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What can trigger destabilizing of Atlantic passive margins?

Subject Area Geophysics
Term from 2019 to 2022
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 432168024
 
Final Report Year 2024

Final Report Abstract

Since formation of the first subduction zone on the Earth, which would have probably been the start of plate tectonics, Earth’s outer layer (lithosphere) has been regularly recycled into the mantle. The evidence of continuous subduction of oceanic lithosphere into the mantle comes from many geological and geophysical records. Understanding how new subduction zones form is essential for completing plate tectonic theory. However, despite the vital role that subduction zones play in plate tectonics, our knowledge about how subduction zones form is limited. This is mainly due to: (a) the scarcity of present-day locations of subduction initiation and (b) overprinting of the geological/geophysical evidence of early periods of subduction initiation by later subduction related processes such as volcanism and erosion/sedimentation and collision. Some localities such as intra-oceanic transform faults/fracture zones, extinct mid-oceanic ridges and passive margins have been proposed as the location of trench formation. Geological observations confirmed the validity of subduction initiation along some of the proposed locations. However, lack of Cenozoic examples makes the subduction initiation along passive margins as a debatable subject. The widely acceptance of passive margins as the favourable site for trench formation comes from the key role that they play in Wilson Cycle, which explains the repeated opening and closing of ocean basins in geological time. The conversion of a passive margin into an active one is vital in the closing phase of the Wilson cycle. Most of previous modelling studies were not successful to simulate conversion of an old passive margin into a subduction zone with realistic parameters. Here we aimed to answer to the following question: Whether an old oceanic lithosphere along a passive margin can subduct spontaneously? To address this issue, we used 3d numerical models.

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