Granulites and related rocks in variscan median Europe: A dualistic interpretation

摘要: Abstract On the basis of differences in structural, petrological and radiometric features, two main clear-cut groups can be distinguished for granulites Variscan median Europe. Group I comprises lenses eclogite-granulite scattered internal zones Hercynian belt, whereas II includes granulitic slices related to deep-seated Alpine lineaments xenoliths scavenged by recent volcanoes. belong early thrust nappes orogen; they display high-pressure assemblages are commonly associated with eclogites garnet-peridotites. From data, this HP granulitic-eclogitic metamorphism happened around 450-400 Ma throughout A subduction context is suggested low T/P gradient, occurrence contemporaneity some blueschist-facies rocks. characterized massive occurrences, intermediate-pressure granulite-facies parageneses absence eclogites. Granulitic paragneisses often a pronounced depletion granitophile elements may appear as degranitized restites. Numerous basic-ultrabasic complexes occur interpreted deep-seated, layered igneous intrusions emplaced during metamorphism. Radiometric dating indicates late (ca. 300 Ma) age. The high synchronous basic post-collision suggest event due major thermal anomaly. cycle thus granulite-forming episodes. “Older granulites” type result from an compressive stage crustal “younger granulites”, which originated upper mantle annealed deepest parts belt. broadly similar duality genesis rocks anticipated other collisional belts.