Abstract
The ptygmatic veins under consideration are localized in foliated biotite hornfelses in immediate proximity to the contacts of granitoid batholiths. Ptygmatic veins as well as simultaneously formed ordinary plane veins are composed of quartz-oligoclase aplite. The ptygmatic veins were not formed either as a result of plastic deformation of some pre-existing flat veins or by magmatic injection in a cavity or crack of corresponding form. Aplite veins both ptygmatic and flat are controlled in shape and position by the structural elements of the host rock. Peculiarities of the composition of the veins, their structural position as well as relations between the veins and granitoids indicate that the formation of the ptygmatic veins has happened by replacement of hornfelses along sets of echelon tension fractures under influence of fluids migrating from the magma in an advanced stage of formation of the granitoid batholiths.
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