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Wyszukujesz frazę "Zircon" wg kryterium: Temat


Wyświetlanie 1-3 z 3
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:
Ambiguous geological position of Carboniferous rhyodacites in the Intra-Sudetic Basin (SW Poland) clarified by SHRIMP zircon ages
Autorzy:
Kryza, R.
Awdankiewicz, M.
Powiązania:
https://bibliotekanauki.pl/articles/2058977.pdf
Data publikacji:
2012
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Sudetes
Variscan orogeny
Carboniferous
SHRIMP zircon dating
volcanism
subvolcanic intrusions
Opis:
Rhyodacite sheets (the Sady Górne Rhyodacites) in the lowermost part of the Permo-Carboniferous Intra-Sudetic Basin molasse fill have been mapped as intrusives but, later on, based on ambiguous field and petrographic evidence, reinterpreted as lower Carboniferous lavas and tuffs; if so, they would mark the earliest episode of late-orogenic volcanism in the Intra-Sudetic Basin and in the whole Sudetes region in SW Poland. However, re-examination of field relationships and new observations are consistent with an intrusive emplacement of the rhyodacites as conformable to semiconformable, simple to composite sheets. SHRIMP zircon study indicates that the rhyodacites contain rare inherited zircons of ca. 560 Ma, and ca. 470 Ma (or slightly older), and a main population of zircons with an average concordia age of 306.1 š2.8 Ma. This latter age documents the emplacement of the rhyodacites during a mid/late late Carboniferous (Westphalian) stage of volcanism in the Intra-Sudetic Basin in the Central European Variscides. This post-orogenic volcanism was possibly initiated several million years later than previously assumed, and could have comprised a few pulses over a relatively prolonged time span of millions of years.
Źródło:
Geological Quarterly; 2012, 56, 1; 55-66
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-3 z 3

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