Structural geology . n from original random positions. This process may beaided by granulation and slicing of the original mineral , unequidimonsional mineral fragments are often strewn outin such a manner that their longer dimensions lie approximatelyparallel. Evidence of rotation is seen principally in the quartz FLOW CLEAVAGE 83 and feldspar, which have not much effect in producing rock cleav-age. It is concluded, then, that the rotation of original particles,diversely oriented, to a parallel position is a minor factor quitesubordinate to the dominant process of recrystalliz
Structural geology . n from original random positions. This process may beaided by granulation and slicing of the original mineral , unequidimonsional mineral fragments are often strewn outin such a manner that their longer dimensions lie approximatelyparallel. Evidence of rotation is seen principally in the quartz FLOW CLEAVAGE 83 and feldspar, which have not much effect in producing rock cleav-age. It is concluded, then, that the rotation of original particles,diversely oriented, to a parallel position is a minor factor quitesubordinate to the dominant process of recrystallization. (See Figs. -10, 41, 42 43.) In the incipient stages of rock flowage the larger and morebrittle particles are granulated and elongated. At the same timerecrystallization, beginning on the finer particles, builds up newminerals. In the intermediate and advanced stages it graduallydominates over granulation and ultimately obliterates any evidenceof it. It may be inferred that granulation aids recrystallization in. Fig. 41. Sliced feldspars in micaceous and chloritic schist from southernAppalachians. that it grinds the particles into small pieces and affords greatersurface upon which the chemical process may act. In experimental deformation the conditions are not favorablefor recrystallization, and granulation is the important process. Slipping or twinning along the cleavage planes of minerals, calledgliding—such as may be observed in calcite and ice crystals—has been cited as a possible cause of the elongation and parallelarrangement of mineral particles. This has been observed only inminerals of the calcite type, which are not important in cleavablerocks; and even in the calcite of schistose rocks gliding has beenfound to be subordinate to processes of recrystallization andgranulation. In experimental deformation of marble it seems toplay a greater part, because conditions of recrystallization are notpresent. There is no evidence that the flattening of original mineral
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