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  • 04. Solid Earth::04.04. Geology::04.04.05. Mineralogy and petrology  (3)
  • AGU  (1)
  • ICC97 Organizing Committee, Ottawa (CAN)  (1)
  • Nature Publishing Group
  • 2010-2014  (3)
  • 1985-1989
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Years
Year
  • 1
    Publication Date: 2017-04-04
    Description: Mineralogical and textural variations in Upper Pleistocene and Holocene clay sediments from three cores taken in different depositional environments: the Venetian lagoonal littoral zone, the South Yellow Sea and the Yangtze River Delta, are reported. The compositional variations of clay layers from the three sites are attributed to major global climatic changes. Although the compositional difference of clay sediments of the three sites reflects the petrology of their different areas of provenance, the relative abundance and textural variations show a correlation with climatic-driven changes in their depositional environment. In the Venice lagoon the carbonate content decreases from cold to warm periods whereas in the Yangtze River delta and in the South Yellow Sea carbonates are absent or not significant, and the most noticeable changes are given by the total clay mineral content variations (chlorite, smectite, mixed-layer clay minerals and muscovite) and feldspar. There is a general increase in abundance of clay minerals and a decrease in feldspar content during warm periods. The cores from all three study sites have overconsolidated continentally-derived clay layers at the Pleistocenel/Holocene (ca. 10,000 BP) boundary. The overconsolidated nature of these hard clay layers is due to long subaerial exposure under a cold and dry climatic regime before the Holocene (Flandrian) transgression.
    Description: Published
    Description: Ottawa, Canada
    Description: 3A. Ambiente Marino
    Description: open
    Keywords: Mineralogical and textural variations ; Upper Pleistocene and Holocene clay sediments ; Venetian lagoonal littoral ; South Yellow Sea ; Yangtze River Delta ; 04. Solid Earth::04.04. Geology::04.04.05. Mineralogy and petrology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Conference paper
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  • 2
    Publication Date: 2017-04-04
    Description: In recent decades, geophysical investigations have detected wide magma reservoirs beneath quiescent calderas. However, the discovery of partially melted horizons inside the crust is not sufficient to put constraints on capability of reservoirs to supply cataclysmic eruptions, which strictly depends on the chemical-physical properties of magmas (composition, viscosity, gas content etc.), and thus on their differentiation histories. In this study, by using geochemical, isotopic and textural records of rocks erupted from the high-risk Campi Flegrei caldera, we show that the alkaline magmas have evolved toward a critical state of explosive behaviour over a time span shorter than the repose time of most volcanic systems and that these magmas have risen rapidly toward the surface. Moreover, similar results on the depth and timescale of magma storage were previously obtained for the neighbouring Somma-Vesuvius volcano. This consistency suggests that there might be a unique long-lived magma pool beneath the whole Neapolitan area.
    Description: Published
    Description: article 712
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: 3.5. Geologia e storia dei vulcani ed evoluzione dei magmi
    Description: 3.6. Fisica del vulcanismo
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: N/A or not JCR
    Description: open
    Keywords: magma ; campi flegrei caldera ; 04. Solid Earth::04.04. Geology::04.04.05. Mineralogy and petrology ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
    Publication Date: 2017-04-04
    Description: Accepted for publication in Reviews of Geophysics. Copyright (2010) American Geophysical Union
    Description: Greigite (Fe3S4) is an authigenic ferrimagnetic mineral that grows as a precursor to pyrite during early diagenetic sedimentary sulfate reduction. It can also grow at any time when dissolved iron and sulfide are available during diagenesis. Greigite is important in paleomagnetic, environmental, biological, biogeochemical, tectonic, and industrial processes. Much recent progress has been made in understanding its magnetic properties. Greigite is an inverse spinel and a collinear ferrimagnet with antiferromagnetic coupling between iron in octahedral and tetrahedral sites. The crystallographic c-axis is the easy axis of magnetization, with magnetic properties dominated by magnetocrystalline anisotropy. Robust empirical estimates of the saturation magnetization, anisotropy constant, and exchange constant for greigite have been obtained recently for the first time, and the first robust estimate of the low-field magnetic susceptibility is reported here. The Curie temperature of greigite remains unknown, but must exceed 350°C. Greigite lacks a low-temperature magnetic transition. Based on preliminary micromagnetic modeling, the size range for stable single domain behavior is 17-200 nm for cubic crystals and 17-500 nm for octahedral crystals. Gradual variation in magnetic properties is observed through the pseudo-single domain size range. We systematically document the known magnetic properties of greigite (at high, ambient and low temperatures, and with alternating and direct fields) and illustrate how grain size variations affect magnetic properties. Recognition of this range of magnetic properties will aid identification and constrain interpretation of magnetic signals carried by greigite, which is increasingly proving to be environmentally important and responsible for complex paleomagnetic records, including widespread remagnetizations.
    Description: In press
    Description: 2.2. Laboratorio di paleomagnetismo
    Description: JCR Journal
    Description: open
    Keywords: greigite ; 04. Solid Earth::04.04. Geology::04.04.05. Mineralogy and petrology ; 04. Solid Earth::04.04. Geology::04.04.08. Sediments: dating, processes, transport ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism ; 04. Solid Earth::04.05. Geomagnetism::04.05.07. Rock magnetism ; 04. Solid Earth::04.05. Geomagnetism::04.05.09. Environmental magnetism
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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