**4.2 Subgrain rotation**

The deformation bands formed during the recovery tighten progressively, creating a grid determined by subgrain walls that developed successively within the grain. The subgrains are fragments of larger grain with fine boundaries. As a result of rotation, the crystalline axis

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of the subgrain becomes slightly misoriented relating to the axes of the adjacent subgrains or the main grain/crystal; the misorientation angle usually reaches max. 5º (FitzGerald et al., 1983; White & Mawer, 1988 fide Passchier & Trouw, 1998). During the rotation recrystallization the mylonitic and porphyroblastic/porphyroclastic rocks are formed.

Another (however not so common) mechanism of subgrain development can be observed in the rocks of the gypsum cap-rock - the process is called kinking and leads to formation of 'kink bands' (Means & Ree, 1988 fide Passchier & Trouw, 1998), which are represented by narrow accumulation of kink folds; see fig. 25. They are formed in brittle-ductile system and correspond to the initial shearing along the planes oblique to the dense anisotropic planes (sedimentary, metamorphic, lattice anisotropy) under the influence of parallel (to those planes) or close to parallel compression at rather high surrounding pressure (Dadlez & Jaroszewski, 1994). This process has been observed in few mm to few cm lenticular, cigarshaped gypsum crystals; see fig. 26. and 27.
