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Faccini, Barbara ; Rizzo, Andrea Luca ; Bonadiman, Costanza ; [weitere]

Elsevier

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Publikationsdatum: 2023-10-25

Beschreibung: Calc-alkaline and alkaline magmatic activity is generally separated in space and/or in time. The Eastern Transylvanian Basin in Romania is one of the few places where, during Pleistocene, alkaline eruptions occurred contemporaneously with the calc-alkaline activity. Mantle xenoliths entrained in Perşani Mts. alkaline volcanic products have been studied in order to investigate the interaction of metasomatic agents of different magmatic affinities with the mantle wedge. Based on mineral major and trace element and noble gases in fluid inclusions, two main events have been recognized. The first was a pervasive, complete re-fertilization of a previously depleted mantle by a calc-alkaline subduction-related melt, causing the formation of very fertile, amphibole-bearing lithotypes. This is shown by the a) increased amounts of modal clinopyroxene up to 21.9 % with Al2O3 contents up to 8.16 wt%, higher than what is expected for clinopyroxene in Primordial Mantle; b) 4He/40Ar* ratios up to 1.2, within the reported range for mantle production; c) 3He/4He in olivine, opx and cpx of 5.8 ± 0.2 Ra, among the most radiogenic values of European mantle, below the typical MORB mantle value (8 ± 1 Ra), reflecting recycling of crustal material in the local lithosphere. The second event is related to later interaction with an alkaline metasomatic agent similar to the host basalts that caused slight LREE enrichment in pyroxenes and disseminated amphiboles and precipitation of vein amphiboles with a composition similar to amphiboles megacrysts also found in the Perşani Mts. volcanic deposits. This is highlighted by the 4He/40Ar* and 3He/4He values found in some opx and cpx, up to 2.5 and 6.6 Ra, respectively, more typical of magmatic fluids.

Beschreibung: Published

Beschreibung: 105516

Beschreibung: 1T. Struttura della Terra

Beschreibung: 1V. Storia eruttiva

Beschreibung: 2V. Struttura e sistema di alimentazione dei vulcani

Beschreibung: 3V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcanici

Beschreibung: JCR Journal

Schlagwort(e): Mantle refertilisation ; Eastern Transylvanian Basin ; Noble gases ; Post-collisional ; Subduction-related metasomatism ; Solid Earth ; 04.01. Earth Interior

Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

Materialart: article

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Origin and hazard of CO2 and H2S emissions in the Lavinio-Tor Caldara zone (Metropolitan City of Rome Capital, Italy) (2020)

Carapezza, Maria Luisa ; Ranaldi, Massimo ; Tarchini, Luca ; [weitere]

Elsevier

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Publikationsdatum: 2023-11-21

Beschreibung: Highlights -He isotopic R/Ra of emitted gas decreases moving away from Albani Hills volcano -Total soil flux of endogenous CO2 at Lavinio-Tor Caldara is estimated to 20 ton/day -Tor Caldara gas has the highest H2S content (up to 6.3 vol.%) of central Italy -Repetition of soil CO2 flux survey shows that flux increases during earthquakes -Gas air concentration monitoring shows that H2S is the killer gas of small animals

