122,407 research outputs found
Structural features of the shallow plumbing system of Vulcano Island Italy
No full textAbstract In this study, we integrate information gathered
from surface geology and tectonics with the results of a
shallow (0–2 km b.s.l.) seismic tomography of Vulcano
Island (Italy), obtained from the analysis of local
earthquakes. The observed low Vp regions correspond
to caldera filling products, mainly consisting of pyroclastics,
tuffs, lava flows and hyaloclastites. High-velocity
anomalies represent intrusive bodies. The striking correspondence
between the stratigraphy from deep wells and
the calculated velocity structure allows us to reconstruct
the geometry and distribution of a main intrusion and to
recognize some intra-caldera depressions. The shape and
location of the high and low Vp anomalies are consistent
with NW–SE and N–S strikes. Eruptive centres younger
than 42 kyr, as well as the structural depressions of
Vulcano and of the neighbour Lipari Island, align along a
N–S direction. The combined interpretation of the
available structural data and of the results from the
tomography suggests that magmatic reservoirs of Vulcano
at shallow depth (>0.5 km) align along a NW–SE strike
but their shape is controlled by N–S striking normal faults
and/or cracks that accommodate the right-lateral movements
of the NW–SE strike-slip fault system.Publishedreserve
Continuous SO2 flux measurements for Vulcano Island, Italy
No full textThe La Fossa cone of Vulcano Island (Aeolian Archipelago, Italy) is a closed conduit volcano. Today, Vulcano Island is characterized by sulfataric activity, with a large fumarolic field that is mainly located in the summit area. A scanning differential optical absorption spectroscopy instrument designed by the Optical Sensing Group of Chalmers University of Technology in Göteborg, Sweden, was installed in the framework of the European project "Network for Observation of Volcanic and Atmospheric Change", in March 2008. This study presents the first dataset of SO2 plume fluxes recorded for a closed volcanic system. Between 2008 and 2010, the SO2 fluxes recorded showed average values of 12 t.d–1 during the normal sulfataric activity of Vulcano Island, with one exceptional event of strong degassing that occurred between September and December, 2009, when the SO2 emissions reached up to 100 t.d–1.</p
Geografie mostruose : Frankenstein, il ghiaccio e il vulcano
No full textL'intervento si concentra sulla relazione fra l'eruzione del vulcano Tambora nell'aprile del 1815, con le conseguenze climatiche eccezionali che essa genera, e la composizione del romanzo di Mary Shelley. Il mito di Frankenstein, da una parte, è strettamente connesso al ghiaccio e alle montagne, inserendosi nella dimensione del sublime, dall'altra all'elettricità e al fuoco. La narrazione si conclude con l'immagine di una grande pira funebre, emblema della morte del mostro e del suo ricongiungimento con la figura del creatore, che evoca un'eruzione vulcanica
Rare Sulfosalts from Vulcano, Aeolian Island, Italy,. IV Lillianite
No full textExcellent samples of lillianite, a rare Pb-Bi sulfosalt, have found around a high-temperature fumarole at the La Fossa crater, Vulcano Island, Italy. The mineral is associated with cannizzarite and, subordinately, with galenobismutite and rare sulfosalts, as wel as sphalerite and selenian galena. Lillianite occurs as laths and fibers up to 100-130 /um in length, and about 20-30 and 1 /um in width, respectively. Electron-microprobe analyses show that the lillianite from Vulcano has a composition close to the ideal Pb3Bi2S6. Particularly interesting is the absence of Ag and Cu, which makes the lillianite from Vulcano unique in its putity, with minor incorporation of Cd. Like in other sulfosalts from Vulcano, significant Se concentrations are invariably present (1.38-2.22 wt. %). Traces of chlorine were found in some crystals due to the high Cl activity in the fumaroles, and are noted for first time. The general empirical formula,Pb3-x Bi2+2x/3(S6-y Sey)6, reflects the narrow composition field for the lillianite from Vulcano. The X-Ray powder-diffraction data, as well as microhardness and reflectance measurements, are given for distinct crystals with a different Pb/Bi value. The unit-cell constants are a=13.576(9), b=20.606(8), c=4.119(2) A for the crystal with Pb/Bi =1.50, and a=13.56(1), b=20.57(1), c=4.115(2) A for the one with Pb/Bi=1.41. In both films, h+l=2n reflections correspondto the space group Bbmm.The lower value of microhardness of the Bi-rich sample may reflect the less well-ordered structure and the effect of heterovalent substitution 3Pb2+ -> 2Bi3+ + vac.. A comparison between the lillianite from Vulcano and the synthetic homologous Phase III is also given
Rare Sulfosalts from Vulcano, Aeolian Islands, Italy,. V Selenian Heyrovskyite
