Shear sense indicators
© All photographs on this webpage may be downloaded and used for teaching purposes only. The photographs may not be reproduced in any publications - commercial or scientific - without permission by Ralf Hetzel.
Picture 1: Oblique grain shape fabric in quartzite
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Thin section (cross-polarized light) of quartz oblique grain shape fabric in greenschist-facies quartz mylonite (Menderes Massif, SW Turkey). The main foliation, defined by compositional layering and white mica is horizontal; the oblique grain shape fabric defined by the long axes of quartz grains is at an angle of ~35° to the main foliation (from upper right to lower left). Shear sense is dextral. Width of photograph is 2.5 mm.
Related Publications:
Hetzel et al. (1995). Miocene NNE-directed extensional unroofing in the Menderes Massif, SW Turkey. Journal of the Geological Society of London 152, 639-654.
Picture 2: Shear bands, macroscopic view
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Field photograph of extensional shear bands in highly deformed greenschist-facies sediments of a crustal-scale extensional shear zone (Menderes Massif, SW Turkey). Shear sense is dextral. Coin is 3 cm in diameter. For thin section of this rock see Picture 3.
Related Publications:
Hetzel et al. (1995). Miocene NNE-directed extensional unroofing in the Menderes Massif, SW Turkey. Journal of the Geological Society of London 152, 639-654.
Picture 3: Shear bands, microscopic view
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Thin section photograph (plane-polarized light) of extensional shear bands in highly deformed greenschist facies sediments (sample from outcrop of Picture 2). Biotite is unstable during the deformation and transformed to chlorite. Note growth of fine-grained chlorite along the discrete shear bands. Shear sense is dextral. Width of picture is 5 mm.
Related Publications:
Hetzel et al. (1995). Miocene NNE-directed extensional unroofing in the Menderes Massif, SW Turkey. Journal of the Geological Society of London 152, 639-654.
Picture 4: Delta-structure around andalusite porphyroblast
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Thin section photograph (plane-polarized light) of δ (delta) structure that developed around an andalusite porphyroblast which has grown in the contact aureole of a granodiorite intrusion. Picture provides evidence for ongoing deformation after the intrusion of the granodiorite. Shear sense is dextral. Width of photograph is 2.5 mm.
Related Publications:
Hetzel et al. (1995). Miocene NNE-directed extensional unroofing in the Menderes Massif, SW Turkey. Journal of the Geological Society of London 152, 639-654.
Picture 5: Muscovite mica fish
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Thin section photograph (cross-polarized light) of muscovite mica fish in mylonitized greenschist-facies metasediments (Menderes Massif, SW Turkey). Shear sense is dextral. Width of photograph is 5 mm.
Related Publications:
Hetzel et al. (1995). Miocene NNE-directed extensional unroofing in the Menderes Massif, SW Turkey. Journal of the Geological Society of London 152, 639-654.
Picture 6: Biotite mica fish
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Thin section photograph (plane-polarized light) of biotite mica fish in a mylonitized granodiorite (Salihli granodiorite, Menderes Massif, SW Turkey). Shear sense is dextral. Width of photograph is 4 mm.
Related Publications:
Glodny J., Hetzel, R. (in press). Precise U-Pb ages of syn-extensional Miocene intrusions in the central Menderes Massif, western Turkey. Geological Magazine.
Hetzel et al. (1995). Miocene NNE-directed extensional unroofing in the Menderes Massif, SW Turkey. Journal of the Geological Society of London 152, 639-654.
Picture 7: S-C fabric in granitoid
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Photograph of S-C fabric in ductily deformed granodiorite (Menderes Massif, SW Turkey). Shear sense is dextral. Coin is about 1 cm in diameter.
Related Publications:
Glodny J., Hetzel, R. (in press). Precise U-Pb ages of syn-extensional Miocene intrusions in the central Menderes Massif, western Turkey. Geological Magazine.
Hetzel et al. (1995). Miocene NNE-directed extensional unroofing in the Menderes Massif, SW Turkey. Journal of the Geological Society of London 152, 639-654.
Picture 8: Shear bands in granite
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Photograph of extensional shear bands in deformed granite in a crustal-scale shear zone (Middle Urals). Shear sense is dextral. Scale bar is 32 mm in length.
Related Publications:
Hetzel R. and Glodny J. (2002). A crustal-scale, orogen-parallel strike-slip fault in the middle Urals: age, magnitude of displacement, and geodynamic significance. International Journal of Earth Sciences 91, 231-245.
Picture 9: Slickenfibres on brittle fault plane
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Photograph of brittle fault with light-colored mineral fibres (Menderes Massif, SW Turkey). The orientation of the mineral fibres and their geometry (thickness of individual fibres increases towards the observer) demonstrate that the missing block (the one that was once located above the fault plane) moved toward the observer. Coin is 3 cm in diameter.
