducing conditions prevail, due to the presence of several active hydrothermal vents. This agrees with previous studies and with the data recorded by the deployed observatory. Collected samples have been analyzed for the chemical and isotope (carbon, helium and argon) composition of the dissolved gases as well as for the major, minor and trace element concentrations. The results indicate that the morphology of the crater allows the buildup of persistent anomalies that extend from the bottom up to the lowest crater-rim level at about 250-meter depth. We will discuss the temporal variability of the Kolumbo venting dynamics and the explore in detail the resulting vertical gradients in the crater funnel.

Volcanic eruptions stand as formidable threats to adjacent communities, unleashing a spectrum of hazards such as earthquakes, tsunamis, pyroclastic flows, and toxic gases. The imperative for proactive management of volcanic risks cannot be overstated, particularly in densely populated areas where the potential for widespread devastation looms large. Kolumbo, an active submerged volcano located approximately 7 kilometers northeast of Santorini Island in Greece at 500m depth, serves a pertinent case. Its historical record is marred by an eruption in 1650 AD which triggered a relentless tsunami. The aftermath witnessed havoc on neighboring islands, coupled with casualties stemming from noxious gases in Santorini. Eyewitness accounts mention maximum water run-up heights of 20m on the southern coast of Ios, a staggering 240m inundation on Sikinos, and a disconcerting flooding of up to 2km² of land on the eastern coast of Santorini.Recent studies suggest that a potential future explosive eruption of Kolumbo poses a substantial hazard to the northern and eastern coasts of Santorini. Unfortunately, the absence of a concrete management protocol, leaves these areas vulnerable to an impending threat that demands immediate attention. Therefore, it is recommended that a comprehensive approach be adopted, involving scientific research (active monitoring, hazard maps), community engagement, preparedness planning with government agencies, and the development of timely response strategies to reduce the associated risks, prevent casualties, and mitigate the consequences on the region's economy and infrastructure. Our team has multidisciplinary data from past oceanographic expeditions that will help us to understand Kolumbo’s behavior. These include a) High-resolution multibeam bathymetry data and optical data., b) a dense network of sub-seafloor seismic reflection profiles, c) a series of the seafloor and sub-seafloor samples of microbial mat and sediments, d) CTD data, e) several polymetallic (Au, Ag, As, Sb, Pb, Hg, Mo, Zn, Cu, Tl) CO2 diffuser chimney samples and f) tephra in marine sediment cores. Despite the current knowledge that we managed to obtain, monitoring is needed to efficiently assess potential hazards and create early warning systems and management protocols for an imminent eruption from Kolumbo. In the current context, advanced sensors have been deployed to monitor Kolumbo's active hydrothermal field as part of the SANTORY project. The SANTORY project aims to create innovative communication tools and establish interregional monitoring protocols, providing the scientific community, policymakers, and stakeholders with the means to assess hazard warning codes effectively.

