The Tepla(?)/Saxothuringian suture in the Karkonosze–Izera massif, western Sudetes, central European Variscides

Abstract

The southern and eastern Karkonosze±Izera massif (northern Bohemian Massif) exposes blueschist facies rocks and MORB-type magmatic complexes. During Late Devonian to Early Carboniferous times, these were overthrust within a nappe pile toward the NW onto the pre-Variscan Saxothuringian basement composed of the Izera±Kowary metagranitoids and their envelope. The lowermost nappe (or parautochthonous?) unit of the pile is the low-grade metamorphosed Jete Ï d complex, comprising a Devonian to Early Carboniferous sedimentary succession of the Saxothuringian passive margin. This is tectonically overlain by the South Karkonosze complex, which represents Ordovician±Silurian volcano-sedimentary infill of the Saxothuringian basin, affected by Late Devonian HP metamorphism. The uppermost nappe is the Early Palaeozoic epidote±amphibolite grade Leszczyniec MORB-like complex, cropping out on the eastern margin of the Karkonosze±Izera massif. It probably represents a fragment of obducted Saxothuringian basin floor. The nappe pile was stacked beneath the overriding upper plate margin, now concealed below the Intra±Sudetic basin and hypothesized to represent a fragment of the Tepla±Barrandian terrane. The nappe stacking, triggered by buoyancy-controlled upward extrusion of the subducted continental slab, was the main mechanism for the exhumation of HP rocks. The final stages of the NW-ward nappe stacking were accompanied and followed by SE-directed Early Carboniferous extensional collapse. The lower plate of the suture zone was uplifted at that time and intruded by the~330-Ma-old, nearly undeformed Karkonosze granite pluton. As a result of the collapse, the Tepla±Barrandian(?) upper plate was downthrown on shear zones and brittle faults and buried under several km-thick synorogenic Late Tournaisian(?) through Namurian and post-orogenic Late Carboniferous±Early Permian succession of the Intra± Sudetic basin. The south and east Karkonosze suture most probably is a fragment of the Tepla/Saxothuringian (Münchberg±Tepla) suture belt known from the western Bohemian Massif.

U-total Pb timing constraints on the emplacement of the granitoid pluton of Stolpen, Germany

“…The belt,which resulted from continent-continent collision, shows the emplacement of many granitic bodies (Finger et al 1997). The greatest magmatic activity took place during the Late Carboniferous and was related to transpressional-transtensional tectonics (Finger and Steyrer 1990;Diot et al 1995;Mazur and Aleksandrowski 2001). The plutons located at the northern extreme of the Bohemian Massif were emplaced during this period.…”

Isotopic Re-Os age of molybdenite from the Szklarska Poręba Huta Quarry (Karkonosze, SW Poland)

“…It com prises two main el e ments: the Variscan Karkonosze gran ite in tru sion and its Neoproterozic-Pa leo zoic meta mor phic cover. The lat ter shows remark able di ver sity in stra tig ra phy and meta mor phic his tory, which en able dis tinc tion of four con sec u tive struc tural units: Izera-Kowary, Ješted, South Karkonosze and Leszczyniec, arranged as a stack of nappes formed in the Late De vo nian and re-ar ranged in the early Car bon if er ous (for de tails see Mazur and Aleksandrowski, 2001). Dur ing the Variscan orog eny the nappe struc ture was in truded by the Karkonosze gran ite which re sulted in the for ma tion of an ex ten sive con tact au re ole (Mierzejewski and Oberc-Dziedzic, 1990).…”

Magmatic and post-magmatic phenomena in the Karkonosze granite and its metamorphic envelope (West Sudetes, SW Poland)

“…This part of the Sudetes is associated with the Saxothuringian zone (e.g., Franke and Żelaźniewicz 2002) which is believed to plunge eastward beneath the Teplá-Barrandian domain, now buried below the infill of the intra-Sudetic basin, only to be re-exposed within an accretionary wedge in front of the Brunia domain (East Avalonia; e.g., Mazur and Aleksandrowski 2001;Chopin et al 2012;Mazur et al 2015;Szczepański and Ilnicki 2014).…”

“…1). The Izera orthogneisses are embedded in a metasedimentary succession (mica schists with paragneisses, quartzofeldspatic rock, amphibolites, calc-silicates, crystalline limestones) and together they were interpreted as a single tectonic entity, the Izera-Kowary unit (Mazur and Aleksandrowski 2001). The succession is also split by the Karkonosze pluton and its major part is located to the south (the Velká Úpa group of Chaloupský et al 1989), whilst to the north it forms four, roughly sub-parallel and narrow belts (Textfigs 1, 2) with the southernmost (the Szklarska Poręba belt) hornfelsed by the intrusion.…”

“…1) where several magma batches were emplaced in a dextral strike-slip regime during the initiated extensional collapse, uplift and unroofing of the host rocks initiated at ca. 335-337 Ma (Aleksandrowski et al 1997;Mazur and Aleksandrowski 2001;Marheine et al 2002). During the intrusion the envelope of the granite, comprising Palaeozoic metavolcanic-sedimentary successions, developed a pronounced, ca.…”