Podrobnosti záznamu

    Geochemical and geochronological arguments for heterogeneous nature and complex development of Variscan lower continental crust: Náměšť Granulite Massif (Bohemian Massif, Czech Republic)
    Fanning, Mark
    Hasalová, Pavlína
    Janoušek, Vojtěch
    Kusbach, Vladimír
    Schulmann, Karel
    Ulrich, Stanislav
Typ dokumentu
    článek ve sborníku
Zdrojový dokument - monografie
    Géologie de la France
    Akce: 2012 ; Sassari
Výraz tezauru
    granulites, Moldanubian Unit, Náměšť, geochemistry, age, SHRIMP, genesis
Klíčové slovo
Abstrakt (anglicky)
   The felsic granulites of the Náměšť Granulite Massif represent a subducted Early Devonian continental crust, while the associated tholeiitic metabasites were probably generated during Cambro-Ordovician rifting. Based on these characteristics and contrasting P-T data we adopt a model of lower crustal relamination of low-density continental crust below autochthonous dense mafic root of the Moldanubian Continent. The difference in Zrn ages attributed to the HP metamorphic climax between the Náměšť granulite (~353 Ma) and other granulite massifs (~340 Ma; e.g., Wendt et al., 1994; Kröner et al., 2000; Friedl et al., 2011) is interpreted in terms of diachronous emplacement and different time scale of thermal maturation of western and eastern portions of the relaminated crust. Our work also shows that the mantle was refertilized before its incorporation into the crust, a feature typical of asthenospheric mantle below slow spreading rifts. Therefore, it is very likely that the Late Devonian h
   istory recorded in the mantle fragment (whose cooling was constrained by the Sm-Nd Grt-Px age of ~370 Ma: Medaris et al., 2006) reflects heterogeneous nature of the local subcontinental mantle lithosphere related to the Devonian rifting (most likely in back-arc of the Saxothuringian subduction), i.e. unrelated to the surrounding felsic granulites. The place of juxtaposition of the mantle fragment to the granulite is impossible to determine, but the likely Late Devonian age coincides well with the onset of the magmatic-arc related plutonic activity in the Teplá-Barrandian Unit (Štěnovice and Čistá plutons, as well as orthogneisses in the roof pendants of the Central Bohemian Plutonic Complex; Košler et al., 1993; Žák et al., 2011).
    Česká geologická služba
Kód přispěvatele
    ČGS (RIV)
Zdrojový formát
Datum importu
    15. 10. 2014