Multi-scale controls of subduction dynamics on the development of ore deposits and magmatism in the eastern Mediterranean
Résumé
Spatial and temporal evolution of subduction-related ore deposits and magmatism is intimately controlled by the 3D geometry and dynamics of the subducting slab. Understanding these relations is therefore fundamental for large-scale prospection. In this work, we propose new kinematic reconstructions of the eastern Mediterranean region during subduction along the Tethyan margin, which take into account the distribution of magmatic products and mineralization in space and time. Two metallogenic periods were identified. (1) From late Cretaceous to lower Paleocene, calc-alkaline magmatism and porphyry Cu deposits emplaced in the Balkans, along a long linear cordillera. (2) Since the Oligocene, Au-rich deposits and related K-rich magmatism emplaced in a back-arc extensional context during a fast slab retreat episode. Back-arc extension and associated rising of the isotherms seems to have induced the partial melting of the lithospheric mantle or the base of the crust, where Au was previously stored. Emplacement at shallow level of this mineralization was then largely controlled by large-scale structures such as detachments that drained the magmatic-hydrothermal fluids. Besides a general southward migration of this magmatic-hydrothermal activity since the late Cretaceous, a secondary westward migration is observed during the Miocene from the Menderes massif to the Cyclades. We propose this secondary migration to be related to slab tearing event and associated mantle flow below western Anatolia. We tested the effects of slab retreat and tearing on the flow and temperature field within the mantle, by means of 3D high-resolution thermo-mechanical numerical models. Results suggest that the asthenospheric flow induced by the retreat of a torn slab controls the progressive lateral replacement of crustal-derived molten materials by mantle-derived magmatic products at the base of the stretched crust, affecting the distribution of potentially fertile magmas in the upper crust.