Beschreibung: Gas hazard was evaluated at Lavinio-Tor Caldara, the southernmost gas-discharging zone of the quiescent Albani Hills volcano in central Italy. Also this zone, like the other gas discharges of this volcanic complex, is located above a structural high of the buried Mesozoic carbonate basement, which represents the main reservoir for gas rising from depth. All extensional faults affecting the carbonates are leaking pathways along which gas may rise to the surface creating hazardous conditions. Gas is dominated by CO2 (〉90 vol.%) and the second component at Lavinio-Tor Caldara is H2S that displays the highest content (4.0-6.3 vol.%) of all gas manifestations of the Rome region. This H2S enrichment corresponds to a marked decrease in 3He/4He (R/Ra) isotopic ratio suggesting that gas was contaminated in an upper crustal environment. The main gas discharge occurs at the natural reserve of Tor Caldara, in zones where past sulphur mining excavations removed the surficial impervious cover, or along a ditch. Comparison of the results of four soil CO2 flux surveys carried out in 2005-2018 at Miniera Grande within Tor Caldara, indicates that the highest soil CO2 release occurs shortly after local earthquakes. Continuous monitoring of CO2 and H2S air concentration and of wind speed has been carried out for four months in twelve anomalous gas realising sites of Tor Caldara. Results indicate that only H2S reaches lethal concentration (〉250 ppm) near the soil in no wind nights, explaining the presence of small dead animals. At Lavinio, the main soil gas release occurs near old water wells that likely produced a gas blowout during drilling. A total release of over 20 tons/day from 2.93 km2 of gas of endogenous origin, has been estimated for the Lavinio-Tor Caldara area by a detailed soil CO2 flux survey (2,572 measurement points over an area of 3.65 km2). The main structural lineaments of the area have N-S and W-E directions, but also NE-SW and NW-SE directions are well represented. Some sectors of the investigated area are exposed to a severe gas hazard for people and animals and precautionary measures should be adopted.

Beschreibung: Published

Beschreibung: 106985

Beschreibung: 6V. Pericolosità vulcanica e contributi alla stima del rischio

Beschreibung: JCR Journal

Schlagwort(e): •Lavinio-Tor Caldara, southern periphery of Albani Hills volcano ; •He isotopic R/Ra values ; •Soil CO2 flux surveys ; •CO2 and H2S air concentration monitoring ; •Gas chemistry ; •Gas hazard assessment ; 04. Solid Earth

Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

Materialart: article

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Explosive mud volcano eruptions and rafting of mud breccia blocks (2020)

Mazzini, Adriano ; Akhmanov, Grigorii ; Manga, Michael ; [weitere]

Elsevier

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Publikationsdatum: 2023-11-21

Beschreibung: Azerbaijan hosts the highest density of subaerial mud volcanoes on Earth. The morphologies characterizing these structures vary depending on their geological setting, frequency of eruption, and transport processes during the eruptions. Lokbatan is possibly the most active mud volcano on Earth exhibiting impressive bursting events every ∼5 years. These manifest with impressive gas flares that may reach more than 100 meters in height and the bursting of thousands of m3 of mud breccia resulting in spectacular mud flows that extend for more than 1.5 kilometres. Unlike other active mud volcanoes, to our knowledge Lokbatan never featured any visual evidence of enduring diffuse degassing (e.g., active pools and gryphons) at and near the central crater. Only a very small new-born gryphon was intermittently active in 2019 (with negligible flow). Gas flux measurements completed with a closed-chamber technique reveal extremely low values throughout the structure with average CH4 = 1.36 tonnes yr−1 and CO2 = 11.85 tonnes yr−1. We suggest that after eruptive events, the mud breccia is able to seal the structure preventing gas release and thereby promoting overpressure build-up in the subsurface. This self-sealing mechanism allows a fast recharge of Lokbatan resulting in more frequent and powerful explosive episodes. Our field observations reveal the presence of large (up to ∼50,000 m3) stratified blocks that were originally part of a large crater cone. These blocks were rafted 〉1 km from the vent on top of mud breccia flows. We use a model based on lubrication theory to show that it is reasonable to transport blocks this large and this far provided the underlying mud flow was thick enough and the blocks are large enough. The presence of large rafted blocks is not a unique phenomenon observed at Lokbatan mud volcano and is documented at other large-scale structures both onshore and offshore.

Beschreibung: Published

Beschreibung: 116699

Beschreibung: 6A. Geochimica per l'ambiente e geologia medica

Beschreibung: JCR Journal

Schlagwort(e): Lokbatan mud volcano Azerbaijan ; rafted mud breccia megablocks ; gas flux ; self-sealing ; explosive eruptions ; lubrication theory ; Solid Earth ; Geochemistry

Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

Materialart: article

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