Lithospheric mantle beneath NE part of Bohemian Massif and its relation to overlying crust: new insights from Pilchowice xenolith suite, Sudetes, SW Poland

The Oligocene/Miocene basanite from Pilchowice (Sudetes Mts., SW Poland) carries numerous small xenoliths of mantle peridotite, mostly harzburgite. The Pilchowice xenolith suite is dominated by harzburgites and dunites containing olivine Fo 90.2-91.5 (group A). The peridotites of group B (olivine Fo 88.6-89.4), and C (olivine Fo 83.2-86.5) are subordinate. The peridotites suffered from significant melt extraction (20-30%) and were subsequently subjected to metasomatism. Three different trace element compositional patterns of group A clinopyroxene occur, which are typical of silicate melt, carbonatite melt and silicate-carbonatite melt metasomatism, whereas groups B and C were affected by silicate melt metasomatism only. The Pilchowice basanite occurs at the contact of Karkonosze-Izera Block and Kaczawa Complex, two major geological units of Sudetes. The Pilchowice xenolith suite documents underlying lithospheric mantle of composition and depletion degree similar to those described in the whole Lower Silesian mantle domain, which forms NE termination of Saxo-Thuringian zone of the European Variscan orogen. The crustal structure of the orogen is, therefore, not mirrored in the mantellic root.