http://hdl.handle.net/2122/279 2013-06-19T06:16:58Z http://hdl.handle.net/2122/8610 Title: Trioctahedral micas in xenolithic ejecta from recent volcanism of the Somma-Vesuvius (Italy): crystal chemistry and genetic inferences. Authors: Balassone, G.; Dipartimento di Scienze della Terra, Università “Federico II”, via Mezzocannone 8, I-80134 Napoli, Italy; Scordari, F.; Dipartimento di Scienze della Terra e Geoambientali, Università degli Studi di Bari, via Orabona 4, I-70125 Bari, Italy; Lacalamita, M.; Dipartimento di Scienze della Terra e Geoambientali, Università degli Studi di Bari, via Orabona 4, I-70125 Bari, Italy; Schingaro, M.; Dipartimento di Scienze della Terra e Geoambientali, Università degli Studi di Bari, via Orabona 4, I-70125 Bari, Italy; Mormone, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Piochi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Petti, C.; Dipartimento di Scienze della Terra, Università “Federico II”, via Mezzocannone 8, I-80134 Napoli, Italy; Mondillo, N.; Centro Museale “Musei delle Scienze Naturali”, Università “Federico II”, via Mezzocannone 8, I-80134 Napoli, Italy Abstract: This study reports the first crystal chemical database resulting from a detailed structural investigation of trioctahedral micas found in xenolithic ejecta produced during the AD 1631, 1872 and 1944 eruptions, three explosive episodes of recent volcanic period of Vesuvius volcano (Southern Italy). Three xenolith types were selected: metamorphic/metasomatic skarns, pyrometamorphic/hydrothermally altered nodules and mafic cumulates. They are related to different magma chemistry and effusive styles: from sub-plinian and most evolved (AD 1631 eruption) to violent strombolian with medium evolution degree (AD 1872 eruption) to vulcanian-effusive, least evolved (AD 1944 eruption) event, respectively. Both xenoliths and micas were investigated employing multiple techniques: the xenoliths were characterized by X-ray fluorescence, inductively-coupled plasma-mass spectrometry, optical microscopy, X-ray powder diffraction, and quantitative energy-dispersive microanalysis; the micas were studied by electron probe microanalysis and single crystal X-ray diffraction. The mica-bearing xenoliths showvariable texture and mineralogical assemblage, clearly related to their different origin. Based on the major oxide chemistry, only one xenolithic sample falls in the skarn compositional field fromthe Somma-Vesuvius literature, some fall close to the skarns and cumulate fields, others plot close to the syenite/foidolite/essexite field. A subgroup of the selected ejecta does not fall or approach any of the compositional fields. Trace and rare earth element patterns show some petrological affinity between studied xenoliths and erupted magmas with typical Eu, Ta and Nb negative anomalies. Strongly depleted patterns were detected for the 1631 metamorphic/metasomatic skarns xenoliths. Three distinct mica groups were distinguished: 1) Mg-, Al-rich, low Ti-bearing, low to moderate F-bearing varieties (1631 xenolith), 2) Al-moderate, F- and Mg-rich, Ti-, Fe-poor varieties (1872 xenolith), and 3) Al-, Ti- and Fe-rich, F-poor phases (1944 xenolith). All the analyzed mica crystals are 1Mpolytypes with the expected space group C2/m. Micas from xenoliths of the 1631 Vesuvius eruption are phlogopites characterized by a combination of low extent of oxy-type and variable extent OH−→F− substitutions, as testified by the range of F concentration (from ~0.20 to 0.80 apfu). Micas from xenoliths of the 1872 Vesuvius eruption exhibit structural peculiarities typical of fluorophlogopites, i.e. OH−→F− substitution is predominant. Micas from the xenolith of the 1944 Vesuvius eruption display features typical of oxy-substituted micas. The variability of the crystal chemical features of the studied micas is consistentwith the remarkable variation of their host rocks. Micas from1631 nodules are related to metasomatic, skarn-type environment, deriving from the metamorphosed wall-rocks hosting the magma reservoir. The fluorophlogopites from the 1872 xenoliths testify for strongly dehydrated environmental conditions compared to those of the 1631 and 1944 hosts. Finally, magma storage condition at depth, associated to a decreasing aH2O may have promoted major oxy-type substitutions in 1944 biotites. 