No full textHeyrovskyite, a rare Pb-Bi sulfosalt, was found around a fumarole of ca. 500 °C at the La Fossa crater, Vulcano Island, Italy. The mineral occurs in the thin sulfosalt-rich crust covering the brecciated altered rocks of fumaroles, mainly admixed with selenian varieties of lillianite and cannizzarite, with subordinate galenobismutite and galena. Heyrovskyite occurs as thin needle-like crystals up to 300 /um in length and less than 1 /um in width. No traces of a breakdown texture have been noticed in any of the crystals studied. Electron-microprobe analyses show that the heyrovskyite from Vulcano has a composition close to the ideal Pb-rich composition of synthetic Phase ii, Pb6Bi2S9, obtained by Salanci &Moh in 1969. Particularly interesting is the absence of Ag and Cu, which makes the heyrovskyite from Vulcano unique, with respect to cations; only a minor amount of a Cd impurity is present. Like in other sulfosalts from Vulcano, significant Se concentrations are invariably present /(0.95-2.5 wt. %). The compositional field of heyrovskyite from Vulcano, expressed in terms of the mol.% Bi2S3, ranges from 14.23% (the most Pb-rich composition) up to 15.24% (the most Bi-rich), averaging 14.73 mol.%. This very narrow compositional spread (1 mol. %) is in the range attributable to analytical error;the composition of heyrovskyite from Vulcano is thus quite constant in terms of Pb- for-Bi substitution. The calculated average composition corresponds to the empirical formula (Pb5.95Cd0.02)5.97 Bi2.06 (S8.53Se0.44)8.97, which is close to the ideal end-member, Pb6Bi2S9. The cell parameters, resulting from an X-ray powder-diffraction study, are a=13.734(7), b=31.28(3), c=4.135(3) A. The reflections having h+l=2n are indicative of space group Bbmm. The cell parameters of heyrovskyite from Vulcano have been compared with those in the literature for heyrovskyite from various deposits and with those of synthetic Phase II. There is not general agreement among the data reported by different authors. These data, together with the compositional differences, in terms of mol.% Bi2S3, among various natural and synthetic products, suggest that the range occupied by synthetic Phase II consists of many chemically and structurally very similar compounds. In particular, the Pb-rich part of the compositional field of the Phase II might be considered as the synthetic analogue of heyrovskyite from Vulcano
Aeromagnetic data provide new insights on the volcanism and tectonics of Vulcano Island and offshore areas (southern Tyrrhenian Sea, Italy)
No full textThe active Vulcano Island (Southern Tyrrhenian Sea)
represents the southernmost portion of a NW-SE elongated
volcanic ridge that includes also Lipari and Salina islands.
The ridge is affected by a regional, NW-SE to N-S striking
fault system. The elaboration and analysis of data from
three high-resolution aeromagnetic surveys carried out
between 1999 and 2004 on Vulcano and offshore allow us
to recognize high intensity magnetic anomalies related to
volcanic centers/conduits or shallow intrusions. Previously
unreported offshore submarine vents have been also
recognized. Some of them may correspond with source
areas of outcropping exotic pyroclastics on Vulcano. The
spatial analysis of the recognized magnetic anomalies and
volcanic structures shows that they are preferably aligned
along the strikes of the main regional faults that affect the
volcanic ridge. Submarine volcanic conduits revealed by
the aeromagnetic survey might represent potential sources
for future submarine, effusive or explosive activity.PublishedL153053.8. Geofisica per l'ambienteJCR Journalreserve
Data for the synthesis of oligo-gamma-glutamylglutamines as model compounds for gamma-glutamyltransferases (GGTs) and for normalization of activities of different GGTs
No full textgamma-Glutamyltransferases (GGTs) are widespread, conserved enzymes that catalyze the transfer of the gamma-glutamyl moiety from a donor substrate to water (hydrolysis) or to an acceptor amino acid (transpeptidation) through the formation of a gamma-glutamyl enzyme intermediate.
Although the vast majority of the known GGTs has a short sequence called lid-loop covering the glutamate binding site, B. subtilis GGT and some other enzymes from Bacillus spp. lack the lid loop. In order to assess the possible role of the lid loop of GGTs in substrate selection, synthetic oligo-gamma-glutamylglutamines containing up to three gamma-glutamyl residues were used as model substrates. The activities of the enzymes under investigation were standardized with respect to a common reaction to ensure comparable results. The activity of an engineered mutant enzyme containing the amino acid sequence of the lid loop from E. coli GGT inserted into the backbone of B. subtilis GGT was compared to that of the lid loop-deficient B. subtilis GGT and the lid loop-carrier E. coli GGT (Calvio, Romagnuolo, Vulcano, Speranza, Morelli Enz. Micr. Technol. 2018 [1]). Here we report the experimental procedures for the synthesis of model substrates gamma-glutamylglutamines through the method of the N-phtaloyl-L-glutamic acid anhydride and the spectral data of the synthetized compounds. The data obtained in the normalization procedure of the activities of the three enzymes are also reported
Diffuse CO2 soil degassing and CO2 and H2S air concentration and related hazard at Vulcano Island (Aeolian arc, Italy).
