The emplacement of Variscan HT metamorphic rocks linked to the interaction between Gondwana and Laurussia:structural constraints in NE Sardinia (Italy)

The emplacement of Variscan HT metamorphic rocks in Sardinia (Italy) occurred in a transpressive regime related to the oblique collision between Gondwana and Laurussia during the Early Visean (c. 340 Ma)–Bashkirian (c. 320 Ma). The restored directions of the main structural features in NE Sardinia allow us to infer a NE–SW-oriented direction of shortening during this time, as has been established for the French Massif Central and the Maures-Tanneron Massif, which could lead to the exhumation of HT rocks by telescoping processes. Field evidence and finite strain analysis emphasize that the exhumation of HT metamorphic rocks could be driven by a restraining bend that developed in NE Sardinia along dextral transpressive shear zones. The tectonic model proposed in this paper allows us to conclude that crustal melt production, usually attributed to extensional regimes, can be related to compressional ⁄ transpressional regimes.