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  • Blackwell Science Inc  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Inc
    Journal of metamorphic geology 19 (2001), S. 0 
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Antitaxial non-deforming strain fringes from Lourdes, France, show complex quartz, calcite and chlorite fibre patterns that grew around pyrite in a slate during non-coaxial progressive deformation. Development of these fringes was modelled using a computer program ‘Fringe Growth 2.0’ which can simulate incremental growth of crystal fibres around core-objects of variable shape. It uses object-centre paths as input, which are obtained from fibre patterns in thin section. The numerical experiments produced fibre patterns that show complex intergrowth of displacement-controlled, face-controlled and intermediate fibres similar to those in the natural examples. The direction of displacement-controlled growth is only dependent on the relative movement between core-object and fringe, so that core-object rotation with respect to the fringe influences the fibre patterns and produces characteristic asymmetric fibre curvature. Object-centre paths should be used for kinematic analysis of strain fringes instead of single fibres since these paths represent the fringe as a whole. The length along the path can be interpreted in terms of finite strain and path curvature in terms of rigid body rotation of fringes with respect to an external reference frame.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Abstract P–T conditions, mineral isograds, the relation of the latter to foliation planes and kinematic indicators are used to elucidate the tectonic nature and evolution of a shear zone in an orogen exhumed from mid-crustal depths in western Turkey. Furthermore, we discuss whether simple monometamorphic fabrics of rock units from different nappes result from one single orogeny or are related to different orogenies. Metasedimentary rocks from the Çine and Selimiye nappes at the southern rim of the Anatolide belt of western Turkey record different metamorphic evolutions. The Eocene Selimiye shear zone separates both nappes. Metasedimentary rocks from the Çine nappe underneath the Selimiye shear zone record maximum P–T conditions of about 7 kbar and 〉550 °C. Metasedimentary rocks from the overlying Selimiye nappe have maximum P–T conditions of 4 kbar and c. 525 °C near the base of the nappe. Kinematic indicators in both nappes are related to movement on the Selimiye shear zone and consistently show a top-S shear sense. Metamorphic grade in the Selimiye nappe decreases structurally upwards as indicated by mineral isograds defining the garnet-chlorite zone at the base, the chloritoid-biotite zone and the biotite-chlorite zone at the top of the nappe. The mineral isograds in the Selimiye nappe run parallel to the regional SR foliation, parallel the Selimiye shear zone and indicate that the Selimiye shear zone formed during this prograde greenschist to lower amphibolite facies metamorphic event but remained active after the peak of metamorphism. 40Ar/39Ar mica ages and the tectonometamorphic relationship with the Eocene Cyclades–Menderes thrust, which occurs above the Selimiye nappe in the study area, suggests an Eocene age of metamorphism in the Selimiye nappe.Metasedimentary rocks of the Çine nappe 20–30 km north of the Selimiye shear zone record maximum P–T conditions of 8–11 kbar and 600–650  °C. An age of about 550 Ma is indicated for amphibolite facies metamorphism and associated top-N shear in the orthogneiss of the Çine nappe. Our study shows that simple monophase tectonometamorphic fabrics do not always indicate a simple orogenic development of a nappe stack. Preservation in some areas and complete overprinting of those fabrics in other areas apparently occur very heterogeneously.
    Type of Medium: Electronic Resource
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