2012-12-31T23:00:00Z http://hdl.handle.net/2122/8416 Title: Discrimination between effects induced by microbial activity and water-rock interactions under hydrothermal conditions according to REE behaviour Authors: Censi, P.; DiSTeM UniPA; Cangemi, M.; DiSTeM UniPA; Madonia, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Saiano, F.; AGROPa UniPA; Brusca, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Zuddas, P.; iSTeP Universitè P. er M. Curie Paris Abstract: Rare Earths (REE) were investigated in siliceous stromatolites forming in the Specchio di Venere Lake in Pantelleria Island. Chondrite-normalised patterns show significant La enrichments and Eu depletions suggesting that fluids involved in stromatolite growth experienced strong rock-water interactions under hydrothermal conditions. At the same time, enrichments of heavy REE (HREE), with respect to intermediate REE (MREE) suggest that hydrothermal fluids interacted with microbial mats during deposition of stromatolites. The above-mentioned features suggest that rock-water interactions and bacterial activity were simultaneously recorded in REE patterns of stromatolites and can be discriminated in terms of amplitudes of La anomaly and HREE/MREE ratio 2013-06-08T22:00:00Z http://hdl.handle.net/2122/8383 Title: Caratterizzazione geochimica delle acque dei fontanili e delle polle a emissione gassosa della Riserva Naturale Regionale Monterano Authors: Cinti, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Procesi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia Abstract: L’area della riserva naturale Monterano è ubicata nel settore occidentale del distretto vulcanico Sabatino, in un contesto geochimico caratterizzato dalla presenza di numerose manifestazioni termali ed emissioni gassose (Baldi et al., 1973; Dall’Aglio et al., 1994; Minissale et al., 1997; Minissale, 2004). Tali manifestazioni sono frequenti nel settore peri-Tirrenico dell’Italia centrale (Duchi e Minissale, 1995; Chiodini et al., 1995, 1999; Barberi et al., 2007; Frondini, 2008; Frondini et al., 2009) e sono comunemente associate all’attività magmatica seguita ai movimenti tettonici distensivi avvenuti durante il Neogene (Buonasorte et al., 1987; Barberi et al., 1994). Dal punto di vista geologico i prodotti vulcanici del distretto Sabatino ricoprono una sequenza sedimentaria che comprende, dal basso verso l’alto: 1) la formazione dei Calcari Mesozoici, 2) il Flysch Tolfetano di età Cretacico-Oligocenica e 3) la formazione delle sabbie e argille del Miocene e Quaternario. I Calcari Mesozoici sono sede di un acquifero termale, esteso su scala regionale, a composizione Ca-SO4(HCO3), e di una fase gassosa ricca in CO2. Le vulcaniti sabatine e la formazione del Flysch Tolfetano contengono acquiferi freddi di limitate dimensioni, a composizione rispettivamente Ca(Na, K)-HCO3 e Ca(Mg)-HCO3. Le formazioni pre-vulcaniche sono state interrotte nella loro continuità laterale da faglie distensive che hanno generato un’alternanza di alti e bassi strutturali (horst e graben). E’ in corrispondenza delle zone di alto strutturale e lungo i bordi tra alti e bassi che si osserva la risalita di fluidi di origine profonda (acque termali e gas) che possono mescolarsi con le acque fredde superficiali e/o raggiungere la superficie. Il presente studio si propone di fornire un’accurata caratterizzazione geochimica dei fluidi (acque e gas) presenti all’interno della riserva naturale Monterano, al fine di stabilirne l’origine, le modalità di circolazione e risalita verso la superficie e i processi di interazione acqua–gas–roccia. 2011-12-31T23:00:00Z http://hdl.handle.net/2122/8276 Title: Geochemical features of the gas phase extracted from sea-water and rocks of the Marsili seamount (Tyrrhenian sea, Italy): implications for geothermal exploration projects Authors: Italiano, Francesco; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Caso, Carlo; D.I.G.A.T., Università G. D’Annunzio, Chieti, Italy; Cavallo, Andrea; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Favali, Paolo; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Fu, Chen; NTU, National Technical University, Taipei, Taiwan; Iezzi, Gianluca; D.I.G.A.T., Università G. D’Annunzio, Chieti, Italy; Martelli, Mauro; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Mollo, Silvio; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Paltrinieri, Diego; Eurobuilding SpA, Servigliano, Italy; Paonita, Antonio; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Rizzo, Andrea; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Signanini, Patrizio; D.I.G.A.T., Università G. D’Annunzio, Chieti, Italy; Ventura, Guido; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia Editors: Hilton, David; Scripps Institution, La Jolla, California Abstract: A new target for worldwide geothermal exploration and exploitation is represented by the submarine hydrothermal activity. A geologically young (Upper Pliocene – Pleistocene) area in the Tyrrhenian sea, on the west shore of Italy, provides important heat sources from some seamounts. The heat flow data are characterized by positive anomalies comparable to those of onshore geothermal fields. A geothermal exploration program of the Marsili seamount, the