High-precision zircon geochronology constrains early Permian exhumation of the deep Adriatic crust in the western Italian Alps

Understanding whether deep crustal exhumation is continuous or occurs through episodic and high-rate pulses is key to linking the tectonic evolution of the continental lithosphere with magmatic processes. However, this remains challenging because of the limited precision of many geochronological methods, especially when resolving closely spaced and ancient metamorphic events. By integrating high-precision U–Pb zircon geochronology with metamorphic P–T estimates from deep crustal migmatitic gneiss, this study quantifies the average exhumation rate of the Valpelline Series within the fossil Permian extensional system of the western Italian Alps. The migmatitic gneiss of the Valpelline series record a metamorphic transition from conditions of 0.8–1.0 GPa and 870–890 °C (M1) to 0.4–0.6 GPa and 680–760 °C (M2), reflecting cooling and exhumation from deep to middle crustal levels. The changing P–T conditions mark a shift from a late- to post-collisional thermal relaxation regime to extensional tectonics characterized by a higher thermal gradient. CA-ID-TIMS dating constrains this transition to between 294.29 ± 0.38 Ma (M1) and 286.76 ± 0.27 Ma (M2), yielding an exhumation rate of 2.0 ± 1.0 mm/yr restricted to the early Permian and preceding widespread gabbro emplacement at regional scale. The results are consistent with the model that invokes an early Permian transtensional regime across Pangea, marked by high relative plate velocities and a brief duration of less than 20 Myr.