Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: Saxothuringian Terrane

Sortuj według:

Ogranicz wyniki do:

The eastern part of the Saxothuringian Terrane characterized by zircon and monazite data from the Doboszowice Metamorphic Complex in the Sudetes (SW Poland)

Jastrzębski Mirosław, Żelaźniewicz Andrzej, Stawikowski Wojciech, Budzyń Bartosz, Krzemińska Ewa, Machowiak Katarzyna, Madej Stanisław, Białek Dawid, Sláma Jiří, Czupyt Zbigniew, Jaźwa Aleksandra

Annales Societatis Geologorum Poloniae

2023

Vol. 93, No. 3

229--249

In the Variscan Bohemian Massif, orthogneiss complexes of different sizes, derived from early Palaeozoic granitoids, are accompanied by metavolcano-sedimentary successions. They are common in the Sudetes, SW Poland, and belong mainly to the Saxothuringian Terrane. In order to better characterize the evolution of the latter, new U-Pb and O isotopic zircon analyses, combined with zircon typology and new U-Th-Pb isotopic monazite analyses, were performed. The present data show that the S-type granitic precursors of the Doboszowice orthogneisses (Fore-Sudetic Block) and the Śnieżnik gneisses (Sudetes) were formed at ca. 495 Ma from differently evolved magmas. Protoliths of the Doboszowice orthogneisses developed entirely in the crust, whereas the precursors to the Śnieżnik gneisses received some mantle input. Metasediments that accompany the Doboszowice orthogneisses reveal zircon spectra, which point to a late Cambrian-Early Ordovician sedimentary age. These spectra, in addition to predominant grains with Ediacaran ages, contain up to 10% of zircons dated at ca. 1.0 Ga. Therefore, it is suggested that the parent basin was supplied with detritus coming from areas, located in the Libyan-Nubian part of North Africa. Using also earlier published data, such a provenance is assigned to the units that now occur in the eastern part of the Fore-Sudetic Block. Late Cambrian-Early Ordovician granite intrusions and the concurrent accumulation of sediments originated in an extensional setting of the peri-Gondwana rifted continental margin or a back-arc setting. The Pb/U and Pb/Th monazite data constrain the ca. 346–341-Ma peak of the Variscan regional metamorphism in the eastern Saxothuringian Terrane and the prolonged juxtaposition of now adjacent tectonic units at least until 330 Ma.

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

2018

Vol. 62, No. 2

237--256

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.