Abstract
Late Paleozoic (Variscan) magmatism is widespread in Central Europe. The Lusatian Block is located in the NE Bohemian Massif and it is part of the Saxothuringian Zone of the Variscan orogen. It is bordered by two major NW-trending shear zones, the Intra-Sudetic Fault Zone towards NE and the Elbe Fault Zone towards SW. The scarce Variscan igneous rocks of the Lusatian Block are situated close to these faults. We investigated 19 samples from Variscan plutonic and volcanic rocks of the Lusatian Block, considering all petrological varieties (biotite-bearing granites from the Koenigshain and Stolpen plutons, amphibole-bearing granites from three boreholes, several volcanic dykes, and two volcanites from the intramontane Weissig basin). We applied whole-rock geochemistry (18 samples) and zircon evaporation dating (19 samples). From the evaporation data, we selected six representative samples for additional zircon SHRIMP and CA–ID–TIMS dating. For the Koenigshain pluton, possible protoliths were identified using whole-rock Nd-isotopes, and zircon Hf- and O-isotopes. The new age data allow a subdivision of Variscan igneous rocks in the Lusatian Block into two distinct magmatic episodes. The spatial relation of the two age groups to either the Elbe Fault Zone (298–299 Ma) or the Intra-Sudetic Fault Zone (312–313 Ma) together with reports on the fault-bound character of the dated intrusions suggests an interpretation as two major post-collisional faulting episodes. This assumption of two distinct magmatic periods is confirmed by a compilation of recently published zircon U–Pb CA–ID–TIMS data on further Variscan igneous rocks from the Saxothuringian Zone. New geochemical data allow us to exclude a dominant sedimentary protolith for the Koenigshain pluton as supposed by previous investigations. This conclusion is mainly based on new O- and Hf-isotope data on zircon and the scarcity of inherited zircons. Instead, acid or intermediate igneous rocks are supposed as the main source for these I-type granitoids from the Koenigshain pluton.
Highlights
In the Palaeozoic, the closure of the Rheic Ocean and the amalgamation of the supercontinent Pangaea caused the Variscan orogeny in North America, Europe and Asia
We present new whole-rock geochemistry and isotope data (Nd- for whole rocks, Hf- and O-isotopes for zircon) of Variscan granitic and rhyolitic-dacitic rocks of the Lusatian Block to infer on sources of these rocks
For sample BGK1, in addition to in situ U–Pb zircon ages analysed by SHRIMP, the Hf- and O-isotope composition was determined from the same spots on these zircon grains
Summary
In the Palaeozoic, the closure of the Rheic Ocean and the amalgamation of the supercontinent Pangaea caused the Variscan orogeny in North America, Europe and Asia. In the Bohemian Massif, located in the easternmost part of the European Variscides, the orogen is subdivided into a series of orogenic zones by subordinate subduction zones 340 Ma marked the peak metamorphism and the end of plate convergence in the Saxothuringian Zone of Central Europe (Fig. 1, e.g., Schmädicke et al 1995; Kröner and Willner 1998; Tichomirowa et al 2005). During the post-collisional period, transpressional and transtensional tectonics resulted. International Journal of Earth Sciences (2021) 110:2923–2953 10°E 15°E 52°N Berlin EFZ ISF Fig 2a DFZ
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