Timing and kinematics of the Variscan orogenic cycle at the Moldanubian periphery of the central Bohemian Massif
Posted on 16.11.2021 - 09:31
The high-grade complexes along the northern Moldanubian periphery of the central Bohemian Massif provide an outstanding structural record of all episodes of the Variscan collisional evolution. Kinematics and timing of orogenic processes have been examined by structural and microstructural study of middle and lower crustal rocks combined with xenotime and monazite geochronology. Four distinct tectonic events have been identified in the studied units. A first relict sub-horizontal fabric S1 associated with the HP/HT metamorphism is developed only in the lower crustal rocks and was related to back-arc extension or lower crustal flow in a supra-subduction domain. This fabric was at c. 340 Ma completely reworked to the sub-vertical foliation S2 by the major collisional thickening leading to the lower and middle crust juxtaposition. Thereafter, the extensional collapse of thickened orogenic system caused strong refolding to the HT sub-horizontal fabric at c. 325 Ma. The region was subsequently affected by the NNE–SSW oriented horizontal shortening related to the dextral shearing and clockwise rotation of crustal blocks adjacent to the large scale dextral shear zone, the Elbe Zone. It led to the fragmentation and reorientation of the Moldanubian margin to the current position.
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Machek, M.; Soejono, I.; Sláma, J.; Žáčková, E. (2021): Timing and kinematics of the Variscan orogenic cycle at the Moldanubian periphery of the central Bohemian Massif. Geological Society of London. Collection. https://doi.org/10.6084/m9.figshare.c.5708800.v1
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vertical foliation s2variscan collisional evolutiongrade complexes alongcrustal blocks adjacentcentral bohemian massifvariscan orogenic cyclelower crustal rockslower crustal flowoutstanding structural recordmiddle crust juxtapositionfirst relict subnorthern moldanubian peripherymoldanubian peripheryorogenic processesmoldanubian marginsubsequently affectedsubduction domainstudied unitsmonazite geochronologymicrostructural studyht subht metamorphismextensional collapseelbe zonedextral shearingcurrent positioncompletely reworkedclockwise rotationc .</arc extension