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    Wyświetlanie 1-4 z 4
    Tytuł:
    Zircon U-Pb ages of granitoid apophyses in the western part of the Kłodzko–Złoty Stok Granite Pluton (SW Poland)
    Autorzy:
    Mikulski, S.Z.
    Williams, I. S.
    Powiązania:
    https://bibliotekanauki.pl/articles/2059727.pdf
    Data publikacji:
    2014
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Variscan granitoids
    apophyses
    zircon
    SHRIMP geochronology
    Sudetes
    Opis:
    Granitoids from the Graniec–Bardo and Myszak apophyses of the Kłodzko–Złoty Stok (KZS) Granite Pluton that intrude the Upper Paleozoic flysch of the Bardo Unit have zircon U-Pb ages, measured by SHRIMP, of 341.6 ± 2.8 Ma and 341.4 ± 2.2 Ma, respectively. These results augment our previous dating that recorded a short period of Middle Mississippian (Visean) hypabyssal magmatism that produced a variety of KZS igneous rocks of different compositions between ca. 341 and 331 Ma. The Graniec–Bardo and Myszak apophyses belong to the earliest stage of the pluton emplacement. Geochemical and petrographic studies of the dated samples indicate that they are biotite- and hornblende-rich tonalite and syenogabbro of diverse composition and typical of rocks originating from hybrid magmas formed in the geotectonic transition from an early stage collisional granitoid emplacement to its fast orogenic uplift. The polymetallic auriferous ore mineralisation of contact metasomatic type found in intimate contact with the Graniec–Bardo apophysis near Bardo Śląskie may also be of Visean age.
    Źródło:
    Geological Quarterly; 2014, 58, 2; 251--262
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Zircon U-Pb dating of igneous rocks in the Radzimowice and Wielisław Złotoryjski auriferous polymetallic deposits, Sudetes, SW Poland
    Autorzy:
    Mikulski, S. Z.
    Williams, I. S.
    Powiązania:
    https://bibliotekanauki.pl/articles/191720.pdf
    Data publikacji:
    2014
    Wydawca:
    Polskie Towarzystwo Geologiczne
    Tematy:
    zircon
    SHRIMP geochronology
    gold deposit
    porphyries
    Variscides
    Sudetes
    Opis:
    A rhyolite porphyry in the Radzimowice deposit at Bukowinka Hill has a SHRIMP zircon U-Pb age of 314.9 ± 3.1 Ma. This is consistent with previous zircon dating of a monzogranite and a rhyodacite (ca. 315 Ma) in the Żeleźniak sub-volcanic intrusion (ZI), considered to be the igneous rocks, representing the oldest magmatic pulses in the region. First-stage mesothermal auriferous sulphide mineralization in the deposit was connected to hydrothermal processes, associated with the rhyodacite intrusions. This was followed by tectonic activity and younger alkaline magmatism in a post-collisional geotectonic setting. The first-stage Au-bearing sulphide mineralization was cataclased and overprinted by younger epithermal base-metal sulphides with microscopic Au, associated with Bi-Te-Ag minerals. The younger magmatic pulses are represented by porphyritic andesites and lamprophyric dykes, which cut the ZI. Zircon from these dykes yielded ages of 312.8 ± 2.8 Ma for an andesite porphyry and 312.4 ± 4 Ma for a lamprophyre. All these magmatic pulses, evidenced in the Radzimowice deposit, are considered to be the oldest post-orogenic sub-volcanic magmatism cutting the basement of the intramontane basins in the Sudetes, on the NE margin of the Bohemian Massif. A rhyolite porphyry in the famous 'Organy' exposure at Wielisław Złotoryjski (WZ) on the SE margin of the North-Sudetic Basin is younger, 297.5 ± 2.8 Ma. Vein-type auriferous ore mineralization, hosted by Early Palaeozoic graphitic schists in intimate contact with rhyolite porphyry in WZ, is also correlated with this magmatism. The auriferous ore mineralization at Radzimowice and Wielisław Złotoryjski formed at different times, during different magmatic pulses and successive hydrothermal stages, despite several similarities in geologic setting and country- and host-rock compositions. There was a transition from a post-collisional to a within-plate setting over about 20 Ma in Late Carboniferous-Early Permian times, with the older Żeleźniak and Bukowinka sub-volcanic intrusions in the uplifted part of the Kaczawa Metamorphic Complex (ZI) and the younger Wielisław Złotoryjski sub-volcanic intrusion in the metamorphic basement of an intramontane basin.
    Źródło:
    Annales Societatis Geologorum Poloniae; 2014, 84, 3; 213-233
    0208-9068
    Pojawia się w:
    Annales Societatis Geologorum Poloniae
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Wczesnokarboński wiek intruzji platformowych w podłożu krystalicznym NE Polski
    Early Carboniferous age of the cratonic intrusions in the crystalline basement of NE Poland
    Autorzy:
    Krzemińska, E.
