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    The Role of Upper Mantle Forces in Post-Subduction Tectonics: Plumelet and Active Rifting in the East Anatolian Plateau
    (Amer Geophysical Union, 2024) Uluocak, Ebru Senguel; Pysklywec, Russell N.; Sembroni, Andrea; Brune, Sascha; Faccenna, Claudio
    The spatiotemporal interaction of large- and regional-scale upper mantle forces can prevail in collisional settings. To better understand the role of these forces on post-subduction tectonics, we focus on mantle dynamics in the East Anatolian Plateau, a well-documented segment of the Arabian-Eurasian continental collision zone. Specifically, we analyze multiple forces in the upper mantle, which have not been considered in previous studies in this region. To this end, we use a state-of-the-art 3D instantaneous geodynamic model to quantify the dynamics of thermally defined upper mantle structures derived from seismic tomography data. Results reveal a prominent SW-NE-oriented mantle flow from the Arabian foreland to the Greater Caucasus-a plumelet-through a lithospheric channel under the East Anatolian Plateau. This plumelet induces localized dynamic topography (similar to 500 m) around the extensional Lake Van province, favoring NE-directed compression and westward escape of the Anatolian plate. We suggest that the Lake Van region is an active magma-rich intraplate rift in the Africa-Arabia-Anatolian plume-rift system. The rift zone was probably initiated by Neotethyan subduction-related forces and has been reactivated and/or sustained by the plumelet-induced convective support. Our findings are consistent with numerous observations, including the recent low-ultralow seismic velocities with a SW-NE splitting anisotropy pattern, geochemical and petrological studies, and local kinematics showing upper mantle-induced extensional tectonics in the collisional region. Our goal is to better understand the active deformations of post-subduction tectonics. To this end, we ran a 3D thermomechanical model of the East Anatolian Plateau, one of the most intriguing segments of the Arabian-Eurasian continental collision zone. The model integrates seismically defined upper mantle structures and uses an open-source code (ASPECT). Results reveal the significant role of large- and regional-scale upper mantle forces in the study region. At long wavelengths, we find SW-NE-oriented mantle flow and associated dynamic topography. We interpret that such flow-a plumelet (regional upper-mantle plume migration with neither a significant tail extending to the lower mantle nor a mushroom head reaching the hot spots on the surface)-is linked to the large-scale mantle flow from the Arabian plate to the Greater Caucasus. At short wavelengths, we find localized dynamic topography and high stress and strain anomalies in the Lake Van zone. We argue that the plumelet, which became more forceful after the removal of the subducted Neotethyan slab, may have generated mantle tractions that contribute to magma-rich-intraplate rifting in the Lake Van region. Our results are in good agreement with local kinematics, low-speed seismic velocities with SW-NE anisotropy patterns, and geochemical-petrological studies. We present the 3D numerical model and observations related to the Africa-Arabia-Anatolian plume-rift system Our thermomechanical model provides new insight into the magma-rich intraplate active rifting in collisional settings Integrated analyses from the 3D geodynamic model and observations reveal a SW-NE-oriented plumelet and its regional implications
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    The surface tectonics of mantle lithosphere delamination following ocean lithosphere subduction: Insights from physical-scaled analogue experiments
    (Amer Geophysical Union, 2011) Gogus, Oguz H.; Pysklywec, Russell N.; Corbi, Fabio; Faccenna, Claudio
    Many postulated lithospheric removal events occur in regions with an earlier history of subduction, but the relationship between the two processes has not been explored. In this work, we use physical-scaled analogue experiments to investigate the evolution from ocean lithosphere subduction to collision and possible delamination of the mantle lithosphere from the crust. We test how varying the magnitude of plate convergence alters the behavior of the subduction-delamination model. Our experiments show that a retreating ocean proplate can evolve to continental mantle lithosphere delamination. Negative surface topography is supported at the delamination hinge, and this migrates back with the peeling lithosphere. With high plate convergence, delamination is suppressed. Rather, the crust and mantle lithosphere split at the collision zone in a form of flake tectonics as oncoming procrust is accreted on top of the retroplate and the promantle lithosphere subducts below. Localized high topography develops at this zone of crustal accretion and thickening. The results suggest that delamination may be a continental continuation of plate retreat and that lithospheric removal is triggered by the transition from one process to another.