VÝVOJ MYLONITIZACE VÁPENCŮ A KONTRASTNÍ VARISKÁ DEFORMACE TEKTONICKÝCH DOMÉN JIHOZÁPADNÍHO BRUNOVISTULIKA

Roč.8,(2001)

Petr Špaček Rostislav Melichar Jiří Kalvoda Eva Franců

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Abstrakt
The calcite mylonites in the Brunovistulian sedimentary cover developed in frontal thrust area of Moravian nappe units were examined. The inhomogeneous composition of sedimentary protoliths allowed the analysis of the contrasting behavior of matrix and clasts and the interpretation of microfabric evolution during deformation under low temperature conditions. Several tectonofacies with microfabric characteristic for a given position within the progressive/retrogressive deformation path are distinguished. Generally, the progressive phase of mylonitization is characterized by grain growth in the matrix and the grain size reduction of the clasts leading to a stress-determined equillibration of grain size. With rising temperature during deformation, grain growth predominated after grain size homogenization was finished. Large-scale thrusting within the Brunovistulian basement is evidenced by the juxtaposition of calcite and quartz mylonites with contrasting microstructures. In terms of deformational styles of calcite and quartz the lower unit of the Svratka tectonic window differs distinctively from both the lower unit of the Thaya tectonic window and the western margin of the Brno Batholith. Although these differences include such pronounced contrast as the fully brittle vs. fully plastic deformation of quartz, paleothermometric data which are available to date, suggest that the variation in microstructures is not accompanied by major changes in paleotemperatures. This can be explained by an abrupt change of deformation mechanisms in both calcite and quartz at temperatures around 300°C.

Klíčová slova:
Brunovistulicum; Paleozoic limestones; mylonitization; recrystallization; microstructures
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