Geochemistry, single zircon ages and Sm-Nd systematics of granitoid rocks from the Gory Sowie (Owl Mts), Polish West Sudetes: evidence for early Palaeozoic arc-related plutonism

Abstract:

Granitoid gneisses as well as their migmatitic and anatectic derivates were investigated from the Gory Sowie (Owl Mts) Massif of SW Poland in the central West Sudetes. The gneisses and migmatites are tectonically interlayered with paragneisses, and experienced several consecutive tectono-metamorphic events. Geochemically, the granitoid gneisses are calc-alkaline and similar to orogenic granite suites, which therefore lends support to a subduction-related origin. Single zircon Pb-Pb evaporation ages suggest that the gneiss precursors were emplaced between 473 and 488 Ma, and most samples analysed contain zircon xenocrysts with minimum ages between 1124 and 2620 Ma. An early phase of high-grade metamorphism is documented by an age of c. 440 Ma for an anatectically derived granite. Two late Variscan granites have an age of c. 333 Ma. Nd isotope systematics suggest variable involvement of crustal material in the generation of the granitoids. We speculate that the Gory Sowie Massif was part of Avalonia in early Palaeozoic times, derived from the northwestern margin of Gondwana, probably northern South America. Granitoid emplacement in the Ordovician took place along a Japan-type active continental margin while Avalonia drifted towards Baltica and the Tornquist Ocean was consumed. Collision with Baltica occurred in mid-Silurian times. Our data are compatible with an active magmatic arc extending from southern England to the southeastern Sudetes in Cambrian and Ordovician times.

Año de publicación:

1998

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Fuente:

scopus