Record details

Title
    Microstructural and metamorphic evolution of a high-pressure granitic orthogneiss during continental subduction (Orlica-Śnieżnik dome, Bohemian Massif)
Author
    Chopin, F.
    Lexa, Ondrej
    Martelat, J.E.
    Petri, Benoit
    Pitra, Pavel
    Schulmann, Karel
    Štípská, Pavla
Language
    anglicky
Publication type
    článek v periodiku
Source title - serial
    Journal of Metamorphic Geology
Vol./nr.
    Roč. 30, č. 4
Pages
    30
Year
    2012
Thesaurus term
    crust rheology,eclogite granitic orthogneiss,European Variscan belt,petrological modelling,quantitative microstructural analysis
Keyword
    Bohemian
    Continental
    Dome
    During
    Evolution
    Granitic
    High-pressure
    Massif
    Metamorphic
    Microstructural
    Orlica-Śnieżnik
    Orthogneiss
    Subduction
Abstract (in english)
   A microstructural and metamorphic study of a naturally deformed medium- to high-pressure granitic orthogneiss (Orlica-Śnieżnik dome, Bohemian Massif) provides evidence of behaviour of the felsic crust during progressive burial along a subduction-type apparent thermal gradient (∼10 °C km−1). The granitic orthogneisses develops three distinct microstructural types, as follows: type I - augen orthogneiss, type II - banded orthogneiss and type III - mylonitic orthogneiss, each representing an evolutionary stage of a progressively deformed granite. This is consistent with the equilibration of the three types at different positions along a prograde P−T path ranging from ;15 kbar and ;700 °C (type I orthogneiss) to 19-20 kbar and ;700 °C (types II and III orthogneisses). The deformation types thus do not represent evolutionary stages of a highly partitioned deformation at constant P−T conditions, but reflect progressive formation during the burial of th
   e continental crust. The microstructures of the type I and type II orthogneisses result from the dislocation creep of quartz and K-feldspar whereas a grain boundary sliding-dominated diffusion creep regime is the characteristic of the type III orthogneiss. Strain weakening related to the transition from type I to type II microstructures was enhanced by the recrystallization of wide myrmekite fronts, and plagioclase and quartz, and further weakening and strain localization in type III orthogneiss occurred via grain boundary sliding-enhanced diffusion creep. The potential role of incipient melting in strain localization is discussed.
Contributor
    Česká geologická služba
Contributor code
    ČGS (RIV)
Source format
    R
Import date
    15. 10. 2014