Abstract

Petrofabric study of a specimen of quartzite from a shear zone in the Ajibik formation of the Marquette district, Michigan, contributes the following to the quartz lamellae problem:

  1. Excellent orientation relations of the deformation lamellae and crystal axes indicate the control of the quartz orientation by the lamellae rather than by the axes. A translation hypothesis is considered to explain the relations best.

  2. A fixed glide line [m : r] and variable glide planes containing [m : r] satisfy best the irrational lamellae planes and the restricted orientation of the axes associated with them.

  3. The character of the lamellae orientation leads to the tentative conclusion that the strain was nonrotational.

  4. The possibility is mentioned that some of the quartz maxima in recrystallized tectonites may be remnants of axis concentrations related to lamellae which have since been obliterated by the recrystallization.

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