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1

The Saxothuringian Terrane affinity of the metamorphic Stachów Complex (Strzelin Massif, Fore-Sudetic Block, Poland) inferred from zircon ages

Oberc-Dziedzic T., Kryza R., Madej S., Pin C.

Geological Quarterly

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2018

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Vol. 62, No. 2

237--256

EN

The Saxothuringian Terrane defined in the western part of the Bohemian Massif is regarded to have easterly continuations in the Karkonosze–Izera Massif, the Kamieniec Ząbkowicki Belt and the Orlica–Śnieżnik Dome. All these units comprise Early Ordovician (~500 Ma) metagranites associated with mica schists. Even more to the east, ~500 Ma metagranites and metasedimentary rocks occur also in the Strzelin Massif of the East Sudetes, where they are known as the pale and dark Stachów gneisses, respectively. Altogether, these rocks form the Stachów Complex which was thrust on the Strzelin Complex of the Brunovistulicum Terrane during the Variscan Orogeny. The contribution presents lines of evidence for a Saxothuringian affinity of the Stachów Complex rocks: (1) the new SHRIMP U-Pb age data of zircons from both the pale and dark Stachów gneisses; (2) the indication that the zircon age spectra from the ~500 Ma granitoids and their accompanying metasedimentary rocks are similar to those found in other parts of the Sudetes; (3) the “Armorican” age pattern of inherited zircons of the pale Stachów gneisses, as also observed in the Saxothuringian Terrane; (4) the similarity of trace elements and Sm-Nd isotope data of the Stachów gneisses and correlative rocks from the Karkonosze–Izera Massif and the Orlica–Śnieżnik Dome.

2

Last stage of Variscan granitoid magmatism in the Strzelin Massif (SW Poland) : petrology and age of the biotite-muscovite granites

Oberc-Dziedzic T., Kryza R., Pin C.

Geological Quarterly

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2015

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Vol. 59, No. 4

718--737

EN

New petrographic and geochemical data show some differences between Variscan Bt-Ms granites occurring either as small plutons or dykes in the Strzelin Massif (SW Poland). The granites of the Gromnik and Górka Sobocka plutons are rich in micas and crystallized from "wet" magmas; the granites in the dykes and in the Gębczyce pluton are mica-poorer and cordierite-bearing rocks, derived from “dryer” magmas. The lower initial eNd values in the Bt-Ms granites of the dykes, compared with those in the plutons, reflect a more "crustal" signature of the former, possibly due to local crustal assimilation, via AFC, shortly before emplacement. Much more radiogenic initial 87Sr/86Sr ratios in the dykes, up to 0.726, further suggest the involvement of extraneous, hydrous crustal fluids enriched in 87Sr during the evolution of late-stage magma derivatives. The new U-Pb SHRIMP zircon age of 296 ± 6 Ma for the Gębczyce Bt-Ms granite shows that this body belongs to the third stage of magmatism in the Strzelin Massif. The U-Pb SHRIMP zircon data for the Bt-Ms granite dykes provide ages similar to those of their host rocks: c. 295 Ma for the Gęsiniec tonalite and the enclosed Bt-Ms granite, and c. 285 Ma for the Strzelin biotite granite and its Bt-Ms granite dykes. These new data from peraluminous rock-types complement our previous studies focused on the tonalites, granodiorites and biotite granites, and shed light on the late-stage igneous evolution of the Strzelin Massif.

3

Variscan granitoid plutonism in the Strzelin Massif (SW Poland) : petrology and age of the composite Strzelin granite intrusion

Oberc-Dziedzic T., Kryza R., Pin C., Madej S.

Geological Quarterly

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2013

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Vol. 57, No. 2

269–-288

EN

Petrological data and recently published U/Pb zircon SHRIMP ages reveal a protracted Variscan magmatic evolution in the Strzelin Massif (SW Poland), with three main stages of granitoid plutonism: 1 – tonalitic I, 2 – granodioritic and 3 – tonalitic II/granitic. The granitoids of the second and third stages form the Strzelin intrusion that is composed of three varieties: medium-grained biotite granite, fine-grained biotite granite and fine-grained biotite-muscovite granite. New SHRIMP data show that the medium-grained and fine-grained biotite granites comprise different zircon populations that reflect complex and prolonged plutonic processes. Two distinct magmatic events seem to be represented by well-defined zircon populations with apparent 206Pb/238U ages of 303 ± 2 Ma in the medium-grained biotite granite, and 283 ± 8 Ma in the fine-grained biotite granite. These dates, however, do not necessarily reflect the true magmatic ages, possibly being “rejuvenated” by radiogenic lead loss in zircons (impossible to resolve based on routine SHRIMP data). Based on field evidence, the third variety, the biotite-muscovite granite, postdates both types of biotite granites. The petrographic and geochemical features, including Nd isotope signature, along with various zircon inheritance patterns and ages, suggest that the parental magmas of the three granites originated from different crustal sources and were emplaced during three successive magmatic pulses.

