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    Wyświetlanie 1-3 z 3
    Tytuł:
    The Variscan Orogen in Poland
    Autorzy:
    Mazur, S.
    Aleksandrowski, P.
    Kryza, R.
    Oberc-Dziedzic, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/2058949.pdf
    Data publikacji:
    2006
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Bohemian Massif
    Sudetes
    Palaeozoic
    terranes
    metamorphism
    magmatism
    Opis:
    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.
    Źródło:
    Geological Quarterly; 2006, 50, 1; 89-118
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Hydrothermal veins linked with the Variscan structure of the Prague Synform (Barrandien, Czech Republic): resolving fluid-wall rock interaction
    Autorzy:
    Halavínová, M.
    Melichar, R.
    Slobodník, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/2059098.pdf
    Data publikacji:
    2008
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Bohemian Massif
    Palaeozoic
    Variscan veins
    carbonates
    isotope geochemistry
    fluid systems
    Opis:
    Variscan syntectonic hy dro ther mal veins of the Prague Synform are important traces of small-scale fluid migration in Lower Palaeozoic sedimentary rocks — a process induced by late Variscan tectogenesis. Two main structural types of Variscan syntectonic calcite veins were recognised during fieldwork. Veins of Type I have an irregular or sigmoidal shape and are often arranged in en echelon arrays. A shearing regime during the formation of this type is deduced. Veins of a second structural type (Type II) have a more regular and straight shape relative to those of Type I and in some places form a dense network. The structural position of the Type II veins is related to structural elements of Variscan folds. Veins were formed due to interlayer-slip combined with fold- related fracturing that gave rise to the infilling of dilational structures. A tensional regime also permits growth of the fibrous veins. Two princpal directions were distinguished within the Type II veins. The first one is NNW–SSE and the second one shows a perpendicular ENE–WSW orientation. These directions seem to be parallel and/or perpendicular to the nappearchitec ture of the Prague Synform. Variscan syntectonic veins crystallised in a relatively closed, rock-buf fered system. Extraction of chemical components from surrounding rocks is indicated by a combined microprobe/cathodoluminescent study and by isotope geochemistry. The carbon isotope values of hydrothermal calcites reflect the carbon isotope composition of the host rocks. The delta exp.13C values of vein calcites and their host Silurian rocks are between –0.29 and –1.98‰ PDB. The same relationships were found between the veins and the host Devonian limestones (from 1.72 to 2.52‰ PDB). Samples close to the Silurian/Devonian boundary show transition values between 0.25 and + 1.16‰ PDB. The Sr-isotopic signature supports a genetic link between the calcite veins and the host rocks. The 87Sr/86Sr ra tio in calcites ranges between 0.708619 and 0.708738 and in wall rocks be tween 0.708755 and 0.709355. Aqueous and hydrocarbon-rich fluid systems have been found in fluid inclusions. Liquid hydrocarbons show mostly a light blue fluorescence suggesting the presence of higher hydrocarbons. They are more abundant in dark Silurian rocks, which are rich in organic matter. Lower salinities (0.5–8.9 eq. wt.% NaCl) and homogenization temperatures with a maximum around 140gradeC are typ i cal for the aqueous (H2O–NaCl) system. The oxygen isotopic composition of fluids ranges between –2.80 and +3.33‰ SMOW. This indicates that transformed formation waters in teracted with the host rocks and/or deeply circulating isotopically depleted meteoric waters. Intersections with the isochore specify border trapping temperatures between 127 and 160grade C and pressures from 300 to 1070 bars.
    Źródło:
    Geological Quarterly; 2008, 52, 4; 309-309
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Zarys budowy i ewolucji tektonicznej waryscyjskiej struktury Sudetów
    Outline structure and tectonic evolution of the Variscan Sudetes
    Autorzy:
    Mazur, S.
    Aleksandrowski, P.
    Szczepiński, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/2074758.pdf
    Data publikacji:
    2010
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Masyw Czeski
    paleozoik
    tektonostratygraficzne terrany
    tektonika
    deformacja
    uskoki przesuwcze/normalne
    Bohemian Massif
    Palaeozoic
    tectonostratigraphic terranes
    tectonics
    deformation
    strike-slip faults
    Opis:
    The structure and evolution of the Polish part of the Sudetes is reviewed on the basis of published data and interpretations. The Sudetic segment of the Variscides and its adjacent areas were subjected to multi-stage accretion during successive collisional events that followed closure of different segments of the Rheic Ocean. Early Variscan deformations culminated in the Late Devonian due to docking of the Armorican terrane assemblage to the southern margin of Laurussia. The Variscan orogenic activity continued into the Carboniferous and was associated with a new collision and intense folding and thrusting, followed by abundant magmatism, gravitational collapse and resulting exhumation of deeply buried metamorphic complexes as well as by inversion of the foreland basin. In the Sudetes, Variscan tectonostratigraphic units are tectonically juxtaposed and often bear record of contrasting exhumation/cooling paths, constrained by palaeontological and geochronological data. This provides evidence for the presence of allochthonous units, of partly cryptic tectonic sutures and an of overall collage-type tectonics of that area. The main lithostratigraphical components distinguished within the Sudetes are: 1) non-metamorphic to metamorphosed Neoproterozoic igneous suites accompanied by volcano-sedimentary successions, 2) Late Cambrian granitoids gneissified during the Variscan orogeny, 3) variously metamorphosed Ordovician through Devonian volcano-sedimentary successions deposited in pre-orogenic extensional basins, 4) dismembered fragments of a Late Silurian ophiolitic complex, 5) Devonian to Lower Carboniferous sedimentary successions of a passive continental margin, 6) Carboniferous granitoids, and 7) clastic sediments of Devonian and/or Early Carboniferous intramontane basins. All these components are assembled to form part of the internal Variscan orogenic zone largely exposed within the area of the Bohemian Massif. A three-partite subdivision of the Sudetes proposed here reflects different timing of 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 of the Devonian and Carboniferous and during Early Carboniferous, respectively. Problems in extending the classical tectonostratigraphic zonation of the Variscides into the Sudetes are explained as due to activity of Late Palaeozoic strike-slip faults and shear zones, disrupting and dispersing the initially more simply distributed tectonostratigraphic units into the present-day structural mosaic.
    Źródło:
    Przegląd Geologiczny; 2010, 58, 2; 133-145
    0033-2151
    Pojawia się w:
    Przegląd Geologiczny
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-3 z 3

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