Implications of New Geological Mapping and U‐Pb Zircon Dating for the Barrovian Tectono‐Metamorphic Evolution of the Lepontine Dome (Central European Alps)

The Barrovian metamorphism of the Lepontine dome is manifested by isograds that cross-cut tectonic nappe contacts, which commonly interpreted as occurred after emplacement. However, pervasive mineral and stretching lineation in amphibolite facies, associated with top-to-foreland shearing, suggests peak conditions are coeval nappe-overthrusting. Here, we combine mapping U-Pb zircon dating to better constrain relation between overthrusting. Metamorphic rims show two age populations at 31–33 22–24 Ma. younger population locally observed post-foliation dikes (and metasomatism) likely sourced from deep-migmatites exhuming along Alpine backstop. older occurs regionally found syn-kinematic migmatites occur a crustal-scale shear zone. Below this zone, magmatic detrital cores suggest Cima Lunga unit, previously mélange Mesozoic fragments, was pre-Variscan metasedimentary sequence intruded Permian granitic sills, now orthogneisses. This unit strongly sheared top Simano during overthrusting rock pile here-termed Maggia-Adula nappe. large-scale emplacement imprinted regional temperatures until Péclet (1–10) Brinkman (0.002–1.8) numbers, estimated for overthrusting, an advection-dominated heat transfer caused exhumation, some diffusion (conduction) Diffusion contributed discordant thrust. Shear heating important if stress times shearing rate >∼5·10−6 W·m−3 within thermal evolution spatially heterogeneous ca. 22