largest volcanic edifice (~30 km in length) in Europe, suggests the presence of a geothermal activity testified by oxy- and hydroxide-deposits predominantly made up of Fe- and Mn-rich sediments, crusts and nodules. Several rock samples of Marsili volcanic activity were collected during dredging and coring projects. These rocks are lavas, pillows and dikes with a calc–alkaline affinity and ranging in composition from basalt to andesite to trachy-andesite. Some tephra layers were also sampled at the top of the volcano showing shoshonitic to latitic bulk compositions and variable amounts of crystals. Importantly, isotopic ratios of noble gases extracted from selected solid samples have provided novel constrains on the Marsili magmatism. In November 2007 and July 2011, water-column studies were carried out aboard of the R/V Urania and Astrea. Isotope analyses of the gases dissolved in water samples collected at the top the Marsili have evidenced that the He/4He isotope ratio, i.e. a clear indicator of hydrothermal input, is in excess with respect to the background and it is also associated with the anomalous behaviour of hydrothermal-derived gases (CO2, CO, CH4). Although some hydrothermal emissions are known to occur offshore the Aeolian subaerial volcanoes, results from our isotope analyses are the first to confirm the hydrothermal activity of Marsili. The highest 3He values were measured over the shallowest part of the seamount, where hydroxide deposits were found. The chemical composition of the dissolved gases clearly shows the presence of CO2 and CH4 over a wide water column depth range. The same anomalies were found in 2007 and 2011, depicting the presence of a persistent plume related to the deep hydrothermal activity of Marsili. A high heat flow (250 mW/m2) is measured at the uppermost portion of the volcano, reaching the maximum value (500 mW/m2) in the central parts. It coincides with gravity and magnetic anomalies, suggesting the presence of magmatic bodies intruding within shallow and thinned crustal levels. Although direct thermal measurements on the Marsili seamount are still lacking, our results give important constraints on the submarine volcanic and hydrothermal activity. Moreover, they support an ongoing project (carried out by Eurobuilding SpA company on the Italian Minister of Economic Development permission) aimed to drill the first offshore geothermal well at the top of the seamount that may potentially represent one of the most abundant energy resources worldwide; this mainly in response to the large amount and virtually infinite recharge of the circulating fluids. To conclude, it is worth noting that besides the scientific information concerning the geothermal activity, the technologies available at the present time will permit on-site geothermal exploitation and 68 production of electric energy (~1 GW) from a seamount located at ~100 km far from the Italian coasts. 2011-11-28T23:00:00Z http://hdl.handle.net/2122/8151 Title: Volcanic Lakes Authors: Pecoraino, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; D'Alessandro, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Inguaggiato, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia Editors: Rouwet, Dmitri; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Tassi, Franco; UniFi; Christenson, Bruce; GNS Science, New Zealand; Vandemeulebrouck, Jean Abstract: Among surface waters, lakes in volcanic areas display the greatest range in pH values (from negative values up to about 12). The present chapter will be a short review of the main features of alkaline lakes, which belong to the high-pH part of this range. They are characterised by saline or hypersaline waters, pH values higher than 9 and high Na+, HCO3- and CO32- and low Ca2+ concentrations. Alkaline lakes are found in quiescent or recently extinct volcanic areas where neither water vapour nor acidic magmatic gases can reach surface waters. Their occurrence depends on peculiar climatic and geologic conditions that allow evaporative concentration of the water (potentially, evaporation much higher than water inputs and endorheic basins) and on geochemical factors that favour a chemical evolution towards an alkaline environment (composition of the dilute input waters characterised by a ratio between total dissolved inorganic carbon and earth-alkaline elements much higher than 1). Such initial composition, due to evaporative concentration, after the deposition of earth-alkaline carbonate minerals, will lead to the above-mentioned typical composition. Alkaline lakes also host microbial communities sometimes characterised by extremely high productivity. These microbial communities are scientifically remarkable because they comprise some interesting extremophiles, which can grow not only at very high pH and salinity conditions but also in the presence of elevated concentrations of toxic elements (e.g. As, Se, Te). 