Potassium-rich magmatism in the Western Outer Carpathians: Magmagenesis in the transitional zone between the European Plate and Carpathian–Pannonian region

Miocene igneous rocks of the Western Outer Carpathians in Poland and Moravia, Czech Republic, were emplaced in a tectonic setting transitional between the European foreland and the Carpathian–Pannonian arc system. They form medium- to high-K calc-alkaline suites which are compositionally different to each other and to other calc-alkaline sequences in the region. Geographically and compositionally the Moravia rocks can be seen as transitional between the rift-related alkaline magmatism of the foreland and the dominantly calc-alkaline magmatism of the Carpathian–Pannonian region. Certain Moravia rocks are unusually enriched in incompatible trace elements, e.g. Nb ≤ 122 ppm and Th ≤ 31 ppm. The primary magmas of both suites were formed in metasomatised lithosphere mantle of the European plate but the enrichment mechanism differed: in Poland, it was by ancient subduction-related events whereas in Moravia metasomatism was mainly by melts and/or fluids from deeper mantle sources. Partial melting was promoted by impingement of rising asthenosphere on the base of the lithosphere, possibly related to reactivation of trans-lithospheric, NW–SE-trending fault zones.