PhD. thesis - Univerzita Karlova

3.3. Cretaceous transpressional deformation - Trans-Gemer Shear Zone
(TGSZ)
The transpressional deformation is marked by development of a several kilometer wide
zone of NE-SW trending steep cleavage along the southern boundary of the western Vepor
promontory (Fig. 5b). Here, in the Gemer Unit, Carboniferous and Permian cover of the Vepor
basement and Mesozoic rocks of the Meliata accretionary wedge, all previously developed
structures, are intensively reworked under lower greenschist facies conditions. In the strongly
attenuated Gemer Unit, relics of E-W trending GCF fabric and new NE-SW trending cleavage
form a map-scale sigmoidal domain surrounded by highly sheared Late Paleozoic rocks
(Fig. 5b). Locally, the early-developed foliation is refolded by synschistose noncylindrical
folds with steeply to subhorizontally plunging hinges, which become subparallel to horizontall
stretching lineations with increasing finite strain (Fig. 4d). These features are consistent with
progressive folding in transpressional shear zones [Fossen and Tikoff, 1998; Treagus and
Treagus, 1992].
The boundary of the Vepor basement and Late Paleozoic cover is intruded by sheets of
peraluminous granites, which show magmatic fabric parallel to the transpressional shear zone.
In some places, heterogeneous, steep NE-SW trending mylonitic S-C fabric indicates sinistral
shearing. Granite apophyses and dikes are folded and sheared or they crosscut the foliation of
host rocks without internal deformation. All these features are consistent with syntectonic
character of granite emplacement. Shallow level of magma emplacement is documented by
contact metamorphism of host Late Paleozoic schists [500°C and 2 kbars, Vozárová, 1990].
Towards the NE, this 5 km wide zone of steep cleavage continues into central part of the
Gemer Unit (Figs. 3a, 4e). This NE-SW trending zone of shear deformation - the Trans-Gemer
Shear Zone (TGSZ) overprints all previously developed metamorphic fabrics exhibiting a 20 to
25 km sinistral offset of lithological stripes and axial zone of GCF. The displacement and
intensity of deformation gradually vanishes towards the NE edge of the Gemer Unit.
Two several kilometers wide NE-SW trending zones of greenschist facies
transpressional deformation affected internal parts of the Western Vepor promontory (Fig. 5b).
Inside these shear zones, the Variscan as well as Mesozoic mylonitic extensional fabric are
strongly refolded and transposed. The character of folding as well as numerous sense of shear
criteria underline the sinistral sense of movement. These zones are preferentially developed in
weak lithologies such as garnetiferous micaschists or highly anisotropic extensional mylonites.
Outside of these shear zones, weak E-W trending crenulation cleavage affects flat Cretaceous
extensional mylonitic foliation. The structural mapping shows anticlockwise rotation of this
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