Geochemistry of the Drahotín and Mutěnín intrusions, West Bohemian shear zone, Bohemian massif: contrasting evolution of mantle-derived melts
Abstract
In western Bohemia, the Drahotín and Mutěnín intrusions show different origins and evolutions. Parental magmas of the Drahotín intrusion were derived predominantly from enriched mantle sources, and the melts have undergone a significant degree of assimilation-fractional crystallization during their ascent and/or emplacement into the Earth`s crust.
In contrast, the compositional variation of the complex Mutěnín intrusion cannot be explained by similar processes as in the case of Drahotín intrusion, but more likely reflects the involvement of several parental magmas. The gabbronorite was derived from a depleted mantle source, whereas the diorite/syenite stem from a mixed mantle-crust reservoir.
The contrasting evolution of the Drahotín and Mutěnín intrusions may be due to their melt derivation and magma emplacement under different tectonothermal regimes at different times during Variscan orogenesis.