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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Environmental geology 39 (2000), S. 963-976 
    ISSN: 1432-0495
    Schlagwort(e): Key words Larsemann Hills ; Antarctica ; Trace metals ; Water geochemistry ; Anthropogenic contamination
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie
    Notizen: Abstract Fresh water lakes are found in basement rock basins in the Larsemann Hills, East Antarctica, during the summer months. These lakes constitute a relatively simple natural laboratory to investigate the effects of recent and well-documented anthropogenic impact on a “pristine” environment. Larsemann Hills freshwaters have extremely low salinity (typically 〈1‰), and contain very low concentrations of trace elements of environmental significance such as Pb, U, and Zn. Typical Pb concentrations range from less than 5 ppt to 250 ppt. Although trace metal concentrations appear to be higher in lakes situated in the vicinity of stations, they are consistently lower (by several orders of magnitude, for some elements) than Standard International Drinking Water Guidelines. The chemistry of the lake waters is dominated by sea-spray input. Consequently, it is primarily a function of geographical factors, such as distance from the shore and exposure to winds. Shallow-level groundwater and surface water also contribute to the lake chemistry. No evidence was found for contamination from global air circulation. Although contamination resulting from activities at the research stations is generally near or below detection levels, very low levels of trace metal anthropogenic contamination were found in the vicinity of some research stations.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2017-04-04
    Beschreibung: Tectonic activity in convergent plate boundaries commonly involves backward migration (rollback) of narrow subducting slabs and segmentation of subduction zones through slab tearing. Here we investigate this process in the Italian region by integrating seismic tomography data with spatio-temporal analysis of magmatic rocks and kinematic reconstructions. Seismic tomography results show gaps within the subducting lithosphere, which are interpreted as deep (100-500 km) sub-vertical tear faults. The development of such tear faults is consistent with proposed kinematic reconstructions, in which different rates of subduction rollback affected different parts of the subduction zone. We further suggest a possible link between the development of tear faults and the occurrence of regional magmatic activity with transitional geochemical signatures between arc-type and OIB-type, associated with slab tearing and slab breakoff. We conclude that lithospheric- scale tear faults play a fundamental role in the destruction of subduction zones. As such, they should be incorporated into reconstructions of ancient convergent margins, where tear faults are possibly represented by continental lineaments linked with magmatism and mineralization.
    Beschreibung: Unpublished
    Beschreibung: 3.3. Geodinamica e struttura dell'interno della Terra
    Beschreibung: JCR Journal
    Beschreibung: open
    Schlagwort(e): Continental margins: convergent ; Subduction zone processes ; Tomography ; Tectonics and magmatism ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: manuscript
    Standort Signatur Erwartet Verfügbarkeit
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