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Vulcano is part of the Aeolian volcanic arc in the southern Tyrrhenian Sea. Its products were emplaced through multiple episodes of edifice building and collapse since about 120 ka B.P. to present. A major discontinuity in the activity occurred after about 28 ka, while the focus of volcanism moved from SE to NW. The older products are basalts to shoshonites, and have lower K2O than the younger ones, shoshonites to rhyolites. Between these two groups, Lentia latites-rhyolites, Spiaggia Lunga basalts, and Quadrara shoshonite-trachytes, erupted along the western side of Vulcano Island. The Spiaggia Lunga basalts (i) are the most primitive magmas erupted at Vulcano after 28 ka (ii) mark the change between older and younger phases, and (iii) overlap geochemically with a monzogabbroic intrusion of similar age. This work focuses on the Spiaggia Lunga products, discussed within a large dataset of geochemical and radiogenic isotope analyses on the entire Vulcano sequence. Older products have more primitive geochemical and isotope characteristics, and lower incompatible element contents, than younger ones. The Spiaggia Lunga basalts exhibit intermediate geochemical characteristics between the older and the younger groups, and can likely be regarded as a third magmatic phase, which represents a distinct mantle reservoir active during the magmatic history of Vulcano. Significant variations of Sr, Nd, and Pb isotope ratios, and isotopic disequilibrium between phenocrysts and groundmass, are present among the Vulcano products. This variability suggests crustal assimilation in shallow-level magma chambers, which also accounts for the formation of evolved products by combined assimilation and fractional crystallization, particularly in the younger series. Considering only the mafic products, incompatible element patterns with high LILE/HFSE and enriched signatures of Sr, Nd, and Pb isotope ratios, indicate enriched mantle sources. Besides, chemical and isotope variability among older, younger, and Spiaggia Lunga mafic rocks, suggests an origin from geochemically diverse primary melts, derived from distinct mantle reservoirs. Their parent magmas, based on geochemical and isotope patterns, were from both MORB- and OIB-type mantle sources, subject to variable degrees of metasomatism by subducted sediments.

A seguito del violento rilascio di gas, verifica-tosi nel 2002 e 2003, nell'area prospiciente gli isolotti a est dell'isola vulcanica di Panarea, sono state condotte nume-rose ricerche per comprendere l'origine, la natura e gli effetti di queste emissioni. Tali ricerche hanno evidenziato vari punti di rilascio di gas e fluidi idrotermali ricchi di CO2 nel-l'area di mare a est di Panarea e hanno prodotto diverse stime della CO2 totale rilasciata dal sistema sottomarino a partire dal post-glaciale ad oggi. Alla luce di questo, l'ISMAR-CNR e l'ISPRA hanno condotto delle ricerche specifiche tra il 2013 e il 2015 per caratterizzare il campo idrotermale sommerso compreso tra l'isola di Panarea e l'isolotto di Basiluzzo (NE di Panarea), dal punto di vista morfologico, biologico e chimico-fisico, in particolare per ciò che riguarda i flussi bentici diffusi. Le campagne ocea-nografiche hanno consentito di individuare e caratterizzare tre aree con intensa attività idrotermale.

