A thermo-kinematic model to investigate heat transfer through the nappes of the Lepontine Dome

Tagliaferri, Alessia and Schenker, Filippo and Schmalholz, Stefan and Seno, Silvio (2020) A thermo-kinematic model to investigate heat transfer through the nappes of the Lepontine Dome. In: Abstract Volume18th Swiss Geoscience Meeting Swiss Geoscience Meeting 2020 Swiss geoscience Meeting 2020, 6-7.11.2020, Z�rich.

Full text not available from this repository.


Heat transfer during the emplacement of nappes in an orogenic belt is controlled by three processes: advection, diffusion and production of heat. Production is mainly caused by radioactive decay and shear heating. The relative importance of these processes is contentious. Viscosity, velocity and strain rate affect primarily the contribution of advection and shear heating, which can generate a local temperature increase along the thrust surface. In order to evaluate the relative influence of production, diffusion and advection, we performed 2D thermo-kinematic simulations using the finite difference method. The 2D velocity field is prescribed by a kinematic trishear fault model. We investigate the relationship between nappes’ and isogrades’ geometries resulting from simulations characterized by different configurations of the velocity field. We calculate the thermal evolution and peak temperatures in order to compare the numerical results with field and petrological data. We use data from nappes of the Lepontine Dome (Central Alps, Ticino, Switzerland). These nappes show an extremely pervasive mineral and stretching lineation (NW-SE directed) indicating non-coaxial deformation during shearing at similar metamorphic conditions, and metamorphic amphibolite facies isogrades locally dissecting the tectonic contacts. We compare the numerical results with field and petrological data collected along the Simano and Cima Lunga nappes.In the field, the alternation of lithotypes is parallel to the nappe boundaries and constant over their whole, kilometer-scale length. The transition from the Simano to the Cima-Lunga nappe is marked by a progressive change in the texture of gneisses, in which the porphyroblasts become more stretched from the bottom to the top, and by the change in the constituent lithotypes. In the studied area, the Simano nappe is formed mainly by metagranitoids and by minor paragneisses. The Cima Lunga nappe is made of metasediments, mainly quartz-rich gneisses intercalated with amphibolite-gneisses, peridotitic lenses and local calcschists and/or marbles. Finally, the widespread paragneisses frequently contain garnets of different sizes and internal microstructure. Published and own petrological data of these garnet-bearing rocks are used to constrain the numerical simulations. We test multiple tectonic scenarios related to heat transfer during nappe formation, such as: radiogenic heating; additional heat flux at the bottom of the nappes, due to e.g. magmatic underplating or delamination; or shear heating along nappe boundaries. The results show that transport of heat through advection can’t reproduce an inverted metamorphism below the thrust sheet.

Actions (login required)

View Item View Item