2011-12-31T23:00:00Z http://hdl.handle.net/2122/8069 Title: Contatore di impulsi con interfaccia seriale Authors: Romeo, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Urbini, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia 1997-12-31T23:00:00Z http://hdl.handle.net/2122/8052 Title: Geochemistry of the Phlegraean Fields (Italy) proximal sources for major Mediterranean tephras: Implications for the dispersal of Plinian and co-ignimbritic components of explosive eruptions Authors: Tomlinson, E. L.; Department of Earth Sciences, Royal Holloway University of London,; Arienzo, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Civetta, L.; Dipartimento di Scienze Fisiche, Universita` di Napoli Federico II, Napoli, Italy; Wulf, S.; GFZ German Research Centre for Geosciences; Smith, V. C.; Research Laboratory for Archaeology and the History of Art, University of Oxford; Hardiman, M.; Centre of Quaternary Research, Department of Geography, Royal Holloway University of London; Lane, C. S.; Centre of Quaternary Research, Department of Geography, Royal Holloway University of London; Carandente, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Orsi, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Rosi, M.; Dipartimento di Scienze della Terra, Universita` di Pisa,; Muller, W.; Department of Earth Sciences, Royal Holloway University of London; Menzies, M. A.; Department of Earth Sciences, Royal Holloway University of London Abstract: Volcanic activity at Phlegraean Fields, Italy, produced several major marker tephras over a 50 ka period. The caldera forming eruptions of the Campanian Ignimbrite (CI) and Neapolitan Yellow Tuff (NYT) are of particular importance for tephrostratigraphy in Europe. Other key eruptions from this source include the Pomici Principali (PP) and the Tufi Biancastri eruptions. We combine analyses of fresh glasses from proximal locations (i.e., juvenile clasts in proximal flow and fall deposits) with data for key tephra layers from Lago Grande di Monticchio, 120 km to the east. The micron-beam major (EMPA) and trace (LA-ICP-MS) element glass dataset allows us to: (a) distinguish between tephra units produced from the Phlegraean Fields before and during the CI eruption (CI-series), and before and during the NYT and PP eruptions (NYT-series/PP); (b) discriminate between the CI and the geochemically similar Pre-CI pyroclastic deposits; (c) separate the NYT from Pre-NYT tephra units, although both major and trace elements do show significant overlap. The complex compositional overlap between Pre-NYT tephras may present a problem for tephra correlations in the 14–39 ka time window and may have resulted in incorrect proximal–distal and distal–distal correlations. The diagnostic chemical criteria detailed herein permits more accurate matching of distal tephras with their proximal equivalents and hence will improve chronostratigraphy of distal settings and give insight into tephra dispersal. We show that the dispersal of PP tephra was more limited than previously thought. The surge/fall (Lower Member) and subsequent pyroclastic density current (Upper Member) phases of the NYT eruption can be recognised in distal settings. Both the NYT Lower and Upper Members are found in distal localities to the east of the Phlegraean Fields, however the Lower Member is found in the absence of the Upper Member in locations to the far north of Phlegraean Fields. Chemical compositions of the Plinian and ignimbrite phases of the CI eruption overlap extensively, but can be distinguished on a plot of Zr–Th. 2012-04-30T22:00:00Z http://hdl.handle.net/2122/7950 Title: Fluorine adsorption by volcanic soils at Mt. Etna, Italy Authors: D'Alessandro, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Bellomo, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Parello, F.; Università di Palermo, Dipartimento DiSTeM Abstract: Fluorine adsorption experiments were performed on 28 samples of the first 5 cm of topsoil collected on the flanks of Mt. Etna. The soil samples were equilibrated with F-rich rainwater (3.25 mg/L) at a soil/water weight ratio of 1/25. Aliquots of the supernatant were collected after 1, 7, 72, 720 and 5640 h and analysed for F content. The soil samples could be subdivided into three groups based on their F-adsorption behaviours after 1 h and at the end of the experiment: (1) negative adsorption (F released from the soil to the solution) after 1 h and negative or moderately positive adsorption at the end, (2) from negative after 1 h to strongly positive adsorption at the end, and (3) always strong positive adsorption. The adsorption capacity of the soils was positively correlated with the soil pH, the contents of finer granulometric fractions (clay and silt) and the weathering stage (as quantified by the chemical alteration index). The most F adsorbing soils are found at the periphery of the volcano where aquifers are more vulnerable to contamination due to the shallower depth of the water table. This study further evidences the importance of the Etnean soils in protecting groundwater from an excessive magmatic F input. 