4

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

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

Mineralogia

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2012

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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.

5

Late stage Variscan magmatism in the Strzelin Massif (SW Poland): SHRIMP zircon ages of tonalite and Bt-Ms granite of the Gęsiniec intrusion

Oberc-Dziedzic T., Kryza R.

Geological Quarterly

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2012

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Vol. 56, No 2

225-236

EN

The Gęsiniec composite intrusion in the northern part of the Strzelin Massif (Fore-Sudetic Block, SW Poland) was formed in the course of three late Variscan magmatic episodes: tonalitic I, granodioritic, and tonalitic II/granitic. The age of the Gęsiniec tonalite, 295 š3 Ma, is the same as that of another tonalite body in the southern part of the Strzelin Massif, the Kalinka tonalite. The younger biotite-muscovite (Bt-Ms) granite, in a dyke cutting the Gęsiniec tonalite, has an indistinguishable isotopic age of 295 š5 Ma; it contains, however, inherited zircons with ages between ca. 1.5 Ga to 374 Ma, similar to zircon ages from surrounding gneisses. This suggests that the magmatic protolith of gneisses and the magma of the Bt-Ms granite could have come from similar sources, or that the magma of the Bt-Ms granite was contaminated by the gneisses. Both the tonalite and Bt-Ma granite represent a late stage of the granitoid magmatism in the eastern part of the Variscan orogen.

6

Isotopic Re-Os age of molybdenite from the Szklarska Poręba Huta Quarry (Karkonosze, SW Poland)

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

Geological Quarterly

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2012

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Vol. 56, No 3

505--512

EN

New Re/Os isotopic data for molybdenite from the Szklarska Poręba Huta Quarry provide ages of 307 ± 2 Ma and 309 ± 2 Ma, respectively. The quarry is dominated by the porphyritic (“central”) and equigranular (“ridge”) varieties of the Karkonosze granite. Ore mineralisation hosted in aplogranite includes an assemblage of sulphides, sulphosalts, oxides and various rare phases. The molybdenite ages obtained are consistent with a previously published isotopic age of leucogranite (aplogranite?) from the same quarry and are only slightly older than a recently published, refined 2 6Pb/238U age of untreated zircons from the Szklarska Poręba Huta porphyritic granite. The age of the molybdenite corresponds moderately well to the younger stage of post-magmatic, pneumatolitic/hydrothermal activity of the Karkonosze granite (about 312 Ma).

7

Studies on magnetite and pyrite mineralization, and on their early Palaeozoic ocean-floor host-rocks from the Leszczyniec Unit (West Sudetes, Poland)

Oberc-Dziedzic T., Mochnacka K., Mayer W., Pieczka A., Creaser R. A., Góralski M.

Annales Societatis Geologorum Poloniae

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2011

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Vol. 81, No 2

133-160

EN

The Leszczyniec Unit extends along the eastern margin of the Karkonosze-Izera Massif. It comprises the Early Palaeozoic, MORB-like Leszczyniec complex composed of metabasites, metagranites and metasedi- ments. The metabasites host magnetite mineralization encountered in Jarkowice, whereas near Wieściszowice village the pyrite deposit occurs in metasediments and metabasites. The common feature of both sites is the almost complete absence of the accompanying ore minerals. Basing on petrographic, mineralogical, geochemical and microstructural studies, it was found that the metabasic rocks, which host magnetite mineralization, were lava flows, whereas the protoliths of pyrite-bearing schists were basic and acid tuffites accompanied by ocean-floor basalts. The igneous rocks from the Leszczyniec Unit were subjected to the ocean-floor metamorphism, whereas the accompanying sediments were altered by hydrothermal fluids enriched in sulphur ions, which reacted with iron derived from the sediment and promoted crystallization of pyrite. The sources of hydrothermal fluids were adjacent magmatic centres. The estimated age ~480 Ma for pyrite (Re-Os method) is similar to the previously known ~500 Ma age of metabasites (U-Pb, zircon method) from the Leszczyniec Unit, which establishes a temporal link between pyrite accumulation and the ocean-floor environment. The rocks of the Leszczyniec Unit, first altered by the ocean-floor metamorphism and the hydrothermal fluids, were subsequently subjected to the regional metamorphism at 360–340 Ma and the two-stage deformations of various intensities, followed by the third stage of deformations which caused the reorientation of the regional foliation. The zones of ductile and brittle deformations connected with the second deformation event host the accumulations of magnetite formed at the expense of Fe-bearing rock-forming minerals or from iron supplied from adjacent sources. In the pyrite-bearing schists, mineral assemblages formed during the hydrothermal alteration have been subjected to recrystallization and were included into domains defining foliation and lineation, which formed during the first stage of deformation. Pyrite crystals were affected by both deformation stages. At the end of the second stage, the invasion of fluids led to the dissolution of pyrite crystals and to the filling of cracks in pyrite crystals with chalcopyrite and tennantite. This process was followed by the formation of quartz veins with minor amounts of ore minerals.