The underwater volcanic activity associated with deep-seated mantle processes represents a primary driver of the chemical and biogeochemical evolution of the global oceans. Hydrothermal activity is often a manifestation of submarine volcanism, where fluxes of heat and magmatic volatiles confer both potential hazard and opportunities of resource exploitation. Despite this, research on shallow submarine arc volcanoes is still in an early stage and only a few continuous seafloor observing infrastructures have been developed until now. The Kolumbo underwater volcano, located in the Aegean Sea, hosts one of the most active and dynamic hydrothermal vent fields, marking it - along with the proximity to the world-known Santorini island - a severe geohazard for a combination of reasons. Within the framework of the SANTORY (SANTORini’s seafloor volcanic observatorY) project, funded by the Hellenic Foundation for Research and Innovation and with the financial support of the Municipality of Thira, between 2022 and 2023, three oceanographic cruises were performed on submarine Kolumbo volcano. The oceanographic surveys were mainly aimed at the deployment of integrated operating sensors of state-of-the-art technology, for in situ monitoring. A new-generation stand-alone multiparametric observatory has been developed at INGV Palermo and deployed at the bottom of the crater (500 meters depth) for the first time in December 2022. The battery powered module has been able to operate autonomously for a 10-month-long period, collecting a dense, heterogeneous dataset able to describe the activity of the hydrothermal reservoir, highlighting its intense dynamic along the time.In June 2023, the observatory was recovered and re-deployed after brief maintenance operations including battery charging and data downloading. Finally, in October 2023, the observatory was definitely recovered.Here we present for the first time a mid-term-long chemical-physical data series acquired (pH, temperature, hydrostatic pressure, turbidity, conductivity, dissolved methane) along with passive acoustic and the preliminary findings of the system evolution within the observing window. A variety of local VT events likely sourced in the deeper portion of the plumbing system, together with several other minor seismic events related to fluid dynamics inside “fluid-filled” cracks and conduits has been revealed by passive acoustic data. Moreover the acoustic sensor recorded all the signals generated by the bubbles along the water column. The obtained results gave back an up to date picture of the ongoing Kolumbo degassing dynamics, hydrothermal and seismic activity.

Seismic signals coupling to physical (e.g., temperature, pH, Eh, electrical conductivity, flow rate) and geochemical changes in ground and spring waters as well as variations in soil flux regimes (e.g., CO2, CH4, radon) represent a valuable tool to better understand the interaction between tectonics and crustal fluids dynamics (e.g., Italiano et al., 2001, 2004; Wang and Manga, 2021; Chiodini et al., 2020; Gori and Barberio, 2022 and references therein). Pre-, co- and post-seismic modifications are markers of the local tectonic stress acting in the crust and are extremely site-specific due to the local geological and lithological features besides being simultaneously influenced by other environmental conditions (e.g., meteorological and climatic). Therefore, local continuous monitoring of all the involved parameters is needed to delineate crustal fluids response to seismicity site by site.Multiparametric stations have been set up in Italy starting from the end of 2021, placed on the major seismogenic structures, and widely distributed among the Alps, Apennines and Pianura Padana. They are equipped with: (i) sensors installed in water wells measuring water level, temperature, and electrical conductivity; (ii) meteorological sensors measuring atmospheric pressure, temperature, rain, humidity, wind speed and direction; (iii) seismic sensors providing accelerometric and velocimetric datasets; (iv) radon sensors; (v) CO2 soil flux chamber. Data are transmitted in near real-time to an ad hoc developed dynamic relational database (MUDA-geophysical and geochemical MUltiparametric DAtabase) and displayed in a dedicated website (http://muda.mi.ingv.it). The built-in philosophy is to easily compare distinct parameters from the various sensors and possibly recognize cause-effect relationships among them. To our knowledge, our new multiparametric network is the first developed in Italy showing all these features.A statistic approach is also applied to the time-series to investigate intra-annual and inter-annual trends and correlations among different parameters. Alternative methods (e.g., signal decomposition, spike detection) will be presented and discussed. References-Chiodini G., Cardellini C., Di Luccio F., Selva J., Frondini F., Caliro S., Rosiello A., Beddini G., Ventura G., 2020: Correlation between tectonic CO2 Earth degassing and seismicity is revealed by a 10-year record in the Apennines, Italy. Science Advances, https://www.science.org/doi/10.1126/sciadv.abc2938-Gori F., Barberio M.D., 2022: Hydrogeochemical changes before and during the 2019 Benevento seismic swarm in central-southern Italy. Journal of Hydrology, 604:127250-Italiano F., Martinelli G., Nuccio P.M., 2001: Anomalies of mantle-derived helium during the 1997 – 1998 seismic swarm of Umbria-Marche, Italy. Geophysical Research Letters, 28(5):839-842-Italiano F., Martinelli G., Rizzo A., 2004: Geochemical evidence of seismogenic-induced anomalies in the dissolved gases of thermal waters: A case study of Umbria (Central Apennines, Italy) both during and after the 1997–1998 seismic swarm. Geochemistry, Geophysics, Geosystems, 5:11, doi:10.1029/2004GC000720-Wang C.-Y., Manga M., 2021: Water and Earthquakes. Lecture Notes in Earth System Sciences, Springer Cham, 387 pp., https://doi.org/10.1007/978-3-030-64308-9