International audience

Here we report on the first assessment of volatile fluxes from the hyperacid crater lake hosted within the summit crater of Copahue, a very active volcano on the Argentina-Chile border. Our observations were performed using a variety of in situ and remote sensing techniques during field campaigns in March 2013, when the crater hosted an active fumarole field, and in March 2014, when an acidic volcanic lake covered the fumarole field. In the latter campaign, we found that 566 to 1373 t d -1 of SO 2 were being emitted from the lake in a plume that appeared largely invisible. This, combined with our derived bulk plume composition, was converted into flux of other volcanic species (H 2 O ~ 10989 t d -1 , CO 2 ~ 638 t d -1 , HCl ~ 66 t d -1 , H 2 ~ 3.3 t d -1 , and HBr ~ 0.05 t d -1 ). These levels of degassing, comparable to those seen at many open-vent degassing arc volcanoes, were surprisingly high for a volcano hosting a crater lake. Copahue's unusual degassing regime was also confirmed by the chemical composition of the plume that, although issuing from a hot (65°C) lake, preserves a close-to-magmatic signature. EQ3/6 models of gas-water-rock interaction in the lake were able to match observed compositions and demonstrated that magmatic gases emitted to the atmosphere were virtually unaffected by scrubbing of soluble (S and Cl) species. Finally, the derived large H 2 O flux (10,988 t d -1 ) suggested a mechanism in which magmatic gas stripping drove enhanced lake water evaporation, a process likely common to many degassing volcanic lakes worldwide. Key Points First volatile flux record of crater lake gas emissions from Copahue volcano Magmatic gases breaching through the lake surface Magmatic gas stripping drive enhanced lake water evaporation Fil: Tamburello, G.. Università degli Studi di Palermo; Italia Fil: Caselli, Alberto Tomás. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina Fil: Tassi, F.. Università degli Studi di Firenze; Italia Fil: Vaselli, O.. Università degli Studi di Firenze; Italia Fil: Calabrese, S.. Università degli Studi di Palermo; Italia Fil: Rouwet, D.. Istituto Nazionale di Geofisica e Vulcanologia; Italia Fil: Capaccioni, B.. Universidad de Bologna; Italia Fil: Di Napoli, R.. Università degli Studi di Palermo; Italia Fil: Cardellini, C.. Università di Perugia; Italia Fil: Chiodini, G.. Istituto Nazionale di Geofisica e Vulcanologia; Italia Fil: Bitetto, M.. Università degli Studi di Palermo; Italia Fil: Brusca, L.. Istituto Nazionale Geofisica e Vulcanologia; Italia Fil: Bellomo, S.. Istituto Nazionale Geofisica e Vulcanologia; Italia Fil: Aiuppa, A.. Istituto Nazionale Geofisica e Vulcanologia; Italia

A seguito del violento rilascio di gas, verificatosi nel 2002 e 2003, nell'area prospiciente gli isolotti a est dell'Isola vulcanica di Panarea, sono state condotte numerose ricerche per comprendere l'origine, la natura e gli effetti di queste emissioni. Tali ricerche hanno evidenziato vari punti di rilascio di gas e fluidi idrotermali ricchi di CO2 nell'area di mare a est di Panarea e hanno prodotto diverse stime della CO2 totale rilasciata dal sistema sottomarino a partire dal post-glaciale ad oggi. Alla luce di questo, l'ISMAR-CNR e l'ISPRA hanno condotto delle ricerche specifiche tra il 2013 e il 2015 per caratterizzare il campo idrotermale sommerso compreso tra l'isola di Panarea e l'isolotto di Basiluzzo (NE di Panarea), dal punto di vista morfologico, biologico e chimico- fisico, in particolare per ciò che riguarda i flussi bentici diffusi. Le campagne oceanografiche hanno consentito di individuare e caratterizzare tre aree con intensa attività idrotermale. La prima area, situata a Sud-Est dell'isola di Panarea (Secca dei Pesci), è caratterizzata da un'intensa attività esalativa di fluidi acidi, ricchi di DIC, a temperatura ambiente ma con deboli contenuti in metalli. La seconda area, scoperta nel 2015, situata ai piedi della scarpata a Nord-Est dell'isola di Panarea, è stata denominata Smoking Land per la presenza di circa 200 camini idrotermali di dimensioni consistenti (1-4 m di altezza; circa 4 m in media di diametro di base), in parte attivi e in parte quiescenti. L'ultima area, situata a Nord-Est degli isolotti DBLP, è caratterizzata da depressioni circolari, anche esse in parte attive e in parte inattive. In queste ultime due aree, le misure di flussi bentici disciolti hanno evidenziato un andamento a macchia di leopardo con rilascio di fluidi acidi, a temperatura ambiente, ricchi di DIC, Fe e altri metalli (Mn, Zn, Al). Queste due aree sono localizzate ai margini di un avvallamento allungato in direzione OSO-ENE. Esse sono il risultato di una circolazione idrotermale con risalita, lungo faglie distensive, di gas di origine vulcanica mescolati ad acqua di mare penetrata nel sottofondo marino. Adiacenti alle aree attive sono presenti aree inattive, cariche di gas in sovrappressione per la presenza di uno strato superficiale di ossidi e idrossidi di Fe che ne impedisce la fuoriuscita, e aree quiescenti per una degassificazione già avvenuta. Da questo assetto deriva la necessità di un continuo monitoraggio atto a prevedere possibili future situazioni di pericolo per le aree circostanti.

