LAUSR

The western part of the late Variscan Strzegom–Sobótka massif exemplifies an intrusion that formed in a multi-component system. The system shows ambiguous isotopic and geochemical signatures and presents a seemingly composite character [biotite granite with negligible amount of hornblende (HBG) and microgranular mafic enclaves (MMEs)]. The melts responsible for forming granitic rock and its MMEs were not derived from contrasting crustal and mantle sources but from different crustal domains. These melts exhibit hybrid characteristics due to subsequent contamination processes. The data suggest two different stages of hybridization of two geochemically distinct magmas corresponding to granite and enclaves. The processes were temporally and spatially distinct. Heterogeneous protoliths and hybridization made these magma isotopic signatures and trace element patterns ambiguous. The main mechanism involved in developing granitic rocks was fractional crystallization (FC); the mechanism responsible for MME composition was mixing, but other local processes were also involved in rock formation. Generally, the FC signature was not obscured by the hybrid mafic melt input. This felsic-mafic melt interaction was a limited one-sided process. Granitic melt was changed by the presence of small mafic magma blobs, but their influence on granite crystallization was negligible. The massif is thus an ideal example of an environment where MMEs coexist with a granitic body, although MMEs do not determine the actual composite character of the pluton. The early stage of Variscan pluton formation within the Bohemian Massif and adjacent areas was shaped by interacting mantle- and crust-derived melts. The pluton described in this paper belongs to the late stage of Variscan magmatism. It is a multi-component system shaped by the participation of melts derived from heterogeneous crustal domains. The presence of enclaves does not explicitly indicate their dominant role in the formation of composite plutons of crust-mantle origin. It is decisive to determine whether the ambiguous signatures appearing in such cases truly indicate both of these sources.