Record details

    Vertical extrusion and middle crustal spreading of omphacite granulite: a model of syn-convergent exhumation (Bohemian Massif, Czech Republic)
Statement of responsibility
    Pavla Štípská, Karel Schulmann, Alfred Kröner
    Kröner, Alfred
    Schulmann, Karel, 1958-
    Štípská, Pavla
Source title - serial
    Journal of Metamorphic Geology
    Vol. 22, no. 3
    p. 179-198
    10 obr., 4 tab.
    Bibliografie na s. 195-198
    Zkr. název ser.: J. metamorph. Geol.
Classfication no.
Conspectus category
Subject group
    chemismus minerálů
    datování Pb/Pb
    datování U/Pb
    facie eklogitová
    geologie strukturní
    minerály horninotvorné
    podmínky P-T
    proces syntektonický
    vrásnění variské
Geographical name
    Červený Důl (Jeseník, Jeseník)
    Hanušovice (Šumperk, Šumperk)
    Vojtovice (Jeseník, Jeseník)
Abstract (in english)
   exhumation of eclogite facies granulites (Omp-Plg-Grt-Qtz-Rt) in the Rychleby Mts, eastern Czech Republic, was a localised process initiated by buckling of crustal layers in a thickened orogenic root. Folding and post-buckle flattening was followed by the main stage of exhumation that is characterized by vertical ductile extrusion. This process is documented by structural data, and the vertical ascent of rocks from a depth of c. 70 to c. 35 km is documented by metamorphic petrology. SHRIMP 206Pb/238U and 207Pb/205Pb evaporation zircon ages of 342 +- 5 and 341.4 +- 0.7 Ma date peak metamorphic conditions. The next stage of exhumation was associated with sideways fiat thrusting associated with lateral viscous spreading of granulites and surrounding rocks over indenting adjacent Continental crust at a depth of c. 35-30 km. This stage was associated with syntectonic intrusion of a granodiorite sill at 345-339 Ma, emplaced at a crustal depth of c. 25 km.
   The time required for cooling of the sill as well as for heating of the country rocks brackets this event to a maximum of 250 000 years. Therefore, similar ages of crystallization for the granodiorite magma and the peak of eclogite facies metamorphism of the granulite suggest a very short period of exhumation, limited by the analytical errors of the dating methods. Our calculations suggest that the initial exhumation rate during vertical extrusion was 3-15 mm yr-1, followed by an exhumation rate of 24-40 mm yr-1 during further uplift along a magma-lubricated shear zone. The extrusion stage of exhumation was associated with a high cooling rate, which decreased during the stage of lateral spreading
    Česká geologická služba
Contributor code
    ČGS (UNM)
Source format
Entered date
    21. 3. 2008
Import date
    8. 8. 2012