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A geochemical survey of thermal waters collected from submarine vents at Panarea Island (Aeolian islands, southern Italy) was carried out from December 2002 to March 2007, in order to investigate (i) the geochemical processes controlling the chemical composition of the hydrothermal fluids and (ii) the possible relations between the chemical features of the hydrothermal reservoir and the activity of the magmatic system. Compositional data of the thermal water samples were integrated in a hydrological conceptual model, which describes the formation of the vent fluid by mixing of seawater, seawater concentrated by boiling, and a deep, highly-saline end-member, whose composition is regulated by water-rock interactions at relatively high temperature and shows clear clues of magmatic-related inputs. The chemical composition of concentrated seawater was assumed to be represented by that of the water sample having the highest Mg content. The composition of the deep end-member was instead calculated by extrapolation assuming a zero-Mg end-member. The Na-K-Ca geothermometer, when applied to the thermal end-member composition, indicated an equilibrium temperature of approximately 300 degrees C, a temperature in agreement with the results obtained by gas-geothermometry. (c) 2008 Elsevier Ltd. All rights reserved.

The toponym “Terre Calde di Medolla” (literally, “Warm Earths of Medolla”) refers to a farming area, located near the town of Modena (Emilia-Romagna region, northern Italy), which has always been known by the local population for the relatively high temperatures of the soil. This phenomenon is particularly evident in wintertime when the snow cover over this area rapidly melts. A detailed investigation, carried out after the devastating 2012 Emilia earthquake that affected this area, showed soil temperatures up to 44°C, i.e., 20–25°C above the local background value, together with diffuse soil fluxes of CH4 (0–2432 g ×m2×d1) and minor, though significant, CO2 (0–1184 g ×m2×d1), especially from subcircular (a few meters in diameter) zones. Ground heating and gas seepage appear spatially correlated, thus suggesting a close relationship between the two phenomena. The anomalous high ground temperature is not associated with an anomalous geothermal gradient or with the uprising of deep-seated hot fluids. According to the lateral and vertical distributions of the temperatures as well as the chemical and isotopic compositions of the soil gases, the most reliable explanation is the exothermic oxidation of diffusely uprising biogenic methane at very shallow levels (

The toponym Terre Calde di Medolla (literally, Warm Earths of Medolla) refers to a farming area, located near the town of Modena (Emilia-Romagna region, northern Italy), which has always been known by the local population for the relatively high temperatures of the soil. This phenomenon is particularly evident in wintertime when the snow cover over this area rapidly melts. A detailed investigation, carried out after the devastating 2012 Emilia earthquake that affected this area, showed soil temperatures up to 44 degrees C, i.e., 20-25 degrees C above the local background value, together with diffuse soil fluxes of CH4 (0-2432gxm(-2)xd(-1)) and minor, though significant, CO2 (0-1184gxm(-2)xd(-1)), especially from subcircular (a few meters in diameter) zones. Ground heating and gas seepage appear spatially correlated, thus suggesting a close relationship between the two phenomena. The anomalous high ground temperature is not associated with an anomalous geothermal gradient or with the uprising of deep-seated hot fluids. According to the lateral and vertical distributions of the temperatures as well as the chemical and isotopic compositions of the soil gases, the most reliable explanation is the exothermic oxidation of diffusely uprising biogenic methane at very shallow levels (

On 3rd November 2002, at about 3 km off-shore of Panarea Island (Aeolian Islands, Southern Italy), a series of gas vents suddenly and violently opened from the seafloor at the depth of 10-15 m, with an unusually high gas flux and superimposing on the already existing submarine fumarolic field. Starting from the 12th November 2002 a discontinuous geochemical monitoring program was carried out. The emissions consisted in an emulsion whose liquid phase derived from condensation of an uprising vapor phase occurring close to the fluid outlets without significant contamination by seawater. The whole composition of the fluids was basically H2O- and CO2-dominated, with minor amounts of typical «hydrothermal» components (such as H2S, H2, CO and light hydrocarbons), atmospheric-related compounds, and characterized by the occurrence of a significant magmatic gas fraction (mostly represented by SO2, HCl and HF). According to the observed temporal variability of the fluid compositions, between November and December 2002 the hydrothermal feeding system was controlled by oxidizing conditions due to the input of magmatic gases. The magmatic degassing phenomena showed a transient nature, as testified by the almost complete disappearance of the magmatic markers in a couple of months and by the restoration, since January 2003, of the chemical features of the existing hydrothermal system. The most striking feature of the evolution of the «Panarca degassing event» was the relatively rapid restoration of the typical reducing conditions of a stationary hydrothermal system, in which the FeO/Fe1.5O redox pair of the rock mineral phases has turned to be the dominating redox controlling system.