No full textLa Fossa crater on Vulcano Island is quiescent since 1890. Periodically it undergoes “crises” characterized by
marked increase of temperature (T), gas output and concentration of magmatic components in the crater
fumaroles (T may exceed 600 °C). During these crises, which so far did not lead to any eruptive reactivation,
the diffuse CO2 soil degassing also increases and in December 2005 an anomalous CO2 flux of 1350 tons/day
was estimated by 1588 measurements over a surface of 1.66 km2
extending from La Fossa crater to the
inhabited zone of Vulcano Porto. The crater area and two other anomalously degassing sites (Levante Beach
and Palizzi) have been periodically investigated from December 2004 to August 2010 for diffuse CO2 soil flux.
They show a marked variation with time of the degassing rate, with synchronous maxima in December 2005.
Carbon dioxide soil flux and environmental parameters have been also continuously monitored for over one
year by an automatic station at Vulcano Porto. In order to assess the hazard of the endogenous gas emissions,
CO2 and H2S air concentrations have been measured by Tunable Diode Laser profiles near the fumaroles of the
crater rim and of the Levante Beach area, where also the viscous gas flux has been estimated. In addition, CO2
air concentration has been measured both indoor and outdoor in an inhabited sector of Vulcano Porto. Results
show that in some sites usually frequented by tourists there is a dangerous H2S air concentration and CO2
exceeds the hazardous thresholds in some Vulcano houses. These zones should be immediately monitored for
gas hazard should a new crisis arise.INGV-DPC programme - Project V5-Diffuse degassing in Italy; Airplane FIRB project of the Italian Ministry of the University and ResearchPublished130-1441.2. TTC - Sorveglianza geochimica delle aree vulcaniche attiveJCR Journalpartially_ope
Energetics of chemolithoautotrophy in the hydrothermal system of Vulcano Island, Southern Italy
No full textThe hydrothermal system at Vulcano, Aeolian Islands (Italy), is home to a wide variety of thermophilic,chemolithoautotrophic archaea and bacteria. As observed in laboratory growth studies, these organisms may use an array of terminal electron acceptors (TEAs), including O
2, NO-3,Fe(III),elemental sulphur and CO2;
electron donors include H2,Fe2+,H2S and CH4. Concentrations of inorganic aqueous species and gases were measured in 10 hydrothermal fluids from seeps, wells and vents on Vulcano. These data were combined with standard Gibbs free energies ( ) to calculate overall Gibbs free energies (DGr) of 90 redox reactions that involve 16 inorganic N-, S-, C-, Fe-, H- and O-bearing compounds. It is shown that oxidation reactions
with O2 as the TEA release significantly more energy (normalized per electron transferred) than most anaerobic oxidation reactions, but the energy yield is comparable or even higher for several reactions in which, or Fe(III) serves as the TEA. For example, the oxidation of CH4 to CO2
coupled to the reduction of Fe(III) in magnetite to Fe2+ releases between 94 and 123 kJ/mol e–
, depending on the site. By comparison, the aerobic oxidation of H2 or reduced inorganic N-, S-, C- and Fe-bearing compounds generally yields between 70 and 100 kJ/mol e–. It is further shown that the energy yield from the reduction of elemental sulphur to H2 S is relatively low (8–19 kJ/mol e–) despite being a very common metabolism among thermophiles. In addition,for many of the 90 reactions evaluated at each of the 10 sites, values of DGr tend to cluster with differences
< 20 kJ/mol e–. However, large differences in
DGr up to ~ 60 kJ/mol e–) are observed in Fe redox reactions, due largely to considerable variations in Fe 2+, H + and H2 concentrations. In fact, at the sites investigated, most
variations in DGr arise from differences in composition and not in temperature.Published37–58partially_ope
Geology, volcanic history and petrology of vulcano (central aeolian archipelago)
No full textVulcano is an active NW-SE-elongated composite volcano located in the central Aeolian archipelago. Based on available radiometric ages and tephrochronology, the exposed volcanism started at c. 127 ka and spread through eight Eruptive Epochs separated by volcano-tectonic events and major quiescent stages. Various eruptive centres and two intersecting multi-stage calderas resulted from such evolution. Vulcano geological history displays several changes of eruption magnitude, eruption styles and composition of magmas through time. Vulcano rocks range from basalt to rhyolite and show variable alkali contents, roughly increasing during time. Magmas with low to intermediate SiO2 contents and high-K to shoshonite affinity prevail in the early Epochs 1-5 (c. 127-28 ka), whereas intermediate to high-SiO2 shoshonite and potassic alkaline products dominate the last three Epochs (<30 ka). This sharp increase in silicic products is related to the shallowing of the plumbing system and resulting major role of the differentiation processes in shallowlevel reservoirs. Radiogenic isotope compositions are variable (87Sr/86Sr = 0.70424-0.70587, 143Nd/144Nd = 0.51254-0.51276, 206Pb/204Pb = 19.305-19.759, 207Pb/204Pb = 15.659-15.752, 208Pb/204Pb = 39.208-39.559) as a result of both source heterogeneities and shallow-level interaction of magmas with continental crust. The compositional variations of mafic magmatism with time suggest that the source zone changed from a metasomatized, fertile, ocean island basalt- (OIB-) like mantle to a metasomatized depleted lithospheric mantle. © The Geological Society of London 2013
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