8

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

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

Geological Quarterly

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2010

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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.

9

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

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

Geologia Sudetica

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2009

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Vol. 41

3-24

EN

Many basement units of the Variscan orogen that are exposed in the Sudetes, SW Poland, comprise widespread ~500 Ma orthogneisses and associated mica schists, the latter often of unknown age and derivation. Our new U-Pb sensitive high resolution ion microprobe (SHRIMP) zircon ages from two samples of the Izera metagranites, both around 503 Ma, are in a good agreement with the well established late Cambrian-early Ordovician magmatism in the West Sudetes. An Archean inherited zircon age of ~ 3.4 Ga is one of the oldest zircon ages reported so far from the Bohemian Massif. The orthogneisses of the Karkonosze-Izera Massif (KIM) have calculated TDM ages of between 1.50 and 1.93 Ga, but these ages are not necessarily evidence for a Mid-Proterozoic crustal derivation: more probably, they reflect the average of several detrital components mixed into the granitoid magma sources. In spite of likely age differences, the Lusatian greywackes, which outcrop to the west, and the mica schists of the KIM display similar geochemical characteristics, suggesting that both could have been derived from similar sources. However, the presence of lower Ordovician products of within-plate volcanism - intercalations of quartzofeldspathic rocks and amphibolites within the mica schists - supports an idea that the mica schist protoliths, derived mainly from crustal rocks, could have also contained an admixture of contemporaneous volcanic materials. The age spectra of inherited zircons from the KIM orthogneisses and their Nd-isotopic signatures are comparable to the Lusatian greywackes: this suggests that the Lusatian greywackes, or very similar rocks, could have been the source material for the granitic protoliths of the KIM orthogneisses.

10

New insights into the mineralization of the Czarnów ore deposit (West Sudetes, Poland)

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

Geologia Sudetica

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2009

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Vol. 41

43-56

EN

This paper provides new data on the mineralogy and mineral chemistry of the Czarnów ore deposit, a polymetallic vein that occurs within the eastern envelope of the Karkonosze Pluton (West Sudetes). New data are also provided on the deposits' geothermometry, mineral succession, and origins. The Czarnów ore vein is about 500 m long, strikes SW-NE, dips 80° SE and continues to a depth of 200 m. It is hosted within the albite-mica schists, quartzofeldspathic rocks and striped amphibolites that comprise the Czarnów Schist Formation (CSF); its western part is composed of almost monomineral arsenopyrite, whereas the southwestern part locally contains a pyrrhotite lens that extends downwards. Although many types of sulphides, sulphoarsenides, sulphosalts and native phases accompanied by oxides and arsenates have been previously reported, this paper describes four minerals that have not been previously identified from the Czarnów deposit: ferrokësterite, ikunolite, bismite and pentlandite. Geothermometry data suggest formation temperatures of arsenopyrite between 551 °C and 420 °C and that of sphalerite between about 400 °C to about 200 °C. Fluid inclusion data from vein quartz gave homogenization temperatures between 430 °C and 150 °C. Integrat on of textural and other data suggests the following primary mineral succession: early arsenopyrite and cassiterite as the high-temperature phases; then combinations of pyrrhotite, pyrite, chalcopyrite and sphalerite, all of which formed over a wide temperature range; finally, low temperature galena and Bi phases. Secondary weathering products overprint the primary sequences. Cataclasis of the first-formed arsenopyrite imply that mineralization was related to at least one tectonic event in the region. The Czarnów ore deposit probably resulted from hydrothermal activity associated with the near Karkonosze granite.

11

Ti remobilization and sulphide/sulphoarsenide mineralization in amphibolites: effect of granite intrusion (the Karkonosze–Izera Massif, SW Poland)

