Slab factory - ocean formation and subduction in the Western Alps

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The deep structure of the Alps has been modified by subducted slabs of lithosphere which will be imaged by seismic methods in the framework of AlpArray. During subduction, slivers of oceanic crust (ophiolites) were sheared off from oceanic slabs and became part of the collisional stack of thrust sheets exposed at the Earth surface. These carry important information about the history of ocean formation, subduction, and collision. The project will study ophiolites in the arc of the Western Alps using a combination of structural geology, U-Pb zircon dating of metagabbros (to determine the age of oceanic spreading), and Lu-Hf garnet dating of eclogites and blueschists (to determine the age of subduction). Using these new data together with the large amount of already existing data, the kinematics of ocean basin opening and subduction will be reconstructed and predictions will be made for the nature of subducted slabs in order to support the interpretation of lithospheric structures recorded by AlpArray and serve as input for models of the tectonic evolution (Activity Field F of the SPP, 4-D MODELING). These results will be particularly important for understanding the southern end of the Western Alps and transition into the Apennines and Ligurian Sea, the subject of AF-B (LOBSTER). In collaboration with the AF-B projects, we will reconstruct the kinematic evolution of the Alps-Apennines transition.The project is part of Activity Field E (Geological activites) and deals with Research Themes 1 (Reorganizations of the lithosphere) and 3 (Deformation of the crust and mantle).