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.

Paleozoic evolution of pre-Variscan terranes: From Gondwana to the Variscan collision

“…Avalonia: Is, Istanbul; Mg, Meguma; Mo, Moesia; sP, south Portuguese; Zo, Zonguldak. (Dean et al, 2000, proposed an Avalonian origin for the Istanbul Paleozoic; see also Seston et al, 2000, andWinchester, 2002). Cadomia: AA, Austro-Alpine; Cm, Cadomia; He, Helvetic; Ib, allochthons from northwestern Iberia; Lg, Ligerian; MD, Moldanubian; Pe, Penninic; SM, Serbo-Macedonian; Sx, Saxo-Thuringian.…”

Palaeozoic amalgamation of Central Europe: an introduction and synthesis of new results from recent geological and geophysical investigations

“…In this event the orogenic wedge in the West Sudetes generally propagated from east to west. In the Karkonosze-Izera complex (central West Sudetes) this is shown by: a) early kinematic indicators in mylonitic ductile shear zones (Mazur 1995;Seston et al 2000); b) the decrease in metamorphic grade from garnet zone in the east to chlorite zone in the NW (Baranowski et al 1990;Kachlfk & Pato~ka 1998;Collins et al 2000); c) the decrease of 41)Ar-39Ar cooling ages towards the west (Marheine et al 1999); d) diminishing ages of flysch sedimentation onsets towards the west showing that tectonic exhumation was much earlier in the east. In addition, pre-late Devonian unconformities occur in the central West Sudetes between the Ktodzko metamorphic complex and the Bardo Unit (Hladil et al 1998;Kryza et al 2000), while late Devonian coarsegrained clastic sedimentary fills derived from exhumed metamorphic complexes to the east were deposited in syntectonic basins (Aleksandrowski & Mazur 2002).…”

“…Oliver et al 1993;KrOner & Hegner 1998). Others suggested that the absence of supporting geological evidence for an arc edifice at the time makes it more likely that chemical characteristics of the intrusions were inherited from extensive melting of the calc-alkaline Cadomian basement (Kryza & Pin 1997;Aleksandrowski et al 2000: Floyd et al 2000. Subsequent dominantly basic magmatism was associated with clastic basin-fill metasedimentary rocks, typical of magmatism associated with an extensional tectonic setting.…”

“…Analytical results from the basic rocks, using a database of over 600 full analyses (e.g. Floyd et al 1996Floyd et al , 2000Winchester et al 1995Winchester et al , 1998, argue that the magmatic range is more likely to result from the interaction of an enriched plume with both asthenospheric and sediment-contaminated lithospheric mantle sources (Floyd et al 2000). Although the volume of magmatism preserved is smaller than younger plume-influenced magmatic provinces, it has widespread correlatives in many parts of Western Europe including the Massif Central (Briand et al 1991(Briand et al , 1995 and Massif des Maures (Briand pers.…”

“…in France and from NW Spain (e.g. Peucat et al 1990). Floyd et al (2000 also suggested that plume-induced magmatism can also explain the amount of heat needed to melt substantial volumes of lower crust to produce the major granitoid bodies, and provides one possible mechanism for the fragmentation of the Armorican Terrane Assemblage (ATA) as it separated from Gondwana, and the repeated rifting of crustal fragments from the Gondwana margin, including Avalonia and the ATA.…”