Record details

Title
    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
Author
    Kröner, Alfred
    Schulmann, Karel, 1958-
    Štípská, Pavla
Language
    anglicky
Source title - serial
    Journal of Metamorphic Geology
Vol./nr.
    Vol. 22, no. 3
Pages
    p. 179-198
Year
    2004
Notes
    10 obr., 4 tab.
    Bibliografie na s. 195-198
    il.
    Zkr. název ser.: J. metamorph. Geol.
Classfication no.
    552
Conspectus category
    552
Subject group
    chemismus minerálů
    datování Pb/Pb
    datování U/Pb
    exhumace
    facie eklogitová
    geologie strukturní
    granodiorit
    granulit
    minerály horninotvorné
    ochlazování
    ortorula
    podmínky P-T
    proces syntektonický
    protolit
    silesikum
    vmístění
    vrásnění variské
    zirkon
Geographical name
    Červený Důl (Jeseník, Jeseník)
    ČR-Morava
    Hanušovice (Šumperk, Šumperk)
    Vojtovice (Jeseník, Jeseník)
Keyword
    Bohemian
    Crustal
    Czech
    Exhumation
    Extrusion
    Granulite
    Massif
    Middle
    Model
    Omphacite
    Republic
    Spreading
    Syn-convergent
    Vertical
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
Contributor
    Česká geologická služba
Contributor code
    ČGS (UNM)
Source format
    U
Entered date
    21. 3. 2008
Import date
    8. 8. 2012