Since the exhalative crisis of 2002 cruises were carried out to investigate morphology, magnetic and gravity fields, fluid escape, plume anomalies, biological and microbiological activity, benthic fluxes, early diagenesis, mineralogy and geochemistry of water and sediments of the hydrothermal system of Panarea. The volcanic complex was mapped by multibeam, including backscatter analysis, and magnetometric surveys were done to detect low magnetization in areas with hydrothermal activity, i.e., vents, sulphide deposits, chimney fields. CTD by ship and on ROV detected acidic plumes at bottom (minimum pH value 6.5) and mid depths. An Automatic Benthic Chamber was deployed on a terrace (40m) and in depressions with gascharged and hydrothermally altered sediments (80m). At the 40m site, strong releases of Dissolved Inorganic Carbon (DIC) and Fe, Mn, Zn (75.7, 2.0, 2.9, 3.4 mmol m-2 day-1) were found. Average decrease of pH in the chamber was ~4 units day-1 with a H+ benthic flux of 0.32 mmol m-2 day-1). DIC values of seawater had average 2.3, increasing to 3.1 on degassing vents, while 7.5 mmol was measured on top of a bubbling core. ROV dives explored and sampled several sites; active chimneys (black, red crusts and yellowishorange precipitates at top) were recovered on the SE flanks of Basiluzzo; pH value of 5 was measured aboard on sediments. XRD and XRF data on the external crust showed Fe-Mn oxyhydroxides, including goethite and opal, with Co, Ce, Sr, Zn and Cu enrichments, whereas the inner part are depleted of Fe, Mn and other metals, mostly under detection limits. SEM imagery shows porous filamentous minerals, that are probably bacterial in origin. Dives to SW discovered fields of partially or totally relict chimneys at the same depth (~200m). Chimneys are present on the edges of slope failures and settled on areas of relative lower positive magnetic anomaly, indicating possible shallow depth level of hydrothermal alteration. Reddish crusts and sediments, and acid, gas boiling water (pH 5.5) were cored at 90 m depth upslope of the 'active' chimneys; upslope from the 'relict' chimney's fields, oxized-normal sediments were found. Biological investigations on the sediments revealed a community strongly dominated by the amphipod Ampelisca ledoyeri (43.8 % of the total abundance), probably dwelling in the tubepatches. Rare species were detected on the chimney's samples. The phylogenetic diversity of microbial communities in the precipitates collected on chimneys and on Bottaro vent was analyzed by bacterial and archaeal 16S rDNA clone libraries, showing a dominance of sulfur-oxidazing epsilon and gamma proteobacteria. Very interesting groups of archaea were revealed including methanotrophic Thermoplasmatales and members of SM1 candidate division. Overall prokaryotic diversity was found similar to that of deep sea hydrothermal vents and other sulfidic habitats. White microbial mats were found in an area S of Panarea, on a NS oriented fracture.

Copahue volcano is part of the Caviahue-Copahue Volcanic Complex (CCVC), which is located in the southwestern sector of the Caviahue volcano-tectonic depression (Argentina-Chile). This depression is a pull-apart basin accommodating stresses between the southern Liquiñe-Ofqui strike slip and the northern Copahue-Antiñir compressive fault systems, in a back-arc setting with respect to the Southern Andean Volcanic Zone. In this study, we present chemical (inorganic and organic) and isotope compositions (?13C-CO2, ?15N, 3He/4He, 40Ar/36Ar, ?13C-CH4, ?D-CH4, and ?D-H2O and ?18O-H2O) of fumaroles and bubbling gases of thermal springs located at the foot of Copahue volcano sampled in 2006, 2007 and 2012. Helium isotope ratios, the highest observed for a Southern American volcano (R/Ra up to 7.94), indicate a non-classic arc-like setting, but rather an extensional regime subdued to asthenospheric thinning. ?13C-CO2 values (from - 8.8? to - 6.8? vs. V-PDB), ?15N values (+ 5.3? to + 5.5? vs. Air) and CO2/3He ratios (from 1.4 to 8.8 × 109) suggest that the magmatic source is significantly affected by contamination of subducted sediments. Gases discharged from the northern sector of the CCVC show contribution of 3He-poor fluids likely permeating through local fault systems. Despite the clear mantle isotope signature in the CCVC gases, the acidic gas species have suffered scrubbing processes by a hydrothermal system mainly recharged by meteoric water. Gas geothermometry in the H2O-CO2-CH4-CO-H2 system suggests that CO and H2 re-equilibrate in a separated vapor phase at 200°-220 °C. On the contrary, rock-fluid interactions controlling CO2, CH4 production from Sabatier reaction and C3H8 dehydrogenation seem to occur within the hydrothermal reservoir at temperatures ranging from 250° to 300 °C. Fumarole gases sampled in 2006-2007 show relatively low N2/He and N2/Ar ratios and high R/Ra values with respect to those measured in 2012. Such compositional and isotope variations were likely related to injection of mafic magma that likely triggered the 2000 eruption. Therefore, changes affecting the magmatic system had a delayed effect on the chemistry of the CCVC gases due to the presence of the hydrothermal reservoir. However, geochemical monitoring activities mainly focused on the behavior of inert gas compounds (N2 and He), should be increased to investigate the mechanism at the origin of the unrest started in 2011.

