Abstract
Ultrapotassic plutonic rocks located in the Bohemicum (the Chotělice Intrusive Complex) are geochemically and isotopically sharply different from ultrapotassic plutonic rocks of Variscan age in the Moldanubian Zone (voluminous intrusions of durbachites, i.e. porphyritic amhibole-biotite melasyenites) and, therefore, also their mantle sources should be distinct. Dykes of minettes and kersantites from both areas display much broader spectrum of Sr and Nd isotopic compositions compared to plutonic masses.
This fact suggests the ability of low-volume magma portions to sample various local domains of heterogeneous lithospheric mantle. Most likely, enriching fluids and/or melts of other origins beside deeply subducted rocks of granitic composition (proposed by Janoušek and Holub 2007 as the source of enrichment in genesis of durbachites) were involved in preparation of mantle sources for various potassic and ultrapotassic magmas.