The microfabric of calcite tectonites from the Helvetic Nappes (Swiss Alps)

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Abstract
Summary: The crystallographic orientations of calcite in tectonites from the Morcles Nappe and the Glarus Overthrust have been measured by X-ray texture goniometry. The orientation data are represented by pole figures, inverse pole figures and as orientation distribution functions. The patterns of preferred orientation observed in the specimens from the Morcles Nappe are correlated with intracrystalline slip mechanisms. The patterns exhibit quasiaxial symmetry and in some cases the axis of symmetry is oblique to the symmetry of the macroscopic fabric. This obliquity is interpreted as the result of a rotational strain path and may be used to infer direction and sense of shear. Some specimens of the Lochseiten mylonite from the Glarus Thrust show no strong preferred crystallographic orientation. This suggests that grain boundary sliding was the major deformation mechanism.