Variscan tectonics of the Elbtalschiefergebirge, Saxo-Thuringian Zone – Evidence for two consecutive burial-exhumation cycles

The Elbe Zone serves as an example for the intricate architecture of the Central European Variscides. In the Elbtalschiefergebirge, remnants of a heterogeneously deformed and metamorphosed nappe complex are juxtaposed with the crystalline blocks of the Lausitz and the Erzgebirge. The preserved Paleozoic lithologies contain the record of the Variscan orogeny postdating marine sedimentation on a vast Peri-Gondwana shelf. However, the relationship between sedimentation, magmatism and Variscan tectonics remains contentious. Here, we present a tectonic model for the Elbtalschiefergebirge that is characterized by two consecutive burial-exhumation cycles. Late Devonian marine facies differentiation and bimodal magmatism marks the onset of the Variscan Orogeny. These sedimentary to volcanoclastic successions were then affected by low-grade regional metamorphism, followed by nappe stacking. The deposition of Early Carboniferous synorogenic marine sediments on top of the exhumed crustal pile marks the transition into the second cycle, which is characterized by renewed burial and subsequent heterogeneous dextral transpressional deformation of the Elbe Zone. Shearing at the northeastern boundary of the Elbtalschiefergebirge is accompanied by a prograde high-temperature metamorphic overprint, probably associated with the emplacement of the synkinematic Meissen granitoids. Shearing in the southwest resulted in the formation of the brittle-ductile to brittle Mid-Saxon Shear Zone, which is related to the final exhumation of the Erzgebirge complex into upper crustal levels. The end of the pervasive dextral strike-slip activity is marked by the intrusions of the undeformed Markersbach-Granite and Late Carboniferous rhyolite dykes as well as by the unconformable deposition of Permo-Carboniferous sediments of the Döhlen Basin.