SANTORY is a state-of-the-art project dedicated to advancing submarine volcanic hazard monitoring and risk mitigation in the Aegean Sea. Located in Kolumbo submarine volcano, northeast of Santorini Island, this groundbreaking observatory employs advanced imaging, geophysical and geochemical measurements, and real-time monitoring technologies to address one of the most significant volcanic threats in the region.Over the past two years, SANTORY has provided unparalleled insights into Kolumbo’s geological dynamics and processes and potential hazards. High-resolution 3D mapping has identified steep slopes, mass-wasting deposits, and hydrothermal vent fields, crucial for assessing seafloor instability and the risks associated with eruptions and submarine landslides. Novel hyperspectral imaging and autonomous video systems have documented persistent hydrothermal venting, bubbling plumes, and environmental changes, offering a comprehensive baseline for tracking volcanic activity and geohazard precursors.Autonomous sensors on the crater floor have continuously monitored hydrothermal outflow temperature, pressure, and fluid chemistry, capturing variations driven by tides and magmatic activity. These continuous datasets are critical for identifying precursor signals of volcanic unrest, such as changes in subsurface permeability and magmatic degassing. Chemical and isotopic analyses of hydrothermal fluids have confirmed the degassing of CO2-rich fluids with a mantle-like 3He/4He signature, underscoring Kolumbo’s potential for hazardous eruptions and its significance as a high-risk volcanic system.SANTORY goes beyond scientific exploration; it is a transformative initiative aimed at improving volcanic hazard assessment and developing mitigation protocols. By integrating cutting-edge technologies and multidisciplinary expertise, the project delivers actionable insights to enhance early warning systems and protect vulnerable coastal communities.

During years 2021–2022, an unusual seismic swarm was recorded at crustal level beneath the Monts Dore volcanic province (France). Complementary field and remote measurements were performed. Together with the time series recorded on the seismological and GNSS national networks, these measurements were fundamental for monitoring the evolution of the seismic swarm and deciphering its origin. Although a potential vertical migration of the seismic events is suggested, the complementary measurements presumably discard the hypothesis of magma intrusion at shallow crustal level. The ascent of a CO2-rich fluid originating from the mantle might instead have reacted with the hydrothermal system beneath the Monts-Dore since at least the summer 2021 leading to the reactivation of pre-existing tectonic structures with known associated seismicity. Feedback on the management of the 2021–2022 seismic swarm prompts for several recommendations that should be considered in future to better face and address at the national level the issues raised at long-dormant volcanic provinces in mainland France.

