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The Variscan overthrust of the Lower Palaeozoic gneiss unit on the Cadomian basement in the Strzelin and Lipowe Hills massifs, Fore-Sudetic Block, SW Poland: is this part of the East-West Sudetes boundary?

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Oberc-Dziedzic T. , Madej S.

Geologia Sudetica

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2002

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tom Vol. 34

39-58

EN

The problem of the position of the boundary between the geological structures of the West and the East Sudetes has been a topic of discussion since 1912, when F.E. Suess developed the concept of the Moldanubian overthrust as a boundary between the Moldanubian and Moravo-Silesian zones. The West Sudetes comprise gneisses of Cambro-Ordovician protolith age with inclusions of high pressure metamorphic rocks. The Cadomian basement, referred to as the Brunovistulian and overlain by Devonian rocks, is characteristic of the East Sudetes. The location of the East-West Sudetes boundary is well-defined in the mountainous part of the Sudetes but still a matter of debate in the Fore-Sudetic Block. This paper puts forward a new approach to this problem. The Proterozoic Strzelin gneiss with its Proterozoic (the older schist series) and Devonian envelope (the Jegłowa beds) are tectonically overlain by the Early Palaeozoic Gościęcice gneiss and the light Stachów gneiss with its envelope. The former occurs in the footwall and the latter in the hanging wall rocks of the Strzelin Thrust. This juxtaposition resembles the situation along the East-West Sudetes boundary separating two domains with contrasting protolith ages. Consequently, the Strzelin Thrust is considered part of the border zone between the East and West Sudetes, i.e. the northern continuation of the Ramzova/Nyznerov thrust to the Fore-Sudetic Block. At the present erosion level, the hanging wall rocks of the Strzelin Thrust are separated from their roots and form klippen. The minimum transport distance along the thrust is estimated at 10 km. The Strzelin Thrust forms a generally shallowly dipping domed surface. It becomes steeper east of the Strzelin massif, where it is hidden beneath Cenozoic sediments, and west of the Lipowe Hills, where it follows the eastern border of the Kamieniec Ząbkowicki Metamorphic Complex. The hanging wall is probably rooted in the strongly mylonitised mica schists exposed along the Mała Ślęza river. The thrust zone is a wide mylonitic belt carrying relatively HT and HP garnet-bearing amphibolites in the northern part of the Strzelin massif and the strongly mylonitised Henryków gneiss and quartzites in the southern part at the Lipowe Hills. This paper discusses the problem of the East-West Sudetes boundary, mainly in the framework of the Strzelin massif. The attitude of this boundary in other parts of the Fore-Sudetic Block is still unclear because of poor exposure and numerous faults of E-W and NW-SE orientation that displace it from its original position.

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The granitoids of the Lipowe Hills (Fore-Sudetic Block) and their relationship to the Strzelin granites

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Oberc-Dziedzic T. , Pin C.

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tom Vol. 33, nr 1

17-22

EN

Muscovite-biotite granites, medium-grained biotite tonalites and fine-grained granodiorites from three boreholes situated in the middle part of the Lipowe Hills were characterized. It was found that the muscovite-biotite granites from the boreholes correspond to the Górka Sobocka granite known from the northern part of the Lipowe Hills. This granite was in turn compared to the light coloured granitoids, the so-called Gębczyce and Biały Kościół granites, from the Strzelin crystalline massif. The age link between the muscovite-biotite granites from the Lipowe Hills crystalline complex and those from the Strzelin massif was confirmed by the result of the whole-rock Rb-Sr analyse of a muscovite-biotite granite sample collected in the Górka Sobocka quarry. This result plots on the isochron obtained previously for the muscovite-biotite granites from the Strzelin and Gębczyce quarries at ca 330 Ma, with an initial 87Sr/86Sr ratio of 0.7055.

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Ore mineralization in the Miedzianka area (Karkonosze-Izera Massif, the Sudetes, Poland): new information

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Mochnacka K. , Oberc-Dziedzic T. , Mayer W. , Pieczka A.

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tom Vol. 43, iss. 3/4

155--178

EN

The Miedzianka mining district has been known for ages as a site of polymetallic ore deposits with copper and, later, uranium as the main commodities. Although recently uneconomic and hardly accessible, the Miedzianka ores attract Earth scientists due to the interesting and still controversial details of their ore structure, mineralogy and origin. Our examination of the ore mineralization from the Miedzianka district was based exclusively on samples collected from old mining dumps located in the vicinity of Miedzianka and Ciechanowice, and on samples from the only available outcrop in Przybkowice. In samples from the Miedzianka field, chalcopyrite, pyrite, galena, bornite, chalcocite, digenite, arsenopyrite, magnetite, sphalerite, tetrahedrite-tennantite, bornite, hematite, martite, pyrrhotite, ilmenite, cassiterite and covellite are hosted in quartz-mica schists and in coarse-grained quartz with chlorite. In the Ciechanowice field, the ore mineralization occurs mainly in strongly chloritized amphibolites occasionally intergrown with quartz and, rarely, with carbonates. Other host-rocks are quartz-chlorite schist and quartzites. Microscopic examination revealed the presence of chalcopyrite, pyrite, sphalerite, galena, tetrahedrite-tennantite, bismuthinite, native Bi, arsenopyrite, löllingite, cassiterite, cobaltite, gersdorffite, chalcocite, cassiterite, bornite, covellite, marcasite and pyrrhotite. Moreover, mawsonite and wittichenite were identified for the first time in the district. In barite veins cross-cutting the greenstones and greenschists in Przybkowice, we found previously-known chalcopyrite, chalcocite and galena. The composition of the hydrothermal fluids is suggested to evolved through a series of consecutive systems characterized, in turn, by Ti-Fe-Sn, Fe- As-S, Fe-Co-As-S, Cu-Zn-S and, finally, Cu-Pb-Sb-As-Bi compositions.

