Southern Uralides and Variscides: comparison of their anatomies and evolutions

Abstract

The Uralides and the Variscides are two Palaeozoic orogenic belts located on the eastern and south-western borders of the East-European Precambrian craton (Russo-Baltica), respectively. Both belts have common characteristics (nappe tectonics, opposite vergences on both sides) and have been formed within roughly the same time-span (500-270 Ma for the Variscides, 500-230 Ma for the Uralides). Nevertheless they exhibit striking differences in shape, preservation of ophiolites and island arcs, grade and type of metamorphism, and erosion level, which reflect different accretionary histories. The Variscides were formed by collision of large continental blocks involving major continental stacking and thickening, which resulted in strong heat production and related high-temperature metamorphism, crustal melting and late-orogenic denudation. The Uralides were formed by accretion of island arcs and micro-continents against a large East-European continent, associated with much lower heat production, low-temperature, high-pressure metamorphism, restricted crustal melting and minor erosion.