2012-05-31T22:00:00Z http://hdl.handle.net/2122/7872 Title: Total CO2 output from Vulcano Island (Aeolian Islands, Italy) Authors: Inguaggiato, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Mazot, A.; GNS Science Wairakei Research Center; New Zealamd; Diliberto, I. S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Inguaggiato, C.; Universita' di Palermo, Italy; Madonia, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Rouwet, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Vita, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia Abstract: Total CO2 output from fumaroles, soil gas, bubbling gas discharges and water dissolved gases discharged from the island, was estimated for Vulcano island, Italy. The CO2 emission from fumaroles from the La Fossa summit crater was estimated from the SO2 crater output, while CO2 discharged through diffuse soil emission was quantified on the basis of 730 measurements of CO2 fluxes from the soil of the island, performed by using the accumulation chamber method. The results indicate an overall output of ≅500 t/day of CO2 from the island. The main contribution to the total CO2 output comes from the summit area of the La Fossa cone (453 t/day), with 362 t/day from crater fumaroles and 91 t/day from crater soil degassing. The release of CO2 from peripheral areas is ≅20 t/day by soil degassing (Palizzi and Istmo areas mainly), an amount comparable to both the contribution of water dissolved CO2 (6 t/day), as well as to seawater bubbling CO2 (4 t/day measured in the Istmo area). Presented data (September 2007) refer to a period of moderate solphataric activity, when the fumaroles temperature were 450°C and gas/water molar ratio of fumaroles was up to 0.16. The calculated total CO2 emission allows the estimation of the mass release and related thermal energy from the volcanic-hydrothermal system. 2012-02-28T23:00:00Z http://hdl.handle.net/2122/7835 Title: Regional variations in the chemical and helium–carbon isotope composition of geothermal fluids across Tunisia Authors: Fourré, E.; Di Napoli, R.; Aiuppa, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Parello, F.; Gaubi, E.; Jean-Baptiste, P.; Allard, P.; Calabrese, S.; Mamou, A. Ben Abstract: Tunisia has numerous thermo-mineral springs. Previous studies have shown that their chemical composition and occurrence are strongly influenced by the regional geology. However little work has been done so far to study the isotopic composition of volatiles associated with these geothermal manifestations. Here, we report on the results of an extensive survey of both natural hot springs and production wells across Tunisia, aimed at investigating the spatial distribution of thermal fluids' geochemical characteristics and He–C isotopic composition. The chemistry of the analyzed samples highlights the heterogeneity of the water mineralization processes in Tunisia, as a consequence of the complex geological and tectonic setting of the country. In terms of chemical composition, we are able to conclude, however, that dissolution of halite and gypsum plays a key control on groundwater chemistry. Helium and carbon isotope systematics confirm the prevalently crustal origin of the volatiles interacting with the aquifer systems, consistent with the absence of any recent magmatism. Most samples are characterized by crustal-type helium (3He/4He in the range 0.02 Ra–0.4 Ra) associated with a CO2 predominantly metamorphic in origin (with the exception of the Saharan platform where the carbon content is low and mostly organically-derived). In Eastern Tunisia, however, a few samples have He–C isotope compositions which suggest (at least partial) mantle derivation of the dissolved gas phase : the 3He/4He ratio reaches 2.4 Ra (corresponding to 30% of mantle-derived helium) at the Ain Garci site, a CO2 rich mineral spring located some 30 km south of the city of Zaghouan. This mantle signature is consistent with the fact that the Pelagian Block, to which Eastern Tunisia belongs, has been deeply affected by extensional and transtensional tectonics since the opening of the Tethys, a process which is still ongoing in the Sicily channel (Pantelleria Rift). As a whole however, our results show that the Italian mantle gas anomaly only marginally extends to Northwestern Africa. 2010-12-31T23:00:00Z