A structural model for the western-central Sudetes: a deformed stack of Variscan thrust sheets

Abstract

A model based on new structural and geochemical data is presented. It unifies the structural history of the Izera, Rudawy Janowickie and Kaczawa complexes with the Fore Sudetic block, despite their current separation by the Intra-Sudetic and Marginal Sudetic faults. Above the granitoid Izera, Kowary and Wa¸droże gneisses, at the base of the structural sequence, the ductile Kowary shear zone marks the basal decollement of the Świerzawa thrust sheet, comprising often highly strained metasediments associated with enriched tholeiitic and alkaline metabasites. Above it, the ductile Kaczorów shear zone, corresponding to the main mylonitic zone within the Leszczyniec shear zone in the Rudawy Janowickie Complex, marks the base of the Dobromierz thrust sheet, characterized by voluminous MORB-like meta-tholeiites and minor metasediments in the higher parts of the Rudawy Janowickie and Kaczawa complexes and the Pyszczyńska Hill area of the Fore-Sudetic Block. In the east the Sle¸za ophiolite and the Góry Sowie Block override the entire nappe stack. Kinematic fabrics in the major and related shear zones indicate D 1 compressional transport towards the northwest, followed by minor D 2 extensional movements. The thrust stack was deformed during D 3 by southwest verging folds, was subsequently intruded by post-orogenic granites, and later disrupted by the Intra-Sudetic, Marginal Sudetic and associated faults.