Ultramafic xenoliths provide valuable insights into the physico-chemical, compositional and thermal characteristics of Earth’s mantle along with its heterogeneities. Integrating petrography and mineral chemistry data with the determination of volatile concentrations and isotopic fingerprints in fluid inclusions (FI) in these xenoliths has become the state-of-the-art approach, as it provides not only important information on the nature and evolution of the lithospheric mantle, in terms of melting and metasomatic processes, but also illustrates the storage and migration pathways of volatiles throughout the lithosphere. This tandem approach makes the Comoros Archipelago (Mozambique Channel, Western Indian Ocean) ideal candidates to explore, because the characteristics of the local lithosphere are intimately tied to the complex regional geodynamic setting. Indeed, the origin of the Comoros magmatism remains enigmatic and controversial despite extensive documentation in the literature, as it has been attributed to either a plume-related hot spot or to a passive response to lithospheric break-up.In this study, we investigate a unique suite of ultramafic xenoliths from Mayotte island by combining petrographic observation, mineral phase major and trace element analysis with the geochemistry of noble gases (He, Ar, Ne) and CO2 hosted in olivine (ol), orthopyroxene (opx) and clinopyroxene (cpx) FI. Mineral major elements results show refractory compositions in terms of MgO (Mg#Ol > 90.5, Mg#Opx > 91 and Mg#Cpx > 91.5) and Al2O3 contents (ranging from about 1.60 to 3.00 wt.% for opx and from 2.50 to 3.60 wt.% for cpx, respectively), with Cr# of spinel falling between about 0.4 and 0.55. Overall, these features indicate that the local lithosphere experienced relatively high degrees of melting, from ~20% to 25%. This is also supported by highly depleted chondrite-normalized rare earth element (REE) patterns for cpx, where HREE are roughly (1.5)N.Volatile concentrations and isotopic fingerprints in FI hosted in Mayotte xenoliths are variable, with CO2 standing out as the most abundant gas species. The air-corrected 3He/4He isotopic ratios (5.6 to 6.8 Ra) are intermediate between the typical signatures of MORB (8±1 Ra) and the SCLM (6.1±2.1 Ra) mantle, as measured in local subaerial (Liuzzo et al., 2021) and submarine (Fani Maoré Seamount, Mastin et al., 2023) gas emissions. The relationships between 3He/4He and the extrapolated air-free mantle 21Ne/22Ne ratios, together with 40Ar/36Ar versus 3He/36Ar systematics, suggest a dominating MORB-like component in the upper mantle below the Comoros archipelago, mixed with recycled crustal and atmospheric components, in agreement with recent data of ultramafic xenoliths from Grande Comore island (Ventura Bordenca et al., 2023). ReferencesBordenca, C.V., Faccini, B., Caracausi, A., et al., 2023. Geochemical evidence for a lithospheric origin of the Comoros Archipelago (Indian Ocean) as revealed by ultramafic mantle xenoliths from La Grille volcano. Lithos, 462, 107406.Liuzzo, M., Di Muro, A., Rizzo, A.L., et al., 2021. Gas geochemistry at Grande Comore and Mayotte volcanic islands (Comoros archipelago), Indian Ocean. Geochemistry, Geophysics, Geosystems, 22, e2021GC009870.Mastin, M., Cathalot, C., Fandino, et al., 2023. Strong geochemical anomalies following active submarine eruption offshore Mayotte. Chemical Geology, 640, 121739.

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. ReferencesColtorti, 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.

MUDA (geophysical and geochemical MUltiparametric DAtabase) is a new infrastructure of the National Institute of Geophysics and Volcanology (INGV, www.ingv.it) serving geophysical and geochemical multiparametric data, designed and developped in the framework of Dynamic Planet -Working Earth project (https://progetti.ingv.it/it/pian-din). MUDA is a dynamic and relational database based on MySQL (https://www.mysql.com) with a web interface realised in php (https://www.php.net) using a responsive design technique. The multi-parametric data are stored and organised using a table-structure able of correlating different types of data that allow possible future integration with new type of data acquired through both real-time and off-line transmission vectors. MUDA collects information from different types of sensors, such as seismometers, accelerometers, hydrogeochemical sensors, sensors for measuring the flux of carbon dioxide on the ground (CO2), sensors for detecting the concentration of Radon gas and weather stations with the aim of making possible correlations between seismic phenomena and variations in environmental parameters such as the level of groundwater as well as its temperature and electrical conductivity. MUDA archives and publishes data of multiparametric stations belonging both to permanent (i.e. the National Seismic Network, RSN, https://www.fdsn.org/networks/detail/IV/) or temporary (e.g. PDnet, Massa et al., 2021, https://www.fdsn.org/networks/detail/ZO_2021/) INGV seismic networks, as well as data from a multi-parametric Salse di Nirano Reserve (MO) site in cooperation with the PD PROMUD 2023-2025 (Definition of a multidisciplinary monitoring PROtocol for MUD volcanoes) project and two additional multi-parametric sites installed in the inter-mountain basin of Norcia, as a part of the GEMME 2023-2025 project. Data from Radon stations belong to the INGV-IRON national network (Italian Radon Monitoring Network, https://www.ingv.it/en/monitoring-and-infrastructure/monitoring-networks/ingv-and-its-networks/iron). MUDA daily publishes multi-parametric data updated to the previous day and offers the chence to view and download dynamic time series for all available data and for different periods, up to a maximum of 30 days. For longer periods, users can request data to muda@ingv.it. MUDA is now published at http://muda.mi.ingv.it

