Intrusive and deformation history of the Sevetin Pluton, Moldanubian Batholith: record of polyphase tectonic evolution of the Blanice Graben, Bohemian Massif
Abstract
The Sevetin Pluton, located c. 15 km NNE of Ceske Budejovice, is a small, isolated, petrologically and structurally complex intrusive body that is genetically related to the youngest intrusions of the Moldanubian Batholith. As documented in this study, its overall shape, internal magmatic fabric as well as brittle structures (dikes, veins, joints, faults) are, however, related to the formation and polyphase tectonic evolution of the Blanice Graben, an about 200 km long and 5-15 km wide NNE-SSW-trending, deep-seated fault zone that cuts across the Moldanubian Unit.
In total, one pre-intrusive and three syn- to post-intrusive tectonic phases have been distinguished. The oblique, NW-SE oriented compression controlled both the intrusion of the Sevetin biotite-muscovite granite and the early stage of its brittle deformation.
Sigmoidal pattern of magnetic foliations in this pluton documents its mostly solid-state deformation during oblique sinistral movements on the main faults of the Blanice Graben. The subsequent strike-slip phase was characterized by E-W oriented subhorizontal extension and can be correlated with the intrusion of c. 270 Ma old microgranodiorite dikes.
The last extensional phase was associated with the formation of subeconomic Pb-Zn-(Ag?) quartz-calcite veins at c. 265 Ma.