Processes of Pangea construction: correlation of Variscan and Central Asian orogenic belts

This ‘Thematic Edition’ originated thanks to a symposium of the European Union of Geosciences held in Vienna in 2022. It is a collection of 14 contributions covering a wide spectrum of approaches and concepts ranging from mantle convection models, geophysical crustal characterization, regional synthesis of detrital zircon data, geochemistry, modern geochronology and synthesis of temperature/pressue data at orogenic scale. The Thematic Edition thus covers studies from North African Variscan outcrops, Variscan Europe from Iberia to Poland, and the southern part of the Altaids from NW China and Mongolia to NE China. Such an exceptional synthesis shows major differences between the North African–European Variscan belt and the Altaids in the final constitution of Pangaea in Late Carboniferous to Permian times. The western part of Pangaea was subject to deformation and thermal reworking associated with major collisions between Gondwana and the Variscan Collage at its northern margin, and Laurussia. The remnants of the main crustal thickening event are preserved in NW Africa in the form of high-pressure granulites, while Variscan Europe experienced transpressive reworking and oroclinal bendings related to dextral translation of Laurussia followed by indentation of Gondwana promontories. The eastern part of Pangaea experienced the arrival of a ribbon-like collage constituting the Tarim, Dunhuang, Alxa and North China blocks to the north and simultaneous shrinking of the Palaeo-Asian Ocean. During late Paleozoic times, and because of these processes, opposite subduction of the Palaeo-Asian oceanic plate operated beneath Mongolian blocks to the north and the Tarim–North China Collage in the south. This long-lasting subduction resulted in the formation of numerous intra-oceanic and Andean-type arcs and back-arcs later transformed into ephemeral oceans. All these oceanic basins were closed during the Permian, leading to the final mid-Permian to Triassic collision of Precambrian blocks with the Mongolian and Kazakhstan collages to the north. This resulted in multiple indentation effects and the formation of giant oroclinal structures reflected in the shape of the Altaids. All these events have one common link, namely the progressive opening and closure of the wedge-shaped Palaeo-Tethys Ocean south of the Variscan, Kazakhstan, Mongolian and Tarim–North China collages.