Preferred lattice orientations of plagioclase from amphibolite and greenschist facies rocks near the Insubric Line (Western Alps)

Preferred lattice orientations of plagioclase, measured by the universal stage, from deformed amphibolite and greenschist facies rocks near the Insubric Line (Western Alps), reflect the type and orientation of the strain system: either (001) or (010) are oriented parallel or subparallel to the schistosity and form more or less complete girdles around the stretching direction. By the preferred orientation patterns dominant (010) [001] slip is indicated and, additionally, slip on (001) parallel to the a direction, possibly at somewhat higher temperatures and/or at a higher An content of the plagioclase. It is suggested that obliquities of the symmetry-planes of the orientation patterns against the principle axes of strain are related to the sense of shearing.