Search results for "BASAL"
showing 10 items of 920 documents
First observational evidence for the CO<sub>2</sub>-driven origin of Stromboli's major explosions
2011
Abstract. We report on the first detection of CO2 flux precursors of the till now unforecastable "major" explosions that intermittently occur at Stromboli volcano (Italy). An automated survey of the crater plume emissions in the period 2006–2010, during which 12 such explosions happened, demonstrated that these events are systematically preceded by a brief phase of increasing CO2/SO2 weight ratio (up to >40) and CO2 flux (>1300 t d−1) with respect to the time-averaged values of 3.7 and ~500 t d−1 typical for standard Stromboli's activity. These signals are best explained by the accumulation of CO2-rich gas at a discontinuity of the plumbing system (decreasing CO2 emission at the surfa…
Rapid onset of mafic magmatism facilitated by volcanic edifice collapse: MAFIC MAGMATISM FACILITATED BY VOLCANIC EDIFICE COLLAPSE
2015
Volcanic edifice collapses generate some of Earth's largest landslides. How such unloading affects the magma storage systems is important for both hazard assessment and for determining long-term controls on volcano growth and decay. Here we present a detailed stratigraphic and petrological analyses of volcanic landslide and eruption deposits offshore Montserrat, in a subduction zone setting, sampled during Integrated Ocean Drilling Program Expedition 340. A large (6–10 km3) collapse of the Soufriere Hills Volcano at ~130 ka was followed by explosive basaltic volcanism and the formation of a new basaltic volcanic center, the South Soufriere Hills, estimated to have initiated <100 years after…
Atmospheric sources and sinks of volcanogenic elements in a basaltic volcano (Etna, Italy)
2011
Abstract This study reports on the first quantitative assessment of the geochemical cycling of volcanogenic elements, from their atmospheric release to their deposition back to the ground. Etna’s emissions and atmospheric depositions were characterised for more than 2 years, providing data on major and trace element abundance in both volcanic aerosols and bulk depositions. Volcanic aerosols were collected from 2004 to 2007, at the summit vents by conventional filtration techniques. Precipitation was collected, from 2006 to 2007, in five rain gauges, at various altitudes around the summit craters. Analytical results for volcanic aerosols showed that the dominant anions were S, Cl, and F, and…
Crater Gas Emissions and the Magma Feeding System of Stromboli Volcano
2013
Quiescent and explosive magma degassing at Stromboli volcano sustains high-temperature crater gas venting and a permanent volcanic plume which constitute key sources of information on the magma supply and dynamics, the physical processes controlling the explosive activity and, more broadly, the volcano feeding system. The chemical composition and the mass output of these crater emissions (gases, trace metals, radioactive isotopes) were measured using different methodologies: within-plume airborne measurements, ground-based plume filtering, and/or in situ analysis, remote UV and open-path Fourier transform infrared absorption spectroscopy. The results obtained, summarized in this paper, demo…
Large- and Fine-Scale Geochemical Variations Along the Andean Arc of Northern Chile (17.5°– 22°S)
1994
Geochemical data from 37 volcanic centres from the active volcanic front in the Central Andes between 17.5° and 22°S of northern Chile provide constraints on crustal contributions to arc magma genesis in that region. Crustal thickness, distance from the trench, height above the seismically active subduction zone, and sediment supply to the trench are all constant along this segment of the arc. The only significant variable along the current arc segment is in mean crustal age (Palaeozoic in the south to Proterozoic in the north). In addition, the crustal thickness has varied through time from around 40 km in the Lower Miocene to about 70 km today. Variations along the N-S chain of the volcan…
Mercury concentration, speciation and budget in volcanic aquifers: Italy and Guadeloupe (Lesser Antilles)
2009
Abstract Quantifying the contribution of volcanism to global mercury (Hg) emissions is important to understand the pathways and the mechanisms of Hg cycling through the Earth's geochemical reservoirs and to assess its environmental impacts. While previous studies have suggested that degassing volcanoes might contribute importantly to the atmospheric budget of mercury, little is known about the amount and behaviour of Hg in volcanic aquifers. Here we report on detailed investigations of both the content and the speciation of mercury in aquifers of active volcanoes in Italy and Guadeloupe Island (Lesser Antilles). In the studied groundwaters, total Hg (THg) concentrations range from 10 to 500…
Mercury content and speciation in the Phlegrean Fields volcanic complex: evidence from hydrothermal system and fumaroles
2009
Abstract Mercury is outstanding among the global environmental pollutants of continuing concern. Although degassing of active volcanic areas represents an important natural source of mercury into the atmosphere, still little is known about the amount and behaviour of Hg in volcanic aquifers, especially regarding its chemical speciation. In order to assess the importance of mercury emissions from active volcanoes, thermal waters were sampled in the area surrounding La Solfatara, Pozzuoli bay. This is the most active zone of the Phlegrean Fields complex (coastal area north–west of Naples), with intense hydrothermal activity at present day. Studied groundwaters show total Hg (THg) concentratio…
An Overview of the Hypogene Caves of Sicily
2017
Karst in Sicily develops in both Messinian gypsum and Mesozoic or Tertiary limestone rocks. Caves are also found in the basalts of Mount Etna. Except for some rare cases, until recently most caves developed in limestone were considered to be of epigenetic origin. The discovery of gypsum in some of these caves, and especially detailed morphological studies, have allowed defining a hypogenic origin for a dozen of caves up to now. In some of these, the hypogenic evidences are very clear, while others remain in doubt because of the widespread presence of well-developed condensation-corrosion morphologies not necessarily related to hydrothermal fluids. This paper reports the present knowledge of…
Investigation of the He solubility in H2O-CO2 bearing silicate liquids at moderate pressure: a new experimental method
2000
We have designed the first available experimental method capable to investigate the solubility of inert gases in H2O–CO2 bearing silicate melts in a large range of pressures. The method overcomes the difficulties imposed by the physical state of volatiles at room conditions. Experiments were done by using an internally heated pressure vessel, where sealed capsules containing the sample are introduced. The peculiarity of the method consists in the capability of loading, in accurately known proportions (even lower than ppm), volatiles in a gaseous state at room conditions. Gas is loaded as a weighed amount of a gas-bearing glass, which was previously prepared by using the same gas as a pressu…
Sources, degassing, and contamination of CO2, H2O, He, Ne, and Ar in basaltic glasses from Kolbeinsey Ridge, North Atlantic
2005
Abstract New volatile data (CO2, H2O, He, Ne, and Ar) are presented for 24 submarine basaltic glasses from the Kolbeinsey Ridge, Tjornes Fracture Zone and Mohns Ridge, North Atlantic. Low CO2 and He contents indicate that magmas were strongly outgassed with the extent of degassing increasing toward the south, as expected from shallower ridge depths. Ne and Ar are significantly more abundant in the southernmost glasses than predicted for degassed melt. The strong atmospheric isotopic signal associated with this excess Ne and Ar suggests syn- or posteruptive contamination by air. Degassing, by itself, cannot generate the large variations in δ13C values of dissolved CO2 or coupled CO2-Ar varia…