Panarea seafloor hydrothermal system is associated with a range of mafic to felsic volcanic rocks. The hydrothermal system is active at present and discharges magmatic-hydrothermal fluids and precipitates massive sulfides. The sulfides exhibit multi-stage deposition, evident in the alternation of several mineral generations that follow a general temporal precipitation sequence: marcasite → alunite → opal. Sr-Nd-Pb isotope data indicate that most of the metals in the sulfides are derived predominantly from the Panarea volcanic rocks with some contribution from ambient seawater and/or local sediments. A remarkable feature of these sulfides is their chondrite-normalized rare earth element (REEN) distribution pattern with a pronounced negative Eu anomaly, which has not been observed previously. Our study demonstrates that this REEN pattern reflects the REE fractionation during sulfide deposition. The ionic radius mismatch between Eu2+ (the main form of Eu in reduced, high-temperature hydrothermal fluids) and the only possible site for REE substitution in the marcasite, that of Fe2+, suggests a crystallographic control on the REEN pattern. Apparently, marcasite precipitation can generate a sulfide deposit with a negative Eu anomaly due to discrimination against Eu2+ relative to REE3+ in the Fe2+ crystallographic site.

The Sciacca basin (southern Sicily, Italy), well known since the Roman times for the importance of its thermo-mineral waters, is characterized by a large occurrence of thermal fluid discharges whose main thermal aquifer is located within the Triassic carbonate rocks. This reservoir represents the deepest formation cropping out in the area. Shallower and cooler thermal aquifers are located within the Tertiary limestone and Quaternary sand and gravel deposits. In this work new geochemical and isotopic data of thermal waters and dissolved gases from springs and wells were investigated to assess the origin of thermal fluids and the structure of the hydrothermal system. The main thermal aquifer, at about 60 °C and located at 43 m a.s.l., is fed by an 18O-enriched (?18O~+4?;?D~0?) thermal marine end-member, affected by cooling and dilution (1:2) caused by mixing with inland-originated meteoric waters (?18O~-8?; ?D~-58?). This meteoric recharge is likely related to the area of Ficuzza and San Genuardo Mts., located 12 and 23 km N of Sciacca, respectively, at an altitude comprised between 900 and 1180 m a.s.l. After this primary dilution, the deep thermal aquifer, emerging at the "Antiche Terme Selinuntine" discharging site, is not apparently affected by further dilution processes in the Sciacca area, where the sedimentary cover does not allow infiltration of local meteoric waters down to the Triassic reservoir. Conversely, the shallower thermal aquifers hosted within the Tertiary-Quaternary sedimentary horizons are locally supplied by direct infiltration of meteoric water occurring at variable altitudes, up to about 400 m a.s.l. (San Calogero Mt.). With the only exception of the Molinelli thermal spring, direct contribution from the deep thermal end-member to thermal springs fed by the shallower aquifers can be considered negligible.

Thermal water and gas discharges south-east of El Chichón volcano, Mexico are associated mainly with NW-SE oriented fault systems. Spring discharges include i) waters with Na-Cl composition and TDS>3000 mg/L; ii) waters with Ca-SO4 composition and TDS values between 1400 and 2300 mg/L; iii) waters with Na-Cl composition and TDS of 800 to 2400 mg/L and sulphate content up to 650 mg/L and iv) waters with Ca-HCO3 composition and low salinity (TDS