Palaeozoic accretion of Gondwana-derived terranes to the East European Craton: recognition of detached terrane fragments dispersed after collision with promontories

Abstract

AbstractRecent work in Central Europe, combined with emerging information about basement massifs in SE Europe and NW Turkey, permits a new look at the relationships between crustal blocks abutting the East European Craton (EEC) along the Trans-European Suture Zone (TESZ). The simplest model indicates that the end-Cambrian establishment of the Bruno-Silesian, Lysogory and Malopolska terranes close to their present location on the SW margin of the EEC formed a major promontory on this margin of the continent. Moesia may also have formed part of this block. Both late Ordovician accretion of Avalonia and early Carboniferous accretion of the Armorican Terrane Assemblage (ATA) attached new continental material around the Bruno-Silesian Promontory (BSP). Palaeozoic faunal affinities and inherited isotopic signatures similar to those of Avalonia seen in the Istanbul block of NW Turkey, and in minor thrust slices in Moravia and Romania, suggest that easternmost Avalonia was severed, on collision with the BSP, and migrated east along the southern margin of the EEC. Likewise, the similarities to the ATA of the Balkan, Istranca, Sakarya and eastern Pontides blocks suggests that more easterly components of the ATA were detached at the BSP and migrated east. All the newly accreted blocks contain similar Neoproterozoic basement indicating a peri-Gondwanan origin; Palaeozoic plume-influenced metabasite geochemistry in the Bohemian Massif may explain their progressive separation from Gondwana before their accretion to the EEC. Inherited ages from Avalonia contain a 1.5 Ga 'Rondonian' component arguing for proximity to the Amazonian Craton at the end of the Neoproterozoic; Armorican terranes lack such a component, suggesting that they have closer affinities with the West African Craton. Models showing the former locations of these terranes and the larger continents from which they rifted, or later became attached to, must conform to both these constraints and those provided by palaeomagnetic data. In the late Neoproterozoic and Palaeozoic, these smaller terranes, some containing Neoproterozoic ophiolitic marginal basin and magmatic arc remnants, probably fringed the end-Proterozoic supercontinent as part of a 'Pacific-type' margin. When this margin fragmented, most resulting fragments accreted to the EEC.