The Cadomian Orogeny in the northern Bohemian Massif – geochronology, basin development, crustal growth, and geotectonic setting

During Ediacaran to earliest Cambrian times, the Cadomian Orogen formed a system of magmatic arcs and marginal basins at the northern periphery of the Gondwana supercontinent. The orogenic belt was structured in the geotectonic style of the recent western Pacific. The Saxo-Thuringian Zone forms part of the northern Bohemian Massif and contains a number of good preserved fragments derived from the peri-Gondwanan Cadomian Orogen (e.g. the Schwarzburg Antiform, the Lausitz Block, the Eastern Sudetes). Here, we present a massive dataset of LA ICP-MS U-Pb ages and Hf-isotopes from detrital and magmatic zircon of sedimentary and igneous rocks from these areas. Sedimentary rocks are represented by arc-derived greywacke and mudstone turbidites in a back-arc and retro-arc setting. Further, glacio-marine diamictites and high-mature quartzites display passive margin deposits situated more proximate to the cratonic hinterland. U-Pb ages of detrital zircon form populations, which point to a West African hinterland during the time of deposition. The stratigraphic age of the basin fillings is bracketed between the maximum depositional age of the sedimentary rocks at c. 560 Ma and the age of intrusion of c. 539 Ma old granodiorite plutons, which intruded the isoclinal deformed greywacke-mudstone deposits of the marginal basins in the Cadomian orogenic system. The Cadomian crustal evolution is dominated by the recycling of continental crust from the West African hinterland as suggested by the dominance of zircons with negative εHf values. Juvenile arc magmas became contaminated by the recycling of Eburnian and Archaean crust during long Cadomian magmatic arc activity.