Formation and Exhumation of Ultrahigh-Pressure Terranes

The reigning paradigm for the formation and exhumation of continental ultrahigh-pressure (UHP) terranes is the subduction of crust to mantle depths and the return of crustal slices within the subduction channel— all at plate tectonic rates. Additional processes beyond the paradigm are needed to explain the diversity of geological observations gathered from the growing study of UHP terranes—for example, variations in the size, degree of deformation, petrologic evolution, timing of UHP metamorphism, and exhumation rates. Numerical models that evaluate physical parameters in time and space have produced new insights into the formation and exhumation of UHP terranes.

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December 2025 --The Variscan Orogeny in Europe – Understanding Supercontinent Formation

The Variscan orogen formed between 380 and 300 million years ago through several accretionary and collisional cycles, culminating with the construction of the Pangea supercontinent. This process occurred via sequential opening and closure of oceanic basins, synchronous detachment of Gondwana derived continental ribbons, and their outboard amalgamation onto the Laurussia margin. The Variscan orogen is rather unique compared with other orogenic belts on Earth: its overthickened and dominantly magmatic crust in the central belt, surprisingly minor mantle involvement in the magmatic and geodynamic processes, coherent and pulsed magmatism along the collision suture, and its complex accretionary history. Because its final product, Pangea, is the youngest and best-understood supercontinent on Earth, the Variscan orogeny offers clues for understanding the mechanisms of supercontinent formation.