Burial-exhumation cycles in the continental crust derived from Mediterranean field studies and numerical modelling

Abstract

When tectonic plates converge, one plate gets buried (subducted) below the other. The subducted plate can be of continental origin and part of that plate may return (exhume) to the Earth’s surface driven by deep Earth and surface processes as documented in the Mediterranean region. Such continental burial-exhumation cycles influence the architecture of mountain belts, which are an expression of a dynamic planet. This thesis aims at unravelling how continental subduction zones evolve through time by using a wide range of methodologies. Field geological investigations in eastern (Greece) and western (SE-Spain) Mediterranean regions portray the tectonic burial and exhumation of rocks during the Africa-Eurasia convergence and the changes they undergo. Combining field geological observations with petrological investigations and radiometric dating of rocks allowed to better understand the structural and temporal evolution of continental subduction zones in the studied regions. The results show that the rocks can be subject to multiple burial-exhumation cycles during Africa-Eurasia convergence and that mechanical heterogeneities control the place where deformation occurs within the buried continental crust. The subduction of continents below oceanic plates leads to the emplacement of a heavy oceanic plate, called ophiolite, on top of light continental plate. Numerical simulations were used to understand how this process of obduction works. The results show that the subducted continental crust is squeezed upwards against the overlying oceanic plate which then breaks apart, leading to the emplacement of the ophiolites far away (up to hundreds of kilometres) from their origin.