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The Sudetic geological mosaic : Insights into the root of the Variscan orogen

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Kryza R. , Mazur S. , Oberc-Dziedzic T.

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tom Vol. 52, nr 8/2

761-773

EN

The Sudetes in the NE part of the Bohemian Massif stretch between the NW–SE-trending Odra Fault Zone and Elbe Fault Zone and represent a structural mosaic which was shaped, predominantly, during the Variscan orogeny. They are composed of various geological units, including basement units in which Neoproterozoic to Carboniferous rocks are exposed, and a post-orogenic cover of younger deposits. During the long history of geological research, the Sudetes have become a “type locality” for a range of important geological phenomena, such as granites and orthogneisses, ophiolites and (meta)volcanic sequences, granulites, eclogites and blueschists, nappe tectonics and terrane concepts. In spite of significant recent achievements, many key problems need further study, and a selection of them is proposed in this paper: (a) the presence of older, Neoproterozoic (Cadomian) rocks and their position within the Variscan collage, (b) the character and emplacement setting of Palaeozoic, pre-Variscan sedimentary successions and magmatic complexes (including ophiolites), (c) structural evolution, metamorphism (in particular HP/T grades) and exhumation of deeper crustal blocks during the Variscan orogeny, and (d) post-orogenic development. Future investigations would require an interdisciplinary approach, combining various geological disciplines: structural geology, petrology, geochemistry, geophysics and geochronology, and, also, multilateral interlaboratory cooperation.

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Variscan multistage granitoid magmatism in Brunovistulicum: petrological and SHRIMP U-Pb zircon geochronological evidence from the southern part of the Strzelin Massif, SW Poland

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Oberc-Dziedzic T. , Kryza R. , Białek J.

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tom Vol. 54, No 3

301-324

EN

U-Pb SHRIMP ages of one granodiorite and two tonalite samples from the Strzelin Massif, northern part of Brunovistulicum, reveal three distinct stages of Carboniferrous-early Permian granitoid magmatism: tonalitic I - 324 Ma, granodioritic - 305 Ma and tonalitic II/granitic - 295 Ma. The first stage of magmatism coincided with the first migmatization event which took place shortly after the first deformation. The second stage of granitoid plutonism was coeval with the second migmatization event which produced abundant pegmatites. It took place after compressional phases of the second deformation and was related to decompression at the beginning of tectonic denudation. The third, most abundant stage of magmatism was connected with late extension in that part of the Variscan Orogen.

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Granitoids of the Odra Fault Zone: late- to post-orogenic Variscan intrusions in the Saxothuringian Zone, SW Poland

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Oberc-Dziedzic T. , Żelaźniewicz A. , Cwojdziński S.

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tom Vol. 32, nr 1

55-71

EN

There are 5 occurrences of granodioritic to monzogranitic rocks found subsurface along the Odra Fault Zone a Permo-Mesozoic horst defining the northeastern edge of the Bohemian Massif. These are generally unfoliated, I-type granitoids with low A/CNK and initial Sr/Sr ratios making them geochemically and petrographically akin to late- to post-kinematic Variscan granitoids of the West Sudetes, being closest to those of the eastern part of the Fore-Sudetic Block (Strzelin, Niemcza). They represent late/post-orogenic, collisional intrusives of Early-Late Carboniferous age which are widespread throughout the Saxothuringian and Moldanubian zones in the Bohemian Massif. The country rocks to the granitoids are mica schists and paragneisses attaining staurolite-grade. The granitoids lack evidence of ductile or brittle strike-slip movement of Late Carboniferous-Permian age along the Odra Fault Zone, which thus has to be taken as a dip-slip fault zone, rather than a late Variscan dextral strike-slip feature. Brittle to semi-brittle deformation of the Odra granitoids relates to the formation of the horst during Permo-Mesozoic times. A Silurian-Early Devonian magmatic arc of the Mid-German Crystalline Rise, identified further to the west in Germany, probably does not have an easterly prolongation into Poland because there is no evidence for arc-related magmatism of that age in the Sudetes and Fore-Sudetic Block.

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Granitoids of the Odra Fault Zone: Late- to Post-Orogenic Variscan intrusions in the Saxothuringian Zone, SW Poland

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Oberc-Dziedzic T. , Zelazniewicz A. , Cwojdzinski S.

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1999

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tom 32

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nr 1

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The Orthogneiss and Schist Complex of the Karkonosze-Izera Massif (Sudetes, SW Poland): U-Pb SHRIMP zircon ages, Nd-isotope systematics and protoliths

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Oberc-Dziedzic T. , Kryza R. , Pin C. , Mochnacka K. , Larionov A.

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tom 41