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  • Author or Editor: Jaromir Ulrych x
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Three major groups (A-C) of Central European Variscan granitoids can be distinguished based on petrologic and chemical data: A. Low-K, high-Na, calc-alkaline, alkali-calcic, met/peraluminous, I- and S-type, trondhjemitic (slightly granodioritic)-suite, mostly magnesian granitoids formed at the early stage of continent-continent collision (353-356 Ma). These types of granitoids occur in the northern part of the Central Bohemian Plutons (CBP) in the Moldanubian Zone or in the Austroalpine Zone of the outer belt of the Western Carpathian Plutons (WCP). The granitoid melt source originated from partially melted oceanic and continental crusts due to compression. B. High-K, high-Mg, calc-alkaline, metaluminous, I-type, monzonitic-suite granitoids with lamprophyre-derived small, ultrapotassic, Mg-rich intrusions formed in the post-collision zone, where the melts originated from the partially melted, uplifted, LIL-rich mantle and continental crust, due to extension (334-354 Ma) after earlier compression. These intrusions can be found in the southern part of the CBP, the eastern part of Southern Bohemian Plutons (SBP) and northwestern part of the Tisia Terrain. Later on (314-303 Ma), as a result of interaction of melts originated from depleted mantle and partial melted lower crust, low-K, high-Na, calc-alkaline-type granitoids formed during extension, occurring in the inner part of the WCP. C. Peraluminous, S- or S/A-type granodioritic-suite, small intrusions with some K-subalkaline and alkaline characters, formed in post-orogenic or probably rifting settings at the main tectonic zones, e.g. the Periadriatic-Balaton Lineament (Velence Mts, Gemericum) during the Lower Permian (274±1.7 Ma). The most unstable part of the Variscan orogenic belt was where the high K, Mg-calc-alkaline granitoid and ultrapotassic intrusions occur (Massif Central, Vosges, Black Forest, the southern part of the CBP, the eastern part of the SBP and the northwestern part of the Tisia Terrain). They formed the innermost part of the Variscan Belt; only the Tisia Terrain occurs in allochthonous positions, which originated from the Moldanubian Zone and were completely separated from it since mid-Cretaceous times.

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