The present work would like to illustrate a new concept of multiparametric stations to characterize the crustal fluids-tectonic interaction in specific geological contexts. The dynamics of crustal fluids in relation to tectonics is a complex and sometimes intricate issue. Several factors act and mutually influence themselves, so that in each tectonic and geological context they follow a specific behavior, and a comprehensive cause-effect rule is hard to find. Changes in water chemistry and levels and in soil flux regimes (e.g., CO2, CH4, radon) are just a few examples well documented in the literature as being pre-, co- and post-seismic modifications as well as being markers of the local tectonic stress acting in the crust. A regional study combined with a long-lasting multiparametric monitoring is needed to prepare to a seismic sequence in a given place. The field infrastructure was set up starting from the end of 2021, and multiparametric stations have been installed in correspondence of active seismogenic sources initially located in Northern Italy. Data are transmitted in real-time and archived in an ad hoc developed relational database. Monitoring is mainly focused on groundwater parameters (water level, temperature, and electrical conductivity) of aquifers showing distinct degrees of confinement and lithologies. Sites are also equipped of meteorological sensors (pressure, temperature, rain, humidity, wind speed and direction), radon sensors and surface and borehole seismic stations providing accelerometric and velocimetric data. A mud volcano field is also monitored and holds the installation of a permanent CO2 soil flux station. A statistical analysis working flow is also proposed for a preliminary evaluation of the acquired time-series. In particular, a couple of tools to detect, and thus filter, anthropogenic and meteorological effects on a groundwater level series is described. We wish to provide a model of approach to analogous study cases in other potentially seismic areas.

The 2021 Tajogaite eruption at La Palma has represented a unique opportunity to investigate the characteristics of the mantle source feeding modern volcanism in the Canary Islands. With the aim of track the fingerprint of carbon in the local oceanic lithosphere-asthenosphere system, we report the isotopic composition of CO2 (δ13C values versus Vienna Pee Dee Belemnite) in olivine- and clinopyroxene-hosted fluid inclusions (FI) from the 2021 Tajogaite lavas and from lavas/ultramafic xenoliths (olivine-clinopyroxenites, clinopyroxenites, dunites and harzburgites) from the nearby 1677 San Antonio eruption cone/lavas, in an attempt to characterize the origin and evolution of carbon within the local mantle source. Our results indicate that the 2021 and 1677 lavas exhibit δ13C values ranging from −4.94‰ to −2.71‰ and CO2/3He ratios from 3.37 to 6.14 × 109. Ultramafic xenoliths fall in a comparable range of values despite showing higher CO2 concentrations. Our δ13C values fall within the range of carbon isotope results previously reported for the Dos Aguas cold spring located in the Taburiente Caldera (northern La Palma), suggesting an apparent carbon isotope homogeneity at the scale of the entire island. The (relatively narrow) δ13C vs. CO2/3He ratio range of La Palma samples is interpreted to reflect either i) variable extents of open-system degassing of a common mantle endmember having δ13C of ∼1.7‰, or ii) mixing between depleted mantle-like carbon (−6‰ < δ13C < −4‰) and crustal carbon (δ13C = 0‰) endmembers. Both models testify a crustal carbon component recycled in the local mantle. This component, also detected in mantle xenoliths from the neighboring island of El Hierro and the easternmost Lanzarote, indicates a regional characteristic of the mantle beneath the Canary Islands, interpreted as a result of infiltration of carbon-rich melts during past metasomatic events in the local mantle.

