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Photos - serie 1

4.2) Structure 4.3) Examples 4.4) Formation

Observed veins in the field are of various form: symmetrical, perpendicular or oblique to the main schistosity or in a sigmoidal form. These features imply a component of pure AND simple shear (non-coaxial flow). Veins can appear in quartz interboudins*, in symmetric interboudin or associated to a shear zone.

Sigmoidal Knauern
Example of a sigmoidal vein
(High [151 ko] / Low [58 ko] resolution)

Knauern in shearing zone
Crystallisation of aluminosilicate, plagioclase and white micas in shearing planes crossing a pre-existing quartz vein. Quartz marks a contrast of competence in micaschists and thus supports formation of a vein.
(High [142 ko] / Low [50 ko] resolution)

Symmetrical Knauern
Symmetrical vein, cutting perpendicularly the schistosity. In contrast to sigmoidal vein, this schistosity is quite not deflected at vein border.
(High [120 ko] / Low [45 ko] resolution)

1) Introduction | 2) Structural | 3) Thermobarometry | 4) TENSION GASHES | 5) Cartography | Bibliography | Thanks
Aluminosilicate-bearing veines: 4.1) Mineralogy | 4.2) Structure | 4.3) EXAMPLES | 4.4) Formation

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Photo - serie 2

Uni Lausanne || Geology 2003-2005 © Xavier Maeder & Julien Allaz
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Created: 10th May 2003
Last update: 3rd March 2012