Budowa strukturalna środkowej części pasma łupkowego Szklarskiej Poręby (Góry Izerskie)

Abstract

 Przedstawiono wyniki badań strukturalnych prowadzonych w środkowej części pasma łupkowegoSzklarskiej Poręby. Wyróżniono cztery generacje mezostruktur fałdowych oraz związanych z nimi struktur planarnych. Wyodrębniono kilka obalonych, izoklinalnych makrofałdów o amplitudzie i promieniu od kilkudziesięciu do kilkuset metrów. Stwierdzono dwie duże dyslokacje - Czerwonego Potoku oraz Wysokiego Kamienia. Dokonano próby określenia ich wieku i charakteru.   STRUCTURE OF THE MIDDLE PART OF THE SZKLARSKA PORĘBA SLATE RANGE(IZERA MTS) Four stages (phases?) of tectonic deformations D1 - D4 were distinguished, leading to development of mesofolds and corresponding planar structures. Morphology and spatial orientation of individual generations of mesostructures prove gradual development of deformations in varying field of forces and increasing competence of deformed rocks. Amidst sedimentary structures there are only planes of primary stratiphication so that seem to have forced directions of further tectonic deformations. Outside bend zones of folds these planes usually agree with penetrative foliation S1.Macroscopic fold structures have been probably formed only during the first two deformations Dl and D2. The deformation D2 resulted in re-orientation of structures developed during the stage D1. Within the slate range of Szklarska Poręba several overturned, isoclinal and usually narrow macrofolds F2 were formed in that time, with amplitudes and radii ranging from several dozen to several hundred meters. Further deformations, younger than D2, resulted in only local development of new (already non-penetrative) generations of mesostructures, having no macroscopic equivalents. They influenced only slightly a general structural pattern of the Szklarska Poręba range, developed during the second deformation stage. Axial fissure schistosity (S4?) of some fault mesofolds of the youngest generation (F4?) are occasionally used by aplites, geneticaly connected with the Karkonosze - Izera pluton (Karkonosze massif). These structures are therefore slightly older or at the outmost synchronic with this Variscite intrusion.In the studied area two dislocations of regional significance were noted. The fault of Czerwony Potok(CzP) is of rotation type. It is younger than the second deformation of rocks of the Izera metamorphic complex D2 after the Famennian but still 310 - 320 Ma ago. On the other hand it precedes the penetrative for the whole area, regional fissures formed during final stages or after the intrusion of Variscite granitoids was formed (about 300 Ma ago). These fissures have not been rotated at sides of this dislocation in contrast to structures of first and second generations. They indicate the same orientation either in granitoids as well as in hornfelses that form their northern mantle. Displacements of rock masses noted in this paper seem to have occurred along the described fault during the interval from 310 (320) to 300 Ma ago that is before consolidation of granites of the Karkonosze -Izera intrusion. The fact that this faults cuts now at certain distance also the Variscite granitoids, can suggest its further and possibly repeated rejuvenation.The fault of Wysoki Kamień (WK) is probably of throw type (eastern wing is lowered ?). It agrees with a large, regional dislocation zone noted at satellite photographs Landsat (B. Mroczkowska et al.,1984). This zone cuts also the granitoids of the Karkonosze-Izera (Karkonosze) massif besides theIzera metamorphic massif.