Próba określenia wieku głównych faz deformacji w metamorfiku sowio górskim (Dolny Śląsk)

Abstract

ATTEMPT OF DATING OF MAIN DEFORMATION PHASES IN METAMORPHIC ROCKS OF THE SOWIE MTS. (LOWER SILESIA) Summary The paper presents an attempt to date each deformation phase in metamorphic complex of the Sowie Mts. (Central Sudetes, southwestern Poland). This attempt was based on relations between Variscan granites and paragneissic-migmatic complex in the quarry at Piława Dolna (Fig. 1). The so-called Niemcza granites are represented there generally by a fine-grained quartz monzodiorite. Amidst monzodiorites there are blocks and lenses of various sizes that are also composed of monzodiorites. Fabric of monzodiorites indicates generally quite a constant orientation (about 300/65°). Amongst various types of paragneisses and migmatites there are also blocks and lenses of monzodiorites. Penetrative foliation of paragneisses and migmatites is usually parallel to borders of monzodiorite blocks and lenses. Textural analysis and interpretation of a new geologie survey proves that monzodiorites are located within the Sowie Mts. unit between deformation phases D2 and D3. The monzodiorites noted within the quarry can belong to a group of Hercynian synorogenic granites (320- 370 Ma) of marginal zones of the Bohemian Massif. According to the author the deformation phase D3 and the syndeformational metamorphism M3 are to be correlated at present with the Breton Phase (Upper Devonian-Lower Carboniferous). The deformation phase D2 that precedes a location of quartz monzodiorites (some of Niemcza granites) is to be correlated with the Acadian Phase (Middle Devonian - Upper Devonian). A detailed dating of main deformation phases D2 and D3 in the metamorphic complex of the Sowie Mts. seems to be possible after isotopic determinations of quartz monzodiorite at Piława Górna and adjacent gneisses and migmatites.