Mineralogical and geochemical characteristics of the Sedemte Prestola potassic alkaline pluton

The Sedemte Prestola pluton is an intermediate to acid plutonic body of Variscan age (308.7 ± 9.1 Ma). Despite its small size, several petrographic varieties are present: syenites, quartzsyentes and granites. It is composed of potassium feldspar, quartz, sodic-calcic amphibole; biotite, when present, is often rimmed by amphibole or strongly altered; zircon, titanite, apatite and ilmenite are the accessory phases. The rocks display pronounced potassic character with up to 10.4 wt% K2O, peralkaline tendency, and significant trace element enrichment for REE, Zr, Th, U, and Ba. The rocks also show enriched isotopic characteristic with 87/86Sri between 0.7107 and 0.7111, and 143/144Ndi between 0.51193 and 0.51182. The geochemical features of the Sedemte Prestola pluton imply orogenic geodynamic setting of formation as a product of more primitive magma fractionation. Isotopic characteristics and high LILE, Th and U contents support the derivation from enriched mantle source – phlogopite-bearing peridotites in the spinel stability field.