Abstract

The resolved shear-stress coefficient for twinning and translation was determined graphically for each forumla plane in every grain of two representative fabric samples of Yule marble for six different stress orientations. The rotation of crystal elements in each grain was computed as a function of strain of the aggregate using the methods of metallurgists under two widely different hypotheses of the deformation of granular aggregates: (a) “heterogeneous” and (b) “homogeneous” deformation. Predicted fabrics are then constructed for different stress orientations and different degrees of deformation. Comparison of predicted and observed (Part III) fabrics shows that predictions under the heterogeneous hypothesis are not in agreement with observed fabrics. Fabrics predicted under the homogeneous hypothesis of Taylor are very similar to those observed. This provides evidence for the complementary roles of twinning and translation on forumla and the subordinate roles of other glide planes in the case of calcite marble deformed under the conditions described in Part I.

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