Charakterystyka i znaczenie lineacji ekstensyjnej

Zbigniew Cymerman



The present paper is aimed at the presentation of genesis and characteristics of extensional (stretching) lineation and at its significance for structural analysis. Extensional lineation is formed on foliation surfaces in ductile shear, ductile-brittle shear, and brittle shear zones. This lineation is mostly marked out by morphological forms of linear structures of mineral lineation type or rodding lineation type. The orientation of extensional lineation tends to almost total co-axiality with X - axis of finite strain ellipsoid during an activity of simple shear mechanisms. The extensional lineation is often orientated approximately parallel to the axes of synchronic sheath folds.
Development of extensional lineation, like as of shear zones, is connected with thrust tectonics and/or strike-slip tectonics. Orientation of trajectories of extensional lineation on structural maps (together with other kinematic indicators) facilitates reconstruction of geometry and evolution of shear zones. Therefore, regardless limitations, the orientation of extensional lineation is one of the basic kinematic indicators, which is used (among other things) for qualification of movements of lithosphaeric plates - from Proterozoic times till recent movements.
The extensional lineation also occur in Sudety Mountains, where i t was hitherto regarded as lineation "type B", i.e. as a lineation developing parallel to the axis "Y" of finite strain ellipsoid. Detailed studies on extensional lineation in different shear zones in Sudety Mts. will probably modify or even reject existing ideas on structural evolution of this eastern part of European Variscides.

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