Następstwo deformacji serii metamorfiku Śnieżnika w okolicy Kątów Bystrzyckich

Abstract

 Omówiono kolejne fazy deformacji tektonicznych (D_1­–D4) i związane z nimi mezoskopowe struktury.

Naszkicowano najważniejszy rys budowy tektonicznej – superpozycję starszych leżących, generalnie wydłużonych południkowo, makrofałdów i otwartych, często wąskopromiennych, makrofałdów F₃ związanych z trzecim etapem deformacji.

ON THE SUCCESSION OF DEFORMATIONS IN THE SNIEZNIK METAMORPHIC SERIES IN THE VICINITIES OF KĄTY BYSTRZYCKIE

The studied area, situated in central part of the Snieżnik metamorphic massif (Western Sudety Mts), is built of two petrogenetic series: Stronie and Granitogneisses Series. The former, highly differentiated, mainly comprises micaceous paragneisses and schists with intercalations of quartzites and amphibolites and the latter – two varieties of gneisses: Gierałtów Gneisses, usually laminated and often migmatic, and Snieżnik Gneisses, usually large-eye or layered (Figs. 1–4).

Four major generations of mesostructures to (D₁ to D₄), differentiated here, show that deformations of the above mentioned rock series were developing by stages. The oldest generation of megastructure comprises relic, isoclinal folds F₁, synchroneously developing penetrative foliation S₁ and intersecting lineations L₁, originating at crossings of surfaces S_o and S₁. Variability in orientation of these mesostructures is primarily related to subsequent reorientation in younger deformation phases.

In kink zones of folds F₂, axial planes are accentuated by subsequent foliation, S₂ (Fig. 5).

Folds F₂, more differentiated in morphology and scale than the older, are accompanied by rich and diversified set of lineations L₂ (rodding, gufrae, intersective lineation, etc.). Structures of the phase are markedly varying in orientation but WNW–ESE strikes generally predominate in western part of the studied area, and E and NNE–SSW strikes – in the eastern.

The present spatial position of structures of the phase D₂ is the effect of transformations in the deformation phase D₃. Folds F₃, usually open, are accompanied by lineation L₃, i.e. major crystallizational lineation. Axial planes of folds F₃ are often accentuated crenulation cleavage.

Deformation phase D₄ resulted in origin of faulty deformations and folds of the kink bands type, characterized by fairly stable spatial orientation (Fig. 8).

The macrotectonics of the studied area is determined by superposition of older, laying meridional structures (deformation phases D₁ and D₂) and younger, open macrofolds F₃ with varying orientation of axes.