Kinematically unrelated C-S fabrics: an example of extensional shear band cleavage from the Veporic Unit (Western Carpathians)
Abstrakt
Discontinuous and kinematically unrelated C-S fabrics have been recognized along the contact between the Gemeric and Veporic Units in the Western Carpathians. The formation of S and C fabrics within orthogneiss, quartzite and chloritoid-kyanite schist of the Veporic Unit is associated with Cretaceous syn-burial orogen-parallel flow and subsequent exhumational unroofing.
The formation of the two fabrics characterized by distinct quartz deformation microstructure and metamorphic assemblage is separated by an inter-tectonic growth of transversal chloritoid-, kyanite-, +/- monazite-bearing assemblage. The monazite U-Th-Pb concordia age of 97 +/- 4 Ma was obtained by the laser ablation ICP-MS dating method.
The age of this inter-tectonic metamorphic stage together with existing Ar-40/Ar-39 ages on exhumation of the Veporic Unit indicate that despite the similar appearance to shear bands or C-S mylonites there is a time span of at least 10 Myr between the formation of homogeneous S fabrics and superposed discrete C fabrics in the studied rocks.