Provenance of Precambrian basement of the Brunovistulian Terrane: New data from its Silesian part (Czech Republic, Poland), central Europe, and implications for Gondwana break-up

Abstract

Brunovistulia is a complex superterrane in central Europe, the western part of which became tectonically involved in the Variscan belt and formed its Precambrian basement. The Silesian part of the Brunovistulian Terrane embraces metasediments and metavolcanic rocks whose protolith ages, provenance, geotectonic setting and pre-Variscan palaeogeography are still poorly known. Our LA-ICP-MS U-Pb zircon data, supported by geochemical studies of these rocks, show that paragneisses and quartzites in the Desná and Keprník domes stemmed from sedimentary basin(s) whose the maximum depositional age is c. 560–570 Ma. Detritus was mainly supplied from Cryogenian-Ediacaran source areas. Precambrian mica schists of the inner Velké Vrbno Dome had mainly Mesoproterozoic detrital component. The accompanied metavolcanics rocks mainly originated as subalkaline E-MORB-like basaltic effusives at c. 610–595 Ma that evolved in the within-plate environments of the retro-arc at the rear of the Ediacaran magmatic arc built of granitoids which were formed at 640–550 Ma. Because the detrital zircon age spectra indicate contributions from the sources bearing 2.2–1.1 Ga components, it is expected that the sedimentation and volcanism presumably occurred at the Amazonian part of the Gondwana mainland. A compilation of new and the existing data further indicates the complex structure of Brunovistulia. The Silesian and Moravian domains of the Brunovistulian superterrane differ in terms of lithology, age of magmatic rock units and isotopic characteristics. The two domains may have developed as different fragments of the same magmatic arc system at the Amazonian margin of peri-Gondwana which evolved for c. 100 Myr. Besides, our new data revealed an early Devonian (408 Ma) onset of volcanism in the westernmost margin of the continental Brunovistulian margin, thus c. 30–40 Ma earlier than the well-known late Devonian volcanism in the Vrbno Group further east.