Fig. 2: Model set-up and boundary conditions for the thermomechanical simulations that include partial melting in the deep crust.

a Model geometry, parameters and boundary conditions, temperature, and strength as a function of depth for the experiments with a crustal root together with the locations of Lagrangian markers used to track deformation history and finite strain in the central part of the model (E–W cross-section is at 38° N from the model of ref. 37). b Model geometry, parameters and boundary conditions, temperature, and strength as a function of depth for the experiments with a flat Moho topography and a laterally varying surface elevation. c Model geometry, parameters and boundary conditions, temperature, and strength as a function of depth for the experiments with a uniform thickness crust (a flat Moho topography and a flat surface elevation); All models are 75 km deep. The purple graph represents the defined starting viscosities within the lithosphere based on a constant strain rate of 1 e⁻¹⁵ s⁻¹. The red graph represents the magnitude of partial melting within the crust. The black, blue, and orange graphs represent the geotherm, solidus, and liquidus, respectively.