Strefy ścinań w metamorfiku izerskim, Sudety

Zbigniew Cymerman




First structural data on the kinematics of deformations of Izera Metamorphic Terrain (IMT) in West Sudeten (SW Poland) are presented in the paper. New structural study of IMT supports the concept of existence of numerous largescale penetrative shear zones. These zones are defined by mylonitic Izera gneisses that deformed Rumburk granites to a different degree. Mylonitic are also three zones of mica schists running evenly with a parallel of latitude. Only lensoidal domains of Rumburk granites are devoid of shearing processes. Lineations in IMT are extensional (Lx) and not of Ly type (i.e. parallel to axis Y of ellipsoid of final deformation) as was previously thought. The kinematic analysis of IMT indicates a complex pattern of displacements with a distinct domination of sinistral transptession. The latter is characteristic for northern and north-eastern parts of IMT. However, in the southern part of IMT dominated conditions of sinistral transpression. Most probably during the sinistral transpression (D1) domains were thrusted towards the south west and the middle crust was tectonic ally thickened. Next during the sinistral transtension in the northern slope of elevated core of dome the crust became extented. In the core of dome the emplacement of Karkonosze granitoids took place. The youngest, rare and non-penetrative dextral shear zones (D3) are related to the later extension during the Stephanian and Early Permian.