High-level volcanic-granodioritic intrusions from Zelezniak Hill (Kaczawa Mountains, Sudetes, SW Poland)

Abstract

New petrological and geochemical data on high level (c. 2 km2 silicic lava domes and laccoliths from the Kaczawa Mountains, Sudetes, SW Poland, are presented. The system comprises a carapace facies of exposed ignimbrites and spherlulitic rhyolites. Recovered core (drilled to 55 m) includes volcanic rocks ranging in composition from andesite to rhyodacite, and a plutonic, facies of microgranite and granodiorite. Country rocks (greenschist-facies metavolcanogenic rocks) are contact metamorphosed to hornfels and cut by kersantite veins and a pipe breccia of diatremic origin. New206Pb-238U zircon mineral ages from the volcanic and granitic rocks yield ages of 315 to 316 Ma, making the Zelezniak Hill complex the oldest magmatic rocks so far dated in Avalonia.