Podrobnosti záznamu

    The fundamental Variscan problem: high-temperature metamorphism at different depths and high-pressure metamorphism at different temperatures
Údaj o odpovědnosti
    Patrick J. O'brien
Další názvy
    Orogenic Processes: Quantification and Modelling in the Variscan Belt (Variant.)
    O'Brien, Patrick J.
Zdrojový dokument - seriál
    Geological society special publication
    Vol. 179
    p. 369-386
    4 obr.
    Obsahuje bibliografické odkazy
    Zkr. název ser.: Geol. Soc. spec. Publ. (London)
Klasifikační znak
Skupina konspektu
Předmětová skupina
    kolize desek
    metamorfóza vysokostupňová
    podmínky P-T
    tepelný tok
    vrásnění variské
    zóna subdukční
Geografické jméno
    Evropa střední
Klíčové slovo
Abstrakt (anglicky)
   The evolution of the crystalline internal zone of the European variscides (i.e. Moldanubian and Saxo-Thuringian) is best understood within a framework of two distinct subduction stages. An early, pre-Late Devonian (older than 380 Ma), subduction stage is recorded in medium-temperature eclogites and blueshcists derived from low-pressure basaltic and gabbroic protoliths now found as minor relics in amphibolite facies meta-ophiolite or gneiss-metabasite nappe complexes. A second subduction and exhumation event produced further nappe complexes containing different types of mantle peridotites, along with their enclosed pyroxenites and high-temperature eclogites, associated with large volumes of high-T-high-P (900-1000 °C, 15-20 kbar) felsic granulites. Abundant geochronological evidence points to a Carboniferous age (c.
   340 Ma) for the high-P-high-T metamorphism as well as an extremely rapid exhumation because the fault-bounded, granulite-peridotite-bearing tectonic units are also cut by late Variscan granitic plutons (315-325 Ma). The massive heat energy for the characteristic, and most widespread feature of the Variscan event, the low-P-high-T metamorphism (750-800 °C. 4-6 kbar) and voluminous granitoid magmatism (325-305 Ma), comes from three sources. An internal heat component comes from imbrication of crust with upper-crustal radiogenic heat production potential in the region parallel to the subduction tone; an external mantle heat component is undoubtedly contributing to the transformation of crust taken to mantle depths (i.e. the granulites); and a heat component advected to the middle and lower crust seems inescapable if the hot granulite-peridotite complexes were exhumed and cooled as rapidly as petrological and geochronological evidence seems to suggest.
   Major mantle delamination and asthenospheric upwelling as a cause of heating in Early Carboniferous times is not supported by geochemical, geophysical or petrological studies, although slab break-off probably did occur
    Česká geologická služba
Kód přispěvatele
    ČGS (UNM)
Zdrojový formát
Datum vložení
    12. 6. 2009
Datum importu
    8. 8. 2012