Evolution of the Corsica–Sardinia Batholith and late-orogenic shearing of the Variscides
Résumé
The Corsica–Sardinia Batholith formed in the late Carboniferous–Permian along the northern Gondwana margin. One or more of the following processes may have raised the Variscan geotherm enhancing melting of the crust and uppermost mantle, such as: i) break-off and detachment of the Rheic oceanic slab, ii) mantle delamination due to gravitational re-equilibration of thickened crust, iii) shear heating, iv) advection of mantle-derived melts, and v) concentration of heat-producing elements. In this paper, we present a simple one-dimensional thermal model to explain the origin of the batholith in a geodynamic setting consistent with intraplate shearing between Gondwana and Cadomian–Avalonian blocks. Input parameters, and boundary and initial conditions of the model crust are derived from a careful re-examination of large petrological, geochronological, and structural datasets. All parameters are varied within a range of geologically realistic values to reproduce thermal histories related to different tectonic processes, and the reliability of models is quantitatively evaluated by comparing the simulated geotherms with a large dataset of pressure–temperature–time (P–T–t) constraints. The best fit to P–T–t constraints is obtained for: i) break-off in the Late Devonian–Early Carboniferous, ii) decreasing exhumation rates from 340 to 280 Ma, and iii) transpression at high average strain rates, mostly coeval with the peak of high-T–low-P metamorphism.