International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

MULTISTAGE EVOLUTION OF THE SHEAR ZONE AT THE BASE OF THE GIEWONT UNIT, TATRA MOUNTAINS (POLAND)

Pages: 337 - 351

Authors: EDYTA JUREWICZ

Abstract: The paper presents a mesostructural and petrotectonic analysis of rocks from the contact zone between the Giewont and Czerwone Wierchy Units (High-Tatric nappes). Rocks occurring in the vicinity of Siadla Turnia and Turnia Olejarnia earlier referred to the “brecciated Campilian” (Late Scythian), are in reality mylonites (mainly dolomitic mylonites), and their unique preservation was possible due to dilatant sites linked with faults developed in the basement of the thrusting Giewont Unit. The mylonitization process as well as the thrusting of the nappe was not a one-stage, but a multi-stage re-activated process. Its cyclicity was determined by the build up and drop of pore fluid pressure, leading to changes of rheological behaviour of the deformation process. Fluids released to the shear zone together with the brecciated rock formed a suspension with low friction values, which acted as a “water pillow” facilitating the movement of the nappe mass. Deformation and mylonitization processes, the temperature of which reached 300 °C in some cases, accompanied further stages of tectonic transport.

Keywords: Tatra Mts, shear zone, dolomitic mylonites, fluid pressure, hydraulic fracturing, pressure solution

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