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Separation of microcontinents is explained by a ridge jump toward the passive margin as a possible consequence of plume-induced rheological weakening, ultimately leading to breakup followed by accretion of the oceanic crust along a new spreading center. In contrast to such a purely extensional case, the separation of continental microblocks from the main body of the African plate during its continuous northward motion and subduction under Eurasia is still poorly understood. Our numerical experiments show the thermal and buoyancy effects of mantle plume impingement on the bottom of the continental part of a subducting plate are sufficient to induce separation of an isolated microcontinental block from the main subducting continent, even during induced plate motion necessary for uninterrupted oceanic and continental subduction. Subsequent continental accretion occurs by decoupling upper-crustal nappes from the newly formed subducting microcontinent, which is in agreement with the Late Cretaceous-Eocene evolution of the eastern Mediterranean.

Plain Language Summary Separation of microcontinental blocks from their parent continent is usually attributed to abrupt relocation of concentrated extension from the mid-oceanic ridge to the adjacent continental margin. In the context of extensional passive margin evolution, previous extensive numerical and analog studies have revealed that hot upwelling mantle flow plays a key role in the mechanical weakening of the passive margin lithosphere needed to initiate a ridge jump. This, in turn, results in continental breakup and subsequent microcontinent isolation. However, the consequences of mantle plume impingement on the base of a moving lithospheric plate that is already involved into subduction are still unexplored quantitatively. Here we present the results of 3-D thermo-mechanical models showing that even in the context of induced plate motion (contractional boundary conditions), which are necessary to sustain continuous convergence, thermal and buoyancy effects of the mantle plume emplaced at the bottom of the continental part of the subducting plate are sufficient to initiate continental breakup and the subsequent opening of a new oceanic basin that separates the microcontinental block from the main body of the continent. With these models, we show that it is physically possible to form microcontinents in a convergent setting without the cessation of subduction.