Santorini Island (Greece) is an active volcano which has alternated between dormant and active periods over the last 650,000 years with the latest volcanic unrest occurring in 2011–2012. Here we report a geochemical survey of fumarolic gases collected at Nea Kameni islet located in the center of the caldera over the period 2015–2022 in order to study the activity of the volcano and changes in hydrothermal conditions. This period is marked by the absence of significant geochemical anomalies compared to the unrest of 2011–2012, implying that no new magma upwelling has occurred. This is evident from the low CO2/CH4 ratio and H2 concentration of fumaroles. An increase of the atmospheric contribution in gases after the 2011–2012 unrest suggests a decrease of the deep gas flow and the chemical and C-He-isotope compositions are compatible with a model of Rayleigh fractionation in which CO2 dissolves in water at decreasing temperatures over time. These results are consistent with temperature estimates obtained using the H2/N2 geothermometer, seismic and geodetic evidences. This implies a slowing of the degassing of the hydrothermal/volcanic system and a cooling of the magma injected at shallow depth in 2011–2012. All these conclusions support a quiescent state of the Santorini volcano over the period 2015–2022.

The exploration of novel geothermal systems, particularly those promising for electrical power generation, plays a fundamental role in incorporating new renewable sources into the energy matrix. Geothermal systems associated with volcanic calderas are considered ideal targets for exploration. This study focuses on the geochemical features of fluids from the Cerro Gal & aacute;n hydrothermal system, which is hosted within a major resurgent caldera with >3.5 Myr of magmatic evolution situated on the Southern Puna (Central Volcanic Zone of the Andes, NW Argentina). The main aim is constructing the first geochemical conceptual model and provide information on the geothermal potential of this interesting resource. The main hydrothermal reservoir consists of a NaCl aquifer with estimated temperatures up to 187 degrees C at depth. This reservoir is likely hosted within the fractured pre-caldera basement rocks, mainly including Miocene-Pliocene volcanic rocks and Proterozoic-Cambrian igneous and metamorphic rocks. The confinement of the deep reservoir is attributed to the deposits of the Toconquis Group and Cueva Negra Ignimbrite, along with the basal section of the Cerro Gal & aacute;n Ignimbrite, which exhibit low permeability due to hydrothermal alteration. The presence of a phreatic explosion crater near one of the hot spring-rich areas is likely indicating past over-pressurization of the hydrothermal aquifer, resulting from efficient sealing. Furthermore, the absence of anomalous soil CO2 flux values on the top of the reservoir, except where the thermal spring discharges are located, can be explained by an effective cap-rock layer. Deep circulation of meteoric water, enriched with atmospheric gases, receives inputs of magmatic fluids (similar to 11% of primordial helium), leading to the development of the hydrothermal NaCl aquifer. However, this deep fluid contribution might be underestimated due to significant crustal assimilation (up to 50%) involved in the magma genesis of the Cerro Gal & aacute;n Volcanic Complex, a process which modifies the He isotopic signature of the magmatic endmember. The hot springs, characterized by high flow rate (up to 459 m(3)/h) are positioned at the intersection between the caldera margins and the NNE-SSW oriented tectonic structures, suggesting favorable permeability conditions. The preliminary geothermal gradient for the Cerro Gal & aacute;n area is estimated at around 98-101 degrees C/km. Such a high gradient can be attributed to the considerable heat flux generated by the transcrustal plumbing system of the Cerro Gal & aacute;n caldera, which includes the shallow crystal mush reservoir (<4 km depth). The preliminary geothermal potential of this giant caldera was performed using the volumetric method along with Monte Carlo simulations. The results indicate a probable power production capacity of 2.09 MWe and 10.85 MWe at 90 and 50% confidence level, respectively. The results presented in this work constitute a foundational knowledge base to promote a more advanced exploration phase for the geothermal resource. Additionally to the local energy demand, lithium and other metal mining operations, which are operating independently from the National Interconnected System, could potentially be interested in power generation through binary cycles.