Journal of

GEOsciences

  (Formerly Journal of the Czech Geological Society)

Original Paper

Němec

Silica-rich felsitic dikes from southeastern part of the Bohemian Massif

Journal of the Czech Geological Society, volume 39 (1994), issue 2-3, 213 - 220

Scarce dikes of Hercynian silica-rich felsitic microgranites and granite porphyries occur in eastern and southeastern parts of the Central Bohemian Pluton, in southern part of the Českomoravská vrchovina highland and in the adjacent Waldviertel in Austria. They are associated with long regional faults. In spite of their vast distribution across a large territory they are mineralogically and chemically uniform. Chemically, they represent acid magmas corresponding to the thermal minimum of the haplogranite system. They are extremely low in CaO and ferric components, and mostly enriched in fluorine. They approach topaz rhyolites not only chemically but also through their links to greisen-like assemblages. The dikes are occasionally affected by greisenization and display spatial relations to plugs and dikes of young, partly greisenized, granites. According to their trace element characteristics, they may be classified as syn-collision granitic magmas.