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Porównanie sekwencji deformacji fałdowych w północnej i południowej okrywie granitoidów Karkonoszy

Gaidzik K., Żaba J.

Przegląd Geologiczny

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2017

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Vol. 65, nr 12

1548--1554

EN

We applied the detailed structural analysis to 394 outcrops in the southern and northern metamorphic cover of the Karkonosze Intrusion. We recognised five generations of fold structures: F1 -poorly preserved tight intrafoliation folds; F2 - the most common generation, with the whole variety of fold geometries, W-E and WSW-ENE-oriented fold axes in the northern contact zone, and W-E and WNW-ESE-oriented fold axes in the southern contact zone; F3 - chevron folds; F4 - kinkfolds observed only in the Stara Kamienica schist belt; and F5 - wide open folds, locally transformed into monoclinal kinkfolds, probably formed during the Variscan intrusion of the Karkonosze pluton. Similarity observed in the structural style in the northern and southern contact zones prove that these lithostratigraphic units had formed a single unit - the Izera-Kowary Unit - and had undergone the same deformational stages before the Karkonosze granitoid intrusion took place.

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The Orlica–Śnieżnik Dome, the Sudetes, in 2002 and 12 years later

Żelaźniewicz A., Jastrzębski M., Redlińska-Marczyńska A., Szczepański J.

Geologia Sudetica

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2014

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Vol. 42

105--123

EN

During the 2002 meeting of Czech, Polish and Slovak tectonic community in Żelazno, the Sudetes, the Central European Tectonic Studies Group (CETeG) was established. 12 years ago, participants of the meeting made an excursion to the eastern part of the Orlica–Śnieżnik Dome (OSD), which was focused on a variety of gneisses with inserts of (U)HP eclogites and various enclaves. The 2014 meeting brought members of the CETeG to the OSD again and an accompanying field excursion was dedicated mainly to evolution of metasedimentary and metavolcanogenic rocks in the region. This paper is a short review of the results of the studies undertaken in the OSD by different research groups in the last 12 years. The review is set against a background of what we knew about the geology of the dome in 2002. A significant progress was made. P-T paths were determined for mica schists and marbles as well as for metarhyolites originated from the continental crust and metabasites derived from the mantle. New light was shed on the origin of various types gneisses in the OSD and their genetic and structural relationships. A plethora of isotopic studies helped to better constrain timing of igneous and metamorphic events in the Orlica–Śnieżnik complex. Ages clustered around 350–340 Ma are repeatedly obtained, yet scarcer older ages up to 390 Ma and their geological significance are open to debate. Tectonic evolution of the dome was revised and new geodynamic concepts were proposed. However the new data has created some new problems and some old problems are still to be resolved in the future.

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Polyphase exhumation of eclogite-bearing high-pressure mica schists from the Fore-Sudetic Block, SW Poland

Nowak I.

Geologia Sudetica

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1998

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Vol. 31, nr 1

3-31

EN

Mica schists with eclogite lenses appear within the Fore-Sudetic Block in the vicinity of Kamieniec Ząbkowicki. In this paper their metamorphic and structural evolution and geotectonic context is discussed. The mica schists registered a clockwise metamorphic P-T path with two peaks of metamorphism - a pressure peak and a temperature peak. This path indicates compression and crustal thickening during the initial stage of metamorphism, continuing until pressure peak conditions were achieved during continental collision. The minimum pressure and temperature conditions for the pressure peak of these mica schists (11-12 kbar and 400-430°C) and the presence of replacement pseudomorphs after lawsonite indicate that during HP metamorphism the mica schists were at shallower depths than the eclogites and the schists experienced borderline blueschist/eclogite facies conditions. In the mica schists, decompression took place under conditions of rising temperature until the temperature peak was achieved under amphibolite facies conditions (579+/-35°C and 7.4+/-0.2 kbar). This was connected to the upwelling of Variscan granitoid magmas. After the temperature peak of metamorphism further decompression was isothermal. The mica schists were deformed at least four times. The earliest structures (F1) are defined by a HP mineral assemblage (phengite, pseudomorphs after lawsonite, kyanite, rutile, chloritoid, paragonite). The exhumation of the mica schists mostly occurred in a low-angle (?) normal faulting regime (F2) producing SW-vergent structures, coeval with the upwelling of the granitoid magmas. Further uplift and exhumation during isothermal decompression went on by transpression and thrusting to the east (F3) in a continued collisional setting. Late orogenic extension (F4) in the Kamieniec Ząbkowicki area was accomplished by normal faulting on zonally reworked WSW-dipping S2 surfaces.