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

Geological Quarterly

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2008

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Vol. 52, No 4

349-349

EN

Our studies focus on ore mineralization in a contact-metamorphic aureole, using the Variscan Karkonosze Granite pluton as an example. The Karkonosze in trusion is enveloped by an Early Palaeozoic (about 500 Ma) metamorphic complex of the Izera–Kowary Unit composed of a diverse assemblage of gneisses, granitic gneisses, schists, amphibolites and marbles. The Budniki ore mineralization site was discovered in the early 1950's at the SE margin of the pluton. The uneconomic Ti-ox ide/sil i cate, Fe-Cu-Ni-Co-sulphide-sulphoarsenide, and uranium mineral deposits are hosted within amphibolites which were subjected to regional metamor phism fol lowed by contact meta - morphism. The Ti mineralization includes an ilmenite-titanite assemblage that originated from regional-metamorphic transformation of igneous Ti-bearing minerals, such as ilmenite and tschermakite, of the basic protoliths of amphibolites. During subsequent contact metamorphism, ilmenite was decomposed and, after wards, Al-rich titanite and rutile were formed. The Ti remobilization was coeval with an early stage of superimposed Fe-Cu-Ni-Co-sulphide/sulphoarsenide mineralization (pyrrhotite, pyrite, pentlandite, arsenopyrite, chalcopyrite, sphalerite and Fe-Ni-Co-As-S phases), related to the activity of the Karkonosze Granite hydrothermal system. The ore minerals formed successively within a wide range of temperatures (625–250gradeC).

12

The Variscan Orogen in Poland

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

Geological Quarterly

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2006

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Vol. 50, No. 1

89-118

EN

The structure and evolution of the Polish part of the Variscan Orogenic Belt is reviewed, based on published data and interpretations. The Sudetic segment of the Variscides, together with adjacent areas, experienced multi-stage accretion during successive collisional events that followed the closure of different segments of the Rheic Ocean. In SW Poland, Variscan tectono-stratigraphic units are tectonically juxtaposed and often bear record of contrasting exhumation/cooling paths, constrained by palaeontological and geochronological data. This points to the collage-type tectonics of this area. A three-partite subdivision of the Sudetes is proposed that reflects timing differences in deformation and exhumation of the respective segments. The Central,West and East Sudetes were deformed and amalgamated during the Middle/Late Devonian, at the turn from the Devonian to Carboniferous and during Early Carboniferous times, respectively. Problems in extending the classical tectono-stratigraphic zonation of the Variscides into the Sudetes are discussed and attributed to activity along Late Palaeozoic strike-slip faults and shear zones, disrupting and dispersing the initially more simply distributed tectono-stratigraphic units into the present-day structural mosaic. Relationships between the Variscan Externides and the foreland basin are explored. Sediments of the foreland basin locally onlap the external fold-and-thrust belt that had undergone an earliest Carboniferous partial tectono-thermal overprint. During the Late Carboniferous, the SW part of the foreland basin was heavily affected by thrusting and folding and incorporated into the Externides. DuringWestphalian C to Early Permian times, localized folding and thrusting affected the distal parts of the foreland basin, probably in response to dextral transpressional movements along NW–SE trending basement faults.

13

Gneiss protolith ages and tectonic boundaries in the NE part of the Bohemian Massif (Fore-Sudetic Block, SWPoland

Oberc-Dziedzic T., Kryza R., Klimas K., Fanning M.C., Madej S.

Geological Quarterly

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2005

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Vol. 49, No. 4

363--378

EN

Published geochronological data, petrology, geochemistry and geological context of orthogneisses in the Strzelin and the Stachów complexes (NE-part of the Fore-Sudetic Block), together with structural observations help to locate the northern extension of the boundary between the East and West Sudetes within the poorly exposed NE margin of the Bohemian Massif. The Strzelin complex, in the east, comprises the Strzelin gneiss, with zircon ages of 600š7 and 568š7Ma, and the Nowolesie gneiss with a mean zircon age of 1020_ 1Ma. The Stachów complex to the west, which forms several tectonic klippen in the Strzelin Massif and in the Lipowe Hills Massif, contains the Gościęcice gneiss and pale Stachów gneiss, both yielding Late Cambrian zircon ages (~500š5 Ma). The orthogneisses in both complexes correspond to peraluminous S-type granites, but have different inherited zircon ages and display contrasting trace element characteristics, indicating different sources and petrogenetic histories. Based on the ages, petrology and overall geological context, the Strzelin orthogneiss is similar to the Keprník orthogneiss of the East Sudetes, whereas the orthogneisses of the Stachów complex correspond to rocks known from theWest Sudetes (e.g. the Izera and Śnieżnik orthogneisses). The Stachów and the Strzelin complexes are separated by the Strzelin Thrust, which may be interpreted as the northern extension of the boundary between the East and West Sudetes, i.e. part of the boundary between the Brunovistulian and Moldanubian terranes of the NE part of the Bohemian Massif.

14

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

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

Przegląd Geologiczny

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2004

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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.

15

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?

Oberc-Dziedzic T., Madej S.

Geologia Sudetica

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2002

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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.

16

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

Oberc-Dziedzic T., Pin C.

Geologia Sudetica

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2000

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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.

17

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

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

Geologia Sudetica

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1999

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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.