    Wiszniewska, J.
    Williams, I.S.
    Powiązania:
    https://bibliotekanauki.pl/articles/2074482.pdf
    Data publikacji:
    2006
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    zircon
    U-Pb SHRIMP geochronology
    closure temperature
    mafic-alkaline magmatism
    Early Carboniferous
    NE Poland
    Opis:
    Three mafic-alkaline intrusive bodies in NE Poland: Ełk, Pisz and Tajno, have been dated recently with U-Pb SHRIMP method. An earlier Rb-Sr whole rock isochron of Ełk syenites pointed to an age 355š4 Ma, while K-Ar age estimates suggested a Late Paleozoic age of Pisz and Tajno rocks, however, in a wide range between 349-291 Ma and 327-289 Ma, respectively. In the paper, we present new geochronological results and discuss the problem of the closure temperatures for different minerals and different isotopic systems used in previous age determinations. Much of the early dating works has been done using K-Ar method. Biotite and K-feldspar retain radiogenic Ar quantitatively below 280 -200şC. Only if magmatic bodies cooled quickly and remained unmetamorphosed, K-Ar and Rb-Sr ages estimate accurately the intrusion emplacement. Zircon used for U-Pb datings has a closure temperature over 800şC, that is comparable to the temperature of magma’s solidus. Therefore U-Pb magmatic zircons dates could be interpreted as an intrusion emplacement ages. The obtained U-Pb results of 347.7 š8 Ma (Ełk) and 345.5š5 Ma (Pisz) have shown very consistent Early Carboniferous age of platform mafic-alkaline magmatic activity. This new U-Pb SHRIMP dating indicates that Ełk and Pisz intrusions are coeval and together with the Tajno alkaline-carbonatite massif could be affined with the Late Devonian Kola Alkaline Carbonatite Province (KACP).
    Źródło:
    Przegląd Geologiczny; 2006, 54, 12; 1093-1098
    0033-2151
    Pojawia się w:
    Przegląd Geologiczny
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Rewizja wieku "najstarszych" skał w podłożu krystalicznym północno-wschodniej Polski
    Revision of the "oldest" rocks age in the crystalline basement of NE Poland
    Autorzy:
    Krzemińska, E.
    Wiszniewska, J.
    Williams, I.S.
    Powiązania:
    https://bibliotekanauki.pl/articles/2074437.pdf
    Data publikacji:
    2006
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    pegmatyt
    monacyt
    ziarna cyrkonu
    mikroskopia elektronowa
    wysokopróżniowy mikroskop skaningowy
    zircon
    monazite
    U-Pb SHRIMP geochronology
    Late Paleoproterozoic
    NE Poland
    Opis:
    The oldest geochronological results between 2.69–2.57 Ga was previously obtained by using K–Ar method on biotite from pegmatite from Jastrzębna IG–1 borehole. In consequence, in many published reports up to 1998, the Mazowsze (or Masovian) granitoid massif has been regarded as Archean age structure. Therewithal, other rocks in the area, e.g. Bargłów gneiss sequence traditionally were described as Archean in age. In the paper we present new U–Pb SHRIMP zircon and monazite results for above mentioned rocks which have been considered as Archean. Cathodoluminescence images and SHRIMP analysis were carried out for zircons and monazites from Jastrzebna IG–1 pegmatite of 514 m depth (a historical sample previously dated by K–Ar method) and for zircon magmatic cores from Bargłów IG–2 orthogneiss of the 708 m depth. The obtained U–Pb ages of 1826 š12 Ma (zircon) and 1789š34 Ma (monazite), and 1835š28 Ma (zircon) for two rock samples respectively have shown Paleoproterozoic origin. Only 4 of the 24 analysed zircons have clearly discordant results, which are all from the Jastrzebna pegmatite, where Pb–loss was possible (in partially metamict U–rich zircon grains). The new U–Pb SHRIMP dating indicates that Jastrzębna pegmatite and Bargłów magmatic protolith of the orthogneiss is only Late Paleoproterozoic in age and in general about 700 Ma younger than previously reported by K–Ar method. Therefore, there is no unequivocal evidence of the presence of Archean rocks in crystalline basement of NE Poland. This study has been undertaken as a part of a collaborative research agreement between the Polish Geological Institute and Geochronology and Isotope Geochemistry Research School of Earth Sciences of the Australian National University in Canberra.
    Źródło:
    Przegląd Geologiczny; 2006, 54, 11; 967-973
    0033-2151
    Pojawia się w:
    Przegląd Geologiczny
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-4 z 4

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