The relationship of the metamorphosed and non-metamorphosed areas in the central part of the Bohemian massif can hardly be explained by the concept of repeated geosynclinal development as many geologists have assumed.
The metamorphic heat front generally depends on energy released from the deep source, on the duration of this activity, and on the mode of its supply to upper levels. In this respect the weakened zones of the deep-seated faults are of the highest importance.
A linear block of metamorphic rocks may be developed when a high rise in temperature is controlled by a deep-seated fault. If two or more closely spaced faults reach down to a subcrustal depth and can transport the heat front, it is possible that their weakened metamorphic zones may coalesce and produce a block of crystalline rocks of polygonal outline.