http://hdl.handle.net/2122/120 Fri, 24 May 2013 01:10:37 GMT 2013-05-24T01:10:37Z http://hdl.handle.net/2122/7421 Title: A CO2-rich magma source beneath the Phlegraean Volcanic District (Southern Italy): Authors: Mormone, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Piochi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Bellatreccia, F.; Dipartimento di Scienze Geologiche, Università Roma Tre, Roma, Italy; De Astis, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Moretti, R.; Centro Interdipartimentale di Ricerca in Ingegneria Ambientale (CIRIAM) & Dipartimento di Ingegneria Civile, Seconda Università degli Studi di Napoli, Aversa (CE), Italy; Della Ventura, G.; Dipartimento di Scienze Geologiche, Università Roma Tre, Roma, Italy; Cavallo, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Mangiacapra, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia Abstract: We present a study of olivine-hosted glass/melt inclusions (MIs) in the most primitive rocks erupted at Procida Island, within the Phlegraean Volcanic District (PVD), Southern Italy. MIs were analyzed by combined Scanning Electron Microscopy coupled with Energy Dispersive X-ray-detectors, Wavelength Dispersive X-rayequipped Electron Microprobe and Fourier Transform Infrared (FT-IR) Spectroscopy; notably, the novel Focal- Plane-Array mode provided high-resolution FT-IR images evidencing the distribution of the C–H–O species across samples. Olivines range in composition from Fo85 to Fo90, do not show chemical zoning and are totally anhydrous. The majority of the MIs are glassy, while only few are completely crystallized. Some MIs, however, show the occurrence of crystal nuclei, i.e., nano- to micro-sized pyroxenes and oxides, and appear as lowcrystallized MIs. The glass of crystal-free and low-crystallized MIs shows K-affinity and a compositional range along the basalt, trachy-basalt, shoshonite, tephrite basanite and phono-tephrite array. H2O and CO2 contents up to 2.69 wt.% and 2653 ppm, respectively, define a major degassing trend with small isobaric deviations. The collected data allow recalculating entrapment pressures from ~350 MPa to b50 MPa and suggest that the magma ascent was dominated by degassing. Crystallization was aminor process, likely also consequent to local CO2-fluxing. Mingling occurred between variable degassed and crystallized magma portions during decompression. The geochemical and isotopic data of Procida glasses and rocks, and the compositional relationship between our MIs and those from slightly more evolved and radiogenic Phlegraean products, indicate that Procida basalts are an adequate parental end-member for the PVD. Our data suggest that a CO2- rich magma source was stored at depths of at least 13–14 km (i.e., 350 MPa) beneath the PVD. Fast ascent of magma batches directly started from this depth shortly before PVD trachy-basaltic to shoshonitic eruptions. Such results have implication on volcanic hazard assessment in the PVD area. Sun, 12 Jun 2011 22:00:00 GMT http://hdl.handle.net/2122/7421 2011-06-12T22:00:00Z http://hdl.handle.net/2122/5891 Title: Radar systems for Glaciology Authors: Zirizzotti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Urbini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cafarella, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Baskaradas, J. A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Editors: Kouemou, G. Abstract: This chapter deals with radar systems, measurements and instrumentation employed to study the internal core and bedrock of ice sheets in glaciology. The Earth's ice sheets are in Greenland and Antarctica. They cover about 10% of the land surface of the planet. The total accumulated ice comprises 90% of the global fresh water reserve. These ice sheets, associated with the ocean environment, provide a major heat sink which significantly modulates climate. Glaciology studies aim to understand the various process involved in the flow (dynamics), thermodynamics, and long-term behaviour of ice sheets. Studies of large ice masses are conducted in adverse environmental conditions (extreme cold, long periods of darkness). The development of remote sensing techniques have played an important role in obtaining useful results. The most widely used techniques are radar systems, employed since the 1950s in response to a need to provide a rapid and accurate method of measuring ice thickness. Year by year, polar research has become increasingly important because of global warming. Moreover, the discovery of numerous subglacial lake areas (water entrapped beneath the ice sheets) has attracted scientific interest in the possible existence of water circulation between lakes or beneath the ice (Kapitsa et al., 2006; Wingham et al., 2006; Bell et al., 2007). Recent studies in radar signal shape and amplitude could provide evidence of water circulation below the ice (Carter 2007, Oswald and Gogineni 2008). In this chapter the radar systems employed in glaciology, radio echo sounding (RES), are briefly described with some interesting results. RES are active remote sensing systems that utilize electromagnetic waves that penetrate the ice. They are used to obtain information about the electromagnetic properties of different interfaces (for example rock-ice, ice-water, seawater-ice) that reflect the incoming signal back to the radar. RES systems are characterized by a high energy (peak power from 10 W to 10 KW) variable transmitted pulse width (about from 0.5 ns to several microseconds) in order to investigate bedrock characteristics even in the thickest zones of the ice sheets (4755 m is the deepest ice thickness measured in Antarctica using a RES system). Changing the pulse length or the transmitted signal frequencies it is possible to investigate particular ice sheet details with different resolution. Long pulses allows transmission of higher power than short pulses, penetrating the thickest parts of the ice sheets but, as a consequence, resolution decreases. For example, the GPR system, commonly used in geophysics for rock, soil, ice, fresh water, pavement and structure characterization, employs a very short transmitted pulse (0.5 ns to 10 ns) that allow detailing of the shallow parts of an ice sheet (100-200 m in depth) (Reynolds 1997). Consequently, in recent years, GPR systems are also employed by explorers to find hidden crevasses on glaciers for safety. RES surveys have been widely employed in Antarctic ice sheet exploration and they are still an indispensable tool for mapping bedrock morphologies and properties of the last unexplored continent on Earth. The advantage of using these remote sensing techniques is that they allow large areas to be covered, in good detail and in short times using platforms like aeroplanes and surface vehicles. Thu, 31 Dec 2009 23:00:00 GMT http://hdl.handle.net/2122/5891 2009-12-31T23:00:00Z